CHEMISTRY 241
Laboratory Manual
University of Washington
Department of Chemistry
Summer 2012
Chemistry 241 A
Spring 2012
TABLE OF CONTENTS
General Information .................................................................................................................................... 2 Course Policies........................................................................................................................................ 2 Notebooks, Prelabs and Lab Reports: ..................................................................................................... 3 Organic Chemistry Laboratory Safety .................................................................................................... 4 Equipment and Glassware....................................................................................................................... 7 Working with Chemicals ........................................................................................................................ 8 Waste Disposal...................................................................................................................................... 10 Laboratory Notebooks .......................................................................................................................... 11 Chemistry Stockroom ........................................................................................................................... 14 Organic Chemistry Glassware .............................................................................................................. 16 Lab 1: Molecular Modeling ...................................................................................................................... 17 Lab 2: Crystallization and Mixed Melting Points ..................................................................................... 25 Lab 3:Acid Base extraction....................................................................................................................... 31 Lab 4: Distillation ..................................................................................................................................... 36 Lab 5: Friedel-Crafts Acylation ................................................................................................................ 41 Lab 6: TLC and Column Chromatography ............................................................................................... 47 Lab 7: Grignard Reaction.......................................................................................................................... 52 Lab 8: Synthesis of Esters ......................................................................................................................... 58 Lab 9: Spectroscopy Worksheet ............................................................................................................... 62 Page i
Chemistry 241 A
General Information Spring 2012
GENERAL INFORMATION
COURSE POLICIES
Classroom Etiquette: Out of respect for your classmates, please arrive to lecture on time and be seated
when the bell rings. If you arrive late for any reason, please enter quietly. Turn off cell phones and
pagers. Do not talk with your neighbors during the lecture or begin to pack up your books or leave
before the bell rings and the lecture is over. Although your grade may not be directly affected, failure to
follow these guidelines will increase your bad karma and decrease your likelihood of succeeding in life.
Missed Labs or Exams: If you miss a lab or exam you need to have an approved absence as
determined by Dr. Tracy Harvey (Bagley 303D, 543-8183, [email protected]). Criteria for
approval are quite strict and include reasons such as a serious illness with a doctor’s note or death of an
immediate family member with appropriate documentation. Reasons such as a broken alarm clock, job
or school interview, missed bus or airline flight will not qualify. The criteria for approved missed exams
are the same. If you miss a lab or exam, notify Dr. Harvey within 72 hours of your absence to determine
if you qualify for an approved absence. It may be possible (based on space available) for the students to
be scheduled into another lab section to complete the missed lab in the same week the lab is offered.
The students need to go to Bagley 271 to determine if space is available in another lab section. If space
is available, they will be added to the attendance sheet of that section.
Exam Policies: There will be assigned seating for the midterm exam. Your seating location will be
based on your lab section. Seating assignments will be posted on the course website. Please make
certain you know the location of your assigned seat in advance so that you can find it quickly and be
seated and ready to begin the exam when the class starts. There is no final exam for this course. There
will be no make-up exams or alternate exam times.
A calculator will be needed for the exam. Headphones, iPods, cell phones, pagers, hats with bills, and
sunglasses are all prohibited during exams.
Lab Safety: You may work in the laboratory only during your scheduled section and under the
supervision of your assigned TA. You are not allowed in the lab before your lab section begins. You
are required by state law to wear approved safety goggles in the lab at all times. Goggles are to be put
on before entering the lab and must be worn until you are out the door. Goggles that have the air vents
removed are not acceptable. Departmental policy states “students not wearing goggles will be dismissed
from the laboratory immediately. A second infraction may result in dismissal for the remainder of the
quarter. No makes-ups will be permitted.”
E-mail: Class announcements sent out via the university automatic class email system go to your
u.washington.edu account and may not get forwarded to other accounts.
Appropriate Clothing: A lab coat is required to be worn over your street clothes. Long pants, socks
and closed-toed shoes are required. All students need to have clothing coverage from neck to toe with
no exposure of skin anywhere. Headphones and/or texting are not permitted in lab.
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Arriving Late to Laboratory: Lab periods start with a safety and procedure overview from the TA. If
you are late, you miss that information and also make your lab partner wait for you unnecessarily. As
such, for all labs other than the three described below, if you are more than 10 minutes late for lab, 10%
of the possible points for that lab will be deducted from your score. For labs 3, 5, and 6 (Acid-Base
Extraction, TLC & Column Chromatography, and Grignard Reaction) you will not be allowed to do the
lab and you will receive a zero for the lab if you are more than 10 minutes late.
Lab Clean-up: At the end of lab, clean up your work area and any areas assigned by your TA. The
procedure for hood clean-up and shutdown is posted in each hood. Turn off all equipment and
water/gas/steam lines. All equipment checked out at the stockroom must be returned by the end of lab.
Place used pipettes in the pipette waste box. Place broken glass in the glass disposal box. Noncompliance with the rules above will result in deduction of points from your lab score.
NOTEBOOKS, PRELABS AND LAB REPORTS:
Use a carbonless copy notebook and a waterproof ballpoint pen with black or blue ink. Spiral notebooks
and pens with water-soluble ink are not acceptable. When performing an experiment write down the
procedure as you do it and note all observations. Include your final results (bp, mp, yields) and a
written conclusion of the experimental outcome. Your lab notebook must contain enough information to
allow another person to replicate the experiment exactly as you performed it. Notebook pages will be
collected regularly and graded periodically throughout the quarter: points will be deducted for
improperly kept notebooks.
At the beginning of each lab the Prelab checklist and questions should be completed and given to your
TA along with a carbonless copy of the pages in your notebook that you completed prior to lab. You
will not be allowed to start the experiment until the Prelab is completed. The Prelab should summarize
the experimental procedure in your own words. Prelabs for the synthetic experiments (Labs 4, 6-9)
should contain a balanced equation for the reaction, a reagent table, indication of possible side reactions,
a summary of the experimental procedure, waste disposal and a schematic representation of the isolation
and purification procedures. A sample preparative Prelab is shown in the Laboratory Notebook section
below. Lab 1 is done on a worksheet - you don’t need to write anything in your notebook.
Post-Lab Reports are due as shown in the syllabus. Post-Lab Reports consist of the Report Sheet found
in the Lab Manual at the end of each experiment along with carbonless copies of all your lab notebook
pages for that experiment. Points will be deducted for late Lab Reports. Reports that are more than 7
days late will not be accepted. Scores are determined by subtracting points for missing or incorrect items
from each of these sections.
Cheating and Student Code of Conduct:
See:
http://depts.washington.edu/grading/pdf/AcademicResponsibility.pdf
http://www.washington.edu/students/handbook/conduct.html
Disabilities: If you wish to request academic accommodations due to a disability, contact Disabled
Student Services, 448 Schmitz, 543-8925. If you have a letter from Disabled Student Services
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indicating you have a disability that requires academic accommodations, please present the letter to me
so that we can discuss the accommodations you might need for class.
ORGANIC CHEMISTRY LABORATORY SAFETY
Non-compliance with the rules and guidelines listed below may result in the removal from lab
and/or a deduction of ‘lab safety/clean up’ points.
Safety in a chemical laboratory is mostly a matter of common sense coupled with knowledge of the
hazards associated with the materials used by you and your neighbors. A good perception of your
surroundings is also very important in a chemical laboratory. This state of mind requires your full
attention. If there is anything that is unfamiliar or doesn’t seem right, stop what you are doing and ask
your TA or the support staff for guidance. Don’t just plow ahead if something looks wrong. No one will
be criticized for asking. It is, however, critical that you arrive prepared for the laboratory, having
worked out the procedures in your own mind and lab notebook so you know what you’re going to do.
Safety is an important aspect of this class and we want you to think about safety as you read this lab
manual and, especially, as you work in the lab.
Approach this course with a communal spirit. The success of a laboratory course of this size depends on
the cooperation of each individual. Take care of yourself and your neighbors. Immediately warn your
neighbor if you see him/her doing something dangerous. Accidents happen, even if you are using
common sense, someone else in the lab probably is not. An example of good communal spirit would be
if you see your neighbor looking at their reaction by putting their head in the hood, remind them to take
their head out of the hood and lower the sash to watch their reaction through the glass. They would
much rather hear this message from you than teaching staff and lose safety points. Respect the fact that
other students use the common laboratory equipment, such as balances, melting point apparatuses,
hoods, etc. Maintain your work area in a reasonable state of neatness so other students will walk into a
clean/organized space just as you did. For example, the balances must be kept clean, hood bench tops
wiped down, and waste jugs emptied. Reagents must be capped and left in their proper place so that
fellow students do not waste time looking for them.
The most important safety rule is to THINK! Safety rules will be strictly enforced with the possible
consequences of removal from the lab and/or a deduction of safety points. What follows is a detailed
description of the safety rules for this class. For additional information on safety, see your text, PLKE
pp. 542-558.
SAFETY GOGGLES ARE TO BE PUT ON BEFORE ENTERING THE LAB AND MUST BE
WORN UNTIL YOU ARE OUT THE DOOR. State health regulations require the wearing of soft
goggles that shield the eyes from above, below, and both sides in the laboratory. Eyes are too valuable
to risk. Students will not be allowed to work in the laboratory without approved standard laboratory
goggles. Failure to observe this state health regulation may result in removal from the laboratory
and will result in a deduction of safety points. Standard laboratory goggles that meet all state
regulations may be purchased from the University Bookstore and the Chemistry Undergraduate
Stockroom in BAG 271. Safety glasses, goggles that have the air vents removed, sports goggles, etc. are
not acceptable. If you already have goggles, stockroom personnel must first approve them before you
can begin working. Because of health regulations, goggles cannot be borrowed from the stockroom.
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DRESS APPROPRIATELY FOR THE LAB. A lab coat is required to be worn over your street
clothes before entering the lab and not removed until after leaving the lab. Lab coats must be full
length as they must extend to your mid-thigh. Short length lab jackets are not acceptable. Lab coats
may be purchased at the University Bookstore and the Chemistry Undergraduate Stockroom (BAG 271).
You will not be allowed into lab if you are not dressed appropriately. All students in the laboratory
are required to have clothing coverage from neck to toe; there can be no exposure of skin anywhere.
Long pants, socks, and closed-toed shoes that cover the whole foot are required. Long hair must
be tied back (regardless of gender) when in the laboratory so that it will not catch on fire or come into
contact with chemicals.
The laboratory is not a good place to wear your favorite clothes. Do not wear clothing so loose or bulky
that it hampers your work and causes a safety hazard. Extra-long jeans, while fashionable, cannot drag
on the ground. If your fashion sense is to have holes in your jeans, carry a roll of duct tape because you
will be asked to cover any holes. Do not wear hosiery or tight leggings as they will “melt” upon contact
with acid and some chemicals.
Closed-toed shoes (with socks) that cover the whole foot are the appropriate type of laboratory
footwear. Sandals, ballet flats, Mary Janes, shoes with open holes or without full foot coverage, flip
flops, etc., are not allowed in the lab. If you are wearing inappropriate shoes for lab, you will be asked
to go to the undergraduate stockroom to purchase yellow booties and receive a deduction of lab safety
points. If you commonly wear the shoes not allowed in lab, it’s advisable to have a pair of sneakers in
your locker to change into before the lab period begins.
Failure to remain safely dressed for the entire lab period (e.g., not wearing goggles correctly) will result
in a loss of safety lab points, and you will be sent out of lab to acquire the correct clothing. If you do not
return in time to complete your work, your absence will be unexcused.
GLOVES ARE AVAILABLE FOR EVERY EXPERIMENT. Remember, gloves are only a
temporary barrier to chemical exposure, and should be replaced whenever they become too
contaminated. Experiments involving hazardous materials and requiring gloves are usually noted in the
manual. Gloves are not to be worn while using the computers in CHB 121. This spreads hazardous
chemicals into common areas and increases the risk of exposure.
IMPORTANT NOTE: Do not wear gloves outside of the lab; if you have to open a door your
gloves must be off! If you wear gloves outside of the lab you will have 10% deducted from your
lab grade for the day. This will be enforced by all TAs, instructors, lab techs, stockroom
personnel, and anyone else you encounter in the Department.
WASH HANDS OFTEN WHEN WORKING IN LAB AND THOROUGHLY BEFORE
LEAVING. Do not taste any chemicals. Do not put your hands, pens, or pencils in your mouth while
working in the lab. If you must leave the lab for any reason such as to use the restroom during your
scheduled time, please inform your TA, friend, or neighbor before leaving the lab.
DO NOT EAT, DRINK, CHEW GUM, OR SMOKE IN THE LABORATORY. Do not even bring
these materials into the laboratory. Also, no make-up or lip balm is to be applied in the lab.
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KEEP COATS, BACKPACKS, AND OTHER NON-ESSENTIAL MATERIALS AWAY FROM
AREAS WHERE PEOPLE ARE WORKING. There are designated areas for the storage of these
items within the lab. If personal belongings are not stowed they become a tripping hazard to your friends
and colleagues. Additionally, with improper storage, hazardous chemicals may come in contact with
your belongings, increasing the risk of exposure outside of the lab. Lockers are the best place for
personal belongings that are not essential for lab.
Bagley Hall lockers (2nd and 3rd floor hallways): You may bring a lock from home and claim an
empty hall locker for use during the quarter. These are ideal for storing coats, backpacks, and other
bulky items during lab, and are the best place to store your goggles, lab coats, and proper shoes when
not in lab. Lockers must be emptied by the end of the quarter; between quarters the locks will be cut off
and the locker contents thrown away.
CELL PHONES AND HEADPHONES MAY NOT BE USED IN LAB. If you take your cell phone
out during lab it will be confiscated for the lab period and you will receive a deduction of lab safety
points. Cell phone use for any reason (including texting, internet surfing, timing reactions or doing
calculations) is not permitted. Protect your cell phone from chemicals by leaving it in your backpack.
Headphones are not allowed in the lab for any reason. If you don’t remove your headphones, you will
be removed from lab and receive a deduction in safety points.
DRUGS, ALCOHOL, OR MEDICATION THAT COULD IMPAIR NORMAL MENTAL OR
PHYSICAL FUNCTIONING ARE FORBIDDEN PRIOR TO OR IN THE ORGANIC LAB. If
you are taking prescription drugs that might fall in this category, please notify your TA or Dr. Tracy
Harvey before attempting any experiments. Anyone who displays questionable behavior, in this or any
other regard, will be removed immediately from the lab and subject to a mandatory meeting with Dr.
Tracy Harvey.
LEARN THE LOCATION AND OPERATION OF THE SAFETY SHOWERS, EMERGENCY
EYEWASHES, AND FIRE EXTINGUISHERS IN THE LABORATORY. In case of a spill onto a
person or clothing, IMMEDIATELY rinse with lots of water. Do not hesitate to yell for help. Use the
safety shower and/or eyewash and don’t worry about the resulting mess. For non-emergencies, do not
use the safety showers as they are designed to deliver ~50 gallons of water before shutting off. Report
all accidents to your TA, who will submit an incident report with your assistance to the University.
All instructors are certified to administer first aid. If you are not familiar with operation of the fire
extinguishers, ask your instructor to show you. Only use fire extinguishers for real emergencies, as the
chemicals they contain can cause considerable damage. For any emergency that requires the fire
department, aid cars, or police, send someone to the stockroom (BAG 271) for assistance.
LEARN THE EMERGENCY EVACUATION PROCEDURES AND KNOW ALL OF THE
EXITS FROM THE LABORATORY AND BUILDING. A repeating siren and flashing of the FIRE
indicator is the building evacuation signal. If this alarm goes off while you are in the lab, turn off any
open flames, grab your valuables if they are immediately accessible, and leave the building as quickly as
possible OR follow instructions being given by your TA. Assemble with your lab section and TA by
Drumheller Fountain (in front of Bagley Hall). Make sure you check in with your TA when you arrive
to the fountain as all TAs will be taking attendance. All students must be accounted for at all times; DO
NOT LEAVE WITHOUT CHECKING OUT WITH YOUR TA. If you must leave while the
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evacuation is still in progress, you must check out with your TA. Failure to check in for attendance at
the fountain and leaving without checking out will result in an automatic 10% deduction from your lab
report.
SCHEDULED LAB TIME: You are not allowed to be in the lab before your lab section begins. Even
if the lab door is open and another TA is present you cannot enter unless your TA has arrived. Students
are allowed to work in the laboratory only during their scheduled sections and under the supervision of
their assigned TA. Removal from the lab and a deduction of safety points will be a consequence to
breaking this rule.
NEVER ATTEMPT ANY UNAUTHORIZED OR UNASSIGNED EXPERIMENTS. Follow the
experimental procedures explicitly, checking and double-checking the identity of all reagents before you
use them. There are potentially hazardous combinations of chemicals present in the laboratory. If you
have an idea for further investigation, discuss it with your instructor.
LAB CLEAN-UP: At the end of each lab period you should clean up your work area and the areas
assigned to you by your TA. In the back of each hood, there is a list stating the proper clean up and
hood shut down procedure. All equipment checked out from the stockroom must be properly returned by
the end of the period. Point deductions may be made if the lab cleanup is not done or is insufficient.
EQUIPMENT AND GLASSWARE
Fume Hoods: Do all experiments and keep all chemicals in the hood. The ventilation system draws the
fumes generated by an experiment away from the person working in the hood. The walls of the hood
enclose the experiment on five sides. Therefore, if an explosion or spill occurs, the experiment can be
contained. The sash should always be kept in a position that is low enough to protect the
individual's eyes; keep the sash lowered as much as possible without impairing your ability to
conduct the experiment. Set up equipment at least six inches from the front edge of the hood. Close
the sash when you are not working in the hood. Never put your head inside the fume hood.
Do not leave Bunsen burners or other heated apparatus unattended. The person working next to
you may not know what is involved with your setup and may be working with a flammable material.
Turn off open flames if you must leave your area. Make sure the gas taps are completely off whenever
the Bunsen burner is not lit.
Hot plates, Bunsen burners & aluminum blocks are hot and pose a significant burn and/or fire
hazard! Do not use flammable liquids near open flames. Most organic liquids are flammable. Diethyl
ether is especially dangerous. Flammable vapors can ignite when exposed to hot plates. Keep papers
and all combustibles away from the hot plate/aluminum block/Bunsen burner. Turn off hot plates when
not in use. Hot plates and aluminum heating blocks will remain hot for a long time after being turned
off. Neither apparatus gives any visual indication that they are hot, so check by holding your hand a
couple of inches away while “feeling” for heat. Only after checking this way should you attempt to pick
up the aluminum heating block or hot plate. If your hot plate or aluminum block is still cooling down,
put a “HOT” sign on them to warn others. “HOT” signs are located under the prep hood in the marked
drawer.
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Do not pick up hot objects with your bare hands. Be sure all apparatus is cool before picking it up
with your fingers. An insulated glove for handling hot objects is located in the red box within the lab if
you need it.
Do not use cracked or chipped glassware. Examine your glassware for “star” cracks. Broken
glassware should be replaced immediately with new glassware from the stockroom. We can fire-polish
chipped glassware so it is usable, but we can’t fix cut hands. Never heat cracked, chipped or severely
etched glassware.
Do not adjust glass tubing connected to rubber stoppers. Severe cuts or puncture wounds may result.
Lubricate rubber tubing. When slipping rubber tubing over connectors, such as filter flasks or
aspirators, lubricate with a drop of glycerin (balance area) or liquid soap (by the sinks in the lab).
Do not use mouth suction when filling pipettes with chemicals. Use a rubber suction bulb. Do not
force pipet bulbs onto pipets. Apply just enough pressure to maintain a seal between the pipet and the
pipet bulb. Forcing the bulbs may cause the pipet to slip and break, leading to severe cuts or puncture
wounds.
Broken glassware, used pipets, melting point capillaries, and TLC capillaries are to be disposed of
in laboratory glass boxes only. There are two in each lab. One is located in front of the pillar by the
balances and for the pipets that have been used with “smelly” chemicals, dispose of these in the
laboratory glass box in the prep hood. Instrument rooms have melting point capillary tube waste bins on
the island with the Mel-Temps as well as a “laboratory glass” box on the floor. No glass goes into the
regular trash. Custodial personnel can be injured by sharps and will stop collecting trash if they find
them in the trash cans.
WORKING WITH CHEMICALS
General Chemical Safety: Horseplay and carelessness are not permitted. Add concentrated acid to
water; adding water to concentrated acid can release a lot of heat and cause splattering. Waft fumes
gently toward your face rather than “sniffing”. Never point a heated test tube toward you or your
neighbor; the contents may erupt (called “bumping”) and cause serious burns. A separatory funnel must
be used in a hood, vented often, and pointed away from you and your neighbor. Don’t walk around
shaking separatory funnels, test tubes, or centrifuge tubes. Leave chemicals in your hood; if you need
advice from your TA, raise your hand or go to them, but leave the chemicals in the hood.
Proper chemical storage: The policy is that all chemicals need to be stored in the upright position,
clearly labeled, and capped, covered, or parafilmed. Beakers are a good tool to use to keep vials in the
upright position. Solids that are being dried until the next period need to be in a labeled beaker loosely
covered with a watch glass or parafilm. Random drawer checks may be done and safety point
deductions will be made for improperly store chemicals.
Reagents: Read the labels (contents and hazards) before using reagents. Take only as much reagent as
you need; they are expensive and time-consuming to prepare. When taking reagents, transfer the
amount you need to a clean beaker or other suitable container for taking the material back to your desk.
Replace the cap. Let your TA know if a reagent stock bottle is empty.
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Never return unused reagents to their storage containers. If you accidentally take an excess amount
of a reagent, share it with a fellow student or dispose of the excess properly.
Clean up spills immediately. The next person to come along has no way of knowing if a clear liquid or
white powder on the lab bench is innocuous or hazardous. Neutralize acid spills with sodium
bicarbonate before cleaning them up.
Keep the dispensing areas clean and pick up any spills immediately. Return all chemical bottles to
the proper location when finished with them. Hand brooms and dustpans are on top of the flammable
cabinets in the lab. Brushes are supplied at each balance. Clean off chemical spills and keep the
common areas clean.
SUGGESTED PROCEDURES FOR CLEANING UP CHEMICAL SPILLS
Solid Reagents: Wipe up small spills with a damp paper towel; rinse the reagent out of the towel with
water, then dispose of the towel in the trash cans. Clean up large spills using the broom and dustpan
(located on top of the yellow cabinet used to store flammable liquids) and dispose of the reagent in an
appropriate waste container. If glass is present in the spill, separate the glass from the reagent before
disposal. DO NOT place solid chemicals in either the trash cans or the glass box. Spills on the balances
should be immediately brushed out using the camel’s hair brush provided; the reagent may then be
disposed as above.
Liquid Reagents (Non-organics of near-neutral pH): Wipe up the spill using a damp paper towel or
sponge; rinse the reagent out of the towel with water, then dispose of the towel in the trash cans.
Acids: Neutralize the acid by sprinkling solid sodium bicarbonate over the area of the spill. Clean up
the bicarbonate residue with either a damp towel or the broom and dustpan, depending upon the amount
used to neutralize the acid. Dispose of the bicarbonate in the solid waste.
Organic liquids: Wipe up the liquid with paper towels. Do not rinse the paper towels or place them in
the trash. Instead, place them in a hood. Allow the liquid to evaporate and then dispose of the paper
towels in the trash cans.
Mercury: Inform your TA of the spill and they will assist you with the cleanup procedure. Obtain a
“mercury sponge” from the instrument room. Moisten the sponge with water and then rub it over the
area of the spill (metal side down). The mercury should quickly become amalgamated with the metal.
When finished, place the sponge back into the plastic bag and return it to the designated white bucket in
the waste hood within the instrument room. During a mercury spill, small droplets may spatter a
surprising distance from the area of the spill, especially if the mercury falls from the bench to the floor.
Be sure to check a wide area around the spill to be sure that all the mercury has been located and notify
others in the lab to avoid the spill area. If you have a large spill, a special mercury vacuum may be
necessary; ask for assistance.
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WASTE DISPOSAL
Dispose of chemical reagents and other materials properly. The proper disposal of chemical wastes
is essential for the protection of our environment. Improper disposal of chemical waste puts the health
and safety of the University and the surrounding community at risk and can have disastrous effects on
the local ecosystem. Chemical wastes must be managed and discarded in the most responsible and
environmentally sound methods available. UW and the Seattle Metro expect your cooperation in
reducing any environmental impact. Your laboratory manual will specify how to dispose of chemicals
used during the laboratory period: make note of these instructions in your lab notebook. Do not put
chemicals into boxes of broken glass or wastebaskets. Waste containers for other materials will be
provided. If you are unsure of how to dispose of a particular material, ask your instructor.
Waste disposal in CHEM 220/241/242/346/347/462: In general, nothing can go down the drain or into
the trash! Use specific waste bottles (acetone, organic solvents, aqueous acid/base) located in your hood
for collecting waste during your lab period. Empty and rinse waste bottles into the corresponding waste
jugs located in the “Instrument Room Waste Hood.” On occasion, there will be waste jugs designated
for use with specific waste or for particular experiments. When in doubt as to what you should do with
your waste, ask your TA or any instructional staff.
Solid chemical waste has its own waste jug. This specific collection is for solid organic waste, Drierite,
and sodium/magnesium sulfates. DO NOT put TLC plates, paper towels, filter paper, or other nonpowders into this jug.
All non-chemical solid waste used in this class should go into the trash, unless otherwise noted. Paper
towels, matches, pH paper, etc. should NOT be placed in the sinks.
Dispose of broken glassware and other sharp objects in the cardboard glass disposal boxes as
mentioned above. Cleaning up broken glass is greatly facilitated by using the broom and dustpan
(located on top of the flammable cabinet). Custodial personnel will stop collecting trash after they find
broken glass in the trashcans!
Hazard Identification: As part of the UW Laboratory Safety Manual, each laboratory has a Chemical
Hygiene Plan (CHP). This is available to all students in the lab at all times. As part of the CHP,
Material Safety Data Sheets (MSDS)** must be readily accessible to all students. MSDS and chemical
information are available at:
http://hazard.com/msds/index.php
www.fishersci.com – type compound name in "product search", then click on "MSDS" link
www.vwrsp.com/search – go to MSDS tab
http://www.sigmaaldrich.com/safety-center.html
The Merck Index - this reference book is located in the instrument room
**Material Safety Data Sheets: Material Safety Data Sheets (MSDS) are provided by the manufacturer
or vendor of a chemical. They contain information about physical properties of the chemical and
identify any hazards associated with the chemical.
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LABORATORY NOTEBOOKS
Of all the costly items that constitute a research lab, the most valuable is arguably your laboratory notebook. If properly kept,
it is a complete record of scientific activities in which you have invested many hours. The sound of a fire alarm has caused
more than a few graduate students to grab their laboratory notebooks before fleeing the building. When it is time to describe
your scientific activities in a report, you will discover that these notebooks are indispensable. The human mind simply
cannot remember every minute detail of every experiment. Additionally, it is not uncommon to attempt to reinterpret
experimental results years after the original observations were made. Without careful records, we are all doomed to
constantly repeat our own work. This handout is designed to aid you in establishing an efficient method of recording your
experiments and their results.
Use a carbonless copy notebook and a ballpoint pen with waterproof black or blue ink.
Handwriting must be legible!
Each bound notebook must have a Table of Contents at the beginning of the book (on the inside of the front or back cover is
OK). You should update the Table of Contents as you fill out the notebook.
The recordings of each day of research should include a date.
Start the notebook description of a new experiment with the chemical reaction being carried out (when appropriate), a list of
all chemicals that will be used, and their structures. A sketch of each apparatus must be provided as well. For simple
operations such as heating an Erlenmeyer flask on a steam bath or filtration through a Buchner funnel, sketch the device the
first time it is used. You don’t have to sketch it again if you use the technique in a subsequent lab. For more complicated
set-ups, i.e. distillation, refluxing, etc., sketch the apparatus each time you use it.
You must record your observations within minutes of making them. If you are collecting recorder output data, you can jot
down some specifics about the experiment (i.e. how much enzyme, inhibitor, chart speed, etc.) on the output, and you should
assemble the data into your notebook with a day or two after the experiment. The details of the design and components of the
experiment should be recorded in your notebook as you set-up the experiment.
All experiments, regardless of whether they "worked", and regardless of whether you are pleased or displeased with the
results, must be recorded. Often the details of failures are the most informative.
If you purify or dry solvents, be sure to write down how this was done (i.e. “dried with sodium sulfate for 5 minutes followed
by decanting off the dried solvent.”).
TLC plates: Draw a picture of the stained plate in your notebook; indicate the solvent and stain used, the color of the spots,
and the measured Rf values.
List the physical state of all synthetic products. If a solid is isolated, measure the melting point.
Draw the structures of molecules, with correct stereochemistry, if they are not obvious.
Nuclear Magnetic Resonance (NMR) spectra should be labeled with the solvent and the assigned chemical shift of the
reference signal. Interpretation of NMR spectra should include chemical shift (in ppm), integration, multiplicity and
coupling constant (J values in Hz) for each signal. Infrared (IR) spectra should list the matrix (i.e. chloroform solution, KBr
disc, neat, etc.), the calibration and a list of important or characteristic bands. GC-MS chromatogram/spectra should include
Gas Chromatography (GC) conditions and retention time(s) of your sample. List the molecular ion (M+) and base peak for
all Mass Spectrometry (MS) data.
For all chromatography: Give the dimensions of the column, the packing material, the flow rate, and the volume of the
fractions that were collected.
Proper Notebook Organization
The following will be taken into account during notebook grading.
The lab notebook should be organized using the following guidelines:
1. Purpose – this section should contain a short summary of the reason for performing the lab, even
for syntheses: “The synthesis of benzoic acid from bromobenzene via a Grignard reaction.”
2. Reaction – for technique labs skip to the data table. For synthetic labs draw the reaction showing
conversion of reactants to products (see sample prep prelab on next page).
3. Data Table – ALL relevant data on the reagents used for the lab. Don’t forget about melting
points (for identification and purity check), densities of liquids, and expected molar amounts of
products.
Page 11
Chemistry 241 A
General Information Spring 2012
4. Procedure – a brief overview of the steps to take. You should NOT recopy the entire procedure
from the manual/text. This is meant to prepare you for the lab and should be a general map of
how the lab will proceed. Also include drawings of any new apparatus used.
5. Data and Observations – This is the complete record of exactly what you do in lab, written as
soon after you perform the actions as possible. This includes reaction time, temperature, percent
yield, melting point, sketches of TLC plates, IR data etc.
6. Conclusions – Any conclusions about the lab, including support for synthesizing a compound or
success of a particular technique. Comment on errors and/or failures and indicate solutions or
improvements.
7. Put the date on every notebook page.
8. The writing must be with water-insoluble ink.
Read PLKE pages 558-565 for more information on Laboratory Notebooks.
Page 12
Chemistry 241 A
General Information Spring 2012
Use the format below, but also see PLKE pgs 563-564
Page 13
Chemistry 241 A
General Information Spring 2012
CHEMISTRY STOCKROOM
Bagley Hall 271
phone: 206-685-9761 & 206-543-1607 (vm)
Chemistry Stockroom Policy:
1. All stockroom sales are final – NO REFUNDS OR RETURNS.
2. All items checked out from the Chemistry Stockroom must be returned at the end of lab.
3. It is good practice to inspect all items borrowed before leaving the stockroom window and report
any damage immediately.
4. After accepting an item from the stockroom, the student is responsible for returning it
undamaged, clean and dry.
5. Replacement glassware can be purchased from the Chemistry Stockroom using your Husky
Card. If you do not have funds on your Husky Card, you may charge purchases to your
chemistry stockroom account (with your Huskey Card) and pay off the charge at a later date.
6. All charge accounts must be settled by the Friday before finals week, each quarter. Accounts not
settled by the end of the quarter will incur a $10.00 late fee and a hold will be placed on all
University records, including registration.
7. No stockroom privileges will be extended to students with delinquent Chemistry accounts.
(delinquent = charges from a previous quarter)
8. There will be a $5.00 charge for all items returned late, without a yellow slip and/or with the
wrong desk number. The fine will accumulate on a daily basis (i.e. $5.00 per day) until the item
is returned. Fines are assessed to encourage the prompt return of materials so that they will be
available for others who need them.
Check-In Procedures
1. Find your name and desk number on the class list posted outside the lab.
2. Go to your station and wait for your TA.
3. The TA will open your drawer and give you a card which lists the glassware and tools contained
within your drawer. Carefully verify the contents of your drawer against this list. If anything is
missing or broken, ask the TA to verify this by filling out a pink slip. Take the pink slip to the
Chemistry Stockroom (BAG 271) and they will give you a replacement. Check-in day is the
only day the stockroom will replace items at no charge to you. Claims made at a later date will
not be honored.
4. Fill out the required information on the card, read and sign the statement on the reverse side of
the card. Take your card to the Chemistry Stockroom (BAG 271) and they will collect your card
and give you a combination lock to put on your drawer. The small silver padlock stays in your
drawer through the duration of the quarter.
5. You are responsible for all the contents of your drawer. If any items break or are missing, you
must purchase a replacement from the Chemistry Stockroom (BAG 271). The Department of
Chemistry cannot honor claims for replacement of stolen drawer materials. Use good
judgment and keep your drawer locked when not in use.
6. The Chemistry Stockroom (BAG 271) can help facilitate an early check-out, if you drop the class
and/or you need to check-out of your drawer before the scheduled check-out day listed on your
syllabus. Failure to check-out of your drawer will result in a $20.00 fee, in addition to charges
for any items that are broken or missing, and a hold on all University records, including
Page 14
Chemistry 241 A
General Information Spring 2012
registration. Check-out is not final until a signed desk card is returned to the stockroom and all
bills are paid.
How to fill out a loan-return slip (yellow slip) in order to check out equipment/supplies from the
Undergraduate Stockroom (Bagley 271)
The stockroom requires a picture student ID or non-picture student ID
with driver’s license to check out equipment.
For quicker retrieval, yellow slips are filed
by this number, not by your name.
No. 10
University of Washington
Chemistry Department
Date _____20__ Charge/Desk No. ___
Name __________________________
RETURN CARD
Keep the top half of the slip. This
portion is given to the attendant
when returning items checked out.
No. 10
LOAN CARD
Write down your charge number. It is posted
by your name on the bulletin board outside
your laboratory classroom.
Date _____20__ Charge/Desk No. ___
Name _________________________
Course __________ Section ______
List the items that you want to
check out on this half.
The bottom half is what we file. It will be
returned to you when you return the items you
have checked out. We use these slips to keep
track of items not returned. It is your
responsibility that you get this half of the
yellow slip back when you return all items.
Page 15
Chemistry 241 A
General Information Spring 2012
Bring this sheet to lab in order to help with check-in and check-out.
ORGANIC CHEMISTRY GLASSWARE
Page 16
Lab 1: Molecular Modeling Spring 2012
Chemistry 241 A
LAB 1: MOLECULAR MODELING
PRELAB CHECKLIST
Name __________________________________________
Last
First
□
Print out and carefully read the syllabus and course guidelines from the course website:
http://depts.washington.edu/chemcrs/course_index.cgi?bulkdisk/
□
Print out and read the General Information from the course website and bring it to lab.
Make sure you include the Organic Chemistry Glassware page to expedite check-in.
□
□
□
□
Print out the Molecular Models worksheet beginning on the following page and bring it to lab.
□
To prepare for the molecular modeling excericise, read Carey 7th edition 3.1-3.4, 3.7-3.12, 7.17.3, 7.5-7.7, 7.10-7.12,
Carey 8th edition 3.1-3.4, 3.7-3.12, 7.1-7.3, 7.5-7.7, 7.11-7.13, or
McMurry 2.5, 2.7-2.11, 6.1-6.2, 6.6-6.11.
□
This lab does not require a written prelab in your lab notebook, so copies of notebook pages will
not be turned in at the beginning of this lab period.
Bring all required lab supplies (Approved safety goggles, lab coat, lab notebook, ball-point pen).
Wear lab-appropriate clothing (see General Information section for more information).
Before lab, read PLKE Technique 1.1 (Laboratory Safety) on pages 542-558, and Techniques 3
and 4 (Laboratory Glassware & How to Find Data for Compounds) on pages 566-580.
During Lab
□
Lab Safety Discussion: your TA will discuss various aspects of lab safety, including use of
goggles, lab coats, gloves and proper laboratory attire. Procedures for proper chemical and
broken glassware disposal will be discussed.
□
Lab Safety Map: once you get acquainted with the laboratory space and know where everything
is, make a sketch of the laboratory, indicating the location of your desk, room exits, fire alarms,
fire extinguishers, the first aid kit, emergency eye wash stations, and showers
Page 17
Chemistry 241 A
Lab 1: Molecular Modeling Spring 2012
MOLECULAR MODELING – (DUE AT END OF THIS LAB PERIOD)
Purpose:
The purpose of this lab is to help you visualize the three-dimensional structure of organic molecules
using molecular models. You will study conformational analysis and stereochemistry of cyclic alkanes
and cyclohexane. Before the lab you should review the appropriate sections in your organic textbook.
Equipment
Each pair of students will check out one model kit from the organic chemistry stockroom (Bagley 271).
The molecular model kit contains plastic balls and sticks to represent atoms and bonds. The black balls
with 4 holes represent carbon atoms, the white balls represent hydrogen atoms, and the colored balls
represent other atoms, such as nitrogen, oxygen or the halogens. Joining the balls together with gray
sticks depicts a bond between two atoms. (The longer gray sticks are used in the formation of double
and triple bonds.) You can use your own molecular model kit if you have one.
Procedure
Partners should take turns building the models so that each student gets hands-on practice. Answer the
questions about each model on the following worksheet, print your name on each page, staple the pages
together and hand it in to your TA before the end of the lab period. There is no additional report for this
lab.
Page 18
Chemistry 241 A
Lab 1: Molecular Modeling Spring 2012
MOLECULAR MODELING WORKSHEET – DUE AT END OF LAB PERIOD
Name __________________________________________
Last
First
Exercise 1: Conformational Analysis of Alkanes
1.
Construct a model of ethane (CH3CH3) by joining two carbon atoms with a single bond and then
attaching three hydrogen atoms to each of the carbon atoms. Sight down the carbon-carbon bond and
rotate one carbon until all the hydrogen atoms attached to the first carbon atom are directly behind the
hydrogen atoms attached to the second carbon atom. This is referred to as the eclipsed conformation.
(a)
Draw both the Newman projection and the sawhorse (using wedges and dashes) for the eclipsed
conformation.
(b)
Rotate one of the carbon atoms about the single bond by 60° with respect to the other carbon.
This is referred to as the staggered conformation. Draw both the Newman projection and the sawhorse
(using wedges and dashes) for the staggered conformation.
(c)
Which conformation is of higher energy? Explain your choice in one sentence.
2.
Construct a model of n-butane (CH3CH2CH2CH3) and arrange it in a fully staggered
conformation (such that the two methyl groups are 180° from each other). This is called the anti
conformation.
(a)
Draw the Newman projection for the anti conformation, sighting down the C2- C3 bond.
(b)
Keeping the position of C3 constant, rotate C2 clockwise by 60°. Draw the Newman projection.
What is this conformation called?
Page 19
Chemistry 241 A
Lab 1: Molecular Modeling Spring 2012
Name __________________________________________
Last
First
(c)
Rotate C2 by another 60° and draw the Newman projection. This is called the gauche
conformation.
(d)
Rotate C2 by another 60° to get the fully eclipsed conformation. Draw the Newman projection.
(e)
Order the above conformations (0°, 60°, 120° and 180°) from lowest to highest energy, and
briefly explain your reasoning.
Exercise 2: Conformational Analysis of Cyclohexanes
3.
Construct a model of cyclohexane by forming a ring with 6 carbons and attaching two hydrogen
atoms to each carbon. Cyclohexane can adopt several conformations, including the “chair” and “boat”
conformation. Arrange your model in the chair conformation.
(a)
Are all the carbon atoms in the chair conformation equivalent?
(b)
Are all the hydrogen atoms in the chair form equivalent? Briefly explain your answer.
(c)
Sight down any C-C bond. Are the bonds staggered or eclipsed?
(d)
Draw the Newman projection sighting down any C-C bond. What is this conformation called
(based on the conformations of n-butane in question 2)?
Page 20
Lab 1: Molecular Modeling Spring 2012
Chemistry 241 A
Name __________________________________________
Last
First
4.
Arrange your model into the boat conformation by holding the chair conformation of the model
so that you view it from the side, and pulling up on the carbon that is pointing down. Call the carbon
that you flipped upward C1 and the carbon furthest away from it C4.
C4
C1
C4
chair
boat
C1
(a)
Sight along the C1-C2 bond. Are the bonds staggered or eclipsed?
(b)
Sight along C2-C3 bond. Are the bonds staggered or eclipsed?
(c)
Predict whether the chair or boat conformation is more stable, and briefly explain your
reasoning.
5.
Flip the cyclohexane model back to the chair conformation. Make a model of
methylcyclohexane by replacing one equatorial hydrogen atom with a methyl group.
(a)
Draw this conformation.
(b)
Convert your molecule to another chair conformation by flipping C1 (the methyl bearing carbon)
to obtain a boat conformation, and then flipping C4 in the opposite direction. Is the methyl group axial
or equatorial?
(c)
Draw this conformation.
(d)
Which conformation is more stable? Briefly explain your answer.
Page 21
Chemistry 241 A
Lab 1: Molecular Modeling Spring 2012
Name __________________________________________
Last
First
6.
Flip back to the original chair conformation (as in 5a). Replace the axial hydrogen on C2 with
an isopropyl group (-CH(CH3)2).
(a)
Are the two groups cis or trans to one another?
(b)
Flip the model to the other chair conformation. Are the two groups cis or trans to one another?
(c)
Draw the more stable conformation and label it as cis or trans.
Exercise 3: Stereoisomers
7.
Construct a model containing a tetrahedral carbon (black ball) with four different atoms attached
(use one each of the green, orange, blue and white balls). This model will be referred to as A. Construct
a second model that is a mirror image of A. This model will be referred to as B.
(a)
Are A and B superimposable?
(b)
What is the relationship between A and B (enantiomers, diastereomers, identical)?
(c)
Switch the white and green balls on B. This model will be referred to as C. What is the
relationship between A and C (enantiomers, diastereomers, identical)?
(d)
If green = chlorine, orange = bromine, blue = NH2 and white = hydrogen, what is the absolute
configuration (R or S) of A?
(e)
Replace the green atoms in A and C with a white atoms to give models referred to as D and E.
Are D and E superimposable? Is either D or E chiral?
Page 22
Chemistry 241 A
Lab 1: Molecular Modeling Spring 2012
Name __________________________________________
Last
First
(f)
Draw D and show any planes of symmetry.
8.
Make a model of 2(R),3(R)-dichlorobutane (use green balls for chlorine atoms).
(a)
Make a line drawing of 2(R),3(R)-dichlorobutane using wedges and dashes to indicate
stereochemistry.
(b)
Is this molecule optically active? Are there any planes of symmetry?
(c)
Convert your model to 2(R),3(S)-dichlorobutane and draw it, using wedges and dashes to
indicate stereochemistry.
(d)
Is this molecule optically active? Are there any planes of symmetry?
(e)
What kind of molecule is it?
(f)
What is the relationship between the 2(R),3(R) and 2(R),3(S) isomers (enantiomers,
diastereomers, identical)?
(g)
Convert your model to 2(S),3(S)-dichlorobutane and draw it (wedges and dashes).
(h)
What is the relationship between the 2(R),3(R) and 2(S),3(S) isomers (enantiomers,
diastereomers, identical)?
Page 23
Chemistry 241 A
Lab 1: Molecular Modeling Spring 2012
Name __________________________________________
Last
First
(i)
Convert your model back to 2(R),3(S)-dichlorobutane. Replace one of the chlorine atoms with a
bromine atom. Is this molecule optically active? Are there any planes of symmetry?
(j)
How many stereoisomers are there for 2,3-dichlorobutane? How many for 2-bromo-3chlorobutane?
9.
Build a model of 1-propene. Replace one hydrogen atom on carbon-1 with one bromine atom
(orange ball) and replace one hydrogen atom on the same side of carbon 2 with one chlorine atom (green
ball). Call this compound A.
(a)
Draw the structure and give the IUPAC name (including E/Z designation).
(b)
Switch the bromine and the hydrogen on carbon one. Call this compound B. Draw the structure
and give the IUPAC name (including E/Z designation).
(c)
What is the relationship between compounds A and B? (enantiomers, diastereomers, identical)?
(d)
Replace the remaining hydrogen atom on carbon-1 with a bromine atom. Draw the structure and
give the IUPAC name (including E/Z designation).
(e)
Replace the bromine atom that is trans to the chlorine atom with another chlorine atom. Draw
the structure and give the IUPAC name (including E/Z designation).
(f)
Does the compound in part (d) have a diastereomer? If so, draw it and give the IUPAC name
(including E/Z designation).
Page 24
Chemistry 241 A
Lab 2: Crystallization and Mixed Melting Points Spring 2012
LAB 2: CRYSTALLIZATION AND MIXED MELTING POINTS
PRELAB CHECKLIST
Name __________________________________________
Last
First
□
□
□
□
Bring all required lab supplies. (safety goggles, lab coat, lab notebook, ball-point pen).
□
Answer the following questions and turn in this sheet at the beginning of lab. (5 points)
Before lab, read PLKE pages 1-13, 21-22, 25-29, 558-565, 581-597, 616-644, 647-662.
Make sure you arrive in lab on time and ready to perform the experiment.
(1 pt) Write a prelab for this experiment in your lab notebook. Turn in carbonless copies of those
pages to your TA at the beginning of the lab period. Carbonless copies must be turned in before you
begin the lab.
1. (1 pt) If your impure sample was dissolved in more than the minimum amount of hot ethanol, how
would that affect the % recovery? Why?
2. (1 pts) List two features of the melting point of an impure compound.
3. (1 pts) List two features of a good solvent for recrystallization. (Hint: see PLKE pages 647-650).
4. (1 pts) A purified unknown has a melting point 121-122 °C. The mixed melting point of this
unknown and benzoic acid (mp 121-122 ºC) is 105-114 ºC. The mixed melting point of the
unknown and succinimide (mp122-124 ºC) is 120-121 ºC. What can you conclude from this data?
Page 25
Chemistry 241 A
Lab 2: Crystallization and Mixed Melting Points Spring 2012
CRYSTALLIZATION AND MIXED MELTING POINTS
The purpose of this lab is to demonstrate the purification of an unknown solid by crystallization and to
determine its identity by mixed melting point. Read techniques 8, 9 and 11 in your text to become
familiar with the technique and theory behind filtration, crystallization and melting points (emphasize
PLKE sections 8.6, 8.7, 9.1 - 9.8, 11.1, 11.2, 11.4, 11.5, 11.8).
This is a “microscale” lab: crystallization and filtration will be conducted in a Craig tube (sections 8.78.8 and 11.4, PLKE pages 625-627 and 656-659). A Craig tube is the preferred method for
crystallization of small amounts of solids (less than 0.1 g). Use of a Craig tube minimizes the number of
transfers of solid material, resulting in a greater recovery of crystals. It also allows for the efficient
separation of the crystals from the mother liquor and for rapid drying of the crystals. The steps involved
are in principle the same as those used for crystallization with a flask and funnel (section 11.3, PLKE
650-655). When crystallization is complete, the mother liquor is removed from the Craig tube by
centrifugation and the crystals are collected.
Crystallization:
Fill a 150 mL beaker about half-full with tap water. This will be your hot water bath for the
recrystallization. Start heating this beaker on your hotplate. Partly fill a test tube with deionized water.
You will use deionized water as your solvent for recrystallization. Place your test tube of deionized
water in the hot water bath. Obtain approximately 0.040 g of an impure unknown. Record the number
of your unknown and the exact mass of your sample. Add your unknown to your Craig tube, add 0.5
mL of deionized water to your unknown, and place the Craig tube in your hot water bath. Stir the
mixture inside your Craig tube with a spatula to encourage dissolution. Stir for at least two minutes
before adding additional solvent to your Craig tube. If you get impatient and add too much solvent
too quickly you will have a hard time obtaining crystals. Your apparatus might look something like
this:
Page 26
Chemistry 241 A
Lab 2: Crystallization and Mixed Melting Points Spring 2012
If your unknown has not dissolved by the time the hot water bath reaches about 80 ºC, begin adding
additional deionized water. Add about three drops every minute, while stirring, until all of the unknown
has dissolved. Once all of the unknown has dissolved, remove the beaker from the hot plate. Cap your
Craig tube with the Teflon plug and allow the system to cool slowly. Remember, the slower crystals
grow, the larger and more pure they will be.
Once the beaker of tap water no longer feels warm, add ice to the tap water. At this point some crystals
should be forming. Allow the crystals to grow for ten or fifteen minutes at 0 ºC. When you feel that
crystallization is complete, prepare your Craig tube for centrifugation. Wrap a long piece of thin copper
wire around the Teflon plug. This length of wire will allow you to remove your Craig tube from the
centrifuge tube. Invert the Craig tube and place it inside a plastic centrifuge tube (your Craig tube may
break a glass centrifuge tube). Make sure that the Craig tube is resting at the bottom of the centrifuge
tube as shown in Figure 8.11 on page 626 of PLKE. Before moving on, your Craig tube assembly
should look something like the apparatus on the left side:
thin copper wire
plastic
centrifuge
tube
mother liquor
(impurities
are here)
crystals
crystals
Centrifugation
Teflon Plug
mother liquor
(impurities
are here)
Craig Tube Assembly before and after centrifugation. See PLKE pages 625-626
Use the centrifuge to separate the crystals from the mother liquor. Make sure to balance the centrifuge
with a plastic centrifuge tube containing water or with your partner’s Craig tube assembly. Spin the
centrifuge for 30 seconds. Stop the centrifuge and remove the Craig tube from the centrifuge tube
(which should contain all of the mother liquor) using the copper wire. Inside your fume hood,
disassemble the Craig tube and collect the crystals by scrapping the crystals off of the Teflon plug and
the inside walls of the tube and into a tared (pre-weighed) small beaker or onto a tared piece of weighpaper.
Weigh the purified unknown sample and calculate the yield of recovered material (%). Record the
melting points of the unpurified and crystallized unknown.
Page 27
Chemistry 241 A
Lab 2: Crystallization and Mixed Melting Points Spring 2012
Mixed melting points: The identity of your unknown can be verified by taking mixed melting
points (see PLKE pages 627-634). The melting point of your purified unknown mixed with an authentic
sample of the same compound should be the same as your original melting point, whereas the melting
point of a mixture of your compound with any other compound will be depressed and broadened. An
impure solid has a melting point that is depressed and has a wide melting range, therefore eliminating
one of the possible unknowns and confirming the other.
For example, if your sample had a melting point of 104 °C, the two possibilities are azelaic acid and otoluic acid (see table of melting point data below). To perform a mixed melting point experiment you
would prepare two melting point capillaries containing your compound mixed with azelaic acid and your
compound mixed with o-toluic acid, respectively. One of these would exhibit a melting point that was
broad and depressed and the other would melt at approximately 104 ºC.
To prepare a sample for a mixed melting point, grind equal amounts of your unknown and a known
compound in a watch glass with a spatula until they are finely powdered and well mixed. Prepare two of
these samples using the known compounds that have melting points closest to that of your purified
unknown compound.
By the end of the lab period, you should have recorded four melting points, as depicted in the figure
below. Since the melting point apparatus holds multiple capillary tubes, you should be able to finish all
four melting point determinations in two runs (two samples in each run). One of your final melting
point samples should show a mixed melting point (characteristic of an impure substance) and the other
should have approximately the same melting point as your second melting point.
Page 28
Chemistry 241 A
Lab 2: Crystallization and Mixed Melting Points Spring 2012
Possible Unknowns:
Component
acetylsalicylic acid
benzoic acid
azelaic acid
Structure
mp (°C)
134-136
121-123
105-106
Component
benzoin
succinimide
o-toluic acid
Waste Disposal: Aqueous waste can go down the drain.
Structure
mp (°C)
134-138
122-124
102-104
Solid waste (excess unknowns etc,)
should go in the solid waste jug also located in the instrument room hood. Do not put weighing paper,
filter paper, Kimwipes, or other non-powders into the solid waste jug.
Page 29
Chemistry 241 A
Lab 2: Crystallization and Mixed Melting Points Spring 2012
POST-LAB REPORT – (DUE AT BEGINNING OF LAB 3)
Turn this in with copies of your notebook pages.
Name __________________________________________
Last
First
Unknown number ________
Identity of unknown: (2 pts)
Original sample weight ________
Crystallized sample weight ________
Percent recovery (4 pts) (show calculations) _______
Melting point of original sample ________
Melting point of crystallized sample ________
List the compounds tested for mixed melting points, describe your observations, comment on your mixed melting point
results and give your conclusions. (4 pts)
Report _________(10 pts)
Notebook ___________(5 pts)
Prelab _____________(5 pts)
Lab safety __________(5 pts)
Page 30
Lab 3: Acid-Base Extraction Spring 2012
Chemistry 241 A
LAB 3: ACID-BASE EXTRACTION
PRELAB CHECKLIST
Name __________________________________________
Last
First
□
□
□
□
□
Bring all required lab supplies (goggles, lab coat, lab notebook, ball-point pen).
□
Your prelab should include a flow chart that shows each extraction, wash, and drying step of the
experiment. Show where each of the three compounds in your unknown mixture is at each step.
See PLKE pg 687 for a sample flow chart.
Before lab read Lab 3 procedure below and PLKE pages 33-40, 454-459, 669-673, 677-688.
Watch this YouTube video concerning separatory funnels: http://youtu.be/ciWpS6SetdY
Arrive in lab on time.
Write a prelab (3 pts) for this experiment in your lab notebook. Turn in carbonless copies of
those pages to your TA at the beginning of the lab period.
□
Answer the following questions and turn in this sheet at the beginning of lab.
1. (2 pts) The pKa of benzoic acid is 4.2. Draw benzoic acid in the appropriate state(s) of protonation :
pH 2.0
pH 12.0
2. (1pt) At which of the above pHs is benzoic acid most soluble in organic solvents? ___________________
3. (2 pts) The pKa of the anilinium ion (the protonated form of aniline) is 4.6. Draw aniline in the appropriate
ionization state:(protonated, deprotonated, or a mix) at pH 1.0, and 14.0:
pH 1.0
pH 14.0
4. (1 pt) At which of the above pHs is aniline most soluble in organic solvents? _______________________
5. (1 pt) When two immiscible liquids are mixed, what physical property determines which solvent layer is
on the top? ____________________________
Page 31
Chemistry 241 A
Lab 3: Acid-Base Extraction Spring 2012
ACID-BASE EXTRACTION
Purpose: The purpose of this lab is to demonstrate the influence of pH on the water solubility of certain
organic compounds. These properties will be illustrated by the separation of a mixture containing a
carboxylic acid, an amine, and a neutral organic compound.
Most organic carboxylic acids (with more than 5 carbons) are not very soluble in neutral water.
Treatment of a carboxylic acid with dilute aqueous NaOH produces the corresponding sodium
carboxylate salt. Due to its ionic character, the sodium carboxylate salt is soluble in water but not very
soluble in organic solvents. If the basic aqueous solution containing the carboxylate salt is then made
acidic by addition of aqueous HCl, the sodium carboxylate salt will be converted back to the carboxylic
acid, which is not water soluble and will precipitate.
Likewise, most organic amines are not soluble in neutral water. Treatment of organic amines with dilute
aqueous HCl produces the corresponding ammonium salt. The ammonium salt is soluble in water but
not very soluble in organic solvents. If the acidic aqueous solution containing the ammonium salt is
then made basic by the addition of aqueous NaOH, the ammonium salt will be converted back to the
original amine, which is not water soluble and will precipitate.
By taking advantage of these solubility properties, it is possible to separate a mixture containing acidic,
basic, and non-ionizable components using sequential extractions with acidic and basic water.
You will receive a mixture of three products. Your task is to separate them and identify them by their
melting points. The mixtures (bottles #1-5) will each contain one acid, one amine, and one nonionizable compound. The possible components of your mixture are shown below:
Before beginning, make sure that you are familiar with the proper techniques for using a separatory
funnel (PLKE, Technique 12.7). You should also make a flow chart that outlines the separation that you
Page 32
Chemistry 241 A
Lab 3: Acid-Base Extraction Spring 2012
are performing (see for example PLKE p. 687). During this lab you will be working with a lot of
colorless solutions and it is easy to get them mixed up. Many students find it helpful to consult their
flow chart throughout the experiment to help them avoid mixing up their solutions. Label all of your
glassware throughout the experiment.
Extraction procedure:
Extracting the amine: Dissolve 1.00 gram of a mixture of an acid, base and neutral (from bottles #1-5)
in 15 mL of diethyl ether. Caution: diethyl ether is extremely volatile and extremely flammable. Keep
ether solutions in the hood at all times. Transfer the ether solution to a separatory funnel and add 5 mL
of 1M aqueous HCl. Gently shake the separatory funnel for several minutes, venting it frequently to
avoid pressure buildup. Place the separatory funnel in a ring stand and allow the ether and aqueous
layers to separate. Uncap the funnel and drain the aqueous (lower) layer into a flask. Repeat the
extraction with another 5 mL of 1M aqueous HCl. Save the ether layer in the separatory funnel for later
use. In a beaker, combine the acidic aqueous extracts and cool them in an ice-water bath. Slowly add
6M aqueous NaOH (~ 2 mL) until the aqueous mixture becomes basic. Use pH paper to monitor the
pH. During neutralization a precipitate will form. Collect the precipitate on a Büchner funnel by
vacuum filtration (PLKE Figure 8.5). Wash the solid with cold water (~ 2 mL) and allow it to air dry.
Extracting the benzoic acid: Extract the ether solution (left over from above) with two 5 mL portions
of 1M aqueous NaOH. Again, save the ether layer in the separatory funnel. Combine the basic aqueous
extracts and cool them in an ice-water bath. Add 6M aqueous HCl (~ 2 mL) until the aqueous mixture
becomes acidic. Collect the precipitate that forms in a Büchner funnel by vacuum filtration. Rinse the
solid with cold water (~ 2 mL) to remove any water-soluble impurities, and then allow it to air dry.
Drying the ether solution and isolating the neutral (non-ionizable) compound: Add 10 mL of
saturated aqueous sodium chloride solution (brine ) to the ether remaining in the separatory funnel and
repeat the shaking and venting procedure from above. Aqueous sodium chloride is more polar than pure
water, and will extract any water (polar) remaining in the ether (nonpolar). Allow the layers to separate
and discard the brine layer. Pour the ether layer into a beaker containing 1 g of anhydrous Na2SO4 and
allow it to stand for about 5 minutes, swirling occasionally. The anhydrous Na2SO4 will remove any
water left in the ether. While your ether solution is drying, weigh a 25 mL Erlenmeyer flask, record the
weight, and label the flask. Pour the ether solution into the 25 mL Erlenmeyer flask, taking care to leave
behind all of the solids. Pouring a liquid away from a solid in this way is called decanting. Evaporate
the ether by using a stream of air directed into the flask (connect amber tubing to your air line and at the
open end, insert a pipette as in figure 7.17A of PLKE on page 612). When all of the ether has
evaporated, weigh the remaining solid (note: if an oil forms instead of a solid, cool on ice until it
solidifies).
Recrystallization of the neutral compound:
The solid isolated from the ether layer
will undergo a semi-microscale recrystallization in an Erlenmeyer flask (see PLKE technique section
11.3). The solvent of choice is hexane. Follow the procedure below:
Page 33
Lab 3: Acid-Base Extraction Spring 2012
Chemistry 241 A
Dissolve your neutral compound in a minimum amount of hot hexane and heat on a steam bath until the
sample dissolves. If necessary, add more hexane, dropwise, until all the solid dissolves. Once dissolved,
set the solution aside and let it cool to room temperature. Once at room temperature, cool the solution
on an ice bath until crystal formation is complete. Filter the crystals on a Büchner funnel and wash them
with cold hexane (approx 0.5 mL).
Identification of the components in the original mixture: Weigh the three
isolated compounds and record their melting points. Remember, each Mel-Temp apparatus can hold
three samples at a time. The melting point values from the literature are:
acidic compound
benzoic acid
o-toluic acid
mp (ºC)
121–123
103–105
basic compound
4-(dimethylamino)benzaldehyde
ethyl 4-aminobenzoate
Waste Disposal:
mp (ºC)
74
89–92
non-ionizable compound
benzophenone
p-dibromobenzene
mp (ºC)
48–50
86–89
All aqueous waste (acidic and basic) goes into the Aqueous Acid/Base waste
jug located in the hood. Ether goes into the Organic Solvent Waste (Do not put aqueous solutions in
this!!). There is also a jug for solid waste (sodium sulfate & organic solids). Do not put filter paper,
cotton, etc into the solid waste jug. Remove chemical residues from those materials, then put them
in the trash.
Page 34
Chemistry 241 A
Lab 3: Acid-Base Extraction Spring 2012
POST-LAB REPORT – (DUE AT BEGINNING OF LAB 5)
Turn this in with copies of your notebook pages .
Name __________________________________________
Last
First
Unknown # ______
Show the structures of the three components of your unknown mixture in the spaces below:
Carboxylic Acid
mp _______
weight _______
% of original sample _______
(show calculations)
Amine
mp _______
weight _______
% of original sample _______
(show calculations)
Non-Ionizable Compound
mp _______
weight _______
% of original sample _______
(show calculations)
Calculate the % by weight not recovered from the original sample.
Report _____________(10 pts)
Notebook ___________(5 pts)
Prelab _____________ (10 pts)
Lab safety ___________(5 pts)
Page 35
Lab 4: Distillation Spring 2012
Chemistry 241 A
LAB 4: DISTILLATION
Prelab Checklist: Lab 4 Distillation
Name __________________________________________
Last
First
□
Bring all required lab supplies: (safety goggles, lab coat, lab notebook, ball-point pen).
□
□
□
Before lab read PLKE pages 51-56 and sections14.1, 14.2 14.4, 15.1-15.4, 22.1.
Make sure you arrive in lab on-time. Points will be deducted for late-arriving students.
(3 pts) Write the detailed procedure that you will be using for this experiment in your lab
notebook, photocopy of those pages and turn it in to your TA at the beginning of lab. Be sure in
include a sketch of the simple and fractional distillation apparatus. Prelab photocopies must be
turned in before you begin the lab.
□
Answer the following questions and turn in this sheet at the beginning of lab.
1. (1 pt) What determines which compound comes off first in a distillation?
2. (1 pt) Will the composition of the first mL of distillate collected be enriched in the lower or higher
boiling point compound?
3. (1 pt) How will the first mL of distillate from the simple distillation differ from the first mL distillate
of the factional distillation?
4. (1 pt) If the thermometer bulb is placed too high how will this affect your results?
Page 36
Lab 4: Distillation Spring 2012
Chemistry 241 A
Distillation & Gas Chromatography
The purpose of this lab is to illustrate the use of distillation for the separation and purification of volatile
liquids. This experiment also illustrates the use of gas chromatography (GC) for identification and
analysis of liquids. Experiment 6A in PLKE will give a general overview of distillation but follow the
procedure given below in order to carry out the distillations. Read sections 14.1, 14.2, 14.4, 15.1-15.4,
15.6, 22.1-22.9, 22.12.
In this lab, you and a partner will distill and analyze an unknown mixture containing two of the liquids
listed below. Note: All unknowns are flammable (no flames allowed!). You and your partner will carry
out a simple and fractional distillation and an unknown mixture. Gas chromatography will be used to
analyze: 1) the original unknown mixture, 2) the first milliliter collected from the simple distillation, and
3) the first milliliter collected from the fractional distillation.
Possible components of the unknown mixture are:
Component
Acetone
n-Hexane
Ethyl acetate
Heptane
Toluene
bp (°C)
57
69
77
98
110
DISTILLATION SETUP:
For a sample setup for a simple distillation, see Figure 14.11 in PLKE,
p. 714 and the diagram below. For a sample fractional distillation apparatus, see Figure 15.11 in PLKE,
p. 724. There is also a sample fractional distillation set up located in the CHB 121 and the simple
distillation set up is located in CHB 118.
Simple Distillation Set-Up similar to the figure on p. 714, PLKE 4th edition
Page 37
Chemistry 241 A
Lab 4: Distillation Spring 2012
Additional Technique Notes:
The Notes below refer to modification in the distillation assembly from p. 714 of PLKE --see diagram on
the previous page.
1. In all experiments, use a graduated cylinder as a receiver instead of the round bottom flask.
Don't forget to collect & save the first mL of distillate in both distillations
2. In all experiments, the heat source should be placed on a block to permit quick removal in an
emergency. In the simple distillation, several blocks may be needed so the assembly will be high
enough to accommodate the graduate cylinder used as a receiver.
3. Put a boiling chip into the COLD mixture to promote smooth boiling. Never put a boiling chip
into hot liquid!!
4. The clamp is the main support of the assembly and must be able to hold the weight of the flask
(and column) if the heater is removed.
5. Accurate placement of the thermometer bulb is essential to measure a true liquid-vapor
equilibrium temperature. The bulb should be below the ring on condensing hot vapor, but not so
low that the drop of liquid on the bulb evaporates. See PLKE p. 714 or the diagram on the
previous page for an example of thermometer placement.
PROCEDURE:
Obtain 30 mL of an unknown liquid mixture and record the unknown number. Place
the unknown and 3 - 4 boiling stones in a 100 mL round bottom flask. An electrical thermowell heater
will be used to heat the distilling flask (see Figure 14.11 on p. 714 of PLKE - do not use a flat hot plate
to heat a round-bottom flask). These heaters will be provided in the balance area. Caution: Plug the
thermowell into the variac outlet, which is the silver plug below your hood space. DO NOT use a
standard electrical outlet. Have your TA inspect your apparatus before you begin your distillation.
Adjust the heating rate so that the mixture distills slowly, approximately one drop every 2 - 3 seconds.
Collect the first milliliter of distillate in a vial and note the temperature of the distilling head. Tightly
cap and immediately analyze this sample by Gas Chromatography (GC)—see below for GC instructions.
You may also analyze a sample of the original mixture at this point. While one partner does the GC
analysis the other will continue on with the distillation and recording the temperature at the distilling
head at intervals corresponding to every additional milliliter of distillate collected. As the distillation
proceeds you may need to increase the heat of the thermowell. Stop the distillation when 2 - 3 mL of
liquid remains in the distilling flask (never boil a flask dry).
Set up a fractional distillation apparatus (see Figure 15.11 on p. 724 of PLKE). Have your TA inspect
your apparatus before you continue. Obtain another 30 mL of the unknown and carry out a fractional
distillation (you may have to turn up the variac setting that was used during the simple distillation). As
in the simple distillation, collect and 1st ml of distillation and analyze by GC and continue recording the
distilling head temperature for every milliliter of liquid collected.
Page 38
Chemistry 241 A
Lab 4: Distillation Spring 2012
For both the simple and fractional distillation, plot graphs of distilling head temperature versus the
volume distilled. From these graphs you may estimate the boiling points of both components in your
unknown and the percent composition of each component in the mixture.
ANALYSIS BY GAS CHROMATOGRAPHY: Your TA will show you the operation of the gas
chromatographs at the beginning of the period. Syringes and brief instructions are also next to each GC.
These syringes may become clogged and fail to draw up the liquid sample. To verify that your syringe
is working properly, draw up 10 L of liquid and depress the plunger to confirm that liquid drips out the
needle. If the syringe is working properly, inject 1 - 2 L of sample into the GC. If your syringe is
clogged, check with your TA for appropriate cleaning procedures. Also, before analyzing a different
sample, be sure to flush the syringe five or six times with the new sample.
Analyze the original unknown and the first milliliter of distillate from the simple and fractional
distillation by GC. Identification of the components can be elucidated by their retention times. It is
important to note that the GC standards of the unknowns (taped near the instrument) can be used as only
a rough guide to identify your components. Retention times tend to drift slightly during the day and are
not dependable as a sole means of identification for these simple gas chromatagraphs.
Estimate the percent composition of each sample by using the h x w1/2 method (see technique section
22.12 of PLKE). Once you calculate the peak areas you will divide the value by the corresponding
correction factor shown below. (When equal volumes of unknowns are injected into the GC you get the
following relative peak areas):
Relative Peak Areas
Acetone
1.0
n-Hexane
1.0
Ethyl acetate
1.4
Heptane
1.2
Toluene
1.5
WASTE DISPOSAL: All distillation waste goes into the Organic Solvent Waste jug (No water!)
Page 39
Lab 4: Distillation Spring 2012
Chemistry 241 A
Lab 3 Report (Distillation) Turn this in with copies of your notebook pages.
Name __________________________________________
Last
First
Results:
For the simple and fractional distillations attach copies of your graphs of still head temperature vs volume distilled, showing
initial and final boiling points. Also attach all GC results to your report.
Unknown # ________
Boiling point of A ________
Boiling point of B ________
GC Retention time A ________
Composition of original mixture (From Graphs):
GC Retention time B ________
%A________ %B__________
Composition of 1st mL of simple distillation (from GC): %A________ %B__________
Composition of 1st mL of fractional distillation (From GC)
%A________ %B__________
Identification of A:________
Identification of B________
Question: Which distillation, simple or fractional, achieved better separation—comment on how you came to this conclusion.
Report (8 pts) _____________
Notebook (5 pts) ___________
Prelab (7 pts) ______________
Lab safety (5 pts) ___________
Page 40
Lab 5: Friedel-Crafts Acylation Spring 2012
Chemistry 241 A
LAB 5: FRIEDEL-CRAFTS ACYLATION
PRELAB CHECKLIST
Name ___________________________________
Last
First
□
□
Bring all required lab supplies. (Safety goggles, lab coat, lab notebook, ball-point pen).
Read PLKE pages 42, 605-606, 674-675, and 777-791. Also read Carey 7th ed. 11.1-11.6, 11.2011.22, 12.1-12.2, 12.7, or Carey 8th ed. 11.19-11.21, 12.2, 12.7, or McMurry 5.1-5.2, & 5.6.
□
□
Make sure you arrive in lab on-time.
□
Answer the following questions and turn in this sheet at the beginning of lab.
(3 pts) Write a ‘Prep’ prelab (see pg 13 or PLKE 563 for an example) for this experiment in your
lab notebook. Turn in carbonless copies of those pages to your TA at the beginning of the lab
period.
1. (3 pts) During this lab you will perform an extraction. Draw a flow chart below that includes all the
pertinent details for the extraction (solvents, products, impurities, drying agents, etc.)
2. (2 pts) The electrophilic acylium ion is drawn below as R-C≡O:+. Draw another reasonable resonance
structure. Which resonance structure makes a larger contribution to the actual structure of the acylium
cation?
3. (2 pts) In this lab you flame-dry your glassware to remove water. Complete the chemical reactions
between reagents and water that are shown below.
Page 41
Chemistry 241 A
Lab 5: Friedel-Crafts Acylation Spring 2012
FRIEDEL-CRAFTS ACYLATION
Purpose: the purpose of this experiment is to acetylate the five-membered cyclopentadienyl rings of
ferrocene, an aromatic metal complex. This reaction is not selective and typically gives a mixture of
products which may include ferrocene, acetylferrocene, and/or diacetylferrocene. You will use Thin
Layer Chromatography (TLC) to characterize your product mixture. In the next lab you will use column
chromatography to separate and purify the products of this reaction.
Friedel-Crafts acylation reactions are a type of electrophilic aromatic substitution reaction. In these
reactions, an acyl chloride (R(C=O)Cl) is combined with a lewis acid catalyst to generate an acylium
cation (RCO+).
The electrophilic acylium cation can then react with an aromatic compound in an electrophilic aromatic
substitution reaction. Although some of the specifics are different, this looks similar to the electrophilic
aromatic bromination experiment that you conducted in the previous week. The acylium ion performs
an electrophilic attack on the aromatic ring to generate the arenium ion. Deprotonation of the arenium
ion restores aromaticity and regenerates the lewis acid catalyst.
In our experiment, the acyl chloride will be acetyl chloride (R = CH3) and the aromatic substrate will be
ferrocene. Ferrocene is a neutral metal complex that contains an Fe2+ ion “sandwiched” between two
planar cyclopentadienyl anions.
The cyclopentadienyl anion has six pi electrons delocalized (note the resonance structures shown below)
throughout the ring, and is thus aromatic. The related compound cyclopentadiene (C5H6) has only four
Page 42
Lab 5: Friedel-Crafts Acylation Spring 2012
Chemistry 241 A
pi electrons, and is therefore not aromatic. Since the cyclopentadienyl moiety contains a carbanion, one
might expect the C5H5– group to be quite reactive. However, complexation to iron stabilizes the
cyclopentadienyl groups, and ferrocene is fairly inert.
In your reaction, both mono- and di- acetylation will occur. Neither recrystallization nor acid-base
extraction will allow you to separate these products, but don’t lose hope! During the next laboratory
period you will learn a powerful technique that will allow you to purify your product mixture.
O
AlCl3
O
Fe
+
Cl
Fe
O
Fe
+
CH2Cl2
O
ferrocene
acetyl chloride
monoacetylferrocene
diacetylferrocene
(C5H5)2Fe
CH3(C=O)Cl
(C5H4COCH3)2Fe
(C5H4COCH3)2Fe
Procedure: Before you start, remove any flammable materials (including organic solvents!) from your
fume hood. To a 5 mL conical vial, add a spin vane and connect an air condenser and a drying tube
packed with Drierite. Use a thin film of grease in between the ground glass joints. Do not use one of
the plastic “caps” to connect your conical vial to your air condenser. The apparatus is pictured below.
Use your Bunsen burner to flame-dry the apparatus. You only need to flame dry the conical vial and the
air condenser; take care not to ignite the cotton inside your drying tube. Once your apparatus has been
flame-dried, place it in the aluminum block and allow it to cool to room temperature. HOT GLASS
AND COLD GLASS LOOK IDENTICAL – be careful not to burn yourself with hot glass.
Page 43
Chemistry 241 A
Lab 5: Friedel-Crafts Acylation Spring 2012
Once the apparatus has cooled to room temperature, briefly remove the air condenser and add 0.150 g of
aluminum chloride and 2.0 mL of methylene chloride to the conical vial. To prevent excess moister
from hampering your reaction, replace the air condenser promptly after the addition is complete. Use a
similar procedure to add the remaining reactants. Add 0.08 mL of acetyl chloride (this should be about
12 drops if you are using a glass Pasteur pipette). Stir the reaction mixture with a stir plate, but do not
heat the reaction. Add 0.100 g of ferrocene dissolved in 0.5 to 1.0 mL of methylene chloride. The
mixture should quickly change from orange to a deep violet color. After replacing your
condenser/drying tube assembly, begin timing the reaction.
While your reaction runs, add 5 mL of ice-water to a 15 mL glass centrifuge tube. Once 15 minutes
have elapsed, use a pipette to transfer your reaction mixture to the centrifuge tube containing ice water.
Neutralize this mixture by adding 25% sodium hydroxide solution (about 0.5 mL). Use pH paper to
confirm neutrality. If you add more NaOH than intended and the pH becomes basic, aluminum salts
will precipitate, but this is OK, since the aluminum salts are essentially waste at this point. Make sure to
mix the aqueous and non-aqueous phases at this point – it is essential to neutralize the acid in BOTH
phases. A pipette is the best method for mixing the phases. Alternatively, you could mix the phases by
shaking the (capped) centrifuge tube and periodically venting (popping off the cap) like you did in Lab 3
with a separatory funnel. However, when the pressure is released solvent tends to squirt a bit so this
second method tends to be messier.
Once the reaction mixture has been neutralized, you will perform a microscale extraction (see PLKE
Technique 12.4, p.674-675). After you separate the methylene chloride layer from the aqueous phase
with a pipette, extract the aqueous phase twice more with 3 mL of methylene chloride. An emulsion
often forms during the extraction, but luckily, centrifugation is one of the best ways to break an
emulsion! If you do not have two discreet layers, briefly spin your sample in the centrifuge. Don’t
forget to balance the centrifuge with an extra tube (filled with the same solvents as your tube) or with
the sample of another group. Combine the extracts in a 25 mL Erlenmeyer flask.
Page 44
Chemistry 241 A
Lab 5: Friedel-Crafts Acylation Spring 2012
Once you have combined your methylene chloride extracts, examine them. Are there drops of water
present in the Erlenmeyer flask? They may be clinging to the walls of the flask or floating. If water
droplets are visible, use a pipette to transfer your methylene chloride solution to a 50 mL Erlenmeyer
flask.
To dry the combined methylene chloride extracts, add approximately 0.100 g of sodium sulfate and let
the solution stand for 15 minutes. Also at this time, take 10 drops of the solution and save in a vial.
This will be used later for TLC analysis. At the end of 15 minutes, add the dried solution to a tared 125
mL Erlenmeyer and wash the remaining sodium sulfate with 2 ml of methylene chloride. The rinse is
then combined with the rest of the dried methylene chloride solution.
Thin Layer Chromatography (TLC) Analysis: The small aliquot from your methylene chloride
extracts that you saved earlier (in the previous paragraph) will be used to prepare TLC plates. Prepare a
TLC plate spotted with your reaction mixture aliquot and with samples of pure ferrocene,
acetylferrocene, and diacetylferrocene. Your undeveloped plate should look like the one below:
undeveloped TLC plate spotted with 4 different samples
1) methylene chloride extracts from
Friedel-Crafts reaction mixture
2) pure ferrocene
3) pure acetylferrocene
4) pure diacetylferrocene
You and your partner should develop your TLC plates in two different solvent systems. One of you
should use 80% hexane / 20% acetone as your solvent mixture and the other should use 50% hexane /
50% acetone as the solvent mixture. Develop your plate as described in PLKE p.44-45. Calculate the
Rf values for all of the spots on your plate and determine which products were formed in your reaction.
If you have time before the end of the period, evaporate the methylene chloride from your 125 mL
Erlenmeyer flask using a pipet attached to the air line in your hood with amber tubing. If you do this,
note the mass of your product mixture after the solvent has evaporated. Otherwise, store the solution in
your drawer (the methylene chloride will evaporate before the next lab period).
Waste Disposal: All solids and solutions from above can be placed in the Aqueous Acid/base waste
jug. TLC plates (below) can be place in the trash cans. Silica Gel, used during the next lab period,
should be placed in the Silica Gel waste once it has been used. Solvent used in chromatography can be
placed in the Organic Solvent waste jug
Page 45
Lab 5: Friedel-Crafts Acylation Spring 2012
Chemistry 241 A
POST-LAB REPORT – (DUE AT BEGINNING OF LAB 6)
Turn this in with copies of your notebook pages.
Name __________________________________________
Last
First
(4 pts) Draw a detailed mechanism for the Friedel-Crafts acetylation of ferrocene to give monoacetylferrocene.
(1 pts) The products of this reaction are acetylferrocene and di-acetylferrocene. Why do the first and
second acetyl groups end up on different ferrocene rings? (Why is the product shown below NOT
observed?)
O
O
Fe
Report _________(5 pts) Notebook ___________(5 pts)
Prelab _________(10 pts) Lab safety _________(5 pts)
Page 46
Chemistry 241 A
Lab 6: TLC and Column Chromatography Spring 2012
LAB 6: TLC AND COLUMN CHROMATOGRAPHY
PRELAB CHECKLIST
Name __________________________________________
Last
First
□
Bring all required supplies for lab. (Safety goggles, lab coat, lab notebook, ball-point pen). You
may also want to bring a pencil and a small ruler for measuring Rfs.
□
□
Before lab read PLKE pages 42-45 and 756-791.
□
□
Make sure you arrive in lab on-time.
□
Answer the following questions and turn in this sheet at the beginning of lab.
Watch these videos concerning chromatography:
http://www.youtube.com/watch?v=EytuRMS1154 and http://www.youtube.com/watch?v=6fzBJ8nuuzk
(1 pt)Write a prelab for this experiment in your lab notebook. Turn in carbonless copies of those
pages to your TA at the beginning of the lab period.
1. (1 pts) Define Rf:
2. (1 pts) Predict the relative Rf values of a mixture of biphenyl, benzoic acid, and benzyl alcohol (i.e.
which will move fastest and which slowest?).
3. (1 pts) When the polarity of the solvent mixture increases, what happens to Rf values?
4. (1 pts) Below is a TLC plate that was spotted with a mixture of three compounds and developed with
80/20 hexane/acetone. Show the locations of compounds A, B, and C on the plate to the right, assuming
that it was spotted with the same mixture but developed with 25/75 hexane/acetone.
Page 47
Chemistry 241 A
Lab 6: TLC and Column Chromatography Spring 2012
THIN LAYER CHROMATOGRAPHY AND COLUMN CHROMATOGRAPHY
Part 1 - Column chromatography of ferrocene, acetylferrocene and diacetylferrocene.
In this part of the experiment you will be separating a mixture of ferrocene, acetylferrocene and
diacetylferrocene by column chromatography. Burette columns will be checked out at the stockroom.
Obtain approx. 50 mL of premixed 90/10 hexane/acetone solvent. To the column add a cotton plug
followed by 1/2 cm of sand, and finally 15 mL of the 90/10 hexane/acetone solvent system. Orient the
column as close as possible to vertical with the clamps. You are now ready to prepare your silica gel
column. You will use the "slurry" method. Read section 19.7 of your text to understand the following
procedure. In a small Erlenmeyer flask, slowly add 25 mL of 90/10 hexane/acetone to 5 g of silica gel.
Swirl the solution a couple of minutes to ensure that slurry is relatively free of trapped air bubbles. Place
a beaker below the column and open the stopcock. Using a glass funnel, add the slurry to the column in
portions, making sure to swirl the slurry before each addition to suspend the silica particles. If you don’t
swirl the slurry immediately before each addition the silica will settle to the bottom of your flask and
won’t end up in your column! As you add silica gel, tapping on the side of the column with a pencil (the
wooden part) will aid in the packing of the silica gel and eliminating air bubbles. Note: Always keep the
solvent level above the silica by adding extra solvent when needed.
Once the solids have settled in the burette and a well-defined, level top has formed, fill the column with
solvent and let it run through. When the solvent has reached 1-2 mL above the silica, fill the column
once more using the solvent from the collecting beaker and drain to ensure a tight pack. The column
should not contain any air pockets at this point. Finally, add 1/2 cm of sand to the top of the silica and
adjust the solvent level so that it is just above the silica (1-2 mm). Note: the solvent level can go below
the level of sand without impacting the column, but not the silica! Remember that the volatile solvent
will evaporate away if left sitting for a long time.
Before moving on, record the masses of three 125 mL Erlenmeyer flasks and label each of them with
their mass (using a pencil). These flasks will be used for collecting your products.
The next step is to apply your sample to your column. Use weigh paper and a spatula to transfer your
solid product from the previous lab to a small conical vial or snap cap vial. In the process, record the
mass of your ferrocene/acetylferrocene/diacetylferrocene mixture. Dissolve your product mixture in the
minimum amount of methylene chloride (0.5 mL should suffice, avoid using more than 1 mL). Add this
solution slowly and evenly with a pipet down the sides of the column as to not disturb the surface of the
silica. The sand acts as a protective layer to help the silica surface remain level. It is critical to use a
minimum amount of solvent to add your sample to the column in order to have thin bands which
will separate cleanly. Carefully open the stopcock to allow the solution to absorb onto the silica. Now
add 1 mL of hexane (or less) evenly down the sides of the column and again drain until the solvent is at
just the same level as the surface of the silica. Repeat this procedure one more time, or until all of the
colored products are loaded onto the silica. At this point all of your compound should be bound on the
Page 48
Chemistry 241 A
Lab 6: TLC and Column Chromatography Spring 2012
silica in a tight band. Now carefully fill the column with eluent (90/10 hexane/acetone). The first few
mLs should be pipetted in slowly as to avoid disturbing the silica surface. Once the column is filled,
you may begin your elution by opening the stopcock. Collect only the colored fractions and add solvent
as needed. You may recycle fractions that are colorless. Try to achieve a flow rate of 1-2 mL per
minute. You can push the solvent through using air from the air-line, but you want to avoid overpressurizing the system. This is done by placing a rubber thermometer adapter at the top of your column
and then inserting a pipet, which is connected by amber tubing to an airline, into the thermometer
adapter. When using this system be sure that the pipet is not too tightly inserted into the adapter as it
needs to be easily pushed out if the air pressure gets too high.
Collect the first colored fraction in a labeled and tared Erlenmeyer flask. After the second fraction is
collected, change the solvent to 50/50 hexane-acetone and continue running the column. Collect the last
colored fraction in a third labeled and tared Erlenmeyer flask. Once you have finished collecting the last
colored material from the column, evaporate the solvent from your fractions in the hood using the airline.
When all of your products have eluted, use air pressure to expel any remaining solvent from the column.
Once the column is fairly dry, collect the silica and sand in a beaker. The best way to do this is to turn
the column upside down and pour the silica out of the large opening at the top of the column. It may be
helpful to apply air pressure from the stopcock side of the burette. Do this in your own hood and not out
by the waste hood. Put the dry, used silica in the silica waste jug. Do not wash your column with water,
as it must be dry for the next section to use it. If you need to rinse your column, use acetone.
Determine the mass and melting points for each of the compounds that you isolated. Literature melting
point values are given below:
Part 2. TLC analysis of column fractions and unknown mixture.
In this part of the experiment you will determine the compounds present in your column fractions. A
80/20 mixture of hexane/acetone will be used to develop the TLC plate. Spot standard samples of
ferrocene, acetylferrocene, and diacetylferrocene, and each of your column fractions in a manner similar
to that described in PLKE Expt 5A. After you finish spotting you should have a TLC plate with six
lanes, as shown below. Develop your plate as described in PLKE p.44-45. Calculate the Rf values for
all of the spots on your plate and determine which products were present in your fractions.
Page 49
Chemistry 241 A
Lab 6: TLC and Column Chromatography Spring 2012
Page 50
Chemistry 241 A
Lab 6: TLC and Column Chromatography Spring 2012
POST-LAB REPORT – (DUE AT BEGINNING OF LAB 7)
Turn this in with copies of your notebook pages.
Name __________________________________________
Last
First
Part 1 - Column Chromatography
Indicate the structure, mass and mp for the first compound to elute from the column.
What percent of your original product mixture did this product account for? (Show your calculations)
Indicate the structure, mass and mp for the second compound to elute from the column.
What percent of your original product mixture did this product account for? (Show your calculations)
Indicate the structure, mass and mp for the third compound to elute from the column.
What percent of your original product mixture did this product account for? (Show your calculations)
Part 2 - Thin Layer Chromatography
Sketch your developed TLC plate. Indicate the Rf values for each spot. Label the spots as ferrocene,
acetylferrocene or diacetylferrocene.
Report _____________(10 pts)
Prelab _____________(5 pts
Notebook _____________(5 pts)
Lab Safety _______(5 pts)
Page 51
Chemistry 241 A
Lab 7: Grignard Spring 2012
LAB 7: GRIGNARD
PRELAB CHECKLIST
Name __________________________________________
Last
First
□
□
□
□
□
Bring all required lab supplies. (Safety goggles, lab coat, lab notebook, ball-point pen).
Before lab read PLKE pages 317-327 and sections 8.3, 11.3, 12.5, 12.7, 12.9, 12.11.
Make sure you arrive in lab on-time.
(4 pts) Write a “Prep’prelab (see pg 13) for this experiment in your lab notebook. Turn in
carbonless copies of those pages to your TA at the beginning of the lab period.
Answer the following questions and turn in this sheet at the beginning of lab
1. (1 pts) Why can’t ethanol be used as a solvent for the Grignard reaction?
2. (1 pts) At what point in the procedure is the reaction no longer water-sensitive? Explain why the
reaction can be exposed to water after that point.
3. (4 pts) After your Grignard reaction is complete you will need to purify the carboxylic acid product.
Outline the purification scheme that you plan to use (chromatography is not an option).
Page 52
Chemistry 241 A
Lab 7: Grignard Spring 2012
GRIGNARD REACTION
Purpose: the purpose of this experiment is to prepare a Grignard reagent (an organomagnesium
compound) and to convert it to a carboxylic acid by reaction with carbon dioxide. A Grignard reagent is
formed by reaction of an alkyl or aryl halide with magnesium metal in diethyl ether.
The alkyl group of the Grignard reagent has partial ionic characteristics and behaves like a carbanion.
Therefore, Grignard reagents are strong bases which are easily protonated by water, alcohols, or
carboxylic acids to afford the corresponding hydrocarbons.
A Grignard reagent also behaves as a good nucleophile and will attack the carbonyl of aldehydes or
ketones to give alcohol products. Grignard reagents will also react with carbon dioxide to give a
carboxylic acid. The resulting magnesium salts may be hydrolyzed by addition of dilute aqueous acid to
afford the alcohol or carboxylic acid products.
Because the Grignard reagent reacts with water, it must be protected from air and moisture. The
reaction apparatus must be rigorously dry, and the ether must be anhydrous (free of water). During the
reaction, a drying tube will be used to prevent water in the air from entering the reaction flask.
In this experiment, bromobenzene, bromotoluene and bromoxylene will be converted to the
corresponding Grignard reagents. Reaction of the Grignard reagent with carbon dioxide will afford a
carboxylic acid.
Page 53
Chemistry 241 A
Lab 7: Grignard Spring 2012
Grignard reagents may also react with alkyl or aryl halides to create a product with a new carbon-carbon
bond. Since the starting materials for this reaction are aryl bromides, this type of reaction will produce
biphenyls. The nucleophilic aromatic substitution reaction between the phenyl Grignard reagent and
bromobenzene is shown below.
For this lab you will be assigned an unknown brominated aromatic that you will convert into the
corresponding carboxylic acid using Grignard chemistry. At the beginning of lab, your TA will
dispense to you one of the following brominated aromatics: Bromobenzene, o-bromotoluene, pbromotoluene or 2-bromo-p-xylene.
The procedure below does not include a purification scheme. It is up to you to decide how to purify the
reaction product to obtain a pure carboxylic acid using techniques that you have learned so far (you
should discuss your proposed purification procedure with your TA before you begin). Purifying your
product via column chromatography will probably be too time consuming and should be avoided. Once
your product has been purified, you may take a melting point of your final product and use the melting
point of your product to identify the carboxylic acid that you synthesized.
Procedure: The apparatus for this reaction is pictured below. Your brominated compound and the
diethyl ether will not be added until the apparatus has been assembled and flame-dried. Since you will
need two drying tubes to protect your reaction mixture from the humid Seattle air, you will need to
check one drying tube out from the stockroom.
Page 54
Chemistry 241 A
Lab 7: Grignard Spring 2012
Caution! Diethyl ether is extremely flammable. NO FLAMES will be allowed when diethyl ether is in
use. Everyone in the lab must complete the operations described in the following paragraph before the
TA will distribute the diethyl ether.
Begin with a clean, dry 250 mL round-bottom two-necked flask. Add a stir bar and 0.7 g of magnesium
turnings. Attach a dry, water-jacketed reflux condenser (also known as a West condenser) and addition
funnel (you are using your separatory funnel as an addition funnel). You should lightly grease the
ground glass joints of your apparatus – this helps prevent moisture from entering the system. Place
drying tubes on both the addition funnel and the condenser (See figure above). Use a Bunsen burner to
flame-dry the apparatus. Let the apparatus cool to room temperature. Attach water hoses to the
condenser (water should enter from below and exit from above) and turn on the cooling water. After
Page 55
Chemistry 241 A
Lab 7: Grignard Spring 2012
everyone has completed the above procedure and put their Bunsen burners away, your TA will distribute
the diethyl ether.
Have an ice bath and a steam line ready to control the rate of reaction. Your TA will give you 0.025
moles of one of the brominated aromatics listed above. Dissolve this reagent in 25 mL of anhydrous
diethyl ether. Make sure to close the stopcock of your addition funnel, then add the ethereal solution to
the addition funnel and replace the drying tube. Add approximately 5 mL of this solution to the flask by
briefly opening the stopcock. Stir the mixture and wait for a reaction to occur. Formation of cloudy
material or a brown solution indicates that the reaction has started. If there is no reaction, heat the flask
gently with steam from the steam line. Only a small amount of steam is needed to bring the ether to
reflux, since diethyl ether boils at 35 ºC. If your mixture has been refluxing for a long time and a
reaction has not started, add a small crystal of I2 to help kick-start the reaction.
When the reaction has started, add the remaining ether solution to the reaction flask at a rate of 1 to 3
drops per second. The rate of addition should be controlled so that the heat liberated by the reaction
causes the mixture to maintain a gentle reflux. If the reflux ring goes above the lower third of the
condenser, slow the addition. Heating should not be necessary since the reaction is exothermic. If the
reaction becomes too vigorous, it can be slowed by cooling with an ice bath. When all the ether solution
has been added, gently reflux the mixture with steam for 15 minutes. The mixture is now ready to be
added to dry ice. If you are not able to get your Grignard reaction to this point by 90 minutes
before the end of the lab period, you will be given a premade mixture to work up.
Crush 10 g (about 1-2 pellets) of dry ice and place it in a beaker. Since dry ice is cold, it tends to
condense water out of the air and become wet. If the dry ice is wet the Grignard reagent may react with
the water instead of the CO2 and decrease your percent yield. Use the dry ice immediately after
crushing to avoid this problem. Remove the condenser and addition funnel from the reaction flask and
decant the solution onto the dry ice (leave behind any unreacted Mg turnings). Stir the reaction
mixture.– it will become quite thick at this point and you will need to add 15 mL of ether to thin out the
reaction mixture enough to stir it effectively. Once the dry ice has been thoroughly mixed into the
Grignard reagent, add a mixture of 15 g of crushed ice and 5 mL of 6M hydrochloric acid to hydrolyze
any unreacted Grignard reagent and protonate the carboxylate product. Isolate the ether layer (which
contains your product). At this point it is up to you to devise and carry out a proper purification
procedure.
Since you will be using the melting point to identify your product, use your Chem 241 lab skills to
isolate high-purity product. If your product is wet you should find a way to dry it before taking the
melting point. Turn in your product to your TA in a container labeled with your name, the identity of
your product, the sample weight, the percent yield and the mp of the product.
Waste Disposal: Dissolve any unreacted magnesium in a couple mLs of 1M HCl. This process will
release hydrogen gas so make sure that it is done in the fume hood. Once the magnesium is dissolved it
can go into aqueous waste.
Page 56
Lab 7: Grignard Spring 2012
Chemistry 241 A
POST-LAB REPORT – (DUE AT BEGINNING OF LAB 8)
Turn this in with copies of your notebook pages.
Name __________________________________________
Last
First
Unknown number ______________
Weight of carboxylic acid ____________
(2 pts) Identity of carboxylic acid:_________________________________
mp ___________
% Yield _________
(show calculations)
Draw a flowchart of your purification scheme, indicating where all molecules (in their correct ionization states) are at each
step. You should end with the dry solid carboxylic acid at the end.
Report _____________(10 pts)
Prelab _____________(10 pts)
Notebook ___________(5 pts)
Lab safety ____________(5 pts)
Page 57
Lab 8: Synthesis of Esters Spring 2012
Chemistry 241 A
LAB 8: SYNTHESIS OF ESTERS
PRELAB CHECKLIST
Name __________________________________________
Last
First
□
□
Bring all required lab supplies. (Safety goggles, lab coat, lab notebook, ball-point pen).
□
□
Make sure you arrive in lab on-time.
Before lab read PLKE exp 56, pages 498-501. Also review use of the sep funnel, (technique
12.7), drying agents (technique 12.9)
(3 pts) Write a ‘Prep” prelab for this experiment in your lab notebook. Turn in carbonless
copies of those pages to your TA at the beginning of the lab period. Carbonless copies must be
turned in before you begin the lab.
□
For the prelab, use 1-pentanol for your alcohol starting material. For this experiment you will be
given an unknown alcohol from the list of pg 498 that you will react with acetic acid.
□
Answer the following questions and turn in this sheet at the beginning of lab. (8 points)
1. (1 pt) Which reagent is used in excess in this reaction?
2. (1 pts) Why is the reagent you listed in question #1 used in excess? Why not have an equimolar
reaction?
3. (2 pts) What signals in the IR can differentiate between starting materials and product? Give specific
bonds and wavenumbers!
Page 58
Lab 8: Synthesis of Esters Spring 2012
Chemistry 241 A
SYNTHESIS OF ESTERS
Note: In this experiment you will use glacial acetic acid and sulfuric acid. Both of these reagents are
corrosive, and sulfuric acid is especially nasty. Avoid contact with these materials: take appropriate
precautions including wearing gloves and all normal lab safety equipment (goggles, lab coat, etc.). If
you do get some of these acids on your skin, immediately wash that area with lots of cold water.
Procedure: Assemble the apparatus depicted below using a 50 mL round-bottom flask, water-jacketed
condenser (also known as a West condenser), and drying tube. Use a heating mantle for heating and,
since you aren’t using a hot plate, add a boiling stone to prevent bumping. Use a thin film of grease on
the ground glass joints. Pack the drying tube with Drierite.
cotton
drying tube
drierite
cotton
H2O out
waterjacketed
condenser
H2O in
roundbottom
flask
boiling stone
Heating Mantle
plugged into variac
(NOT wall outlet)
Record the weight of a 10 mL graduated cylinder. Place approximately 5 mL of your unknown alcohol
into the graduated cylinder and reweigh it to determine the exact mass of your alcohol. Disconnect the
round-bottom flask from the apparatus that you assembled above, and add transfer your alcohol from the
Page 59
Chemistry 241 A
Lab 8: Synthesis of Esters Spring 2012
graduated cylinder to the round-bottom flask. Do not clean or wash the graduated cylinder. Add
approximately 7 mL of glacial acetic acid (MW = 60.1, density = 1.06 g/mL) to the graduated cylinder
(in the hood) and add it to the alcohol already in the flask. This order of operations ensures that a known
amount of the unknown alcohol was added to the reaction. Add 1.0 mL of concentrated sulfuric acid to
the reaction mixture and swirl the flask to mix the contents. Reconnect the round-bottom flask to the
reflux apparatus.
Begin circulating water through the reflux condenser. Plug in the heating mantle and turn it on. Bring
the mixture to a boil and continue refluxing the mixture for 60 to 75 minutes. Once the reflux has
finished, remove your reaction mixture from the heat and allow it to cool to room temperature.
While your mixture is refluxing, acquire an infrared (IR) spectrum of your unknown alcohol.
Disassemble the apparatus and transfer the reaction mixture to a separatory funnel. Leave the boiling
stone in the round-bottom flask. Wash the reaction mixture with 10 mL of water and remove the
aqueous layer. Next, wash the organic layer with 5 mL of 5% aqueous sodium bicarbonate and again
remove the aqueous layer. Finally, wash the organic layer with 5 mL of saturated aqueous sodium
chloride and remove the water layer.
Transfer the remaining organic layer (your crude ester) to a 25 mL Erlenmeyer flask. Add
approximately 1 gram of anhydrous sodium sulfate and cover the flask. Let the mixture stand for ten to
15 minutes. Decant the ester away from the sodium sulfate into a tared vessel. Record the mass of your
ester and calculate the percent yield. Acquire an IR spectrum of your ester.
Page 60
Chemistry 241 A
Lab 8: Synthesis of Esters Spring 2012
POST-LAB REPORT – (DUE AT BEGINNING OF LAB 9)
Turn this in with copies of your notebook pages.
Name __________________________________________
Last
First
Attach your IR spectra.
Unknown number: __________Weight of Ester product______________ % yield______
Show calculation for % yield.
(2 pts) Unknown identity: _______________
(3 pts) Identify the Major absorptions in your IR.
(4 pts) Comment on the success of the reaction and the purity of your product based on the IR spectroscopy that you
performed. Comment of presence or absence of impurities—what is your most likely impurity? If you received low yields
speculate on what could have caused this.
(4 pts) Propose the structure of your unknown alcohol based on the 1H NMR of the ester product your TA provided. Analyze
the 1H NMR based on chemical shift, integration and splitting to support your conclusion.
Report _____________(13 pts)
Prelab _____________(7 pts)
Notebook ___________(5 pts)
Lab safety ____________(5 pts)
Page 61
Lab 9: Spectroscopy Quiz Spring 2012
Chemistry 241 A
LAB 9: SPECTROSCOPY QUIZ
PRELAB CHECKLIST
Name ___________________________________
Last
First
□
□
Bring all required lab supplies. (Safety goggles, lab coat, lab notebook, ball-point pen).
□
Read the following link:
http://chemwiki.ucdavis.edu/Organic_Chemistry/Hydrocarbons/Alkenes/Degree_of_Unsaturatio
n-Another_Aid_to_Identifying_Molecular_Structure
□
You will work in groups of 3-4 to identify an unknown chemical based on IR and 1H NMR
spectra. You will have 50 minutes to identify the molecule and annotate the IR and NMR
signals that match your proposed structure. The remaining time will be used for check-out. All
glassware must be thoroughly cleaned and sorted before you check-out. If you have any broken
or missing items, you will need to have your Husky Card available in order to pay for
replacement before you can check-out.
□
□
□
Turn in your lab 8 report at the beginning of the period.
□
There is no prelab for this lab.
Before lab read PLKE page 833, 847-867, pages 868-870, 873-885.
Also read Carey7th & 8th editions 13.3-13.11, 13.20-13.22, 13.25 or McMurry 13.6-13.12.
1
H NMR Chemical Shifts 
Type of Hydrogen
Saturated primary
C CH3
0.7-1.3
Saturated secondary
H
C C H
C
1.2-1.6
Saturated tertiary
C
C C H
C
1.4-1.8
Allylic
C C
C H
1.6-2.2
O
C C H
Alpha to carbonyl
2.0-2.4
Ar C H
Benzylic
2.4-2.7
Page 62
Chemistry 241 A
Lab 9: Spectroscopy Quiz Spring 2012
C C H
Alkynyl
2.5-3.0
X C H
Alkyl halide (X =Cl, Br, I)
Alcohol (OH)
2.5-4.0
RO-H
2.5-5.0 (variable)
O C H
Alcohol, ether
3.3-4.5
C C
H
Vinyl
4.5-6.5
Ar-H
Aromatic
6.5-8.0
O
C H
Aldehyde
9.7-10.0
O
Carboxylic Acid
C OH
11.0-12.0
Base Values for IR Absorptions
OH
3600 cm-1
NH
3500 cm-1
CH
3000 cm-1
CN
2250 cm-1
CC
2150 cm-1
C=O
C=C
1700 cm-1
1650 cm-1
CO
1100 cm-1
Page 63