Unit 10
Organic Chemistry
What is Organic Chemistry?
 Organic
chemistry
is the study of
carbon compounds.
 Besides carbon, the
most common
elements in organic
compounds are
hydrogen, oxygen,
nitrogen, sulfur, and
the halogens.
Why is it Important?
 Animals,
plants, and other forms of life
consist of organic compounds.
 Organic products are found in foods,
drugs, clothing, fuel, and many other
products that we use everyday.
 Organic chemistry is an enormous field.
o
>90% of all
compounds
are organic.
History of Organic Chemistry
 Scientists
originally thought organic
compounds contained a “vital force”
due to their natural origin.
 Until 1828, when Friedrich
Wöhler made urea (found
in human urine) in the lab
from a mineral.
 Today, many organic
compounds are
synthesized in
the laboratory.
Bonding in Organic Compounds
 Organic
compounds are made of all nonmetals, so they have covalent bonding.
 Their structures almost always obey the
bonding rules in the following table:
Why Carbon is Unique
 Carbon
forms 4 covalent bonds with a
number of different elements, resulting in
many different compounds.
 Carbon atoms readily form multiple bonds.
 Carbon, more than any other element,
displays catenation – the ability of an atom
to form stable C H
n = 1to  (no limit)
n 2n+2
bonds with
SinH2n+2
n = 1 to 6 only
itself, joining
GenH2n+2 n = 1 to 3 only
up into chains
SnnH2n+2 Only SnH4 exists
or rings.
Representing Organic Compounds
 Structural
Formulas show all of the
carbon and hydrogen atoms and how
they are bonded together.
 Line-Angle (Carbon Skeleton) formulas
do not show the hydrogen atoms that
are bonded to carbons. Each angle,
and beginning and end of a line,
represents a carbon atom.
 Space-filling and ball-and-stick models
are three-dimensional representations
of the molecule.
Formulas
Isomers
 Isomers
are different molecules with the
same molecular formula.
o
o
Structural Isomers (aka
Constitutional Isomers)
have a different pattern
of atom attachment.
Stereoisomers have the same atom
attachments, but a different spatial
orientation.
Structural (Constitutional) Isomers
 Compounds
with the same molecular
formula but different structural formulas.
 Ex: n-butane and isobutane both have
the molecular formula of C4H10 but their
structural formulas are quite different.
n-butane
C4H10
isobutane
C4H10
Stereoisomers
 Different
molecules whose atoms are
connected in the same order, but have a
different spatial orientation.
o
o
optical isomers –
nonsuperimposable
mirror images.
Geometric
(cis-trans)
isomers –
cis means
“same side”,
trans means
“opposite side”.
Isomers
Sample Problem
Write line-angle (carbon skeleton)
formulas for the five isomers of C6H14.
Use lines to represent
each carbon-carbon
bond. Remember
that each end
or bend represents
a carbon atom.
Hydrocarbons
 Hydrocarbons
are the simplest organic
compounds, containing only carbon
and hydrogen.
 However, due to the
uniqueness of carbon,
there are many
different kinds
of hydrocarbons.
 Hydrocarbons are commonly used as fuels,
and are the starting materials in the
synthesis of many consumer products.
Alkanes
 Alkanes
are hydrocarbons that contain
only single bonds.
 Alkanes are said to be
saturated, because their
hydrogen content is at
a maximum.
 Names all end in “-ane.”
 General formula is CnH2n + 2
 Methane - butane are gases, Pentane C17H36 are liquids, C18H38 & higher are solids.
 Alkanes tend to be stable molecules, and
not very reactive (other than combustion.)
IUPAC Nomenclature
 Since
there are so many organic
compounds, a systematic method
of nomenclature is required.
 The system recommended by IUPAC
(International Union of Pure and Applied
Chemistry) is used throughout the world.
 Each name consists of 3 parts:
o
o
o
Prefix
Parent 2,5-dimethylhexane
Suffix
prefix parent suffix
(base)
Numbering the Base Chain
 Find the longest continuous
carbon chain.
 Number the chain
from the end closest
to a branch (substituent.)
o

If 2 first branches are at
equal distances from each
end, use the next branch in
to determine where to start.
Use the appropriate base
prefix, followed by the suffix
-ane for an alkane.
X
X
Incorrect
Incorrect
Alkyl Groups
 Name
branches (substituents) as alkyl
groups – carbon-hydrogen groups with
one less H than the corresponding alkane.
 The group does not exist independently
but occurs bonded to another atom or
molecule.
 In naming, the
“-ane” is dropped
and “-yl” is added.
Ex: methane
becomes methyl.)
Substituents
a
substituent is an atom or group of
atoms substituted in place of a
hydrogen atom on the parent chain
of a hydrocarbon.
 Common substituents, other than alkyl
groups, are oxygen, sulfur or nitrogenbased groups, and the halogens.
Naming Substituents
Locate each substituent by preceding
its name with the carbon number on the
chain
 List branches
1
2 3
4
alphabetically

o
do not count
n-, sec-, t-, count iso
5
6
7
8
9
 Use prefix if more 5-ethyl- 4-isopropyl-4-methyl nonane
than one of same
group present
(Ex: di, tri, tetra, penta)
o
Prefixes do not count in alphabetizing
Naming Alkanes
Sample Problem
Write the correct IUPAC names for the
following organic compounds:
a.)
1
2
3
1-bromo- 2,2,3-trimethyl butane
4
b.)
9
8
1
2
3
4
5
6
7
3-ethyl- 2,5,5,7-tetramethyl nonane
Cycloalkanes
 Cycloalkanes
have rings of carbon atoms.
 They have the general formula CnH2n
 In carbon skeleton formulas, assume a C
atom at each corner and enough H’s to
give a total of 4 single bonds to each C.
Naming Cycloalkanes
 The
ring is named by the number of carbons
(as before) but with the prefix cyclo-.
 Number the ring starting from the carbon
with the substituent lowest in the alphabet.
 Number in the direction
that gives the lower
overall substituent
numbers. (To break
a tie, go in the
direction that is
alphabetical).
Naming Cycloalkanes
Sample Problem
Write the correct IUPAC names for the
following organic compounds:
5
6
a.)
3
b.)
chlorocyclohexane
1
4
2
2
1
5
3
4
1-isopropyl- 3-methyl cyclopentane
Alkenes & Alkynes
 Alkenes
have a double bond between 2
carbon atoms. General formula is CnH2n.
 Alkynes have a triple bond between 2
carbon atoms. General formula is CnH2n-2.
 Called unsaturated hydrocarbons since
they’re not loaded to capacity with H.
 Much more reactive than alkanes.
Naming Alkenes & Alkynes
 Change
suffix from
-ane to -ene for
base name of the
alkene, or to -yne
for base name of
the alkyne.
 Number chain from
end closest to the
multiple bond.
 Number in front of main name indicates
first carbon of multiple bond.
Naming Alkenes & Alkynes
Sample Problem
Write the correct IUPAC names for the
following organic compounds:
a.)
1
2
3
4
5
6
4-methyl-2-hexyne
4
b.)
2
1
3
trans- 2-butene
Classification of Hydrocarbons
 All
of the hydrocarbons we have looked
at so far are called aliphatic.
 There is another classification, called
aromatic, which includes any
hydrocarbon containing a benzene ring.
Benzene
 The
benzene molecule is
composed of 6 carbon
atoms joined in a ring, with 1
hydrogen atom attached to
each carbon atom (C6H6.)
 A six-membered ring of
carbon atoms with
alternating single and
double bonds was proposed
for the structure of benzene
by August Kekulé in1865.
Benzene (cont’d.)
 However,
properties of the
benzene molecule and
advanced bonding theory
indicate that the electrons
are actually shared by all
the carbon atoms in the ring.
Aromatic Compounds
 Aromatic
hydrocarbons
contain one or more
benzene rings.
 Although they are often drawn with C=C
bonds, they do not behave like alkenes.
 Many of these compounds have
distinctive, often pleasant, aromas.
 when the benzene ring is
not the base name, it
is called a phenyl group
Naming Aromatic Compounds
Sample Problem
Write the correct IUPAC names for the
following organic compounds:
a.)
1
6
2
3
b.)
1-bromo- 2,6-dichlorobenzene
5
4
1
2
3
4
5
6
7
8
1-phenyl octane
Functional Groups
A
functional group is a characteristic atom or
group of atoms inserted into a hydrocarbon.
 The presence of a
functional group
alters the properties
of a compound,
and determines the
nonpolar
polar, H-bonded
reactions it will
gas
liquid
participate in.
 since the type of hydrocarbon chain is
irrelevant to the reactions, it may be
indicated by the general symbol R
Alcohols
 Alcohols
are organic compounds
containing a hydroxyl group(-OH).
 General formula is R-OH.
 IUPAC names end in -ol.
Number the main chain
from the end closest to
-OH. Include the number
of the -OH group.
 -OH groups are able to
form hydrogen bonds
with H2O, but the longer the hydrocarbon
chain, the less soluble the alcohol is in water.
Ethers
 Ethers
are organic compounds
with the general formula ROR.
 Diethyl ether is a common lab
solvent, and was used as a
general anesthetic.
 To name ethers, name each
alkyl group attached to the O,
then add ether to the end.
List the R groups
in alphabetical
order. If they are
the same, use di-.
Aldehydes and Ketones
 Both
aldehydes and ketones
contain the carbonyl group.
 Ketones have an R group
attached to both sides of
the carbonyl group. IUPAC
names end in -one.
 Aldehydes have at least one H atom
attached to the carbonyl group. IUPAC
names end in -al.
Aldehydes and Ketones (cont’d)
 Many
aldehydes and ketones
have pleasant tastes and
aromas.
 Some are pheromones.
Cinnamaldehyde
3-phenyl-2-propenal
Raspberry Ketone
4-(4-hydroxyphenyl)butan-2-one
Carboxylic Acids and Esters
 Carboxylic
acids have the general
formula RCOOH. Their IUPAC
names end in -oic acid.
 Esters have the general formula
RCOOR’. Their IUPAC names are
based on the corresponding carboxylic
acid. Change the -ic acid ending to -ate.
The R group replacing the H is named as
an alkyl group.
Carboxylic Acids and Esters (cont’d)
 Carboxylic
acids are
weak acids. Like all
acids, they taste sour.
Citric Acid
 Esters are best
2-hydroxypropane-1,2,3-tricarboxylic acid
known for their
sweet smells.
Methyl Butanoate
Ethyl Butanoate
Acetic Acid
Ethanoic acid
Amines
 An
amine is an organic compound
that contains nitrogen, and can
be thought of as a derivative
of ammonia.
 Like ammonia, amines are
weak bases.
 Amines form when proteins
decompose, and are known
for their awful odors.
 Name the alkyl groups
attached to the N, then
add -amine to the end.
Naming w/ Functional Groups
Sample Problem
Write the correct IUPAC names for the
following organic compounds:
a.)
2
1
ethyl phenyl ether
b.)
2-methyl propanoic acid
3
2
1
Naming w/ Functional Groups
Sample Problem (Continued)
Write the correct IUPAC names for the
following organic compounds:
c.)
trimethyl amine
d.)
1
2
3
4
5
6
3-methyl- 2-hexanol
Types of Organic Reactions
 Organic
compounds participate in 3
main types of chemical reactions:
o
o
o
Substitution – atom(s) of
the starting material are
replaced by other atom(s).
Elimination - atoms of the
starting material are“lost”
and a new  bond is
formed.
Addition - atoms are
added to the starting
material.
Substitution Reactions
 Substitution
reactions involve  bonds: one
 bond breaks and another forms at the
same carbon atom.
 The atom being replaced is usually either
a hydrogen or another atom more
electronegative than carbon.
Elimination Reactions
 In
an elimination reaction, 2 groups (X & Y)
are removed from a starting material.
 Two  bonds are broken, and a  bond is
formed between adjacent atoms.
 Most often, X is hydrogen and Y is an atom
more electronegative than carbon.
Addition Reactions
 In
an addition reaction, 2 new groups (X &
Y) are added to the starting material. A 
bond is broken and 2  bonds are formed.
 Addition and elimination reactions are
exact opposites. A  bond is formed in
elimination, and broken in addition.
Types of Organic Reactions
Sample Problem
Classify each of the following as either
substitution, elimination or addition reactions:
a.)
OH
Br
substitution
b.)
addition
elimination
c.)
OH
Polymers
 Polymers
are long, chainlike molecules
composed of repeating units.
 A monomer is the fundamental
repeating unit of a polymer.
Natural Polymers
 Natural
Polymers play an important
role in living organisms.
 Examples: starches,
proteins, and DNA.
Synthetic Polymers
 Synthetics
are man-made
materials that have no
duplicate in nature.
 The first synthetic polymer was
prepared by Leo Baekeland in 1907.
 Due to the scientific approach, chemists
have been able to tailor new molecules
for specific purposes.