Chapter 21: Hydrocarbons
Section 21.1
Section 21.2
Section 21.3
Section 21.4
Section 21.5
Introduction to
Alkanes
Alkenes and Alkynes
Hydrocarbon Isomers
Aromatic Hydrocarbons
Hydrocarbons
Section 1 Objectives:
• Explain the terms organic
• Identify hydrocarbons and • Distinguish between
• Describe where
compound and organic
the models used to represent saturated and unsaturated
hydrocarbons are obtained
chemistry.
them.
hydrocarbons.
and how they are separated.
Organic Compounds
• Chemists in the early 19th century knew living things produced a variety of carbon compounds, called
“_______________________” compounds.
• They were not able to _______________________________________________________ in the lab and labeled them as mysterious.
• _________________________________ was the first to produce an organic compound in the lab.
• ______________________________________________ is applied to all ______________________________-containing compounds with the
primary exceptions of carbon oxides, carbides, and carbonates, which are considered inorganic.
• In organic compounds, carbon nearly always shares its electrons and forms ________________________________________________.
• Carbon atoms are bonded to hydrogen atoms or other elements near carbon on the periodic table.
• Carbon atoms also bond to other carbon atoms and form _____________________________________________________
Hydrocarbons
• The simplest organic compounds are ________________________________________________, which consist of only the elements
_______________________________________________________________________.
• There are thousands of hydrocarbons.
Models of Methane
• Carbon atoms bond to each other by _______________________________________________________ bonds.
• _______________________________________________ hydrocarbons contain only single bonds.
• _______________________________________ hydrocarbons contain at least one double or triple bond.
Refining Hydrocarbons
• Many hydrocarbons are obtained from the ___________________________________________________
• Petroleum, crude oil, is a complex mixture containing more than a thousand different
compounds. In its raw form it is not very useful to humans, it is more useful when separated
into ___________________________________________________ or _________________________________
• ___________________________________________________ involves boiling petroleum and collecting each
group of components as they condense at different temperatures.
• Fractional distillation towers do not yield fractions in _______________________________________
• Heavier fractions are converted to gasoline or other lighter fractions by a process called
__________________________________
– cracking is done in the absence of oxygen and in the presence of a catalyst.
– In addition to converting heavier fractions to gasoline, cracking also produces starting materials for the
synthesis of many different products including plastics, films and synthetic fibers.
• __________________________________ is not a pure substance.
• Most molecules have ________________________________ carbons.
• Gasoline is modified by adjusting its composition to improve performance, resulting in the
__________________________________.
Section 2 Objectives:
• Name alkanes by examining their
• Draw the structure of an alkane when • Describe the properties of alkanes.
structures.
given its name.
Straight-Chain Alkanes
• ________________________ are hydrocarbons that have only single bonds between atoms.
• The names of alkanes end in _____________________________
• Prefixes are derived from ______________________________________
Table 21.1-Simple Alkanes
Molecular Formula
Ethane (C2H6)
Propane (C2H6)
Butane (C2H6)
Structural Formula
•
A series of compounds that differ from one another by a repeating unit is called a _____________________________________.
– For alkanes, the relationship between the numbers of carbon and hydrogen atoms can be expressed as:
_________________________
Branched-Chain Alkanes
• Carbon atoms can bond to __________________________
___________________ other carbon atoms making a variety
of chains possible.
• Straight chains and __________________ can have the same
molecular formula.
• Order and arrangement of atoms in organic
compounds determine __________________________________
• When naming branched chain alkanes, the longest
continuous chain of carbon atoms is called the
_______________________________________________
• All the side branches are known as
__________________________________________________________
•
−
Table 21.2 – First Ten of Alkane Series
Name
Molecular
Condensed Structural Formula
Formula
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
CH3CH3
CH3CH2CH2CH2CH3
CH3CH2CH2CH2CH2CH2CH3
CH3(CH2)8CH3
Naming branched-chain alkanes
Count the number of carbon atoms in the ______________________________________________________ chain.
Table 21.3 – Common Alkyl Groups
Name
Condensed Structural
Formula
Structural Formula
CH3-
CH3CH2-
CH3CH2CH2-
CH3CHCH3
|
CH3CH2CH2CH2-
Number each carbon in the parent chain, starting with the __________________________________ to the substituent group.
This gives all the substituent groups the _______________________________________________________________
− Name each alkyl group ____________________________
− If the same alkyl group appears ________________________ as a branch on the parent structure, use a __________________ to
indicate how many times it appears.
− When different alkyl groups are attached to the same parent chain, place their names in ____________________________
− Write the entire name, using _______________ to separate numbers from words and commas to separate numbers.
Cycloalkanes
• An organic compound that contains a hydrocarbon ring is called a
_________________________________________.
• Cyclic hydrocarbons with only single bonds are called _________________________________.
• The relationship between numbers of carbon and hydrogen atoms in cycloalkanes can be
expressed as: ____________________________________
−
Naming substituted cycloalkanes is the same as _________________________ but with a few
exceptions.
− The __________________________________ is always considered the parent chain.
− Numbering starts on the carbon that is _________________________________________________________
− When more than one carbon has a substituent, number in the
____________________________________________ that gives the ____________________________________________________________________ for
the substituents.
Properties of Alkanes
• Structure affects _________________________________________________. Alkanes are ___________________ and are good solvents for
other nonpolar molecules.
− Physical properties of alkanes: Compared to water, methane boils and melts at __________________________________.
− Methane molecules have little intermolecular attraction compared to water. (Methane molecules are nonpolar and do
not form hydrogen bonds).
− Chemical properties of alkanes: Alkanes have ___________________________ because they are nonpolar and have no charge,
and because they have strong single bonds between carbon atoms.
•
Section 3 Objectives:
• Compare the properties of • Describe the molecular
• Name an alkene or alkyne
• Draw the structure of an
alkenes and alkynes with
structures of alkenes and
by examining its structure.
alkene or alkyne by analyzing
those of alkanes.
alkynes.
its name.
Alkenes
• Unsaturated hydrocarbons that contain at least one or more double covalent bonds between
carbon atoms are called __________________________________.
•
•
•
•
−
•
•
Alkenes are named in much the same way as alkanes.
Alkenes end in ______________________________
When four or more carbon atoms are present, ____________________________________ of the double bond.
Note: Structure 3 is not 3-Butene because it is identical to structure 1.
• When naming branched-chain alkenes, follow the
____________________________________________, with two exceptions.
− The parent chain is always the
_______________________________________________________, whether it is the longest chain or
not.
− The position of the _____________________________, not
the______________________________, determine the numbering.
Use a prefix to designate the number of double bonds.
Alkenes are nonpolar and have low solubility in water.
Alkenes are ______________________________________________ than alkanes because the double bond increases electron density
between the two carbon atoms, providing a good site for _______________________________________________
Alkynes
• Unsaturated hydrocarbons that contain one or more triple bonds between carbon atoms are called
_______________________.
• Straight-chain and branched-chain alkynes are named in the same way as alkenes, except the ending is _________________.
• Alkynes have physical and chemical properties similar to alkenes but are generally more reactive because the triple
bonds cause even _________________________________________________________________ than double bonds.
Section 4 Objectives:
• Distinguish between the two main
categories of isomers—structural
isomers and stereoisomers.
• Differentiate between geometric
isomers with cis- and trans-prefixes.
Structural Isomers
• _________________________ are two or more
compounds that have the same molecular
formula but different molecular structures.
• _____________________________________ have the
same chemical formula but their atoms are
bonded in different arrangements.
•
•
•
•
There are two main classes of isomers:
structural isomers and
__________________________________________.
Structural isomers have different physical and
chemical properties.
The ____________________________________ of a
substance determines properties.
_____________________________________ are isomers in
which all atoms are bonded in the same order
but are arranged differently in space.
• Describe the structural variation in
molecules that results in optical isomers.
______________________________________________________ result from
different arrangements of groups around a double bond.
• ______________________ means on the same side, and
________________________ means across from.
• Geometric isomers have different __________________________ and
___________________________________________.
Chirality
• _____________________________ discovered two forms of crystallized
tartaric acid.
• The forms were mirror images of each other called
_________________________________________________________________
• The property in which a molecule exists in right and left-handed
forms is called ______________________________________________
• Chirality occurs whenever a compound contains an asymmetric
carbon.
• _______________________________________________ is a carbon atom that
has four different atoms or groups attached to it.
• The four groups can be arranged in _________________________________
•
•
•
•
Isomers that result from different arrangements of four different groups around a carbon atom represent the other
class of stereoisomers, called _________________________________________________________________.
Optical isomers have the same physical and chemical properties except in ______________________________________________
where _____________________ is important.
When polarized light passes through a solution containing an optical isomer, the plane of polarization is rotated to the
___________________________________ and to the __________________________________, producing and effect called
______________________
Section 5 Objectives:
• Compare and contrast the properties of aromatic and aliphatic hydrocarbons.
• Explain what a carcinogen is, and list some examples.
The Structure of Benzene
• Even by the middle of the 19th century, __________________________________________________________________________________________
• Michael Faraday first isolated _________________________________ in 1825.
• Chemists knew the formula was ___________________________ and proposed several possible models which would have all
be very reactive, but benzene is ___________________________________
• German chemist Friederich Kekulé claimed to have had a ____________________________________________ in which he realized
the ___________________________________________________________________ structure for benzene.
• Kekulé’s structure explained some of benzene's properties, but not its __________________________________________________.
• Linus Pauling’s _________________________________________________ explained benzene’s lack of reactivity.
• The double bonds in benzene are _________________________________________, but rather the electrons are
_______________________ and shared among _______________________________________ atoms.
Aromatic Compounds
• Organic compounds that contain benzene rings as part of their structure are called
________________________________________________________________________________
• Aromatic was originally used because many benzene related compounds were found in _____________________________
____________________________ that came from plants and plant parts.
• ___________________________________________ are the alkane, alkene, and alkyne hydrocarbons, coming from the Greek word
for ______________________________ because they were obtained by heating ___________________________________
• Substituted benzene compounds are named in the same way as ____________________________________
• Many aromatic compounds were commonly used as _____________________________________________
• Health risks linked to aromatics include ________________________________________________________________________
___________________________________________________________________________________________.
• Some aromatic compounds cause _________________________________________ and are called ___________________________