Chapter 22
“Hydrocarbon Compounds”
(C4H10)
Pre-AP Chemistry
Charles Page High School
Stephen L. Cotton
Section 22.1
Hydrocarbons
 OBJECTIVES:
–Describe the relationship
between number of
valence electrons and
bonding in carbon.
Section 22.1
Hydrocarbons
 OBJECTIVES:
–Define and describe
alkanes.
Organic Chemistry and
Hydrocarbons
 “Organic”
originally referred to any
chemicals that came from
organisms
 1828 - German chemist Friedrich
Wohler synthesized urea in a lab
 Today, organic chemistry is the
chemistry of virtually all compounds
containing the element carbon
Friedrich Wohler
1800 – 1882
Used inorganic
substances to
synthesize urea, a
carbon compound
found in urine.
This re-defined
organic chemistry.
Organic Chemistry and
Hydrocarbons
 Over
a million organic
compounds, with a dazzling array
of properties
 Why so many? Carbon’s unique
bonding ability!
 Let’s start with the simplest of the
organic compounds. These are
the Hydrocarbons
Organic Chemistry and
Hydrocarbons
 Hydrocarbons
contain only two
elements: 1) hydrogen, and 2) carbon
– simplest hydrocarbons called “alkanes”,
which contain only carbon to carbon
single covalent bonds (CnH2n+2)
– methane (CH4) with one carbon is the
simplest alkane. It is the major
component of natural gas
Organic Chemistry and
Hydrocarbons
 Review
structural formulas - p.694
 Carbon has 4 valence electrons,
thus forms 4 covalent bonds
– not only with other elements, but also
forms bonds WITH ITSELF (nonpolar)
 Ethane
(C2H6) is the simplest alkane
with a carbon to carbon bond
Straight-Chain Alkanes
 Straight-chain
alkanes contain
any number of carbon atoms, one
after the other, in a chain pattern meaning one linked to the next
(not always straight)
C-C-C
C-C-C-C etc.
 Names of alkanes always will
always end with -ane
Straight-Chain Alkanes
 Combined
with the -ane ending is a
prefix for the number of carbons
Table 22.1, page 695
 Homologous series- a group of
compounds that have a constant
increment of change
 In alkanes, it is: -CH2- (methylene)
Straight-Chain Alkanes
alkanes used for fuels:
methane, propane, butane, octane
 As the number of carbons increases,
so does the boiling and melting pt.
 Many
– The first 4 are gases; #5-15 are liquids;
higher alkanes are solids
 Condensed
structural formulas?
Note examples on page 696
Naming Straight-Chain
Alkanes
 Names
recommended by IUPAC - the
International Union of Pure and
Applied Chemistry
end with –ane; the root part of the name
indicates the # of carbons
 We
sometimes still rely on common
names, some of which are well-known
Naming Straight-Chain
Alkanes
 IUPAC
names may be long and
cumbersome
 Common names may be easier or
more familiar, but usually do not
describe the chemical structure!
–Methane is natural gas or
swamp gas
Branched-Chain Alkanes
 Branched-chain
means that other
elements besides hydrogen may be
attached to the carbon
–halogens, oxygen, nitrogen,
sulfur, and even other carbons
–any atom that takes the place of a
hydrogen on a parent
hydrocarbon is called a
substituent, or the branched part
Branched-Chain Alkanes
 A hydrocarbon
substituent is called
an alkyl group or sometimes
radicals
–use the same prefixes to indicate
the number of carbons, but -ane
ending is now -yl such as:
methyl, ethyl, propyl, etc.
 Gives much more variety to the
organic compounds
Branched-Chain Alkanes
for naming – go from right
to left - page 698
 Rules
1. Longest C-C chain is parent
2. Number so branches have lowest #
3. Give position number to branch
4. Prefix (di, tri) more than one branch
5. Alphabetize branches (not prefix)
6. Use proper punctuation ( - and , )
- Page 699
Branched-Chain Alkanes
 From
the name, draw the
structure, in a right-to-left manner:
1. Find the parent, with the -ane
2. Number carbons on parent
3. Identify substituent groups (give
lowest number); attach
4. Add remaining hydrogens
- Page 700
Alkanes
 Draw
3-ethylpentane
 Draw 2,3,4-trimethylhexane
 Since the electrons are shared
equally, the molecule is nonpolar
–thus, not attracted to water
–oil (a hydrocarbon) not soluble in
H2O
–“like dissolves like”
Section 22.2
Unsaturated Hydrocarbons
 OBJECTIVES:
–Describe the difference
between unsaturated
and saturated
hydrocarbons.
Section 22.2
Unsaturated Hydrocarbons
 OBJECTIVES:
–Distinguish the
structures of alkenes and
alkynes.
Alkenes
 Multiple bonds can also exist
between the carbon atoms
 Hydrocarbons containing
carbon to carbon double bonds
are called alkenes (CnH2n)
C=C
C-C=C
 Called “unsaturated” if they
contain double or triple bonds
Naming Alkenes
 Find
longest parent that has the
double bond in it
 New ending: -ene
 Number the chain, so that the
double bond gets the lower number
 Name and number the substituents
 Samples on page 702
Alkynes
 Hydrocarbons
containing carbon
to carbon triple bonds are called
alkynes
ethyne
(CnH2n-2)
-C C Alkynes are not plentiful in nature
 Simplest is ethyne- common
name acetylene (fuel for torches)
 Table 22.3, p. 703 for boiling pt.
Section 22.4
Hydrocarbon Rings
 OBJECTIVES:
–Identify cyclic ring
structures.
Section 22.4
Hydrocarbon Rings
 OBJECTIVES:
–Describe bonding in
benzene.
Cyclic Hydrocarbons
 The
two ends of the carbon chain
are attached in a ring in a cyclic
hydrocarbon
– sample drawings on page 709
– named as “cyclo- ____”
 hydrocarbon
compounds that do
NOT contain rings are known as
aliphatic compounds
Aromatic Hydrocarbons
 A special
group of unsaturated cyclic
hydrocarbons is known as arenes
– contain single rings, or groups of rings
– also called “aromatic hydrocarbons”,
because of pleasant odor
– simplest aromatic is benzene (C6H6)
– Term “aromatic” applies to materials with
bonding like that of benzene
Aromatic Hydrocarbons

Benzene is a six-carbon ring,
with alternating double and
single bonds
– exhibits resonance, due to
location of the double and single
bonds-p.710

Benzene derivatives possible:
– methylbenzene, 3-phenylhexane,
ethylbenzene (top page 711)
Aromatic Hydrocarbons

One derivative of Benzene is
called phenylethene, or
commonly named STYRENE.

Foamed styrene is trademarked
by Dow Chemical as
CH2
“styrofoam”
CH

Other manufacturers items
usually just called “foam cups”
Aromatic Hydrocarbons
 Benzene
derivatives can have two
C
or more substitutents:
– 1,2-dimethylbenzene
– 1,3-dimethylbenzene
– 1,4-dimethylbenzene
C
C
 Can
C
use ortho for 1,2; meta for 1,3;
and para for 1,4 (page 711)