Chapter 13
Unsaturated Hydrocarbons
CHEM 2124 – General Chemistry II
Alfred State College
Professor Bensley
Chapter 13 Objectives
 Identify the three major types of unsaturated
hydrocarbons – alkenes, alkynes, and
aromatic compounds.
 Name alkanes, alkynes, and substituted
benzenes.
 Recognize the difference between
constitutional isomers and stereoisomers,
as well as identify cis and trans isomers.
 Draw the products of addition reactions of
alkenes.
Chapter 13 Objectives
 Draw the products of reactions that follow
Markovnikov’s Rule.
 Draw the structure of polymers that are
formed from alkene monomers.
 Draw the products of substitution reactions
of benzene.
Chapter 13 – Unsaturated Hydrocarbons
I. Alkenes and Alkynes
A. Alkenes
B. Alkynes
Chapter 13 – Unsaturated Hydrocarbons
C. Alkene and Alkyne Properties
•What are unsaturated hydrocarbons?
•Drawing Condensed Structures
Nomenclature of Alkenes and Alkynes
HOW TO Name an Alkene or Alkyne
Step [1] Find the longest chain that contains both
C atoms of the double or triple bond.
4 C’s in longest chain
butane ----> butene
6 C’s in longest chain
hexane ----> hexyne
Nomenclature of Alkenes and Alkynes
HOW TO Name an Alkene or Alkyne
Number the carbon chain from the end that
Step [2]
gives the multiple bond the lower number.
1-butene
2-hexyne
Nomenclature of Alkenes and Alkynes
HOW TO Name an Alkene or Alkyne
Step [3]
Number and name
the substituents,
and write the name.
What is a diene?
Chapter 13 – Unsaturated Hydrocarbons
D. Cycloalkenes
2
2
1
CH3
1
CH3
CH3
1-methylcyclopentene
6
1,6-dimethylcyclohexene
Chapter 13 – Unsaturated Hydrocarbons
II. Stereoisomers
2-butene
A. Cis/trans
isomers
Chapter 13 – Unsaturated Hydrocarbons
B. Stereoisomers vs. Constitutional Isomers
Interesting Alkenes in Food and Medicine
Chapter 13 – Unsaturated Hydrocarbons
III. Reactions of Alkenes
A. Addition Reactions
1. Hydrogenation
Chapter 13 – Unsaturated Hydrocarbons
2. Halogenation
3. Hydrohalogenation
Chapter 13 – Unsaturated Hydrocarbons
4. Markovnikov’s Rule
C2 is bonded to 1 H
C1 is bonded to 2 H’s
•C1 has more H’s, so it will bond to the H from HCl.
•2-Chloropropane is the only product formed.
Chapter 13 – Unsaturated Hydrocarbons
5. Hydration
this C has no H’s
CH3
CH3
+
H
OH
H2SO4
OH
H
H
this C has 1 H
H
only product
Figure 13.4
Chapter 13 – Unsaturated Hydrocarbons
IV. Aromatic Compounds
What is a resonance hybrid?
Chapter 13 – Unsaturated Hydrocarbons
A. Nomenclature of Aromatic Compounds
1. One substituent
Chapter 13 – Unsaturated Hydrocarbons
2. Disubstituted Benzenes
ortho-xylene
o-xylene
1,2-dimethylbenzene
meta-xylene
m-xylene
1,3-dimethylbenzene
3. Polysubstituted Benzenes
4-chloro-1-ethyl-2-propylbenzene
para-xylene
p-xylene
1,4-dimethylbenzene
2,5-dichloroaniline
•Some common drugs that contain benzene
rings are:
Chapter 13 – Unsaturated Hydrocarbons
B. Reactions of Aromatic Hydrocarbons
Addition NO
Substitution  YES
Chapter 13 – Unsaturated Hydrocarbons