Chapter 13Unsaturated 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

•What are unsaturated hydrocarbons?

•Drawing Condensed Structures

C. Alkene and Alkyne Properties

Nomenclature of Alkenes and Alkynes

HOW TO Name an Alkene or Alkyne

Step [1] Find the longest chain that contains bothC atoms of the double or triple bond.

4 C’s in longest chainbutane ----> butene

6 C’s in longest chainhexane ----> hexyne

Nomenclature of Alkenes and Alkynes

HOW TO Name an Alkene or Alkyne

Step [2]Number the carbon chain from the end thatgives 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

CH3

12

1-methylcyclopentene

CH3

CH3

12

6

1,6-dimethylcyclohexene

D. Cycloalkenes

Chapter 13 – Unsaturated Hydrocarbons

2-butene

II. Stereoisomers

A. Cis/trans isomers

Chapter 13 – Unsaturated Hydrocarbons

B. Stereoisomers vs. Constitutional Isomers

Interesting Alkenes in Food and Medicine

Chapter 13 – Unsaturated Hydrocarbons

A. Addition Reactions

III. Reactions of Alkenes

1. Hydrogenation

Chapter 13 – Unsaturated Hydrocarbons

2. Halogenation

3. Hydrohalogenation

Chapter 13 – Unsaturated Hydrocarbons

4. Markovnikov’s Rule

•C1 has more H’s, so it will bond to the H from HCl.

•2-Chloropropane is the only product formed.

C2 is bonded to 1 HC1 is bonded to 2 H’s

Chapter 13 – Unsaturated Hydrocarbons

5. Hydration

CH3

H

+ H OH

this C has no H’s

this C has 1 H

OH

H

CH3

H

H2SO4

only product

Figure 13.4

Chapter 13 – Unsaturated Hydrocarbons

IV. Aromatic Compounds

What is a resonance hybrid?

1. One substituent

Chapter 13 – Unsaturated Hydrocarbons

A. Nomenclature of Aromatic Compounds

Chapter 13 – Unsaturated Hydrocarbons

2. Disubstituted Benzenes

ortho-xyleneo-xylene1,2-dimethylbenzene

meta-xylenem-xylene1,3-dimethylbenzene

para-xylenep-xylene1,4-dimethylbenzene

3. Polysubstituted Benzenes

4-chloro-1-ethyl-2-propylbenzene

2,5-dichloroaniline

•Some common drugs that contain benzene rings are:

B. Reactions of Aromatic Hydrocarbons

Chapter 13 – Unsaturated Hydrocarbons

Addition NO

Substitution YES

Chapter 13 – Unsaturated Hydrocarbons