5 Steps to a 5 AP Chemistry

Organic Chemistry  271

HC

H

H

C

H

H

C

H

H

C

H

H

HC

H

H

CC

H

H

C H

H

H

HHC

H

H

C

C

H

C

H

H

H

H

H H C

H

H

H

HHC

Pentane 2-Methylbutane 2,2-Dimethylpropane

C

H

H

H

Figure 18.3 Structural isomers of C 5 H 12.

Here is a practice problem. Name the following compound:

Answer: 5-ethyl-2,2-dimethylnonane
Solution:
First, pick the longest chain. This is bold-faced in the diagram below. The carbons are
attached by single bonds, so this is an alkane. Because the longest chain has nine carbons,
it is a nonane.

Next, the longest chain should be numbered from one end to the other with the lowest
number(s) going to the branches. For the above example the numbering of the chain
(bold-face carbon atoms) would be:
12 3 4 5
6
789
Once these numbers have been assigned, do not alter them later.

H

H

H

HHCH H HHC HH H

HH

H

H CC CH

HHH

CCCCCCCH

HCHH H H H H

H

H HCHH H H H H

HCCC

C

CCC

C

CH

H H H

H

HH H

HH

H H

HH H

CCC

H HH