Question 23.1: Identifying Isomeric Compounds The following condensed struc......
Identifying Isomeric Compounds
The following condensed structures have the same formula, C_8H_{18}. Which of them represent the same molecule?
(a) CH_3\overset{\underset{|}{CH_3}}{CH}CH_2\overset{\underset{|}{CH_3}}{CH}CH_2CH_3
(b) CH_3CH_2\overset{\underset{|}{CH_3}}{CH}CH_2\overset{\underset{|}{CH_3}}{CH}CH_3
(c) CH_3\overset{\underset{|}{CH_3}}{CH}CH_2CH_2\overset{\underset{|}{CH_3}}{CH}CH_3
STRATEGY Pay attention to the connections between atoms. Don’t get confused by the apparent differences caused by writing a structure right-to-left versus left-to-right.
Structure (a) has a straight chain of six carbons with –CH_3 branches on the second and fourth carbons from the end. Structure (b) also has a straight chain of six carbons with –CH_3 branches on the second and fourth carbons from the end and is therefore identical to (a). The only difference between (a) and (b) is that one is written “forward” and one is written “backward.” Structure (c) has a straight chain of six carbons with –CH_3 branches on the second and fifth carbons from the end, so it is an isomer of (a) and (b).