Question 12.4: Cis-Trans Isomerism How many stereoisomers are possible for ...

Introduction to General, Organic and Biochemistry [EXP-46650]

Cis-Trans Isomerism

How many stereoisomers are possible for 2,4-heptadiene?

$CH _{3}- CH = CH - CH = CH - CH _{2}- CH _{3}$ 2,4-Heptadiene

Strategy

To show cis-trans isomerism, each carbon of the double bond must have two different groups bonded to it.

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This molecule has two carbon–carbon double bonds, each of which shows cis-trans isomerism. As shown in the following table, 22 54 stereoisomers are possible. Line-angle formulas for two of these dienes are drawn here.

Double-Bond
$C _{2}- C _{3}$	$C _{4}- C _{5}$
(1) trans	trans
(2) trans	cis
(3) cis	trans
(4) cis	cis

12.4

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