Question

Identify the correct increasing order of the stability of the following alkenes,
$I.cis$-2-butene;
$II.trans$-2-butene;
$III$. isobutene:

• A. $II<III<I$
• B. $I<III<II$
• C. $I<II<III$
• D. $III<II<I$

Answer 1

Answer: (B)

$I<III<II$

The order of stability is $I<III<II$.
The $cis$ -2-butene has the two methyl groups on the same side of a line that runs through the doubly bonded carbons. The steric crowding between the methyl groups causes the $cis$ -stereoisomer to be slightly less stable than the $trans$ -2-butene.