9701 MCQ Solution 37

Question 37: [Organic > Introductory Organic]:

Which compounds show cis-trans isomerism?

1 but-2-ene

2 but-1-ene

3 2-methylpropene

Reference: Past Exam Paper – November 2002 Paper 1 Q37

Solution 37:

Answer: D.

In but-2-ene the unsaturated carbons have 2 pairs of the same group thus can exhibit cis-trans isomerism. 

In but-1-ene one of the unsaturated carbons have a repeated group thus it cannot exhibit cis-trans isomerism. 

Since 2 is incorrect 3 must also be incorrect and the only valid option is D.