Question

Which compound shows cis-trans isomerism?

• A. 1-butene
• B. 2-propene
• C. 2-butene
• D. benzene

Answer 1

The correct option is C 2-butene

Conditions for geometrical isomers:
1) Free rotation must be restricted.
2) Both the terminals must be attached with different groups.
3) Terminals must not be in perpendicular planes.

1-butene has two same groups attached to the one of the terminal carbon of the double bond so it can't show geometrical isomerism

2-propene has two same groups attached to the one of the terminal carbon of the double bond so it can't show geometrical isomerism

2-butene has two different groups $\left(H\right)$ and $\left(C{H}_3\right)$ attached to the terminal carbon of the both double bond so it can show geometrical isomerism.

d can't show geometrical isomerism
hence correct option is c.