Question

But-$2$-ene exhibits cis-trans-isomerism due to

• A. rotation around $C_2-C_3$ double bond
• B. rotation around $C_3-C_4$ sigma bond
• C. rotation around $C_1-C_2$ bond
• D. restricted rotation around $C=C$ bond

Answer 1

Answer: (D)

Due to presence of $>C=C<$ in butene-$2$, it shows restricted rotation. Hence, give two types of arrangements around the space of $>C=C<$ as cis and trans-forms.