Question

Which among the following compounds does NOT exhibit cis-trans isomerism?

• A. H₂C=C(R)₂
• B. R-CH=CHR
• C. R₁CH=CR₁R₂
• D. R₁R₂C=CR₁R₂

Answer 1

Answer: (A)

H₂C=C(R)₂

Answer 2

For cis–trans isomerism to occur, each carbon of the double bond must have two different substituents.

• (A) H₂C=C(R)₂: The left carbon has two identical hydrogen atoms, so it cannot show cis–trans isomerism.
• (B), (C), (D): In these compounds, both carbons have two different groups (assuming R, R₁, and R₂ are distinct), allowing cis–trans isomerism.