Which of the following organic compounds is capable of exhibiting geometrical (cis-trans) isomerism? — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Geometrical isomerism requires restricted rotation (like a $C=C$ double bond) and two different groups attached to each of the doubly bonded carbon atoms. In 1-Phenyl-2-butene ($C_6H_5-CH_2-CH=CH-CH_3$), one double-bond carbon is attached to $-H$ and $-CH_3$, and the other is attached to $-H$ and $-CH_2C_6H_5$. Since both carbons have different groups, it exhibits geometrical isomerism. The others have at least one $sp^2$ carbon with two identical groups (e.g., two hydrogens or two phenyls).