Question

Two isomeric alkenes $A$ and $B$ have molecular formula $C_5{H}_{9}Cl$. On adding $H_2$, $A$ gives an optically inactive compound while $B$ gives a chiral compound. The two isomers are:

• A. $A$ is 4-chloro-2-pentene and $B$ is 4-chloro-1-pentene
• B. $A$ is 3-chloro-2-pentene and $B$ is 2-chloro-2-pentene
• C. $A$ is 2-chloro-3-methyl-2-butene and $B$ is 1-chloro-3-methyl-1-butene
• D. $A$ is 3-chloro-1-pentene and $B$ is 1-chloro-2-pentene

Answer 1

Answer: (B)

$A$ is 3-chloro-2-pentene and $B$ is 2-chloro-2-pentene

Hydrogenation product of $A$ has an axis of symmetry and hence, is optically inactive. In option $B$, after adding $H_2$, $B$ gives an optically active compound with a chiral carbon.