Q. Which one of the following explain, why propene undergo electrophilic addition with$\ HBr$, but not with HCN?
A) $Br^{-}$is better nucleophile than $CN^{-}$
B) $HBr\$being better source of proton as it is stronger acid than HCN
C) HCN attacks preferentially $via$ lone pair of nitrogen
D) The $C - Br$ bond being stronger is formed easily as compared to $C - CN$ bond
Explanation
(b)
$HBr\$being better source of proton. It gives a $H^{+}$ and a $Br^{-}\$ion
$HBr \longrightarrow H^{+} + Br^{-}$
Thus, $H^{+}$attack the $\pi$ bond of propene to form carbonium ion as
[image:12_image317.emf]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.