Question

Which of the following is least reactive in a nucleophilic substitution reaction?

• A. $C{H}_2=CHCl$
• B. $C{H}_{3}C{H}_{2}Cl$
• C. $C{H}_2=CHC{H}_{2}Cl$
• D. $(CH3{)}_{3}C-Cl$

Answer 1

The correct option is A $C{H}_2=CHCl$

Correct answer $C{H}_2=CHCl$

Explanation : Chlorine of Vinyl chloride is not reactive towards nucleophile in nucleophillic substitution reaction because it shows the following resonating structure due to $+M$ effect of $-Cl$ atom

In structure (II) $-Cl$ atom has partial $(+ve)$ charge and double bond character with ${}^{\prime }{c}^{\prime }$ of Vinyl group, so it more tightly attracted towards the nucleus and it doesn't get replaced by nucleophile is $S_N$ reaction.

Vinyl halides are less reactive than alkyl and halides towards nucleophilic substitution reactions.

Hence A is the correct answer.