JEE Main Chemistry question

Chlorine in vinyl chloride is less reactive because

(A)Chlorine's high electronegativity alone strengthens the C–Cl bond, independent of any resonance
(B)The C–Cl bond develops partial double-bond character (through conjugation of Cl's lone pair with the adjacent π system)Correct
(C)The vinylic carbon readily ionizes via an Sɴ1 pathway, stabilised by allylic-type resonance
(D)Steric hindrance from the adjacent double bond blocks backside nucleophilic attack

Answer: (B)

Solution

Resonance donation of chlorine's lone pair into the adjacent C=C π system (Cl⁺=CH–CH₂⁻ ↔ Cl–CH=CH₂) gives the C–Cl bond partial double-bond character, shortening and strengthening it and making it resistant to both the backside attack of Sɴ2 and the ionization of Sɴ1. (A) wrongly attributes the effect to

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Question ID VK-139806