An 'Assertion' and a 'Reason' are given below. Choose the correct answer from the following options.
Assertion (A): Vinyl halides do not undergo nucleophilic substitution easily.
Reason (R): Even though the intermediate carbocation is stabilized by loosely held p-electrons, the cleavage is difficult because of strong bonding.
Assertion (A): Vinyl halides do not undergo nucleophilic substitution easily.
Reason (R): Even though the intermediate carbocation is stabilized by loosely held p-electrons, the cleavage is difficult because of strong bonding.
- (A)Both (A) and (R) are correct statements but (R) is not the correct explanation of (A)
- (B)Both (A) and (R) are wrong statements
- (C)Both (A) and (R) are correct statements and (R) is the correct explanation of (A)
- (D)(A) is a correct statement but (R) is a wrong statement.✓ Correct
Answer: (D)
Solution
The assertion is true: vinyl halides resist nucleophilic substitution because the halogen lone pair conjugates with the double bond, giving the bond partial double-bond character that makes it short and strong. The reason is false: the resistance has nothing to do with a carbocation intermediate, since vinyl halides do not ionise that way. So a correct assertion is paired with a wrong reason.
JEE Main · 2019 · 12 Apr 2019 · Shift 2 · Single correct option