Question

Which of the following is the correct order of solvolysis of following alkyl and aryl halides?

• A. (D) > (A) > (C) > (B)
• B. (A) > (B) > (C) > (D)
• C. (B) > (C) > (A) > (D)
• D. (C) > (D) > (A) > (B)

Answer 1

Answer: (A)

(D) > (A) > (C) > (B)

Answer 2

Solvolysis rate is determined by the stability of the carbocation intermediate. (D) 3-bromocyclopropene forms the aromatic cyclopropenyl cation (2π electrons), which is extremely stable. (A) 7-bromocycloheptatriene forms the aromatic tropylium cation (6π electrons), which is very stable. (C) Allyl bromide forms a resonance-stabilized allyl cation. (B) Bromobenzene is an aryl halide, and the phenyl cation formed upon ionization is highly unstable. The stability order of carbocations is: Cyclopropenyl cation > Tropylium cation > Allyl cation >> Phenyl cation. Therefore, the order of solvolysis rate is (D) > (A) > (C) >> (B).