JEE Main 2025 Jan 23 Shift 2, Chemistry Q10: Introduction to Mechanism of Organic Reaction

JEE Main2025Jan 23, Shift 2Chemistry

The ascending order of relative rate of solvolysis of following compounds is

A
(D) $<$ (A) $<$ (B) $<$ (C)
B
(C) $<$ (B) $<$ (A) $<$ (D)
C
(D) $<$ (B) $<$ (A) $<$ (C)
D
(C) $<$ (D) $<$ (B) $<$ (A)

Solution

Solvolysis under these conditions follows an $S_{N} 1$ pathway, so the rate tracks the stability of the carbocation formed on ionisation.

Ranking the cation stabilities:

$∙$ (C) Ph $_{2}$ CH $^{+}$ : the benzhydryl cation is stabilised by two phenyl groups through extended conjugation, by far the most stable.

$∙$ (B) Tetralin C1 cation : a benzylic secondary cation, stabilised by one fused aromatic ring.

$∙$ (A) Tertiary aliphatic cation on the cyclohexyl framework : stabilised only by hyperconjugation and inductive effects from alkyl groups, no aromatic conjugation.

$∙$ (D) Secondary aliphatic cation : the least stable of the four.

Ascending order of solvolysis rate: $(D) < (A) < (B) < (C)$ .

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JEE Main 2025 Jan 23 Shift 2, Chemistry Q10: Introduction to Mechanism of Organic Reaction

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