JEE Main · 2013 · 07 Apr 2013 · Offline · General Organic Chemistry

The order of stability of the following carbocations:

(A)II > III > I
(B)I > II > III
(C)III > I > II✓ Correct
(D)III > II > I

Answer: (C)

Solution

Carbocations are steadied by spreading the positive charge. The benzylic cation (III) draws on the whole benzene ring for resonance and is the most stable; the allylic cation (I) is stabilised by one neighbouring double bond; the ethyl cation (II), a bare primary carbocation with no such help, is the least stable. The order is III

>

>

II.

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option

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