JEE Main 2026 — Jan 24, Shift 1 — Chemistry solution

JEE Main2026Jan 24, Shift 1Chemistry

Arrange the following carbanions in the decreasing order of stability

[ADD IMAGE: Five para-substituted benzyl carbanion structures. I: p-Br-C6H4-CH2(-). II: C6H5-CH2(-) (plain benzyl carbanion). III: p-CH3O-C6H4-CH2(-). IV: p-CHO-C6H4-CH2(-). V: p-CH3-C6H4-CH2(-).]

Choose the correct answer from the options given below :

A
I > II > IV > V > III
B
I > IV > II > V > III
C
IV > I > II > V > III
D
IV > II > I > III > V

Solution

Carbanions are stabilised by electron-withdrawing groups (which delocalise the negative charge) and destabilised by electron-donating groups.

Ranking by substituent:

IV ( $- C H O$ , strong $- M$ ): most stabilising → most stable

I ( $- B r$ , $- I$ effect dominant over weak $+ M$ ): mildly stabilising

II ( $- H$ , no effect): reference

V ( $- C H_{3}$ , weak $+ I$ , $+ H$ ): mildly destabilising

III ( $- O C H_{3}$ , strong $+ M$ ): most destabilising → least stable

$∴$ Order: IV > I > II > V > III.

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