Chapter 16.SE, Problem 31MP

Interpretation Introduction

Interpretation:

The observation that the N,N,N-trimethylammonium group –N(CH₃)₃, though a meta directing deactivator does not exhibit electron withdrawing resonance effect is to be explained.

Concept introduction:

In planar molecules the overlapping of p orbitals on adjacent carbon atoms takes place leading to the formation of different resonance forms. Resonance is not possible if the molecule is not co-planar.

If the group already present on the benzene ring is electron withdrawing by resonance and/or inductive effect it will deactivate the ring towards electrophiles.

The stability of a resonance hybrid depends on the number of stable individual resonance forms that contribute to the hybrid. More the number, the more stable is the hybrid.

To explain:

The observation that the N,N,N-trimethylammonium group –N(CH₃)₃, though a meta directing deactivator does not exhibit electron withdrawing resonance effect.