Chapter 16.SE, Problem 59AP

Interpretation Introduction

Interpretation:

Using the resonance structures of the potential intermediates, the position and the ring in which nitration of 4-bromobiphenyl is expected to occur is to be stated and explained.

Concept introduction:

In aromatic electrophilic substitution reactions halogens are ortho and para directing as they stabilize the carbocation intermediates for these attacks through resonance. However the halogens are highly electronegative and withdraw electrons from the ring through the inductive effect. Hence halogens also deactivate the ring towards electrophiles.

Resonance structures differ only in the position of the lone pair of electrons and those present in π bonds. There is no change in the position of atoms in the different forms. Curved arrows are used to represent the shift of the electrons. The actual structure of the compound is a hybrid of all possible forms. The stability of a resonance hybrid depends on the number of stable resonance forms that contribute to the actual structure.

To state and explain:

Using the resonance structures of the potential intermediates the position and the ring in which nitration of 4-bromobiphenyl is expected to occur.