Chapter 23, Problem 23.41P

Interpretation Introduction

(a)

Interpretation:

The phenyl group, ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}$, is known to be an ortho/ para-directing group. With that in mind, the product of the given reaction is to be predicted.

Concept introduction:

If the yield of the ortho and para product is more than meta product, then the substituent on the monosubstituted benzene ring is called ortho/para directing group. Ortho position indicates the compound with substituents at the positions 1 and 2 on benzene ring. Para position indicates the compound with substituents at the positions 1 and 4 on the benzene ring.

Interpretation Introduction

(b)

Interpretation:

The phenyl group, ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}$, is known to be an ortho/ para-directing group. The reason for it to be an ortho/para director is to be justified by examining the ortho, meta, and para arenium ion intermediates that would be formed during the course of the reaction.

Concept introduction:

In general, the major product of electrophilic aromatic substitution is the one that is produced from the most stable arenium ion intermediate. If bromination occurs at the ortho position of the attached substituent, and the arenium ion that is produced has more total resonance structures, allowing the positive charge to be delocalized over more number of atoms then the substituent attached to the benzene ring is called ortho director. By contrast, if bromination occurs at the meta position and the arenium ion intermediate has less total resonance structures, the ortho arenium ion intermediate, with its additional resonance structures, is therefore lower in energy (more stable) than the meta intermediate.