Chapter 19.12, Problem 5LTS

Interpretation Introduction

Interpretation:

The synthesis for the following compound has to be designed using benzene as the starting material –

Concept Introduction:

• Benzene is a stable aromatic compound and it is the simplest form of the aromatic compounds. It is a very versatile compound that it furnishes various products with various reagents.

• The most common type of reactions that benzene undergoes is electrophilic substitution reactions. Benzene can be converted to various ranges of compounds with appropriate reagents and reaction conditions. One of the useful method one can adapt to introduce any kind of group or atom onto the benzene ring is electrophilic substitution reaction.

• The various types of electrophilic substitution reactions in benzene are – Chlorination, Bromination, Nitration, Sulfonation, Friedel Crafts Alkylation/Acylation etc.

• The position that the electrophile occupies in the aromatic ring system depends on various factors like – presence of substituents, activation and deactivation of the ring etc.

• The pi electrons of the benzene must be readily available so that the reaction proceeds easily. Presence of many bulk substituents and/or the presence of strong electron withdrawing groups diminish the ability of the delocalizing pi electrons to bond with the electrophile.

• If the presence of substituents enhances the electron density of the ring then the reaction between the benzene ring and the electrophile is triggered readily. Then the ring is said to be activated towards electrophilic substitution reactions.

• If the presence of substituents causes electron drain in the ring then the $\text{π}$ electrons are not available to bond with electrophile. The aromatic ring becomes devoid of electrons and deactivated towards electrophilic substitution reactions.

• Thus the substituents can be widely of two types – activators and deactivators. A

• Activators are the substituents that enhance the electron density of the ring. Deactivators are the substituents that suppress the electron density of the benzene ring.