Nucleophilic Aromatic Substitution An Update Overview

Arene Chemistry Reaction Mechanisms and Methods for Aromatic Compounds, First Edition. Edited by Jacques Mortier. 

Nevertheless, processes are available allowing the conversion of adducts such as (3) to substituted products. These are covered in Chapter 11. Briefly, these may involve oxidation of 

In a chapter of this length, it is not possible to cover the subject area comprehensively, and in the sections that follow, examples are given that hopefully will illustrate some of the main principles involved. For a more complete coverage of the literature and subject area, the readers are referred to the excellent book by F. Terrier [9]. 

There are several pieces of experimental evidence for the formation of a discrete intermediate in aromatic systems. One of the earliest was Meisenheimer s observation [19] that addition of potassium methoxide to 2,4,6-trinitrophenetole or addition of potassium ethoxide to 2,4,6-trinitroanisole produced identical compounds, (5), which on acidification produced in each case a mixture of methyl and ethyl picrates. Meisenheimer complexes, which are anionic a-adducts, are considered later in this chapter. 

FIGURE 6.1 Energy diagrams for bimolecular substimtion (a) and (b) involve an intermediate with, respectively, nucleophilic attack and leaving group expulsion rate limiting (c) represents a conceited mechanism with a single transition state. 

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