A spectroscopic study of the formation of isomeric Meisenheimer complexes from 1-methoxycarbonyl-3,5-dinitrobenzene

Abstract

The covalent addition of methoxide, sulphite, and acetonate ions to 1-methoxycarbonyl-3,5-dinitrobenzene has been studied using ¹H n.m.r. and visible spectroscopy. With each nucleophile initial addition at the 4-position is followed by rearrangement to a mixture of the isomeric adducts. Surprisingly the methoxide ion shows little thermodynamic discrimination for the three hydrogen-bearing ring positions, although with sulphite or acetonate ions addition at the 2-position is thermodynamically favoured. Some corresponding measurements have been made with 3,5-dinitrobenzoic acid.