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The reduction of m-methoxybenzoic acid by the procedure of Chapman and Fitton was studied. It afforded mainly a dihydro product; the p.m.r. spectrum and other data indicated that only 17% of tetrahydrobenzoic acid derivatives were formed.

The sigma complexes formed from the reaction of methoxide ion with 6- nitro-pyrimidine and its monomethoxy derivatives have been examined spectroscopically. Structural ambiguities resulting from the lower symmetry of the nitropyrimidines compared with the trinitrobenzenes have been resolved by selective deuteration. Comparison is made with sigma complex formation from 2,4,6-trinitroanisole and the question of kinetic against thermodynamic control is considered with reference to theoretically derived P.E.-reaction coordinate profiles for protic solvents. The calculations are extended qualitatively to consider reactions in an aprotic solvent.

The conversion of the methine complex (4; R1 = H) into the more stable isomer (5; R1 = R2 = H) is reported.

Contrasting behaviour is observed when 2- and 4-methoxy-3,5-dinitropyridine interact with methoxide ion in dimethyl sulphoxide. The 4-methoxy compound affords both methine and acetal sigma complexes, the latter being thermodynamically more stable. The interconversion is catalysed by methanol. Labelling experiments have established that the sigma complex from the 2-methoxypyridine is formed by addition at C6; no conversion into the acetal could be effected. These observations are rationalized in terms of differential steric and solvation effects. Demethylation and rearrangement reactions of 4-methoxy-3,5-dinitropyridine are reported.