Interaction of heterocycles and nucleophiles: Sigma complexes formed from methoxide ion and some 5-nitropyrimidines and comparison with those from 2,4,6-trinitroanisole

Abstract

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.