The stabilities of Meisenheimer complexes. Part II. Equilibrium constants for the formation of methoxide adducts of low stability and the JM acidity function in methanol–dimethyl sulphoxide

Abstract

A J_M acidity function has been measured for methanol–dimethyl sulphoxide mixtures containing 0·1 M-sodium methoxide in respect of methoxide addition to substituted anisoles. This allows the determination of the thermodynamic equilibrium constants for sodium methoxide addition in methanol to 1,5-dimethoxy-2,4-dinitrobenzene (3·8 × 10^–6 l mol^–1), 2,4-dinitroanisole (4·6 × 10^–5 l mol^–1), 2,6-dinitroanisole (9·0 × 10^–5 l mol^–1), 4-chloro-2,6-dinitroanisole (4·3 × 10^–3 l mol^–1) and 2-fluoro-4,6-dinitroanisole (0·3 l mol^–1).