A spectroscopic study of complex formation between aromatic nitrocompounds and sodium sulphite

Abstract

The interactions of a series of trinitrobenzene derivatives with sodium sulphite in water and in water–dimethyl sulphoxide mixtures have been investigated by ¹H nuclear magnetic resonance and visible spectroscopy. In water each nitro-compound studied gives a 1 : 1 adduct at low sulphite concentrations resulting from covalent addition of sulphite at a ring carbon atom carrying hydrogen, while at higher sulphite concentrations di-adducts are formed by addition of sulphite at two ring positions carrying hydrogen. The equilibrium constants for formation of these complexes have been determined and are compared with the values for addition of hydroxide ion The effects on the stabilities of the complexes of changes of the ionic strength or solvent are discussed.