Oxidative ring cleavage of 2,3-dihydrophthalazine-1,4-dione in aqueous and non-aqueous solutions: Electrochemical and kinetic studies

Abstract

Electrochemical oxidation of 2,3-dihydrophthalazine-1,4-dione (DHP) has been investigated in aqueous and some amphiprotic and aprotic non-aqueous solvents by cyclic voltammetric and controlled-potential coulometric techniques. Our data shows that electrochemically generated phthalazine-1,4-dione (PTD) in water and amphiprotic non-aqueous solvents participates in an oxidative ring cleavage (ORC) reaction to form phthalic acid. The rate of this reaction is dependent. On autoprotolysis constant (K SH) and basicity of the solvent. Therefore, in the aprotic non-aqueous solvents such as acetonitrile and DMSO, the rate of ORC is too slow to be observed on the time-scale of cyclic voltammetry. Electrochemical oxidation of 2,3-dihydrophthalazine-1,4-dione has been investigated in aqueous and a few amphiprotic and aprotic non-aqueous solvents. The electrochemically generated phthalazine-1,4-dione in water and amphiprotic non-aqueous solvents participates in a oxidative ring cleavage reaction to form phthalic acid.