Study of a reaction between 2,3-dichloro-1,4-naphthoquinone and N, N′-diphenyl thiourea involving an EDA adduct as intermediate

Abstract

The reaction between 2,3-dichloro-1,4-naphthoquinone and N, N′-diphenyl thiourea in acetonitrile medium, which yields the product, 2,3-( N, N′-diphenylthioureylene)-naphtho-1,4-quinone has been found to take place in two ways—thermal and photochemical. The thermal (dark) reaction occurs through an electron donor–acceptor (EDA) adduct as intermediate with evolution of HCl and kinetic data fit into the scheme A+ B⇄ AB ( fast)→ product ( slow) Formation constant of the EDA adduct and the rate constant of the slow process have been determined at four different temperatures from which the enthalpy of formation of AB has been determined. The photochemical reaction has been studied with 360 nm ordinary light and also with 365 and 370 nm laser beams. Use of laser causes about 10 3-fold increase in the rate of the reaction but does not affect the quantum yield. The final product has been isolated and characterised by elemental analysis, 1 H and 13 C NMR, IR spectroscopy and mass spectrometry.