P-31 NUCLEAR-MAGNETIC-RESONANCE STUDY OF THE MECHANISM AND KINETICS OF THE HYDROLYSIS OF ZINC(II) O,O-DIETHYL DITHIOPHOSPHATE AND SOME RELATED-COMPOUNDS

31P NMR spectroscopy has been used to investigate the mechanism and kinetics of hydrolysis of Zinc(II) O,O-diethyl dithiophosphate (1) (ZDTP) in 1,2-dimethoxyethane solution at 85°C with ten equivalents of water. All major intermediates and products have been identified and the individual reaction rates determined. ZDTP was found to be hydrolysed (k = 2.35 × 10-4 s_1) to phosphoric acid (7) via O,O-diethyl S-hydrogen dithiophosphate (3) (khyd = 1.35 × 10-2 s-1) and thiophosphoric acid (6) (khyd = 0.78 × 10-5 s-1). O-Ethyl O,O-dihydrogen and O,O-diethyl O-hydrogen phosphorothioates (8), (9), and ethyl dihydrogen phosphate (10) were produced as by-products of the reaction. From a study of the order of appearance of the intermediates and products, a detailed mechanism for the hydrolysis of ZDTP has been proposed. O-Ethyl O,S-dihydrogen phosphorodithioate (4) and dithiophosphoric acid (5) are found to be intermediates.