INHIBITION OF HYDROLYSIS OF NORMAL ZINC(II) O,O'-DI-ISOPROPYL DITHIOPHOSPHATE BY THE BASIC FORM

'Basic' zinc(II) O,O′-di-isopropyl dithiophosphate dissociates in a variety of organic solvents (including xylene, toluene, diethyl ether, chloroform, 1,2-dimethoxyethane, acetone, dimethylformamide, and dimethyl sulphoxide) via a facile equilibrium into its 'normal' salt and zinc(II) oxide. The dissociation is promoted by an increase in temperature and solvent polarity and by an increase in the water content in aqueous 1,2-dimethoxyethane. This equilibrium in favour of the 'normal' salt and zinc(II) oxide is also acid-catalysed. The zinc(II) oxide which arises from the dissociation of the 'basic' form is found to inhibit the hydrolysis of 'normal' zinc(II) O,O′-di-isopropyl dithiophosphate by reaction with its primary hydrolysis product, O,O-di-isopropyl S-hydrogen phosphorodithioate. Eventual hydrolysis occurs after all the zinc(II) oxide has been consumed.