Hydrolysis of the O,O-Dialkyl Phosphorodithioic Acids Used as Extractants in Liquid-Liquid Systems

Article abstract of DOI:10.1021/ac00276a040

At 25 deg C, the title compounds are fairly stable against hydrolysis: the yield of hydrolysis of the bis(2-ethylhexyl)phosphorodithioic acid (DEHPDTA) is less than 10percent after 5 months in contact with H2O or 1 M HCl.The rate of hydrolysis is particularly dependent on the temperature: the half-life of a 0.5 M solution of DEHPDTA is about 80 days at 35 deg C, 24 h at 65 deg C, and only 1 h at 100 deg C.In contrast with their acidic forms, the dialkyl phosphorodithioates (as a salt of sodium or engaged in metal complexes) are stable.Increase in the hydrophobic feature of the alkyl groups enhances the stability; however, even the didodecyl phosphorodithioic acid is rapidly hydrolyzed above 40 deg C.Finally, the replacement of the alkyl groups by aryl groups dramatically enhances the tendency for hydrolysis.For the bis(2-ethylhexyl) phosphorodithioic acid, the reaction of hydrolysis mainly gives H2S<*>, H3PO4, 2-ethylhexanol, and the bis(2-ethylhexyl) phosphorothioic acid.