SOLVENT EFFECTS ON REACTIONS OF HYDROXIDE ION WITH PHOSPHORUS(V) ESTERS - A QUANTITATIVE TREATMENT

Second-order rate constants of reactions of HO- with phosphate, phosph inate and thiophosphinate esters, (PhO)(2)PO.OC6H4NO2-p, Ph(2)PO.OC6H4 NO2-p, Ph(2)PO.SPh, Ph(2)PO.SC6H4NO2-p and Ph(2)PO.SEt, go through min ima with decreasing water content of H2O-MeCN or H2O-t-BuOH. The rate decrease is due to stabilization of the non-ionic ester on addition of organic solvent to H2O. This inhibition is partially offset by stabil ization of the anionic transition states and in the drier solvents par tial desolvation of HO- increases rates.