Solvent effects on reactions of hydroxide ion with phosphorus (V) esters. A quantitative treatment

Article abstract of DOI:10.1002/(SICI)1099-1395(199603)9:3<145::AID-POC763>3.0.CO;2-E

Second-order rate constants of reactions of HO^- with phosphate, phosphinate and thiophosphinate esters, (PhO)₂PO.OC₆H₄NO₂-p, Ph₂PO.OC₆H₄NO₂-p, Ph₂PO.SPh, Ph₂PO.SC₆H₄NO₂-p and Ph₂PO.SEt, go through minima 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 stabilization of the anionic transition states and in the drier solvents partial desolvation of HO^- increases rates.