Solvolysis of organic phosphates. Part IX. Structure–reactivity correlations for the hydrolysis of organic orthophosphate monoesters

Abstract

Three structural parameters have been examined from the viewpoints of reliability and predictability for the linear free energy relationship study of phosphate hydrolysis: (i) stretching vibrational frequencies of P–O–C(alkyl or aromatic) and PO bonds; (ii) the acid dissociation constant for the last dissociating proton of the phosphate (pK_HA); and (iii) the n.m.r. chemical shift for the alcoholic or phenolic proton (δ_OH) of the leaving group. Among them pK_HA and δ_OH were found to be good parameters of high sensitivity with respect to the change in structure of the leaving groups. The extent and nature of anchimeric assistance or intramolecular catalysis in the hydrolysis of organic orthophosphate monoesters have been discussed with reference to the linear free energy relationships.