Solvent effects on the reaction coordinate of the hydrolysis of phosphatesand sulfates: Application of Hammond and anti-Hammond postulates to understand hydrolysis in solution

The mechanism of the alkaline hydrolysis of phosphate and sulfate esters is of great interest. Ab initio quantum mechanical calculations and dielectri c continuum methods are used to investigate the effect of the solvent on th e associative/dissociative and the in-line/sideways character of the hydrol ysis reaction of ethylene sulfate (ES) and ethylene phosphate (EP-), and th eir acyclic counterparts, dimethyl sulfate (DMS) and dimethyl phosphate (DM P-). The gas-phase reaction coordinates are determined by Hartree-Fock and density functional theory. For ES, the reaction coordinate in solution is d etermined: for the other three reactions only the transition state in solut ion is obtained. The alterations in the reaction induced by solvent are int erpreted by use of the Hammond and anti-Hammond postulates.