Product selectivities and third-order rate laws for solvolyses of ethyl phenylphosphonochloridate in aqueous alcohols

Rate constants and product selectivities (S) for solvolyses of ethyl phenyl phosphonochloridate [PhP(=O)OEtCl] in aqueous ethanol and methanol at 0 deg reesC are reported; S =([ester product]/[acid product]) x ([water]/[alcohol solvent]). The results show trends very similar to those previously report ed for solvolyses of diphenyl phosphorochloridate [(PhO)(2)P(=O)Cl] and p,p '-dichlorodiphenyl phosphorochloridate, much more hydrophobic substrates. I mplications of these results are as follows: (i) as S increases about three fold from 99.8 to 90% alcohol-water and only about the same amount from 90 to 40% alcohol-water, the main cause of variations in S does not appear to be medium effects of the solvents; (ii) contrary to the general trend to in crease, values of S may decrease slightly (ca 15%) in highly aqueous alcoho l-water mixtures, even when (as in this case) there is no evidence for mech anistic changes; (iii) the deviations from expected third-order rate produc t correlations previously reported for solvolyses of diphenyl phosphorochlo ridate and the pp-dichloro derivative do not appear to be due solely to the ir high hydrophobicity. Copyright (C) 2001 John Wiley & Sons, Ltd.