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

Abstract

AbstractRate constants and product selectivities (S) for solvolyses of ethyl phenylphosphonochloridate [PhP(O)OEtCl] in aqueous ethanol and methanol at 0 °C are reported; S = ([ester product]/[acid product]) ×­([water]/[alcohol solvent]). The results show trends very similar to those previously reported for solvolyses of diphenyl phosphorochloridate [(PhO)2P(O)Cl] and p,p′‐dichlorodiphenyl phosphorochloridate, much more hydrophobic substrates. Implications of these results are as follows: (i) as S increases about threefold 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 increase, values of S may decrease slightly (ca 15%) in highly aqueous alcohol–water mixtures, even when (as in this case) there is no evidence for mechanistic changes; (iii) the deviations from expected third‐order rate product correlations previously reported for solvolyses of diphenyl phosphorochloridate and the p,p′‐dichloro derivative do not appear to be due solely to their high hydrophobicity. Copyright © 2001 John Wiley & Sons, Ltd.