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 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) 2 P(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.