A series of 1-phenylethyl esters of phosphinic acids has been prepared and their mode of solvolysis studied. Correlation of the rate constants for the solvolysis of 1-arylethyl diphenylphosphinates in 80% ethanol-water at 75'with u+ constants gave ap of-5.10, demonstrating that alkyl-oxygen fission occurs. This value is compared with the value obtained from other 1-arylethyl esters and chlorides. The rate data for the solvolysis of I- ...