Ring-opening reactions of the aziridine rings of Pl-aziridinyl-(la), P-(2-methyl-l-aziridinyl)- (lb), and P-(2, 2-dimethyl-l-rtziridinyl)-N, N, N', N'-tetramethylphosphonic diamide (IC) are described. For those reactions in which mixtures of ring-opened isomers were produced, an estimate of the composition was made from the proton nmr spectra of the mixtures. Reactions of lb with acidic reagents gave mostly the products of direct attack upon the ...