Kinetics of the thermal fragmentation of four N-substituted derivatives of 0-ethyl phosphoramidic acids,(EtO-P (O)(NRR')(OH), were examined. When N contained either of the sterically demanding mesityl or 1-adamantyl groups, the reaction followed first-order kinetics, both in the absence and presence of an alcohol trapping reagent. In the former case, the product was a pyrophosphate (RR'N (EtO)(O) POP (O)(OEt) OH). In the latter ...