Kinetic and isotope effect studies on the intermediacy of ethyl metathiophosphate in ethanolysis of O-ethyl N-1-adamantyl phosphoramidothioate

Article abstract of DOI:10.1016/S0022-328X(96)06484-4

The fragmentation of O-ethyl N-l-adamantylphosphoramidothioate (1a) and its oxygen counterpart 1b was examined in ethanol at 65-100°C. The solvent hydrogen effect k_EtOH/k_EtOD and kinetic nitrogen effect k₁₄/k₁₅ were determined at 80°C. The rates and parameters of activation of ethanolysis of 1a and 1b are slightly different. The solvent effect k_EtOH/k_EtOD was found to be equal to 0.84 ± 0.05 for 1a and 0.83 ± 0.04 for 1b. The nitrogen effect k₁₄/k₁₅ was found to be sensitive to replacement of sulfur by oxygen, and equal to 1.0083 ± 0.0004 for 1a and 1.0065 ± 0.0006 for 1b. The data indicate that proton transfer from the OH group to the amine moiety precedes the P-N bond breakage. The kinetic nitrogen isotope effect for the amine elimination recalculated for the pre-equilibrium step is equal to 1.0232 for 1a and 1.0215 for 1b. These results are consistent with the intermediacy of ethyl metathiophosphate in the solvolysis of 1a.