Synthesis, kinetic study, and reaction mechanism: nucleophilic substitution reactions of butyl methyl chlorophosphate with substituted anilines and deuterated substituted anilines in acetonitrile

This study demonstrated the kinetics of nucleophilic substitution reactions of butyl methyl chlorophosphate (2) with X-anilines (XC$_{6}$H$_{4}$NH$_{2})$ and deuterated X-anilines (XC$_{6}$H$_{4}$ND$_{2})$ in MeCN at 55.0 \textpm\ 0.1 \textdegree C together with the general optimized method for the synthesis of 2 under mild conditions. Different spectroscopic characterizations revealed the formation of 2 with high purity. The free energy relationship with the substituents X in the anilines exhibited biphasic concavity upwards with a break point at X $=$ H, which induced large negative $\rho_{X}$ and small positive $\beta_{X}$ values. The deuterium kinetic isotope effects (DKIEs) were secondary inverse ($k_{H}$/$k_{D}$ \textless\ 1: 0.702--0.918) and the magnitudes were increased with the change of nucleophiles from weakly basic to strongly basic anilines. A concerted mechanism with a rate-limiting leaving group departing from the intermediate is proposed based on the selectivity parameters and the variation of DKIEs with X.