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

Abstract

This study demonstrated the kinetics of nucleophilic substitution reactions of butyl methyl chlorophosphate (2) with X-anilines (XC6 H4 NH2) and deuterated X-anilines (XC6 H4 ND2) in MeCN at 55.0 ± 0.1 °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 ρX and small positive βX values. The deuterium kinetic isotope effects (DKIEs) were secondary inverse (kH /kD < 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.