Kinetics and Mechanism of Anilinolysis of Phenyl N-Phenyl Phosphoramidochloridate in Acetonitrile

The kinetic studies on the reactions of phenyl N-phenyl phosphoramidochloridate (8) with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) have been carried out in acetonitrile at 60.0 degrees C. The obtained deuterium kinetic isotope effects (DKIEs; k(H)/k(D)) are huge secondary inverse (k(H)/k(D) = 0.52-0.69). A concerted mechanism is proposed with a backside attack transition state (TS) on the basis of the secondary inverse DKIEs and the variation trends of the k(H)/k(D) values with X. The degree of bond formation in the TS is really extensive taking into account the very small values of the DKIEs. The steric effects of the two ligands on the rates are extensively discussed for the aminolyses of the chlorophosphate-type substrates on the basis of the Taft equation.