Kinetics and mechanism of the reaction of para-chlorophenyl aryl chlorophosphates with anilines in acetonitrile

The kinetics and mechanism of the nucleophilic substitution reactions of p‐chlorophenyl aryl chlorophosphates (2) with anilines are investigated in acetonitrile at 55°C. Relatively large magnitudes of ρX and βX values are indicative of a large degree of bond making in the TS. Smaller magnitudes of ρX (0.20 for X = H) and ρXY (−0.30) than those for the corresponding reactions with phenyl aryl chlorophosphates (1) (ρX = 0.54 for X = H and ρXY = −1.31) are interpreted to indicate partial electron loss, or shunt, towards the electron acceptor equatorial ligand (p‐ClC6H4O‐) in the bipyramidal pentacoordinated transition state. The inverse secondary kinetic isotope effects (kH/kD = 0.64–0.87) involving deuterated aniline (ND2C6H4X) nucleophiles, and small ΔH‡ and large negative ΔS‡ are obtained. These results are consistent with a concerted nucleophilic substitution mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 632–637, 2002