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 ρ X and β X values are indicative of a large degree of bond making in the TS. Smaller magnitudes of ρ X (0.20 for X = H) and ρ XY (−0.30) than those for the corresponding reactions with phenyl aryl chlorophosphates ( 1 ) (ρ X = 0.54 for X = H and ρ XY = −1.31) are interpreted to indicate partial electron loss, or shunt, towards the electron acceptor equatorial ligand ( p ‐ClC 6 H 4 O‐) in the bipyramidal pentacoordinated transition state. The inverse secondary kinetic isotope effects ( k H / k D = 0.64–0.87) involving deuterated aniline (ND 2 C 6 H 4 X) nucleophiles, and small Δ H ‡ and large negative Δ S ‡ are obtained. These results are consistent with a concerted nucleophilic substitution mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 632–637, 2002