Pyridinolysis of O-Aryl Phenylphosphonochloridothioates in Acetonitrile

The kinetics and mechanism of the reactions of Y-O-aryl phenylphosphonochloridothioates with X-pyridines are investigated in acetonitrile at 35.0 oC. The negative value of the cross-interaction constant, ρXY = −0.46, indicates that the reaction proceeds by concerted SN2 mechanism. The observed kH/kD values involving d-5 pyridine (C5D5N) nucleophiles are greater than unity (1.05-1.11). The net primary deuterium kinetic isotope effects, (kH/kD)net = 1.28-1.35, excluding the increased pKa effect of d-5 pyridine are obtained. The transition state with a hydrogen bond between the leaving group Cl and the hydrogen (deuterium) atom in the C-H(D) is suggested for the studied reaction system. KCI Citation Count: 49