Kinetics and mechanism of the aminolysis of phenyl dithiobenzoates

Abstract

The kinetics and mechanism of the reactions of phenyl dithiobenzoates with anilines in acetonitrile at 55.0 °C have been studied. The large magnitude of β_X(β_nuc) and the signs of cross-interaction constants, ρ^e_XY > 0, ρ_YZ < 0 and ρ_XZ > 0, are all consistent with the carbonyl addition mechanism in which the breakdown of the tetrahedral intermediate, T ^±, is rate limiting. The thiocarbonyl group (CS) is found to favour amine expulsion in contrast to the carbonyl group (CO) which favours the S-bonded nucleofuge expulsion from T^±. The signs of cross-interaction constants, ρ_XY, ρ_YZ and/or ρ_XZ, are shown to provide useful mechanistic criteria for distinguishing, especially, the carbonyl addition mechanism involving the rate-limiting breakdown of the tetrahedral intermediate (T^±) from the concerted S_N2 mechanism.