Elimination mechanisms in the anilinolysis of sulfamoyl chlorides in chloroform and acetonitrile

Abstract

The kinetics of the reaction of various sulfamoyl chlorides, R1R2NSO2Cl (R1 = Ph, Me, c-C6H11, But, R2 = H and R1 = R2 = Me and R1 = R2 = PhCH2) with anilines in chloroform and acetonitrile have been studied. Reaction is first order in both chloride and aniline and pseudo first order and second order rate constants have been determined for various chlorides and para- and meta-substituted anilines. Hammett ρ values vary from –4.76 to –2.63 for varying XC6H4NH2 depending on the halide, X. Substituents in XC6H4NHSO2Cl have only small effects on the rates. There is a ca. 106-fold rate difference between PhNHSO2Cl and (PhCH2)2NSO2Cl reacting with p-anisidine in chloroform at 25 °C. This finding, coupled with the observation of hydrogen/deuterium isotope effects, supports the operation of an elimination mechanism involving an N-sulfonylamine, [PhNSO2], as a transient species. In chloroform an E2-type mechanism is suggested, while in acetonitrile the activation parameters (ΔH, ΔS) may indicate a more E1cB-like E2 mechanism.