Aminolysis of sulfamate esters in chloroform—nonlinear kinetics

Aminolysis in chloroform of sulfamate esters RNHSO2OC6H4NO2-4 principally with a series of imidazoles gives good kobs first-order rate constants under pseudo-first-order conditions. Plots of kobsvs. [amine] display downward curvature leading to saturation and these plots can be fitted to the rate law kobs 4;= 4;Kmk1[amine]/{1 4;+ 4;Km[amine]} where Km and k1 are defined by eqn. (i). The Hammett ρ value for the formation of the complex [S·Amine] is +1.64. Using data derived for the rate-determining step, the breakup of the intermediate is shown to be unimolecular with a ρacyl (substituents in the R part of S) of –1.78 consistent with an E1cB process. Steric effects of the bound-amine in the complex are negligible.