Kinetics of hydrolysis and cyclization of ethyl 2-(aminosulfonyl)benzoate to saccharin

The cyclization of ethyl 2-(aminosulfonyl)benzoate (ASB) to give saccharin was investigated in aqueous solutions at pH between 5.2 and 9.5 and in the temperature range of 296.2–334.2 K. The initial concentration of the reactant was varied between 1.45×10−5 and 3.86×10−4 M. Ultraviolet spectroscopy was used to obtain the kinetic data. The reaction is acid catalyzed and follows pseudo-first-order kinetics. The experimental rate constant, kobs, increases with temperature and pH. Its dependence on the temperature and pH is well described by: kobs=k1[OH−]=[(2.52±0.9)×1016exp(−20.2±1 kcal mol−1/RT) s−1][OH−] A mechanism is proposed and the half-life of ethyl ASB is calculated.