Studies on Sulphamic Acid and Related Compounds. I. Kinetics and Mechanism of Hydrolysis of Sulphamic Acid

Abstract

The kinetics of hydrolysis of sulphamic acid, NH₂SO₂OH + H₂O → NH₄HSO₄, have been studied in water, in aqueous perchloric acid solution, and in acetone-water mixtures. The rate data obtained in water did not give good first-order plots - a fact attributed to a variation in the degree of dissociation of sulphamic acid with concentration, and to the production of hydrogen ions by dissociation of bisulphate ions formed in the reaction - but in the presence of perchloric acid good first-order plots were obtained. The rate data for hydrolysis in aqueous acetone (in the absence of HClO₄) gave good first-order plots. For [water]<l mole l^-1 the rate constant at 35 °C is independent of the water concentration and is about 1000 times that in water at the same temperature. It seems probable that the rate controlling step in aqueous acetone and also in water involves a unimolecular decomposition of the zwitterion form of sulphamic acid, namely ⁺NH₃ SO₃^-.