THE KINETICS AND MECHANISM OF THE SILVER ION-PROMOTED HYDROLYSIS OF THIOLURETHANES IN AQUEOUS-SOLUTION

The hydrolysis of thiolurethanes p-RC6H4NHCOSEt (1, R = Cl, H, OMe) in dilute aqueous acid is promoted by silver ions. The promoted hydrolys is involves the slow decomposition of low concentrations of complexes of 2 Ag+:1-thiolurethane stoichiometry, which are formed from relative ly stable 1:1-complexes. The (positively charged) 1 : 1 -complex (2) u ndergoes N-H dissociation to give a formally neutral 1 : 1 -complex, 3 . The 2:1 -complexes are formed f rom both 2 and 3. The formation cons tants, K1, and the acid dissociation constants, K(a), of (2, R = Cl, H , MeO) have been obtained from a kinetic analysis using a range of sil ver and hydrogen ion concentrations, and different temperatures. The r esults suggest that the 2:1-complexes undergo nucleophilic attack by w ater in an overall A2-like process. Thiolurethanes 1 are ca. 10(5)-fol d more reactive in Ag+ ion-promoted hydrolysis than are the correspond ing ethyl thiolbenzoates.