The mechanism of acyl sulphonate reactions. Part II. Solvolyses of a series of 4- and 5-substituted 2-sulphobenzoic anhydrides in hydroxylic solvents

Rate constants have been determined for the solvolyses of 5-chloro-2-sulphobenzoic anhydride in five alcohols, 4-bromo-, 4-chloro-, 4-methyl-, and 4-nitro-2-sulphobenzoic anhydride in four alcohols, and 4-iodo-2-sulphobenzoic anhydride in three alcohols, each alcohol containing 6·67% ether. Rate constants for the hydrolysis and deuteriolysis of the 4-methyl compound in 90% dioxan were also obtained. Hammett ρ values and solvent effects are interpreted as indicating a synchronous mechanism with a transition state in which bond forming has proceeded further than bond breaking.