Bond scission in sulphur compounds. Part IV. Sulphur–oxygen versus sulphur–chlorine bond scission in the methanolysis of phenyl chlorosulphate. Kinetics and mechanism

Abstract

The reaction of phenyl chlorosulphate with methoxide ion in methanol yields products resulting from S–O and S–Cl bond scission. The yields of phenoxide ion and of methyl phenyl sulphate show a temperature dependence which is consistent with the occurrence of two parallel reactions with different energies of activation. There is an effective compensation in ΔH^‡ and ΔS^‡ in the two reactions. The activation parameters are discussed, in particular the positive ΔS^‡ value for S–O scission. An alternative mechanism, involving a pentaco-ordinate intermediate, cannot be excluded by the results but is considered to be unlikely.