Sulfur–chlorine bond dissociation enthalpies in methane- and benzene-sulfonyl chlorides

Abstract

Sulfur-chlorine bond dissociation enthalpies in methane- and benzene-sulfonyl chlorides, D(RSO₂–Cl), were measured by photoacoustic calorimetry and were found to be equal within experimental error (295 kJ mol^–1). The implicit absence of a stabilizing effect of the phenyl group in PhSO₂˙ is consistent with the known spectroscopic properties of sulfonyl radicals but conflicts with the currently accepted thermochemical data. Appearance energy measurements lead to values for the radical ionization potentials, E_i(MeSO₂)= 8.67 and E_i(PhSO₂˙)= 7.49 eV and for the enthalpy changes associated with the heterolytic cleavages RSO₂Cl→RSO₂⁺+ Cl^– where a substituent effect is observed.