Rate Coefficients for Intramolecular Homolytic Substitution of Oxyacyl Radicals at Sulfur

It is predicted on the basis of ab initio and density functional calculations that intramolecular homolytic substitution of oxyacyl radicals at the sulfur atom in omega-alkylthio-substituted radicals do not involve hypervalent intermediates. With tert-butyl as the leaving radical, free energy barriers Delta G(double dagger) (G3(MP2)-RAD) for these reactions range from 45.8 kJ mol(-1) for the formation of the five-membered cyclic thiocarbonate (8) to 56.7 kJ mol(-1) for the formation of the six-membered thiocarbonate (9). Rate coefficients in the order of 10(4)-10(6) s(-1) and 10(1)-10(4) s(-1) for the formation of 8 and 9, respectively, at 353.15K in the gas phase are predicted at the G3(MP2)-RAD level of theory.