M.E. Tucceri

Theoretical Study of the Heats of Formation of SF, FSO, FSO2 and HSO Radicals

Standard heats of formation of SF, FSO, FSO2 and HSO radicals have been calculated with the hybrid B3LYP density functional using extended basis sets and with CBS-4M, CBS-q, CBS-Q and CBS-QB3 model chemistries. The values computed from bond dissociation enthalpies and atomization energies are typically 2-3 kcal mol-1 higher than those obtained from a large number of isodesmic reactions. Application of isodesmic reactions calculations with energies computed at the CBS-q level of theory yielded our best values of 0.2±1.0, -69.9±2.0, -96.2±3.0, and -4.4±1.5 kcal mol-1 for SF, FSO, FSO2 and HSO respectively. The values for the FSO and FSO2 reduce markedly the literature uncertainties while the values for the SF and HSO are in very good agreement with previous ab initio estimates.

Kinetics of formation of the novel peroxide FC(O)OO(O2)SF

The high-pressure rate coefficient for the formation of the new peroxide FC(O)OO(O2)SF from recombination of FC(O)O and FS(O2)O radicals has been determined by laser flash photolysis at 296 K; density functional theory calculations indicate peroxide stabilization and allow estimation of an O–O bond dissociation energy of 20.6 ± 3 kcal mol−1.