The enthalpy of formation of trioxy radicals ROOO (R  H, CH3, C2H5). An ab initio study

Enthalpies of formation of trioxy radicals, ROOO, with R  H, CH3, and C2H5, are calculated, along with values for the corresponding species R, RO, RO2, RO2H, and RO3H using the G2M(RCC) approach, a modified Gaussian-2 model extrapolating the RCCSD(T)/6-311 + G(3df,2p) level of theory. Where applicable, CBS-QCI/APNO calculations were performed. The enthalpy of formation ΔHf0(298K) of cis-HOOO (2A″) was determined to be 6.1 kcal/mol using the CBS-QCI/APNO model. The HO-OO bond dissociation energy was calculated using the G2M(RCC) formalism to be +1.31 kcal/mol for 0K which is very close to the result of +1.15 kcal/mol using the CBS-QCI/APNO model. The CH3O-OO and C2H5O-OO bond energies were calculated to be −0.87 (G2M(RCC)) and −0.5 kcal/mol (G2M(RCC,MP2)).