Quantum-chemical calculations of the structure of trioxyl radicals

Density functional theory and ab initio methods were used to consider the structure and main channels of consumption of HOOO and CH3OOO. A correct description of these systems required the simultaneous inclusion of the dynamic and static components of electron correlation energy. The MRMP2( 19 × 11)/aug-cc-pVTZ approximation was used to find that both cis and trans structures of trioxyl radicals were stable (the cis isomer was more favorable energetically), whereas the gauche structure corresponded to the top of a potential barrier. The energy barrier to rotations about the RO-OO bond was found to be 10.9–19.7 kJ/mol for HOOO and 18.7–39.1 kJ/mol for CH3OOO. The main channels of the consumption of ROOO radicals were decomposition to the RO radical and molecular oxygen or to the hydroperoxyl radical and a carbonyl compound (the latter reaction occurred if there were α-C-H bonds). The MRMP2(19 × 11)/aug-cc-pVTZ//PBE0/aug-cc-pVTZ method was used to estimate the total energy of dissociation of the O-O bond in HOOO and CH3OOO (20 kJ/mol) and the height of the energy barrier to the isomerization of CH3OOO (8.0 kJ/mol).