Acyclic and cyclic forms of the radicals HO4⋅ CH3O4⋅ and C2H5O4·: ab initio quantum chemical calculations

Acyclic and cyclic structures and total energies of radicals HO4⋅ CH3O4⋅ and C2H5O4· were calculated by ab initio quantum chemical methods. Depending on the computational method and basis sets used, the cyclic conformer of the HO4· radical is 4.8 to 7.3 kJ mol-1 more stable than the acyclic one. For the first two representatives of the homologous series of alkyl tetraoxyl radicals, CH3O4· and C2H5O4, MP2/6-311++G** calculations predict insignificant energy differences (1.2 kJ mol-1) between six-membered cyclic and acyclic conformers. Apparently, these radicals can exist in both forms.