CARBOXYL FREE-RADICALS - FORMYLOXYL(HCOO-CENTER-DOT) AND ACETYLOXYL (CH3COO-CENTER-DOT) REVISITED

The structures of different electronic states of HCOO. were optimized at HF, MP2, MP4, and QCISD(T) levels with basis sets up to 6-311+G(D,P ). Zero point energy (ZPE) corrections were calculated at the HF and M P2 levels and the total energies were evaluated at various high levels of ab initio calculations. The results indicate that the B-2(2) State of formyloxyl has the lowest electronic energy on the vibrationless B orn-Oppenheimer surface. After inclusion of ZPE contributions, the tot al energies of the B-2(2) and (2)A(1) states are within an energy gap of 3 kJ/mol. The ''broken symmetry'' state, (2)A' of C-s symmetry, is predicted to be a local minimum with a total energy comparable to thos e of B-2(2) and (2)A(1). Geometry optimization and frequency calculati ons were also carried out for the acetyloxyl radical at MP2/6-31G(D) l evels. The total energies of the electronic states of CH3COO. were eva luated at MP2+ZPE and G2(MP2) levels. Electronic states identifiable a s B-2-, A(1)-, and A'-like were found. The (2)A'(A') electronic state is predicted to be less than 10 kJ/mol above, and the (2)A'(A(1)) stat e more than 20 kJ/mol above, the (2)A''(B-2) ground state.