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 MP2 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 Born-Oppenheimer surface. After inclusion of ZPE contributions, the total 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 those of B-2(2) and (2)A(1). Geometry optimization and frequency calculations were also carried out for the acetyloxyl radical at MP2/6-31G(D) levels. The total energies of the electronic states of CH3COO. were evaluated at MP2+ZPE and G2(MP2) levels. Electronic states identifiable as 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)) state more than 20 kJ/mol above, the (2)A''(B-2) ground state.