Electronic spectra of H and OH adducts to benzene

Hydrogen and hydroxyl radical adducts to benzene are intermediates in its oxidative degradation. Their presence can be detected by a UV absorption near 310 nm. However, ab initio calculations of the 1,4-cyclohexadienyl structure for the ground state in both adducts suggests the likelihood of an additional absorption in the visible. Calculations indicate that the observed absorption is to the second excited state. Absorption to the first excited state is calculated to have a much smaller oscillator strength than the observed second excited state. The predicted spectra of the H and OH adducts are similar.