Ultraviolet resonance Raman spectra and ab initio vibrational analyses of 1,4-benzoquinone: reassignments of the ν2 and ν3 bands

Ultraviolet resonance Raman (UVRR) spectra excited at 245 and 325 nm are reported for 1,4-benzoquinone and its 18O2 and d4 isotopomers. Depolarization ratios were determined for non-resonance Raman spectra excited at 647 and 441.6 nm and solvent effects were examined for the UVRR spectra. The UVRR bands at 1665 and 1639 cm−1, the latter of which exhibited a much larger 18O2 isotopic frequency shift than the former, are reassigned to ν2 (in-phase CO/CC stretches) and ν3 (out-of-phase CO/CC stretches), respectively, on the basis of the observed 18O2 and d4 isotope frequency shifts and unscaled ab initio vibrational analyses with the MP2 method using an extended basis set.