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

Abstract

Ultraviolet resonance Raman (UVRR) spectra excited at 245 and 325 nm are reported for 1,4-benzoquinone and its 18O 2 and d 4 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 18O 2 isotopic frequency shift than the former, are reassigned to ν 2 (in-phase CO/CC stretches) and ν 3 (out-of-phase CO/CC stretches), respectively, on the basis of the observed 18O 2 and d 4 isotope frequency shifts and unscaled ab initio vibrational analyses with the MP2 method using an extended basis set.