A reinvestigation of the ν2 and ν3 modes of 1,4-benzoquinone on the basis of a quantum mechanical harmonic force field

• Published in: Chemical physics letters 1997-11, Vol.280 (1), p.91-94
• Main Author: Nonella, Marco
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(97)01066-X

The assignment of the modes ν 2 and ν 3 of 1,4-benzoquinone has been the topic of many studies. In a recent investigation Zhao, Imahori, Zhan, Mizutani, Sakata and Kitagawa reported an assignment which differs from the previous assignment of Becker. With small variations of selected force constants of a quantum chemically derived force field, we can achieve good agreement with Becker's data for the ν 2 and ν 3 modes of unlabeled 1,4-benzoquinone and its isotopomers 18O 2 and d 4. In contrast, no satisfactory agreement can be found with the frequencies reported by Zhao et al. A systematic investigation of 18O 2 and d 4 shifts suggests that isotopic shifts of ν 3 assigned by Zhao et al. are most likely incompatible with the theoretical force field.