Solvent effects of 1,4-benzoquinone and its anion radicals probed by resonance Raman and absorption spectra and their correlation with redox potentials
✍ Scribed by Xiaojie Zhao; Teizo Kitagawa
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 320 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
Resonance Raman (RR) and absorption spectra and cyclic voltammograms were measured for 1,4-benzoquinone (BQ) and its anion radical in various solvents. The absorption maxima of around 440 and 320 nm (BQ-~) B Qẽxhibit a good linear correlation both with acceptor numbers (AN) of solvents and the standard reduction potentials of BQ. The wavenumbers of (WilsonÏs notation, CxC stretch) and (C-H in-plane deformation) of BQ show m 8a m 9a linear correlations with the polarizabilities and dielectric constants of solvents, respectively. The and (CxO m 8a m 7a stretch) wavenumbers of can be linearly correlated with solvent AN. In addition, the standard reduction BQ-p otentials of BQ also show good linear correlations with both solvent AN and wavenumbers of of These m 8a BQ-~. results cannot be interpreted by simple hydrogen bonding interactions of carbonyl oxygen with solvent but rather suggest that the p-electrons of and BQ serve as an H-bond acceptor, forming novel H-bonds with the solvent. BQ-T he magnitude of the novel H-bond interaction is estimated to be ca. 7 and ca. 3.5 kcal mol-1 or less for and BQ-B Q in water, respectively.