title: Combined IR/NIR and density functional theory calculations analysis of the solvent effects on frequencies and intensities of the fundamental and overtones of the C ═ O stretching vibrations of acetone and 2-hexanone.
abstract: Vibrational overtone studies primarily focus on X-H stretching overtone transitions, where X is an atom like C, O, N, or S. In contrast, the studies on the C ═ O stretching overtones are very scattered. To advance the research in this field, we measured the fundamental, first, and second overtones of the C ═ O stretching vibration of acetone and 2-hexanone in n-hexane, CCl4, and CHCl3, as well as in the vapor phase using FT-IR/FT-NIR spectroscopy. Density functional theory (DFT) calculations have also been performed to help the assignment of the C ═ O stretching bands and to guide interpretation of the experimental results. It was found that the wavenumbers, absorption intensities, and oscillator strengths of the C ═ O stretching bands show marked solvent dependence. In the fundamental and the first overtone regions, the intensities of the C ═ O stretching vibration were found to be pronouncedly more intense than those of the C-H stretching vibration. In the second overtone region, the intensities of the C-H stretching vibration are comparable to those of the C ═ O stretching vibration. The theoretical and observed decrease in integrated intensity upon going from the fundamental to the first overtone of the C ═ O stretching vibration is around 50, which is significantly larger than those of the O-H, C-H, and S-H stretching vibration. Both the calculated and experimental results suggest that excessive weakness in the C ═ O stretching overtone was shown to be a result of both a low anharmonicity and a substantial reduction in the oscillator strength. These results provide new insight into our understanding of the C ═ O stretching vibration.
authors.affiliation: School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, China.
authors.forename: Yujing
authors.initials: Y
authors.lastname: Chen
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Morisawa
authors.forename: Yoshisuke
authors.initials: Y
authors.lastname: Futami
authors.forename: Mirosław A
authors.initials: MA
authors.lastname: Czarnecki
authors.forename: Hai-Shui
authors.initials: HS
authors.lastname: Wang
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Ozaki
mesh_terms: D000096:Acetone / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D008742:Methyl n-Butyl Ketone / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014732:Vibration
chemical_list: D012997:Solvents; D000096:Acetone; D008742:Methyl n-Butyl Ketone; D002244:Carbon; D010100:Oxygen