Contrast effect of hydrogen bonding on the acceptor and donor OH groups of intramolecularly hydrogen-bonded OH pairs in diols

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2005-11, Vol.62 (1), p.97-104
• Main Authors: Iwamoto, Reikichi, Matsuda, Toshihiko, Kusanagi, Hiroshi
• Format: Article
• Language: English
• Subjects: Diols; Hydrogen Bonding; Hydroxides - chemistry; Infrared spectroscopy; Molecular Structure; Near-infrared spectroscopy; Quantum Theory; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2004.12.007

We studied the influence of hydrogen bonding on the fundamental and overtone bands of the OH-stretching vibration of each OH group in the intramolecularly hydrogen-bonded OH(I)::OH(II) pair in 1,2-, 1,3- and 1,4-diols. The hydrogen bonding between the two OH groups significantly increases in strength from the five-membered ring of a 1,2-diol to the seven-membered ring of a 1,4-diol. Although the hydrogen bonding does not affect the vibrational property of the OH(II) (or acceptor), it significantly influences the OH(I) (or donor). As the hydrogen bonding becomes stronger from a 1,2- to a 1,4-diol, the fundamental band of the OH-stretching shifts downwards by from about 50 to 140 cm −1, and the overtone band markedly decreases in intensity, although the effect on the intensity and bandwidth of the fundamental band varies among 1,2-, 1,3- and 1,4-diols. The quantum-mechanically calculated normal frequencies of the acceptor and donor OH groups in the hydrogen-bonded ring are in good agreement with the observed frequencies. The calculated interatomic distance between the O of an acceptor OH and the H of a donor OH is the shortest for a 1,4-diol, which is consistent with the largest frequency shift caused by the hydrogen bonding.