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Hydrogen Bond Effect on the Raman Shift of the Carbonyl Stretching Mode of Various Amide Solutions
Author(s) -
Lee YingTe
Publication year - 1997
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199701)28:1<45::aid-jrs79>3.0.co;2-c
Subject(s) - raman spectroscopy , chemistry , amide , hydrogen bond , formamide , hydrogen , isotropy , anisotropy , solvent , dilution , molecular vibration , solvent effects , computational chemistry , crystallography , molecule , organic chemistry , thermodynamics , physics , optics , quantum mechanics
The Raman spectra of the C = O stretching mode of formamide, N ‐methylformamide and N , N ‐dimethylformamide mixed with various solvents were systematically studied as a function of concentration. It was found that the hydrogen bond effect plays an important role in reducing the carbonyl stretching wavenumbers for both isotropic and anisotropic vibrational modes. By interpreting the results of Raman shifts through the dilution effect and hydrogen bond‐forming and ‐breaking effects, the relative strengths of various amide–amide and amide–solvent hydrogen bonds were determined. The results also indicated that the anisotropic vibrational wavenumbers are more sensitive to the hydrogen bond effect than to the dilution effect. Moreover, it was found that stronger hydrogen bond formation will decrease the non‐coincidence values of the C = O stretching mode, as has been suggested elsewhere. Both the theoretical predictions based on Logan’s model and the qualitative interpretations are discussed in analyzing the non‐coincidence values of the C = O stretching modes of different solutions. © 1997 by John Wiley & Sons, Ltd.