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Dependence of amide vibrations on hydrogen bonding

Myshakina, NS and Ahmed, Z and Asher, SA (2008) Dependence of amide vibrations on hydrogen bonding. Journal of Physical Chemistry B, 112 (38). 11873 - 11877. ISSN 1520-6106

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The effect of hydrogen bonding on the amide group vibrational spectra has traditionally been rationalized by invoking a resonance model where hydrogen bonding impacts the amide functional group by stabilizing its [ -O-C=NH+] structure over the [O=C-NH] structure. However, Triggs and Valentini's UV-Raman study of solvation and hydrogen bonding effects on e-caprolactum, N,N-dimethylacetamide (DMA), and N-methylacetamide (NMA) (Triggs, N. E.; Valentini, J. J. J. Phys. Chem. 1992, 96, 6922-6931) casts doubt on the validity of this model by demonstrating that, contrary to the resonance model prediction, carbonyl hydrogen bonding does not impact the AmII′ frequency of DMA. In this study, we utilize density functional theory (DFT) calculations to examine the impact of hydrogen bonding on the C=O and N-H functional groups of NMA, which is typically used as a simple model of the peptide bond. Our calculations indicate that, as expected, the hydrogen bonding frequency dependence of the AmI vibration predominantly derives from the C=O group, whereas the hydrogen bonding frequency dependence of the AmII vibration primarily derives from N-H hydrogen bonding. In contrast, the hydrogen bonding dependence of the conformation-sensitive AmIII band derives equally from both C=O and N-H groups and thus, is equally responsive to hydrogen bonding at the C=O or N-H site. Our work shows that a clear understanding of the normal mode composition of the amide vibrations is crucial for an accurate interpretation of the hydrogen bonding dependence of amide vibrational frequencies. © 2008 American Chemical Society.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Myshakina, NS
Ahmed, Z
Asher, SAasher@pitt.eduASHER
Date: 25 September 2008
Date Type: Publication
Journal or Publication Title: Journal of Physical Chemistry B
Volume: 112
Number: 38
Page Range: 11873 - 11877
DOI or Unique Handle: 10.1021/jp8057355
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 1520-6106
MeSH Headings: Acetamides--chemistry; Amides--chemistry; Hydrogen Bonding; Models, Chemical; Vibration; Water--chemistry
Other ID: NLM NIHMS86297, NLM PMC2633779
PubMed Central ID: PMC2633779
PubMed ID: 18754632
Date Deposited: 08 Feb 2013 21:05
Last Modified: 22 Jun 2021 13:55


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