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Communication: Where does the first water molecule go in imidazole?
Julia Zischang1, Juhyon J Lee, Martin A Suhm
1Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
The Journal of Chemical Physics
|August 17, 2011
Summary
Water acts as a hydrogen bond donor to imidazole, not an acceptor. This study used supersonic jet FTIR spectroscopy and isotopic substitution to resolve ambiguities from prior experiments and calculations.
Area of Science:
- Physical Chemistry
- Molecular Spectroscopy
- Hydrogen Bonding
Background:
- Determining the precise role of water in hydrogen bonding interactions with heterocyclic compounds like imidazole is challenging.
- Previous experimental and computational methods yielded ambiguous results regarding water's hydrogen bonding orientation with imidazole.
Purpose of the Study:
- To unambiguously determine whether water acts as a hydrogen bond donor (O-H···N) or acceptor (N-H···O) in its complex with imidazole.
- To resolve long-standing ambiguities in the study of water-imidazole interactions.
Main Methods:
- Utilized supersonic jet Fourier Transform Infrared (FTIR) spectroscopy.
- Employed oxygen-18 ((18)O) isotopic substitution to differentiate hydrogen bonding roles.
- Supported findings with higher-level quantum chemical calculations and studies on methanol complexes.
Main Results:
- Conclusively demonstrated that water preferentially acts as an O-H···N hydrogen bond donor to imidazole.
- Ruled out the N-H···O hydrogen bond acceptor role for water in this complex.
- Results were consistent across multiple experimental and computational approaches.
Conclusions:
- Water's interaction with imidazole is definitively characterized as hydrogen bond donation.
- This study provides a clear molecular-level understanding of water-imidazole hydrogen bonding.
- The findings clarify a complex interaction previously debated in chemical research.
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