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Conformation-changing aggregation in hydroxyacetone: a combined low-temperature FTIR, jet, and crystallographic study
Archna Sharma1, Igor Reva, Rui Fausto
1Department of Chemistry, University of Coimbra, Coimbra, Rua Larga 3004-535, Portugal. asharma@qui.uc.pt
Journal of the American Chemical Society
|October 4, 2011
Summary
Hydroxyacetone (HA) aggregation reveals distinct conformational changes. In gas phase, intermolecular hydrogen bonds form, while in solid state, HA adopts a new conformation with a flipped dihedral angle, confirmed by quantum chemical methods.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Crystallography
Background:
- Hydroxyacetone (HA) exhibits unique aggregation behaviors.
- Understanding molecular conformation is crucial for chemical processes.
Purpose of the Study:
- To investigate the aggregation and conformational preferences of hydroxyacetone (HA).
- To elucidate the role of hydrogen bonding in HA aggregation.
Main Methods:
- Low-temperature Fourier-transform infrared (FTIR) spectroscopy.
- Supersonic jet expansion.
- X-ray crystallography with in situ cryocrystallization.
- Quantum chemical calculations (MP2 and DFT).
Main Results:
- Gas-phase HA aggregation shows partially opened intramolecular hydrogen bonds, forming intermolecular O-H···O-H bonds.
- Crystallization induces significant conformational changes in HA, altering the HOCC dihedral angle.
- Theoretical calculations support the observed conformational changes in the crystalline phase.
Conclusions:
- Hydroxyacetone exhibits distinct aggregation pathways in gas and solid phases.
- Hydrogen bonding plays a critical role in dictating HA's aggregated structures.
- Crystallization leads to a novel HA conformation not observed in the gas phase.
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