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Molecular Structure and Internal Dynamics of 2'-Hydroxyacetophenone by Free-Jet Absorption Millimeter-Wave
Salvatore Boi1, Sonia Melandri1,2,3, Luca Evangelisti2,3,4
1Department of Chemistry G. Ciamician, University of Bologna, 40126 Bologna, Italy.
Molecules (Basel, Switzerland)
|January 8, 2025
Summary
The rotational spectrum of 2'-hydroxyacetophenone was recorded for the first time, revealing its most stable conformer. This study determined the methyl group
Area of Science:
- Molecular spectroscopy
- Quantum chemistry
- Physical organic chemistry
Background:
- 2'-hydroxyacetophenone is an organic compound with potential applications in various chemical processes.
- Understanding its molecular structure and dynamics is crucial for predicting its reactivity and properties.
Purpose of the Study:
- To record and assign the rotational spectrum of 2 '-hydroxyacetophenone for the first time.
- To determine the molecular structure and conformational stability of the most stable conformer.
- To investigate the internal rotation of the methyl group and its associated energy barrier.
Main Methods:
- Stark-modulated free-jet absorption millimeter-wave (FJ-AMMW) spectroscopy was employed to record the rotational spectrum.
- The spectral data were analyzed to determine rotational constants and identify the most stable conformer.
- Quantum chemical calculations (B3LYP-D3(BJ)/Def2-TZVP and MP2/aug-cc-pVTZ) were performed for comparison.
Main Results:
- The rotational spectrum was successfully recorded and assigned for the most stable conformer of 2 '-hydroxyacetophenone.
- Rotational constants (A, B, C) were determined, indicating a Cs symmetry with a strong intramolecular hydrogen bond.
- A potential barrier (V3) of 565.1(5) cm-1 for the methyl group's internal rotation was determined, with estimated tunneling splittings of 51 MHz.
Conclusions:
- The study provides the first high-resolution rotational spectrum and structural determination of 2 '-hydroxyacetophenone.
- The presence of a strong intramolecular hydrogen bond in the most stable conformer was confirmed.
- Computational methods showed varying accuracy in predicting the methyl group's rotational barrier height.
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