Investigation of Intermolecular Ketone-Alcohol Balances via FTIR Spectroscopy

by Charlotte Zimmermann
Doctoral thesis
Date of Examination:2022-08-09
Date of issue:2022-11-24
Advisor:Prof. Dr. Martin A. Suhm
Referee:Prof. Dr. Martin A. Suhm
Referee:Prof. Dr. Ricardo A. Mata
Persistent Address: http://dx.doi.org/10.53846/goediss-9585

 

 

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Abstract

English

Asymmetrically substituted carbonyl groups are predestinated to form two distinguishable hydrogen bridged complexes between the free electron pairs of the carbonyl oxygens and hydrogen bond donors like alcohols. These balances are driven mainly by London dispersion forces competing mainly against steric hindrances. This raises the question if repulsive contributions can be overcome by varying the component substituents, maximizing the respective attractive dispersion contribution. This can be studied by probing ketone-alcohol balances via FTIR spectroscopy in a supersonic jet, determining abundance ratios of the two conformational isomers formed at low temperatures, additionally allowing for experimental benchmarking of theoretically predicted relative conformational energies on a kJ/mol or even finer scale. Interestingly, anharmonicity and zero-point vibrational energy contributions largely cancel in these kinds of systems. Therefore, the relevance of London dispersion and steric hindrances as the driving forces in carbonyl balances on the respective docking side can be determined by varying ketone and solvent alkylation in small molecules. The structural and spectral data used in this work can be found online on the GRO.data side: https://data.goettingen-research-online.de/dataverse/ThesisZimmermann
Keywords: supersonic jet expansion; hydrogen bond; intermolecular interactions; chemistry; dispersion; ketone-alcohol complexes; density functional theory; molecular recognition; vibrational spectroscopy; gas phase; benchmark
 
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