Microwave spectrum, conformation, barrier to internal rotation and dipole moment of pyruvic acid

Microwave spectra of CH 3COCOOH and CH 3COCOOD are reported. The preferred conformation of the molecule is demonstrated to possess a planar HCCOCOOH skeleton with two out-of-plane hydrogens. The two carbonyl groups are trans to each other and a weak five-membered hydrogen bond is formed between the...

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Bibliographic Details
Published in:Journal of molecular structure 1974-01, Vol.20 (2), p.257-267
Main Authors: Marstokk, K.-M., Møllendal, Harald
Format: Article
Language:English
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Summary:Microwave spectra of CH 3COCOOH and CH 3COCOOD are reported. The preferred conformation of the molecule is demonstrated to possess a planar HCCOCOOH skeleton with two out-of-plane hydrogens. The two carbonyl groups are trans to each other and a weak five-membered hydrogen bond is formed between the carboxyl group hydrogen atom and the carbonyl group oxygen atom. The methyl group conformation is discussed. A computer programme based on “the principal axis method” is described in some detail and the results of a least squares analysis of the observed spectra are outlined. The barrier to internal rotation was determined as V 3 = 965±40 cal mol −1 for both isotopic species. Stark effect measurements yielded μ a = 2.27±0.02 D, μ b = 0.35±0.02 D and μ tot = 2.30±0.03 D for the dipole moment and its components along the principal axes.
ISSN:0022-2860
1872-8014
DOI:10.1016/0022-2860(74)85094-5