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A Thermodynamic Study of Infrared Spectroscopy of the Association of 2-Quinolone, Some Carboxylic Acids, and the Corresponding 2- Quinolone-acid Mixed Dimers.

Petersen JC
J Phys Chem 1971 75(8):1129-1135
Self-association of 2-quinolone in carbon tetrachloride was studied by infrared spectroscopy, using the absorption bands in the amide nh and carbonyl stretching regions. 2-Quinolone forms a cyclic dimer from which the enthalpy (ah deg., Kcal/mol), free energy (ag deg. 22, Kcal/mol), and entropy (as deg., Eu) of association are -8.69, - 6.11, and -8.76, Respectively. Dimer formation is via a carbonyl- hydrogen bond, although evidence exists for the formation of a small amount of dimer via a -hydrogen bond. 2-Quinolone was also found to form cyclic mixed dimers with carboxylic acids. Mixed dimers of 2-quinolone with benzoic, cyclohexanecarboxylic, and 4- cyclohexylbutanoic acids gave ah deg. Values of -12.2, -10.3, and - 10.4; Ag deg.22 Values of -6.36, -5.94, and -5.78; and as deg. Values of -19.9, -14.8, and -15.6, Respectively. Thermodynamic data on the acid dimers and spectral data on the different systems studied are also reported. The 2-quinolone-carboxylic acid interaction is of importance because of the simultaneous occurrence of quinolones and carboxylic acids in many biologically derived materials.
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OP 83-71
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J. Phys. Chem, V. 75, No. 8, 1971, PP. 1129-1135
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