Date of Award

1982

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

(beta)-Diketones exist in a tautomeric equilibrium between the enol and the keto forms. The enol form is the most stable because of the formation of an intramolecular hydrogen bond. (beta)-Diketones in solution at 77K exhibit changes in their absorption and phosphorescence spectra upon irradiation with a powerful UV visible source. The changes observed in the molecule result from rupture of the intramolecular hydrogen bond. Once the hydrogen bond has been broken a distribution of conformers of the enol is possible. The formation of a negative ion can also result from the irradiation and a distribution of conformers of the negative ion is also possible. CNDO/S-2 calculations on aromatic (beta)-diketones have been done in order to help understand the spectroscopy of these compounds. Cyclic (beta)-diketones have also been investigated. The form which predominates is dependent upon the size of the ring (strain). The formation of an intramolecular hydrogen bond in some cyclic (beta)-diketones is not possible. The absorption spectra of these diketones in alcoholic, hydrocarbon, acid and basic solvent have been investigated. Two phosphorescences from these compounds are observed when they are in solution at 77K. Some of the observed luminescences are attributed to the dissociated enolic form.

Pages

204

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