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Spectroscopy and Photochemistry of Aromatic and Cyclic beta -Diketones

机译：芳香族和环状β-二酮的光谱学和光化学

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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 77 exp 0 K 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 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 77 exp 0 K. Some of the observed luminescences are attributed to the dissociated enolic form. 43 figures, 16 tables. (ERA citation 07:061864)

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