## LSU Historical Dissertations and Theses

1990

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Chemistry

Robert V. Nauman

#### Abstract

In this work the ultraviolet (UV) absorption and the $\sp1$H and $\sp{19}$F nuclear magnetic resonance spectra of $\beta$-diketones were studied. Potential energy curves for various geometries of the compounds were calculated by means of the MNDO method. The compounds included in the work were acetylacetone, trifluoro- and hexafluoro-acetylacetone, benzoylacetone, dibenzoylmethane, benzoyltrifluoroacetone, 3-methyl-acetylacetone, 1,3-cyclopentanedione, 1,3-cyclohexanedione, 2-methyl-1,3-cyclohexanedione and 2-acetyl-cyclohexanone. The spectra of the neutral enolic, anionic and cationic species were investigated. In addition, the spectra of the reaction products of the compounds with boron trifluoride which were formed in polar and nonpolar solvents were studied. The results were interpreted in terms of the geometries of the molecules. It is hypothesized that the presence of an electron withdrawing substituent on the opposite side of the conjugated system from an electron donating substituent leads to a more nearly planar molecule. The spectra of the anionic species and the potential energy calculations indicate that the predominant geometries of the aliphatic anions are nonplanar and that there are multiple geometries of the anion of hexafluoroacetylacetone. The UV absorption spectra indicate that the phenyl rings of the aromatic diketones rotate out of the molecular plane upon anion formation and rotate to a more nearly planar conformation upon cation formation. The spectra indicate that the reaction of boron trifluoride with the fluorinated diketones results in formation of two types of nonchelated monodentate BF$\sb3$ adducts that are dependent upon the solvent polarity.

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