Date of Award

12-1970

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Chemistry

First Advisor

George B. Samitky

Second Advisor

H. Gastly Spencer

Third Advisor

A. E. Schwertz

Abstract

Due to the diversity within this investigation the presentation was divided into two parts. The first part discusses a new deuteration technique which affords an exact determination of chemical shifts and some coupling constants. This technique is employed in Part I I to evaluate solvent effects on the proton chemical shifts of some monosubstituted benzenes. Part I A deuteration technique which assists in the analysis of proton magnetic resonance spectra at the same time simplifying synthetic procedures has been developed. It consists of deuterating a parent hydrocarbon, in this case benzene , in several selected patterns leaving only one or two protons in the molecule at a time. Subsequently a molecule of interest is synthesized from the deuterated compound under conditions which avoid deuterium exchange. Only one such synthetic route must be devised and is applied to each specifically deuterated compound. The resulting spectra in each case are superpositions of a few simple spectra consisting of singlets and AB quartets leading to direct experimental determination of chemical shifts and important coupling constants. The deuteration technique has been applied to the analysis of the spectra of nitrobenzene and aniline and the results were compared to corresponding results obtained by a computer analysis and were found to agree very favorably. Part I I In an attempt to test the reaction field theory the proton chemical shifts of six monosubstituted benzenes (nitrobenzene: aniline , fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene) were determined at infinite dilution in different solvents, by using isotopomer mixtures of these molecules. The internal chemical shifts showed a good linear relationship with the dielectric function formulated by the reaction field theory over a wide range of dielectric constant. Although the results obtained were generally in poor quantitative agreement with the reaction field theory, indicating that the effects of other specific solute-solvent interactions are not entirely cancelled out by internal referencing technique, they appear to support the basic validity of the reaction field theory. The fluorine-ortho proton coupling constant (JH0 _ F) in fluorobenzene was also found to be approximately linearly dependent upon the function of dielectric constant formulated by the reaction field theory. A possible mechanism to account for this observation is discussed.

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