Conformational analysis of 2-aryl-3-methylpropyl derivatives by nuclear magnetic resonance spectroscopy: The photochemistry of some unsaturated ketones

Date
1970
Authors
Carlson, David Arthur
Contributor
Advisor
Department
Instructor
Depositor
Speaker
Researcher
Consultant
Interviewer
Annotator
Journal Title
Journal ISSN
Volume Title
Publisher
[Honolulu]
Volume
Number/Issue
Starting Page
Ending Page
Alternative Title
Abstract
Conformer populations were estimated by nmr in a series of compounds consisting of a 3-carbon chain containing an asymmetric carbon and different l- and 3-substituents. The energy differences between conformers were estimated from chemical shift differences between geminal methylene protons and vicinal coupling constants. Some mercury adducts of methallylarenes were prepared: they were 3-aryl-2-methyl-2-methoxypropylmercuric halides. Chemical shift differences (Δʋ) of up to 50 Hz were observed, which indicated considerable nonequivalence between methylene groups and suggested some intramolecular interaction. A derivative, 2-methoxy-2-methyl-3phenylbromopropane, showed no nonequivalence. Nonorganic compounds prepared for nmr spectra included the sodium salt of 3-(anisyl)-2-methylpropanol, and 2-methyl-3-phenylpropyllithium. A Grignard reagent, 2-methyl-3-phenylpropylmagnesium bromide, was formed in dimethyl ether and converted to the corresponding alkylborane, alkylcadmium chloride, alkyldichlorophosphine and alkylmercuric chloride. The nmr spectra of these compounds were recorded and some usable spectra were obtained. Increases in Δʋ were seen only for the alkylmercuric chloride. Organic compounds prepared included 2-methyl-3-phenylpropyl bromide and the corresponding iodide, nitrile, acid, amide, amine and nitro compounds. The nitro compound and the amide showed nonequivalence at the methylene a to the entire group. The α-methylene and benzylic groups of 2-methyl-3-phenylpropyl amine showed considerable nonequivalence. In addition, a series of four primary 2-methyl-3-ary1propano1s was prepared and their nmr spectra examined at different temperatures, concentrations and solvents from 100° to -80°. Fairly large effects on chemical shift differences and coupling constants were observed over the temperature range studied on the gemina1 benzylic and amethylene protons, while a derivative, 2-methyl-3-pheny1-1-propy1 methyl ether, showed smaller changes over the same temperature range. Four methods were used to estimate Free Energy Differences (-ΔE) between the most populous conformers of the organic compounds. Two calculations based on Karp1us-type relationships involving vicinal coupling constants gave reasonable and consistent answers to problems of conformer populations. The third was a graphical method which plotted coupling constants against estimated -ΔE. The fourth, another graphical method, plotted chemical shift differences between the benzylic hydrogens against -ΔE. All four methods gave similar results. The values obtained were small (0 to 300 ca1/mo1e) but reasonable and self-consistent. In addition, a Van't Hoff relationship was used to determine enthalpy interactions.
Description
Typescript.
Thesis (Ph. D.)--University of Hawaii, 1970.
Includes bibliographies.
2 pt. in 1 v illus., tables
Keywords
Chemistry, Organic, Nuclear magnetic resonance, Ketones, Photochemistry
Citation
Extent
Format
Geographic Location
Time Period
Related To
Theses for the degree of Doctor of Philosophy (University of Hawaii (Honolulu)). Chemistry; no. 280
Table of Contents
Rights
All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Rights Holder
Local Contexts
Email libraryada-l@lists.hawaii.edu if you need this content in ADA-compliant format.