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I. Efforts Toward the Synthesis of Aliphatic Iodonium Salts. II. Fluorine-19 Nuclear Magnetic Resonance Spectroscopy of Cyclic and Bicyclic Systems

Citation

Dence, Joseph Bernard (1969) I. Efforts Toward the Synthesis of Aliphatic Iodonium Salts. II. Fluorine-19 Nuclear Magnetic Resonance Spectroscopy of Cyclic and Bicyclic Systems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2qcy-bg06. https://resolver.caltech.edu/CaltechTHESIS:02012016-113113097

Abstract

The synthesis of iodonium salts of the general formula [C6H5IR]+X-, where R is an alkyl group and x- is a stabilizing anion, was attempted. For the choice of R three groups were selected, whose derivatives are known to be sluggish in SN1 and SN2 substitutions: cyclopropyl, 7, 7 -dimethyl-1-norbornyl, and 9 -triptycyl. The synthetic routes followed along classical lines which have been exploited in recent years by Beringer and students. Ultimately, the object of the present study was to study the reactions of the above salts with nucleophiles. In none of the three cases, however, was it possible to isolate a stable salt. A thermodynamic argument suggests that this must be due to kinetic instability rather than thermodynamic instability. Only iodocyclopropane and 1-iodoapocamphane formed isolable iododichlorides.

Several methylated 2, 2-difluoronorbornanes were prepared with the intent of correlating fluorine -19 chemical shifts with geometric features in a rigid system. The effect of a methyl group on the shielding of a β -fluorine is dependent upon the dihedral angle; the maximum effect (an upfield shift of the resonance) occurs at 0° and 180°, whereas almost no effect is felt at a dihedral angle of 120°. The effect of a methyl group on a γ -fluorine is to strongly shift the resonance downfield when fluorine and methyl group are in a 1, 3 - diaxial-like relationship. Molecular orbital calculations of fluorine shielding in a variety of molecules were carried out using the formalism developed by Pople; the results are, at best, in modest agreement with experiment.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Roberts, John D.
Thesis Committee:
  • Unknown, Unknown
Defense Date:21 August 1968
Record Number:CaltechTHESIS:02012016-113113097
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:02012016-113113097
DOI:10.7907/2qcy-bg06
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9556
Collection:CaltechTHESIS
Deposited By:INVALID USER
Deposited On:02 Feb 2016 18:04
Last Modified:24 Jun 2021 01:40

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