This work is concerned with the investigation by electron spin resonance (e.s.r.) of organic free radicals in solution. All the radicals investigated contained oxygen functional groups and were all produced by one-electron oxidation or reduction. The thesis is presented in five Parts, Part 1 being an introductory Part in which the basic principles of e.s.r. are discussed and the apparatus described. A flow apparatus, which is able to detect transient free radicals with lifetimes of ca. 10<sup>-2</sup> sec., is described; this apparatus has been used to detect many of the radicals investigated in this work. Part 2 describes the oxidation of monohydric phenols, ArOH, by a one-electron oxidising agent, ceric sulphate, to produce phenoxy radicals, ArO<sup>•</sup>. The e.s.r. spectrum of the unsubstituted phenoxy radical itself, PhO<sup>•</sup> , has been recorded, together with the spectra of some 50 other substituted phenoxy radicals. In a large majority of cases the spectra have been analysed successfully and coupling constants, arising from interaction of the free electron with both the ring protons and the α-protons of alkyl-substituents, have been obtained. It was found that the total spin density associated with the ring carbon atoms C<sub>2</sub>-C<sub>6</sub> is ca 0.80, thus indicating that ca. 20% of the spin density is associated with the phenoxy oxygen atom and the carbon atom to which it is attached. Qualitative trends in the coupling constants of the ring protons were observed and discussed; for example, it was found that the algebraic sum of the ortho and meta coupling constants was approximately constant with different substituents at the para position. This would suggest that the only effect of the para substituents is to cause a redistribution of the spin density between the ortho and meta positions. Part 3 describes the oxidation, both with potassium ferricyanide in alkaline solution and with ceric sulphate in acid solution, of resorcinol and substituted resoroinols, using the flow apparatus in each case. Different spectra were obtained from the oxidation of the same resorcinol under the different conditions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:473995 |
| Date | January 1964 |
| Creators | Stone, T. J. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:50103272-ff6b-44cc-a350-6de17e0b17ee |
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