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Title: An e.s.r. study of some nitrogen substituted free radicals
Author: Clay, John D. R.
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1982
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E.s.r. spectra were obtained of as many amino-1,4- and amino-1,2-semiquinones as possible. This was achieved by means of catalytic hydrogenation of their respective nitro-1,4- and nitro-1,2-dihydroxybenzene precursors in ethanolic solution and subsequent radical generation under standard autoxidative conditions. Assignment of coupling constants in the symmetrical species is obvious. The assignments in the mono-aminosemiquinones are made by a simple graphical procedure and in the asymmetric diamino- and triaminosemiquinones assignments are made by comparison with the corresponding dimethoxy- and tri-methoxysemiquinones. It is observed that the amino-proton coupling constants are substantially smaller than those of the attached nitrogens and this is interpreted in terms of out-of-plane movement by the amino-group. E.s.r. spectra of a wide variety of nitrogen-containing heterocyclic semiquinones were also obtained. Assignments of coupling constants are made by comparison with similar systems and this simple approach is justified by a molecular orbital approach and on grounds of symmetry. It is also found that nitrogen has little effect on the spin density distribution in these heterocycles in comparison to their non-heterocyclic analogues. McLachlan S.C.F. calculations were performed for all the radicals in this investigation and calculated coupling constants were, in general, in reasonable agreement with experimental.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical Chemistry