N.M.R. Investigations of Bicyclic Compounds and Ylides

Murray, Andrew Malcolm (1976) N.M.R. Investigations of Bicyclic Compounds and Ylides. PhD thesis, University of Glasgow.

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Abstract

13C Chemical shifts of 4-substituted tricyclenes, 4-substituted camphors, 1-substituted camphenes and the 15N chemical shifts of diazoalkanes are discussed in terms of correlations with Hammett-type parameters, C.N.D.O./2 calculations, steric effects and with the chemical shifts of similar compounds. The beta-chemical shifts of the camphenes, camphors and tricyclenes are rationalised by estimating distances of the beta-carbon to substituent atoms and relating the shifts to the magnitude and direction of the expected 1, 4 and 1, 5 effects. The contribution of field effects to the total chemical shift of carbons is considered, and the correlation of C(2) chemical shifts in camphenes and camphors with linear free energy parameter, sigmaT is taken as indicating a significant contribution from field effects at these carbons. 15N chemical shifts of diazoalkanes appear to be affected by changes in both the mean excitation energy, AE, and the electron density. Dual Substituent Parameter (D.S.P.) correlations of the S.C.S. and electron densities of meta and para-substituted, 1',1',1'-trimethylammonio 2'-benzimides, 1',1'-dimethyl 2'-benzoylhydrazides and acetophenones provide a means of examining electronic transmission in these series. In addition, it is shown that inclusion of a contribution from bond order to the effective electron density accounts for the shift changes observed at the carbonyl carbon. Extended or reduced conjugation between the benzene ring and a O = C - N - N(Me3) group does not appear to alter the mechanism of electronic transmission to the carbonyl carbon, as monitored by the 13C chemical shifts of para-substituted 1',1',1'-trimethylammonio 2'-cinnamimides and 2'-phenylacetimides, although in the latter case electronic transmission to the carbonyl carbon is severely reduced. Long range proton-proton couplings between H3exo and H5 exo in 4-substituted camphors and their nitrimines are shown to correlate with sigmaI and the nitrimine shows diminished values with respect to the parent ketones. From this it is tentatively suggested that the carbon-nitrogen double bond in nitrimines is less polar than the carbonyl bond.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1976
Depositing User: Enlighten Team
Unique ID: glathesis:1976-78715
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:59
Last Modified: 30 Jan 2020 14:59
URI: http://theses.gla.ac.uk/id/eprint/78715

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