Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1270050701pmid: N/A

Jones, R. A. Y.

doi: 10.1002/mrc.1270050712pmid: N/A

doi: 10.1002/mrc.1270050711pmid: N/A

Abraham, R. J.; Monasterios, J. R.

doi: 10.1002/mrc.1270050702pmid: N/A

The complete AA′BB′X analysis of the 1H and 19F NMR spectrum of CH2F.CH2OCO·CCl3 (1) as a neat liquid and in various solvents is given and considered in detail. The differentiation of the two conjugate solutions is obtained both from the X spectrum and by analysis at two field strengths. The coupling constants obtained show that the compound exists almost entirely in the gauche rotamer in all solvents.

Voelter, Wolfgang; Breitmaier, Eberhard

doi: 10.1002/mrc.1270050703pmid: N/A

Der Einfluß des anomer verknüpften Adeninrestes auf die 13C‐chemischen Verschiebungen von Aldopyranosen wird für eine Reihe von Pyranosyladeninen diskutiert. Anomere Kohlenstoffatome mit axial verknüpftem Heterocyclus absorbieren stets bei höherem Feld als entsprechende mit äquatorial orientiertem Adenin. Diese Regel kann zur Bestimmung der Pyranosekonformation verwendet werden. Wird die anomere Hydroxylgruppe durch einen Adeninrest ersetzt, dann verschiebt sich die Resonanz von C‐5 des Pyranoserestes nach tieferem Feld.

Ewing, D. F.

doi: 10.1002/mrc.1270050704pmid: N/A

The change in chemical shift with solute concentration (dilution effect) has been determined for a model compound—1‐iodonaphthalene—in cyclohexane and carbon tetrachloride. The data and assignments for this compound differ from those of previous work. A simple model is proposed to account for dilution shifts in aromatic solutes and their sensitivity to proton position. Solvent shifts are also discussed.

Brink, Maud; Larsson, Erik

doi: 10.1002/mrc.1270050705pmid: N/A

Die chemischen Verschiebungen der Methoxyprotonen in etwa 60 verschiedenen Carbonsäuremethylestern wurden in CCl4 und C6D6 bestimmt. Ihre Abhängigkeit von Konstitution und Lösungsmittel wird diskutiert. Ferner wird gezeigt, dass sie für ein bestimmtes Molekül als eine Summe von Parametern ausgedrückt werden, die für die Substituenten charakteristisch sind.

Haddon, Virginia R.; Jackman, L. M.

doi: 10.1002/mrc.1270050706pmid: N/A

Accurate parameters for the two title compounds have been obtained by the aid of a spectral subtraction technique in conjunction with analysis by LAOCN3. It is observed that J1eq, 6eq and J1ax, 2ax are abnormally large and small, respectively, and the significance of these and other coupling constants are discussed in terms of the probable geometry of tert‐butylcyclohexane. The tert‐butyl group affects the chemical shifts of the 4‐protons, indicating that tert‐butylcyclohexyl derivatives are poor models for fixed conformers of monosubstituted cyclohexanes. The deuterium isotope effects on proton chemical shifts appear to be influenced by the same factors as proton‐proton coupling constants.

Nikiforov, G. A.; Markaryan, Sh. A.; Plekhanova, L. G.; Sviridov, B. D.; Rykov, S. V.; Ershov, V. V.; Buchachenko, A. L.; Pehk, T.; Saluvere, T.; Lippmaa, E.

doi: 10.1002/mrc.1270050707pmid: N/A

Thermal decomposition of 4‐diazo‐2,6‐di‐tert‐butyl‐2, 5‐cyclohexadien‐1‐one in perhalogenated solvents has been investigated. The decomposition reaction proceeds via a carbene intermediate first to a singlet and then to an effectively triplet free encounter radical pair formed in a halogen abstraction reaction. The polarisation of the stable reaction product is determined by competing processes in the primary cage, intersystem crossing and escape from the cage.

Rudakov, E. S.; Mastikhin, V. M.; Popov, S. G.; Rudakova, R. I.

doi: 10.1002/mrc.1270050708pmid: N/A

The oxidation of dimethyl sulphide to dimethylsulphoxide with nitric acid displays CIDNP effects of protons and the phenomenon of frontal kinetics. The process is autocatalytic, with N2O4 as the catalyst and the primary oxidant of sulphide. In the presence of the inhibitor (methylmercaptan) the frontal reaction takes place: in purified samples—the usual volume reaction. The interaction of ethyl, n‐propyl and n‐butyl sulphides with NO2 is accompanied by integral polarisation of the α‐CH2‐protons. In all the cases sulphide is negatively polarised and sulphoxide positively polarised. The reaction mechanism proposed includes the formation of a radical pair during the interaction of sulphide with N2O4. Disproportionation of the radical pair leads to the formation of polarised sulphoxide and the decay results in re‐generation of sulphide. The rate of oxidation of sulphide during the volume reaction is proportional to the product polarisation.