Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1270080811pmid: N/A

doi: 10.1002/mrc.1270080801pmid: N/A

Hagaman, Edward W.

doi: 10.1002/mrc.1270080802pmid: N/A

13C n.m.r. single‐frequency off‐resonance decoupled (sford) CH multiplet resonance which deviate from normally assumed, isolated AnX spin descriptions have been characterized. Methylene carbons whose appended protons are nonequivalent generate doublets of doublets in sford spectra provided the proton chemical shift difference exceeds c. 3 × (Jgem). The isolated moiety–CHH′–closely approximates an AMX spin system. The strong chemical shift nonequivalence of geminal aminomethylene protons induced by the nitrogen lone pair in some N‐substituted piperidine derivatives is accompanied by preferential modification of the one‐bond CH coupling constants of the α‐amino protons. In N‐methyl‐4‐t‐butylpiperidine the natural coupling constants were shown to differ by 6–12 Hz. The 13C sford resonances of protonated carbons display varying degrees of second‐order coupling depending on the coupling strength of a carbon's appended protons with a strongly coupled spin set, the number of nuclei in the spin set, and the magnitude of the carbon's residual one‐bond splitting. Qualitative criteria that allow the classification of degrees of second‐order coupling have been established and utilized in signal assignment and structure analysis.

Revel, Monique; Roussel, Jean; Navech, Jacques; Mathis, Ferdinand

doi: 10.1002/mrc.1270080803pmid: N/A

Les spectres de RMN du proton d'une série de dérivés des méthyl‐4 (ou phényl‐4) dioxa‐ et dithiaphospholanes‐1,3,2 sont analysés. La configuration de ces composés est précisée. L'angle de torsion de la liaison C4C5 est calculée et la conformation du cycle à l'état dissous est proposée.

Roca, Claude; Kraemer, Raymond; Majoral, Jean‐Pierre; Navech, Jacques; Brault, Jean François; Savignac, Philippe

doi: 10.1002/mrc.1270080804pmid: N/A

Les spectres de RMN du proton de quelques nouveaux oxazaphosphorinanes‐1,3,2 sont analysés. La stéréochimie et la conformation du cycle sont précisées. La valeur de l'enthalpie libre conformationnelle et de l'angle de torsion des liaisons C‐4C‐5 et C‐5C‐6 est calculée pour quelques uns de ces oxazaphosphorinanes‐1,3,2.

Dorman, Douglas E.; Paschal, Jonathan W.

doi: 10.1002/mrc.1270080805pmid: N/A

The 13C n.m.r. spectra of some dimeric Catharanthus alkaloids are reported and assigned. Methods devised to aid in the assignment of resonances in complex molecules are described. The 13C n.m.r. spectra of several derivatives of vinblastine are discussed.

Marshall, James L.; Seiwell, Ruth

doi: 10.1002/mrc.1270080806pmid: N/A

A tabulation has been compiled for twenty 13CH coupling constants of various carboxylic acids and includes 2J(C,H), 3J(C,H) and 4J(C,H) values of olefins (both cis and trans); 3J(C,H), 4J(C,H) and 5J(C,H) values of aromatics; 3J(C,H) and 4J(C,H) values of acetylenes; and 2J(C,H) and 3J(C,H) values of rigid aliphatics. This tabulation has been completed in the present study by the spin‐tickling proton n.m.r. study of 13C‐carboxyl‐endo‐1,2,3,4,7,7‐hexachloronorbornene‐5‐carboxylic acid, which has established that the 2J(C,H) value is negative and the 3J(C,H) values (both cis and trans) are positive in this system. A plot of these twenty J(C,H) values vs the corresponding J(H,H) values of geometrically equivalent model systems (where there is a proton in place of a carboxyl group) gives a correlation coefficient of 0·975 (with a slope of 0·62), indicating that carbon–proton and proton–proton couplings operate by similar mechanisms throughout this broad series of structural types.

Couperus, P. A.; Clague, A. D. H.; van Dongen, J. P. C. M.

doi: 10.1002/mrc.1270080807pmid: N/A

An extensive carbon‐13 nuclear magnetic resonance study of selected model olefins dissolved in deuteriochloroform has been carried out under standardized conditions. Assignments of the chemical shifts have been made. The influence of the nature of the solvent and the effect of changing the concentration of the solute have been investigated. The results are intended to provide a practical aid for the analysis of olefinic materials.

Siemion, Ignacy Z.

doi: 10.1002/mrc.1270080808pmid: N/A

The amounts of boat (A) and planar (B) forms for the equilibrium state in D2O and CD3OD/d6‐DMSO (1:1) were calculated for seven proline‐containing cyclic dipeptides from their 13C n.m.r. spectra. For c‐Pro‐Val the thermodynamic functions for the conversion between the boat and planar forms have been obtained from measurements of equilibrium constants at different temperatures.

Vandenbosch, J. C.; Zimmermann, D.; Reisse, J.

doi: 10.1002/mrc.1270080809pmid: N/A

The intermolecular Overhauser effect {1H}13C is studied on two binary systems chloroform/carbon disulfide and chloroform/acetone. Some comments are made concerning the use of these measurements for the study of intermolecular interactions in solution.