Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1270050812pmid: N/A

doi: 10.1002/mrc.1270050811pmid: N/A

doi: 10.1002/mrc.1270050801pmid: N/A

Lochmüller, C. H.; Souter, R. W.

doi: 10.1002/mrc.1270050802pmid: N/A

A number of carbonyl‐bis‐(amino acid esters) have been examined by proton and carbon‐13 nuclear magnetic resonance techniques. All but one of the compounds were synthesized with two chiral centers of like‐configuration. In one series, the diastereotopic nonequivalence of isopropyl methyl groups attached to the asymmetric centers is apparent in both the proton and the carbon spectra, and the relative magnitude of the observed nonequivalence increases slightly with increasing ‘bulk’ of the neighboring ester groups. Carbon‐13 chemical shifts are reported, and a linear correlation of Taft σ* inductive constants with ester carbonyl carbon chemical shifts and with amide proton chemical shifts (for a series in which only variation of the ester substituent occurs) is presented. In addition, the effect in terms of chemical shift differences of keeping the same ester group at the asymmetric centers while varying the other substituent group, is examined.

Bravo, R.; Durand, M.; Laurent, J.‐P.

doi: 10.1002/mrc.1270050803pmid: N/A

Les spectres de résonance magnétique nucléaire (1H, 11B, 19F et 31P) des complexes RnMO·BF3 formés par le trifluorure de bore et des sulfoxydes, aminoxydes, phosphinoxydes et arsinoxydes ont été obtenus. Les paramètres (déplacements et couplages) caractérisant ces spectres sont comparés à ceux de composés similaires renfermant également une liaison de coordination O·B.

Kimtys, L.; Mikulskis, P.; Shape'ko, N. N.

doi: 10.1002/mrc.1270050804pmid: N/A

The NMR dilution chemical shifts of phenol in the cyclohexane, methylcyclohexane and carbon tetrachloride solutions at temperatures +10, +20, +40, +50, +60, +70 and +80°C have been interpreted applying the quasi‐chemical approximation. The interchange energies for the OH…O bonding and the chemical shifts of hydroxylic protons in associated phenol molecules have been determined and their temperature dependences studied.

Humm, Françoise; Romanetti, Robert; Tordo, Paul; Bouscasse, Lue; Phan‐Tan‐Luu, Roger

doi: 10.1002/mrc.1270050805pmid: N/A

Une méthode de résolution des spectres RPE par régression non linéaire est décrite. On ajuste le modèle théorique avecle spectre expérimental. Le calcul de l'erreur sur chaque paramètre est décrit. On applique cette méthode à la résolution des spectres anions nitro‐2‐méthyl‐4‐thiazole, p‐nitro phényl‐4‐thiazole et p‐nitro phényl‐5‐thiazole.

Abraham, R. J.; Cooper, M. A.; Indyk, H.; Siverns, T. M.; Whittaker, D.

doi: 10.1002/mrc.1270050806pmid: N/A

The proton magnetic resonance spectra of β‐pinene pinocarvone and the cis‐ and trans‐pinocarveols have been completely assigned at 220 and 300 MHz. On the basis of the proton‐proton spin‐spin couplings derived, conformations have been deduced for these molecules with greater certainty than has hitherto been possible. Pinocarvone is Y‐shaped, while in all the other compounds the conformation is intermediate between a Y‐shape and a bridged chair, with the C3 atom bent away from the gem dimethyl groups. These conformations are discussed in terms of the steric interactions in these systems and are compared with related molecules.

Bendorf, G.; Rosenberger, H.; Funk, M.; Madeja, K.

doi: 10.1002/mrc.1270050807pmid: N/A

Der Ligandenaustausch von 1,10‐Phenanthrolin zwischen der diamagnetischen, komplexgebundenen (mitden Zentralionen: [Zn]2+, [Fe]2+, [Co]3+) und der freien Lage wird mit Hilfe der Protonenresonanzspektroskopie untersucht. Die mittleren Aufenthaltsdauern des Liganden in den Systemen mit Zn bzw. Fe als Zentralatom konnten durch eine vollständige Linienformanalyse bzw. durch Näherungsformeln bestimmt werden. Aus der Temperaturabhängigkeit der Aufenthaltsdauern wurden die Aktivierungsenergie, die freie Aktivierungsenthalpie, die Aktivierungsenthalpie und die Aktivierungsentropie bestimmt.

Lazzeretti, P.; Moretti, I.; Taddei, F.; Torre, G.

doi: 10.1002/mrc.1270050808pmid: N/A

The proton chemical shift of several derivatives of styrene oxides have been obtained in different solvents in order to check the relative importance of different contributions to the shielding of oxirane protons. It seems likely that ‘ring current’ and electrostatic effects can explain differences within the several compounds examined. An investigation of the conformational requirements of the phenyl group in these systems shows that the preferred conformation present in styrene oxide is also likely to be maintained in other compounds, where groups cis and trans to the phenyl ring are present. A discussion of the possibility of employing ‘ring currents,’ obtained both in the Johnson and Bovey scheme and with an SCF treatment for conformational analysis is given and it seems that this contribution, when considered alone, can only give very approximate information regarding the geometrical pattern of the molecule.