Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1260290101pmid: N/A

Lewis, P. M. E.

doi: 10.1002/mrc.1260290102pmid: N/A

Katritzky, Alan R.; Hitchings, Gregory J.; King, Roy W.; Zhu, Dong W.

doi: 10.1002/mrc.1260290103pmid: N/A

1H and 13C NMR studies were carried out on 1‐ethenylnaphthalene, 2‐ethenylnaphthalene, 9‐ethenylanthracene, 9‐ethenylphenanthrene, 1‐ethenylpyrene and 1‐ethenylperylene. Assignments of proton and carbon resonances were made with the aid of 2D COSY, 2D HETCOR, 2D COLOC, 2D COLOCS, 3J(H,C) INAPT, and NOE difference spectral techniques.

Axenrod, T.; Liang, B.; Dave, P. R.

doi: 10.1002/mrc.1260290104pmid: N/A

The 1H and 13C NMR spectra of several saturated polynitropolycyclic molecules were unambiguously assigned using aromatic solvent‐induced shifts, NOE difference spectra, 1H–1H COSY spectra and 2D 13C–1H shift correlated spectra, optimized either for one‐bond or long‐range 13C–1H couplings.

Müller, Arndt; Nonnenmacher, Gerhard; Kutscher, Bernhard; Engel, Jürgen

doi: 10.1002/mrc.1260290105pmid: N/A

The complete assignment of all 1H and 13C NMR signals of acrihellin in chloroform solution is presented. The analysis of the 1H and 13C NMR spectra was performed using the heteronuclear 2D NMR techniques H,C‐COSY and H,C‐COLOC. For an unambiguous assignment of the 13C NMR spectrum the elucidation of carbon–carbon connectivities via 2D‐INADEQUATE was most important. The INADEQUATE experiment was also applied to hellebrigenin in DMSO‐d6 solution. This experiment confirmed a recently published carbon assignment.

Uhrínová, Stanislava; Uhrín, Dušan; Liptaj, Tibor; Batta, Gy.

doi: 10.1002/mrc.1260290106pmid: N/A

One‐dimensional COSY is shown to be a promising technique for the detection of small, unresolved proton‐proton coupling constants. Under certain circumstances the method can be more effective than two‐dimensional phase‐sensitive COSY. A detailed analysis of the experimental conditions is presented. The possible application of the method in oligosaccharide sequencing is outlined. Another potential use of one‐dimensional COSY is in the evaluation of coupling constants in macromolecules. In this case the efficiency of the polarization transfer is decreased owing to the fast transverse relaxation times of the protons. DISCO analysis was applied for the determination of coupling constants in unresolved multiplets.

Bönzli, Peter; Neuenschwander, Markus

doi: 10.1002/mrc.1260290107pmid: N/A

The 1H NMR spectra of selected heptafulvenes 2a–e were analysed under high‐resolution conditions. The results are in agreement with a symmetrical boat conformation for 2a and with a nearly planar conformation of 2e. Within the series 2a–e, ring planarization and π‐delocalization increase. Substituent effects on NMR parameters are discussed.

Field, Leslie D.; Bampos, Nick; Messerle, Barbara A.

doi: 10.1002/mrc.1260290108pmid: N/A

The iron dihydride FeH2(PP3) [PP3 = P(CH2CH2CH2PMe2)3] is fluctional, with the terminal co‐ordinated phos‐phine groups undergoing intramolecular exchange in addition to the iron‐bound hydrides. The exchange kinetics of the metal‐bound hydrides was examined using a magnetization inversion–transfer–recovery method, and the activation energy was ca. 64 kJ mol−1 at 260 K. The effect of spin–spin coupling on the magnetization transfer was examined.

Brown, David A.; Glass, William K.; Mageswaran, Rajeswary; Mohammed, Salima Ali

doi: 10.1002/mrc.1260290109pmid: N/A

1H and 13C NMR studies of N‐methyl‐substituted hydroxamic acids, RCON(CH3)OH (R = CH3, C2H5 and C6H5), show that the series exhibits cis–trans isomerism about the CN bond. The Z/E ratio increases in the series CH3 < C2H5 < n‐C5H11 < n‐C6H13 for a given solvent, indicating that steric interaction between R and the OH group is more important than that between R and the CH3 group. In DMSO‐d6 the Z isomer is preferentially stabilized by solvation, whereas in C6D6 and toluene‐d8 the unsolvated E form is thermodynamically more stable, as predicted by ab initio molecular orbital calculations. (12) At high concentrations (in CDCl3, CD2Cl2, C6D6 and toluene‐d8) the E isomer may also be stabilized by intermolecular association. In the O‐methyl‐substituted series, RCONHOCH3 (R = CH3, C6H5), although the Z isomer predominates in all solvents, at low temperatures there is evidence for enolic forms.

Keniry, Max A.; Poulton, Gerald A.

doi: 10.1002/mrc.1260290110pmid: N/A

A one‐dimensional version of the heteronuclear multiple bond correlation experiment (HMBC) is shown to be an excellent alternative to the full two‐dimensional experiment when the carbon resonances are well resolved. The quaternary resonances of lambertellin, a metabolite of Ciboria gordonii Funk, are correlated to the previously assigned proton resonances by selective transfer of zero and double quantum coherence to observable proton magnetization by a frequency‐selective carbon decoupler pulse.