Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1260270401pmid: N/A

Hallas, E.; Emons, H.‐H.; Siedler, M.; Thomas, B.

doi: 10.1002/mrc.1260270402pmid: N/A

Conventional liquid‐state 27Al NMR spectra of concentrated solutions of the AlCl3‐water‐N,N‐dimethyl‐N‐Dimethylformamide formamide system contain comparatively broad non‐structured lines. Application of MAS leads to a reduction in the line width and a structuring of the spectra. This allowed the experimental determination of the chemical shifts of [Al(H2O)6−x(DMF)x]3+ (x = 0−6) mixed‐ligand complexes. The investigations demonstrate an example of the applicability to liquids of the NMR MAS technique, which was originally developed for solids. They underline the existence, in a reduced form, of ‘solid‐type’ interactions within the investigated solutions.

Sumner, Susan C. J.; Moreland, Charles G.; Carroll, F. Ivy; Brine, George A.; Boldt, Karl G.

doi: 10.1002/mrc.1260270403pmid: N/A

Carbon‐13 NMR data for salts of methadone and methadol in the solid‐state were used to elucidate the crystalline forms of the compounds and to determine if more than one conformer contributes to a single crystalline form. A comparison of 13C NMR isotropic chemical shift data for these compounds in the solid‐state and in various solvents was used to correlate solution and solid‐state conformations (determined from x‐ray data). Three‐bond 1H13C and 1H1H coupling constants, measured by various one‐ and two‐dimensional NMR techniques, were compared with those calculated from x‐ray dihedral angle data in order to confirm or dispute the conformational predictions based on chemical shift comparisons.

Johnston, Milton D.; Salazar, Miguel; Sims, Larry D.; Zektzer, Andrew S.; Castle, Raymond N.; Martin, Gary E.

doi: 10.1002/mrc.1260270404pmid: N/A

The 1H and 13C NMR spectra of phenanthro[9,10‐b]thiophene were totally assigned using a combination of twodimensional NMR techniques. Direct hetcronuclear correlations were established using heteronuclear chemical shift correlation with semi‐selective proton decoupling. Two methods were employed to establish the identity of vicinal neighboring protons: heteronuclear relayed coherence transfer and low‐pass J‐filtered heteronuclear relayed coherence transfer. The versatilities of the two techniques were compared. Quaternary carbon resonance assignments and the orientations of individual spin systems relative to one another were accomplished using the proton‐detected long‐range heteronuclear multiple quantum coherence experiment (HMBC). Key long‐range inter‐ring proton homonuclear spin couplings served to confirm the orientations of the proton spin systems.

Wilt, James W.; Peeran, Mehboob; Ramakrishnan, Subramanian; Crumrine, David S.

doi: 10.1002/mrc.1260270405pmid: N/A

The 13C NMR chemical shifts for a series of exo‐ and endo‐3,3‐diphenyltricyclo[3.2.1.02,4]octanes are reported. Comparisons with the parent exo‐ and endo‐tricyclo[3.2.1.02,4]octanes and with bicyclo[2.2.1]heptanes show that most of the chemical shifts are additive. Substituent effect constants are presented for the tricyclo[3.2.1.02,4]octyl system. Pronounced deshielding effects are seen in the endo series for C‐6 and −7 of the alkene endo‐3,3‐diphenyltricyclo[3.2.1.02,4]oct‐6‐ene, the epoxide endo‐3,3‐diphenyltricyclo[3.2.1.02,4]octan‐6,7‐exo‐oxide, and the tetracyclic exo‐3,3‐diphenyltetracyclo[3.3.1.02,406,8]nonane. The chemical shifts of C‐3 and −8 are diagnostic for endo vs. exo substitution.

Iyer, R. K.; Karweer, S. B.; Jain, V. K.

doi: 10.1002/mrc.1260270406pmid: N/A

The reactions of Al3+ ion with a series of aminopolycarboxylic acids containing coordinating sites (denticity, n) ranging from 3 to 8 were studied by potentiometric and 27AI NMR methods. Hydrolysis constants of the complexes were determined by potentiometry. The 27Al {1H} NMR data indicate a nearly linear relationship between the 27Al chemical shift of the normal complex and denticity of the ligand up to n = 6. Hydroxo complexes form in all systems, and at high pH (ca. 10) aluminate forms. Protonated complexes were formed in some cases. Diprotonated complexes of EDTA and PDTA have been identified by 27Al NMR spectroscopy. Maximum deshielding of the 27Al resonance was observed for the octahedral [Al(EDTA)]− complex. The Al‐NTA complex appears to be the most symmetric of the complexes.

Wasser, R.; Kellerhals, M.; Diehl, P.

doi: 10.1002/mrc.1260270407pmid: N/A

Solvent effects on the structures of benzene and chlorobenzene were studied by NMR of partially oriented molecules in six liquid crystals. Allowing for the correlation between vibration and rotation, a unique solvent‐independent rα structure could be determined for both molecules. The contributions of equivalent bonds to the orientation energy of the two molecules were found to differ slightly.

Sustmann, Reiner; Brandes, Dieter; Lange, Fritz; Tashtoush, Hasan I.

doi: 10.1002/mrc.1260270408pmid: N/A

ESR spectral parameters of methoxy‐, hydroxy‐ and cyano‐substituted cycloheptatrienyl radicals are reported. The radicals were obtained in adamantane matrices by the rearrangement of substituted bicyclo[3.2.0]heptadienyl radicals. The hyperfine splitting parameters are interpreted in terms of the effect of donor and acceptor substituents on the degeneracy of the relevant singly occupied ψs or ψA ABMO of the cycloheptatrienyl radical. In addition, an attempt was made to study the deuterium isotope effect on the degenerate MOs at low temperatures in a [2H16]adamantane matrix.

Yoshino, Akihiro; Yoshida, Tadayoshi; Takahashi, Kensuke

doi: 10.1002/mrc.1260270409pmid: N/A

The behaviour of water in the reversed micelles of the glycerol α‐monooleate (GMO)–decane‐2H2O system was investigated by deuteron nuclear magnetic resonance. The chemical shifts (δ) and the spin–lattice relaxation times (T1) of heavy water were found to be dependent on temperature. The temperature dependence of the T1 and δ values reveals that the structural change in heavy water induced by the inhalation anaesthetic enflurane is very different below and above ca. 300 K. Below ca. 300 K a cage of a water polyhedron builds up around an enflurane molecule. Above ca. 300 K there is no water polyhedron cage because of the cleavage of the hydrogen bonds in the polyhedron water, and some of the water molecules are tightly adsorbed on the enflurane molecules.

Osborne, Alan G.

doi: 10.1002/mrc.1260270410pmid: N/A

The 13C chemical shifts and 13C1H coupling constants of some methoxycoumarins are reported. Some earlier spectral assignments, including those for citropten (limettin), require revision. Methoxy substituent effects on longrange 13C1H couplings in coumarins are highlighted. Peri‐proximity effects for the methyl‐methoxy and methoxy‐methyl couples are derived, and the value of these effects in the assignment of peri‐substituted compounds is illustrated.