Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1260270901pmid: N/A

Katritzky, Alan R.; Gallos, John K.; Durst, H. Dupont

doi: 10.1002/mrc.1260270902pmid: 34034432

Available data on the structures, electronic substituent effects and 13C NMR spectra of aromatic polyvalent iodine compounds, particularly iodoso and iodoxy derivatives, are summarized and discussed. A series of aromatic tri‐ and penta‐valent iodine compounds were synthesized, their 13C NMR spectra were measured and the substituent chemical shifts (SCS) for several polyvalent iodine functional groups were calculated. As the oxidation state of iodine increases (I → II → V), the strong shielding of the ipso‐carbon atom by iodine in aryl iodides due to the ‘heavy‐atom effect’ (30 ppm) decreases substantially, and this decrease is apparently general for stable hypervalent iodine compounds. Possible explanations are discussed and correlations between chemical shifts, structures and/or electronic effects are proposed.

Aguilera, J. L.; Sosa, G.; Reynolds, W. F.; Diaz, E.; Barrios, H.

doi: 10.1002/mrc.1260270903pmid: 34034430

The constitution, configuration and conformation of three N‐hydroxydiphenylpiperidines were established by 1H and 13C 2D NMR spectroscopy. The products were obtained using phase‐transfer conditions.

Aksnes, D. W.; Ramstad, Kari

doi: 10.1002/mrc.1260270904pmid: 34034439

Carbon‐13, deuterium and proton NMR line shapes of polycrystalline tert‐butyl iodide (1) have been studied between 200 K and the melting point (239 K). Carbon‐13 and deuterium spin‐lattice relaxation times (T1) were measured between 313 and 200 K in the liquid and solid phases of 1.

Mao, Xi‐An; You, Xiao‐Zeng; Dai, An‐Bang

doi: 10.1002/mrc.1260270905pmid: 34034437

Two‐dimensional 119Sn exchange spectroscopy was applied to study the hydrolytic kinetics of the hexachloro‐stannate anion, SnCl62−. Two 119Sn exchange spectra for SnCl4 · 5H2O solutions with various HCl concentrations are presented. Magnetization exchanges, which are related to the hydrolysis processes, occur in the SnCl62− hydrolysis series. The exchange rate constants, the hydrolysis rate constants and the hydrolysis equilibrium constants were evaluated.

Matthews, R. S.; Jones, M.; Banks, J.

doi: 10.1002/mrc.1260270906pmid: 34034436

Three methods, two empirical and one semi‐empirical, for predicting 13C chemical shifts in six poly‐chloroheterocyclics are considered. It was found that the semi‐empirical correlations with CNDO/2 calculated charges, although useful, could not be used in isolation from the other two methods. Of these, the MSCS (multiple substituent chemical shifts) method could be used to predict all eighteen carbon shifts in perchloroquinoline and perchloroisoquinoline, whilst the NIMS method (hypothetical nitrogen insertion method) was limited to the carbons in the heterocyclic ring. In brief, it was found that the MSCS method was the most accurate (less than ± 1 ppm) for predicting chemical shifts, intrinsically compensating for some of the errors arising from mutual atom‐atom interactions.

Zhang, Yongkang; Xu, Guangzhi

doi: 10.1002/mrc.1260270907pmid: 34034435

The ability of ten cyclic nitrones, 5‐alkyl‐5‐methyl‐1‐pyrroline N‐oxides, to trap a variety of short‐lived free radicals has been investigated using ESR spectroscopy. Stereospecific spin trapping by these nitrones has been demonstrated by comparison of the ESR spectra of their adducts with the ESR spectra of the corresponding 5‐alkyl‐5‐methyl‐1‐tetrahydropyrrolyl‐1‐oxyls. Phenyl radical trans addition to these nitrones has also been proved.

Craik, David J.; Higgins, Kerry A.; Hall, Jon G.; Andrews, Peter R.

doi: 10.1002/mrc.1260270908pmid: 34034428

Natural abundance 75 MHz 13C NMR spectral assignments are reported for bovine and porcine zinc insulin in solution. A large number of protein resonances are well resolved, and approximately 80% of these have been assigned to either residue types or to specific sites within the protein. Assignment techniques included consideration of free amino acid or peptide shifts pH studies and comparison of sequence and spectral differences between bovine and porcine insulin, in addition to the use of NMR relaxation times. The DEPT spectral editing technique was also found to be particularly valuable as an assignment aid. This technique allows subspectra containing only CH, CH2 or CH3 carbon types to be generated. The method also produces signal enhancement relative to broad band decoupled 13C NMR spectra of large proteins which generally have reduced nuclear Overhauser enhancements.

Gogoll, Adolf; Tanner, David

doi: 10.1002/mrc.1260270909pmid: 34034427

After correlation of the majority of signals by COSY and one‐bond heteronuclear correlation, the complete assignment of the 1H and 13C NMR spectra of the macrolide antibiotic venturicidin A required the application of long‐range CH coupling information. This was accessible by the COLOC‐S and selective INEPT experiments, and the sensitivity of these experiments is discussed. Steric information was obtained from a NOESY spectrum, and the solution structure compared with that in the crystal.

Sohár, Pál; Bernáth, Gábor; Stájer, Géza; Szabo, Angela E.

doi: 10.1002/mrc.1260270910pmid: 34034442

Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene‐azetidinone‐fused 3,1‐oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments.