bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron spin resonance study of spin‐trapped radicals from gamma irradiation of glucose oligomers
Authors: Thiéry Jean M. , Thiéry Corinne L. , Agnel Jean‐Pierre L. , Vincent Patrice B. , Battesti Christine M. , Raffi Jacques J. , Evans Jeffrey C. 
Published: May 2005

AbstractRadicals produced in aqueous solution by gamma irradiation of the five first glucose oligomers were trapped using 2‐methyl‐2‐nitrosopropane (MNP) and separated by high‐performance liquid chromatography. The electron spin resonance (ESR) spectra were analysed on a microcomputer with a general interactive simulation program (VOYONS). The ESR coupling constants of five radical adducts, which were found in all the oligomers, are reported. A comparison with the coupling constants previously obtained from α‐D‐glucopyranosyl,‐0‐methyl‐α‐D‐glucopyranose, O‐α‐D‐glucopyranosyl‐(1 →4)‐α‐D‐glucopyranose or polyols, irradiated in the liquid phase or in the powder state, provides new information on the chemical structures of the radicals radioinduced in glucose oligomers. As the powder ESR spectra and the main radiolytic products from the gamma‐irradiated oligomers have been found to be comparable to those from irradiated starches, this work is the first step in the elucidation of the radiolysis mechanism of starch.
Conformational study of the 4,9‐dihetero‐(Z,Z)‐cyclodeca‐1,6‐diene ring system; the mono‐ and di‐benzo analogues
Authors: Kleinpeter E. , Hartmann J. , Schroth W. 
Published: May 2005

AbstractThe dynamic 1H and 13C NMR spectra of a series of mono‐ and bis‐annelated 4,9‐dihetero‐(Z,Z)‐cyclodeca‐1,6‐dienes were obtained and are discussed with respect to ground‐state conformers and the barriers to ring inversion, and to the restricted rotation about exocyclic partial C,N double bonds. The ten‐membered rings are, with one exception, anancomeric chair conformers and interconvert via a combination of single bond rotations and bond angle bendings. Depending on the heteroatoms present, the series of decreasing barriers to ring inversion S > NH > O was obtained. Benzannelation decreases the free energy of activation of the same dynamic process owing to greater intramolecular transannular H,H interactions.
Comparison of one‐ and two‐dimensional techniques in the unambiguous 13C NMR spectral assignment of ellipticine and related indole derivatives
Authors: Gogoll Adolf , Plobeck Niklas A. 
Published: May 2005

AbstractThe 13C NMR spectra of several indole derivatives have been completely assigned by reverse detected one‐bond and long‐range CH correlation spectra (HMQC) and by selective INEPT experiments. The resolution and sensitivity of the two techniques are discussed. As a result, the literature assignments for the previously known compounds have been revised.
Through‐space 13C–19F couplings in highly‐crowded systems: Radial dependence and electronic effects
Authors: Hsee Li C. , Sardella D. J. 
Published: May 2005

AbstractThe helical molecule 1‐fluorobenzo[ c] phenanthrene shows a large (17.4 Hz) 13C–19F coupling resulting primarily from direct through‐space overlap between a fluorine lone pair and the sterically opposed CH bond. After application of corrections for estimated through‐bond contributions, comparison of the magnitude of this coupling with the analogous couplings in 4‐fluorophenanthrene, 10‐fluorobenzo[ a] pyrene, 11‐fluoro‐5‐methylchrysene and 7‐fluorobenzo[b] fluoranthene reveals an exponential decrease with increasing H …︁ F internuclear distance, consistent with theoretical predictions. No evidence was found for an angular dependence of the coupling. HETCOR experiments showed the signs of n+1J(HF) in 1‐fluorobenzo[ c] phenanthrene, 4‐fluorophenanthrene, 10‐fluorobenzo[ a] pyrene and 11‐fluoro‐5‐methylchrysene to be opposite to those of the corresponding nJ(CF), hence negative. Substituents at both positions 4 (para to fluorine) and 9 (para to the sterically opposed CH bond) exert only a minor influence on 5J(CF), the couplings in the latter series responding largely to sterically induced distortions of the molecular framework, and in the former series to both steric distortions and an electronic effect. The difference in 5J(CF) between isomers is a measure of the electronic effect of the substituent. Electron‐withdrawing substituents para to fluorine reduce the magnitude of the through‐space coupling whereas electron‐releasing substituents increase the coupling.
Selective excitation techniques in 13C NMR. II—new sequences for fast heteronuclear correlation
Authors: Berthault P. , Perly B. , Petitou M. 
Published: May 2005

AbstractThe potential of Gaussian soft pulses in the selective excitation of individual 13C multiplets is demonstrated for heteronuclear 13C–1H NMR spectroscopy. The efficiency of these techniques is demonstrated for the rapid and accurate recording of both proton chemical shifts and heteronuclear coupling constants in multi‐labelled oligosaccharides.
13C NMR of coumarins. V—3‐prenylated coumarins
Authors: Macias F. A. , Hernández‐Galán R. , Massanet G. M. , Rodriguezluis F. , Vasquez M. , Salvá J. 
Published: May 2005

Abstract13C NMR data of nineteen coumarins, twelve of which bear a prenyl (isoprenoid) side‐chain at C‐3, are reported and compared with those of the C‐3 unsubstituted compounds. Unlike the linear isomers, no γ‐effect is observed in the corresponding angular derivatives; this is proposed as spectroscopic criterion for distinguishing between these isomers.
13C NMR of some chlorinated diphenyl ethers
Authors: Dawson Brian A. , Chu Ih , Viau Andre 
Published: May 2005

Abstract13C NMR chemical shift assignments for 15 chlorinated diphenyl ethers, containing from two to seven chlorine substituents, were measured and interpreted. Chemical shift data for 12 of these compounds have not been previously reported. Data are based on a number of 1D and 2D experiments performed at 9.4 T.
Carbon‐13 NMR spectral analysis of oxazine derivatives and precursors
Authors: Moloney Gerard P. , Craik David J. , Iskander Magdy N. 
Published: May 2005

Abstract13C NMR chemical shifts are reported for six pyridoxal‐derived and fourteen salicylaldehyde‐derived oxazines and their immediate precursors. Similar data for seven vitamin B6‐related compounds are also reported.
Conformational dependence of the one‐bond carbon–proton coupling constants in oligosaccharides
Authors: Hricovíni Miloš , Tvaroška Igor 
Published: May 2005

AbstractA study is presented of the dependence on conformation of one‐bond carbon‐proton coupling constants in three 1‐4‐linked disaccharides. Calculated 1J(CH) values are based on the FPT formulation in the semi‐empirical INDO MO method. The configuration at the anomeric carbon influences the 1J(CH) value, and the 1J(C‐1′, H‐1′) values are 20–30 Hz higher than the 1J(C‐4, H‐4) values. The conformational dependence of 1J(CH) on the dihedral angle about the CO bonds is satisfactorily expressed in the analytical form 1J(CH) = A cos 2ϕ + B cos ϕ. The constants A‐E are different for the α‐ and β‐anomers. Calculated average values 〈1J(C‐1′, H‐1′)〉 = 163.7 Hz and 〈1J(C‐4, H‐4)〉 = 146 Hz for methyl β‐xylobioside using PCILO‐calculated abundances of conformers agree well with the experimental values of 162.7 and 147.5 Hz, respectively.
A proton and carbon NMR spectral study of 4‐substituted and 4,6‐disubstituted dibenzothiophenes
Authors: Katritzky Alan R. , Perumal S. 
Published: May 2005

AbstractThe proton and carbon NMR spectra of several 4‐substituted‐ and 4,6‐disubstituted‐dibenzothiophenes have been measured, and their chemical shifts assigned employing spin decoupling and COSY and HETCOR two‐dimensional techniques. This work rectifies several literature misassignments of 13C chemical shifts of 4‐substituted dibenzothiophenes and also examines the effects of substituents on the chemical shifts. Hence this study will be useful in the future structure determinations of mono‐ and multisubstituted dibenzothiophenes.
Studies on complex species of aluminium with aminocarboxylic acids by 27Al NMR spectroscopy
Authors: Karweer S. B. , Pillai B. P. , Iyer R. K. 
Published: May 2005

AbstractThe reactions of Al3+ ion with glycine, picolinic acid, 1,2‐propylenediaminetetraacetic acid and triethylenetetra‐minehexaacetic acid (HpL) were studied by potentiometric and 27Al NMR methods, and the complex species in solution at different pH values were identified. Acidic hydrolysis of the Al‐PDTA complex results in the formation of [AIL]−, [Al(H2O)LH] and [Al(H2O)2LH2]+ prior to dissociation, while base hydrolysis takes place through the monohydroxo species. Although TTHA is a decadentate ligand, the maximum number of donor sites utilized in the formation of the 1:1 Al‐TTHA complex is only five.
13C and 15N NMR study of 2,3‐diphenyltetrazolium‐5‐olate and 5‐thiolate
Authors: Kozminski W. , Jazwinski J. , Stefaniak L. , Webb G. A. 
Published: May 2005

Abstract13C and 15N NMR chemical shifts are reported for 2,3‐diphenyltetrazolium‐5‐olate and ‐5‐thiolate and some of their derivatives. The data for N‐1 and C‐5 provide a very satisfactory means of distinguishing between O and S as the exocyclic substituent. The reported chemical shifts are consistent with the presence of the cyclic structures shown, rather than of the corresponding non‐cyclic structures.
Preparation and stereostructure of norbornane/ene‐condensed phenyl‐substituted O,N‐heterocycles
Authors: Sohár PÁL , Bernáth Gábor , Frimpong‐Manso Samuel , Szabó Angela E. , Stájer Geza 
Published: May 2005

AbstractNorbornane/ene di‐exo‐condensed isoxazolines were reduced to amino alcohols and then cyclized to 1,3‐oxazines. The phenylimino analogues, 1,3‐oxazin‐2(3H)‐ones, the corresponding 2(3H)‐thiones and 1,4‐oxazepin‐3(4H)‐ones were also prepared. The structures, configurations and conformations of the new compounds were proved via 1H and 13C NMR studies, using DR, DNOE, DEPT and 2D‐HSC measurements in addition to the routine spectra.
One‐ and two‐dimensional 15N NMR spectroscopy of tris(trimethylsilyl)‐, tris(trimethylstannyl)‐, tris(trimethylplumbyl)‐amine and tetrakis(trimethyistannyl)hydrazine: Sign determination of various scalar coupling constants
Authors: Wrackmeyer Bernd , Zhou Hong 
Published: May 2005

AbstractThe signs of the coupling constants 1J(29Si15N) and 1J(119Sn15N) are positive and negative, respectively, in tris(trimethylsilyl)‐ and tris(trimethylstannyl)‐amine. This results from two‐dimensional (2D) 15N/1H heteronuclear shift correlations [at natural abundance of 15N, based on long‐range couplings 3J(1N 1H), with respect to the positive coupling constants 2J(29SiC 1H) and 2J(119SnC 1H)]. The same type of experiment proves the negative sign of 1J(119Sn15N) in tetrakis(trimethylstannyl)hydrazme and it allows the unambiguous assignment of 1J(119Sn15N) and 2J(119SnN 15N). In tris(trimethylplumbyl)‐amine, the largest value (335.7 Hz) reported so far for 1J(207Pb 15N) of plumbylamines is observed. In the case of tris(trimethylstannyl)amine, the 2D 15N/1H experiment also gave the sign of 4J(119SnNSnC1H) (positive), and this is used in the 2D 119Sn/1H experiment to prove a negative sign for 2J(119Sn 117Sn).
High‐resolution solid‐state NMR study of reversible 1,5‐proton shifts in organic solids
Authors: Vila Alejandro J. , Lagier Claudia M. , Olivieri Alejandro C. 
Published: May 2005

AbstractHigh‐resolution CP‐MAS NMR analyses of solid organic samples where fast 1,5‐proton shifts occur between tautomeric structures are described. Attention is focused on the available techniques to establish the existence of such reactions. Dynamic interconversion is unambiguously characterized where complete line shape study involving multiple sites is possible. Reconciliation between this information and that provided by diffraction methods is stressed, the latter often suggesting the presence of unique, static structures in crystals. In cases in which reactions are in the fast limit at all accessible temperatures, the combination of CP‐MAS spectra, x‐ray or neutron diffraction data at variable temperatures and theoretical calculations of molecular properties may be helpful in establishing double minimum potential wells for the proton motion. Among these, porphyrins, arylazonaphthols and 1,3‐diketones in rigid and non‐rigid skeletons are interesting examples of current interest.
1H and 13C nuclear magnetic resonance studies of ethenyl‐substituted benzenoid aromatic compounds
Authors: Katritzky Alan R. , Hitchings Gregory J. , King Roy W. , Zhu Dong W. 
Published: May 2005

Abstract1H 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.
Detection of long‐range couplings in oligomers and evaluation of coupling constants in polymers. Application of the 1D COSY technique
Authors: Uhrínová Stanislava , Uhrín Dušan , Liptaj Tibor , Batta Gy. 
Published: May 2005

AbstractOne‐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.
Long‐range deuterium isotope effects on 13C NMR shifts of intramolecularly hydrogen‐bonded 9‐hydroxyphenalen‐1‐ones
Authors: Engdahl Carin , Gogoll Adolf , Edlund Ulf 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 9‐hydroxyphenalenone (1) and 9‐hydroxy‐2‐methylphenalenone (2) have been completely assigned. Primary and secondary deuterium isotope effects were determined in three solvents (chloroform, acetone and dimethyl sulphoxide), including the effect of temperature on the secondary isotope effects. Both negative and large long‐range secondary isotope effects were found for both 1 and 2. The average secondary isotope effects for corresponding carbons follow the same sign and magnitude pattern in both compounds.
Two‐dimensional NMR study of eledoisin
Authors: Yang Ta‐Horng , Chang Tsung‐Yi , Yu Chin 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of eledoisin, an antidiuretic hormone, were studied by two‐dimensional NMR techniques. All the 1H and 13C NMR resonances were unambiguously determined from a combination of the 2D homo‐ and hetero‐nuclear NMR spectra.
Dynamic NMR study of the electronic state of heteroaromatics. IX—π‐Electron deficiency of various substituted thiazinethiones, thiazinium salts and analogous pyrimidines by means of barriers to rotation about exocyclic partial C,N double bonds
Authors: Kleinpeter E. , Schroth W. , Pihlaja K. 
Published: May 2005

AbstractThe 1H NMR spectra and the barriers to rotation about exocyclic partial C,N double bonds of various series of thiazinethiones 1, the corresponding thiazinium salts 5–9 and some pyrimidinethiones 10–13 are reported and discussed with respect to the π‐electron deficiency of these heteroaromatic compounds. Substituent influences are critically considered; in particular, the C,N barrier differences of C,NMe2 and C, pyrrolidino were used to estimate the type of dynamic process, which is different in pyrimidinethiones 10–13 and thiazinethiones/thiazinium salts 1–9. The compounds studied corroborate the pseudo‐chalcogeno analogy principle. Previously studied compounds are included to display the π‐electron deficiency influence of the heterocyclic system on the 1H chemical shifts of NR2, phenyl, the H‐5 protons and the exocyclic barriers to C,N rotation; adequate quantitative estimations are reported.
Inverse editing of protons in two‐dimensional homonuclear and heteronuclear relayed COSY spectra
Authors: Wollborn U. , Leibfritz D. 
Published: May 2005

AbstractSeveral 1D and 2D inverse proton editing pulse sequences have recently been introduced. One of these, the REPAY sequence, allows the individual editing of XH or XH2 groups. Some new 2D combinations of one‐ and two‐dimensional REPAY experiments with a COSY or TOCSY transfer are described. These combinations provide various possibilities for structural elucidation: the determination of heteronuclear long‐range coupling constants nJ(CH) (n = 2, 3), the editing of XH or XH2 groups in two‐dimensional H,H COSY spectra and the editing of XH or XH2 groups in X,H COSY spectra followed by a relayed transfer. In contrast to earlier versions of SHIPPED‐COSY experiments, the spectra show improved sensitivity and offer the possibility of selecting XH2 groups only, and contain no 1J(XH) coupling because of heteronuclear X decoupling.
NMR spectra and conformational analysis of substituted 2,3‐dihydro‐[1,5]benzoxazepin‐4(5H)‐one derivatives
Authors: Ott Jürgen , Hiegemann Monika , Duddeck Helmut 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 26 2,3‐dihydro‐[1,5]benzoxazepin‐4(5H)‐one derivatives and four thiono analogues are interpreted in terms of conformational equilibria. Similar to 1,3,4,5‐tetrahydro‐2H‐1,5‐benzodiazepin‐2‐ones, these compounds favour boat conformations of the seven‐membered ring. In the lactams the conformational energy difference is very low, whereas a difference of 0.3 kcal mol−1 is recorded for the thionolactams, the conformation with the quasi‐axial methyl group also being preferred.
Carbon‐13 NMR relaxation study of the overall and internal motions in compounds containing n‐octyl chains
Authors: Bull Lucy M. , Gillies Duncan G. , Matthews Stephen J. , Sutcliffe Leslie H. , Williams Antony J. 
Published: May 2005

AbstractThe 13C nuclear relaxation behaviour of n‐alkyl chains in a variety of compounds can be described in terms of two relaxation times, one for tumbling (τc) and one for each carbon nucleus for the internal motions (τc). Relaxation data for the quaternary carbon nuclei of n‐octylbenzene and n‐octyl cyanide have been used to determine τc) and their activation energies [Ea(τc)]. These values have enabled τe and their associated activation energies [Ea(τe)] to be calculated for each carbon in the alkyl chains of the two compounds. In these compounds the values for C‐6 appear to be invariant with τe(298) = 15 ± 2 ps and Ea(τc) = 15 ± 1 kJ mol−1. Assuming that these are universal values for all n‐octyl chains, we have used them to calculate τe and Ea(τe) for other simple n‐octyl compounds, thus allowing τc and E.a(τc) to be determined. It was found that Ea(τc) values correlate well with those for Ea(n/T) obtained from viscosity measurements. Di‐n‐octyl ether shows motional properties similar to those of the straightchain compounds.Simultaneous fitting of relaxation rate and NOE enhancement data measured over a range of radiofrequencies and temperatures permits a wealth of motional properties to be discerned when there is a suitable frequency dispersion. Both tri‐n‐octylamine and polydecene tumble sufficiently slowly to allow both relaxation rate and NOE data to be used to evaluate τc and τe and their activation energies without making any assumptions about C‐6. The values of τc(298) and Ea(τc) obtained from C‐6 for tri‐n‐octylamine are 314 ± 12 ps and 18.5 ± 0.4 kJ mol−1, respectively, and the corresponding values for polydecene are 576 ± 41 ps and 16.1 ± 1.3 kJ mol−1, respectively.
13C, 13C coupling constants of isotopically perturbed molecular systems: Cyclohexane, benzene
Authors: Roznyatovsky Vitaliy A. , Sergeyev Nickolay M. , Chertkov Vyacheslav A. 
Published: May 2005

Abstract13C, 13C coupling constants in benzene and cyclohexane were measured using monodeuteriated derivatives where 13C, 13C two‐spin subsystems become slightly non‐equivalent (benzene, 1J = 55.88, 2J = 2.46, 3J = 10.04; cyclohexane, 1J = 33.10, 2J = 2.12, = 3J 2.05; all couplings in hertz within the error limits of 0.01 Hz). 12C/13C isotope effects for the 13C chemical shifts were found to be non‐additive.
Boron‐11 quadrupole coupling constants deduced from nuclear relaxation of closo‐borane and carborane solutions
Authors: Pascal Y. L. , Convert O. 
Published: May 2005

AbstractAn analysis of the 11B relaxation rates was carried out for different solutions of closo‐borane dianions B12H and B10H and for a solution of o‐carborane, C2B10H12. The temperature dependence of these relaxation rates shows the similar interactions of these molecules with the medium. For o‐carborane, 13C relaxation rate measurements provide an evaluation of the correlation time τc and of the microviscosity of the medium. By using these values it is possible to estimate the quadrupole coupling constants for the borane dianions. The results are supported by theoretical data on the electric field gradient using the STO‐3G method.
The double‐DANTE sequence applied to NMR of complex carbohydrates
Authors: Poppe Leszek , van Halbeek Herman 
Published: May 2005

AbstractThe double‐DANTE sequence was implemented in 1D TOCSY and NOESY experiments to overcome some typical problems in the NMR of carbohydrates. In the 1D TOCSY experiment the double‐DANTE sequence serves to invert simultaneously two resonances belonging to the same scalar‐coupled spin system, thereby substantially increasing the sensitivity of the technique for subspectral editing and providing a valuable alternative to relayed TOCSY in overcoming small‐J bottlenecks in monosaccharides such as galactose and sialic acid. Spin‐diffusion artifacts in 1D NOESY experiments that are mediated by more than one spin can be effectively eliminated by applying a double‐DANTE pulse train for saturation of the mediators during the mixing time. In certain cases, the double‐DANTE sequence is also capable of eliminating the three‐spin effect in 1D 13C{1H} NOE difference spectroscopy.
Through‐bond transmission of polar substituent effects in the bicyclo [2.2.2]octane ring system as monitored by 119Sn NMR chemical shifts: A 119Sn NMR study of 10‐substituted 9‐trimethylstannyltriptycenes
Authors: Adcock William , Iyer V. Sankar 
Published: May 2005

AbstractA series of 10‐substituted(X)‐9‐trimethylstannyltriptycenes (2a) were synthesized and characterized and the 119Sn chemical shifts measured. Comparisons were made of the 119Sn substituent chemical shifts (SCS) of 2a and the corresponding values of 4‐substituted(X)bicyclo[2.2.2]oct‐1‐yltrimethylstannanes (1a), which confirm the previous conclusion that ‘through‐three‐bond’ effects or double‐hyperconjugation strongly regulate the 119Sn shifts of the latter system. A more restricted series of 10‐substituted(X)‐9‐methyltripycenes (2c) were acquired and their 13CH3SCS compared with those of the corresponding bicyclo[2.2.2]octanes (1c). Significant ‘through‐bond’ contributions are also indicated for the latter system.
ESR parameters of 5,5‐dimethylpyrrolidine 1‐oxide (DMPO) spin adducts in the photochemical decomposition of azo compounds
Authors: Cholvad Vladimir , Szaboova Katarina , Staško Andrej , Nuyken Oskar , Voit Brigitte 
Published: May 2005

AbstractSplitting constants and g values are reported for 5,5‐dimethylpyrrolidine 1‐oxide spin adducts with radicals such as substituted‐Ph˙, NaSO3˙, PhS2˙, and others observed in the photochemical decomposition of azo compounds in various solvents.