bluuebunny/crossref_metadata_2025_split huggingface dataset:
1H NMR spectra of diastereomeric aromatic dipeptides (Phe‐Phe) in aqueous solution
Authors: Chu Yen‐Ho , Wang Kung‐Tsung 
Published: May 2005

AbstractThe 1H NMR chemical shifts and spin‐spin coupling constants of phenylalanylphenylalanine (Phe‐Phe) dipeptide diastereomers have been completely analysed at 100 MHz. Assignment of the observed signals to individual residue protons is proposed, based on characteristic shifts and standard double resonance experiments. The rotamer populations have also been determined. The spectra of the aromatic regions of the dipeptidyl diastereomers, L‐Phe‐L‐Phe and L‐Phe‐D‐Phe, are very different at pH 1.95 in D2O but similar at pH 9.15 in CD3CND2O (34:66). These results are correlated with the retention behaviour on a C18 reversed‐phase HPLC column.
Study of 1H29Si coupling constants in triethoxysilanes and silatranes by multiple quantum NMR
Authors: Liepinš E. , Birǧele I. , Tomsons P. , Lukevics E. 
Published: May 2005

Abstract29Si1H coupling constants across two and three bonds in silatranes and model triethoxysilanes were measured from 1H spectra by multiple quantum NMR. There was an increase in the 29SiOCH coupling in the equatorial position and a decrease in that in the axial position of the silicon trigonal bipyramid compared with the tetracoordinated silicon.
Line width considerations in 33S nuclear magnetic resonance of aqueous samples
Authors: Mahendroo Prem P. , Dean Sherry A. 
Published: May 2005

AbstractA series of sulfur compounds have been examined by 33S NMR at 15.3 MHz. The sharpest resonances were found for the inorganic sulfates, with line widths varying from 3.6 Hz for ammonium sulfate to 9.0 Hz for sodium sulfate. Increasing the viscosity of the solvent did not affect the line widths appreciably. Other anions and molecules examined, and their corresponding line widths, included cysteic acid (30 Hz), sodium thiosulfate (60 Hz), ammonium sulfamate (300 Hz), carbon disulfide (400 Hz), concentrated sulfuric acid (1200 Hz) and dimethyl sulfate (2000 Hz). A comparison of the measured line widths and the spin‐lattice relaxation times, T1, for five of these samples indicated that exchange processes may contribute to and often dominate the 33S resonance line widths in aqueous samples. No signals were observed in concentrated aqueous solutions of cysteine, adenosine monosulfate or chondroitin sulfate after overnight scans.
Conformational equilibria and torsional barriers of the isopropyl groups in N,N‐diiso‐propylbenzamide and its thio and seleno analogues
Authors: Berg Ulf , Pettersson Ingrid 
Published: May 2005

AbstractThe conformations of the isopropyl groups and the barriers to conformational interconversion in N,N‐diiso‐propylbenzamide (1), and its thio (2) and seleno (3) analogues have been studied by dynamic 1H NMR spectroscopy. In 1 only one conformation is observed, whereas 2 and 3 exist as mixtures of three conformations. The use of the strongly deshielding CX (X = O, S, Se) group and comparison with earlier results on similar systems allows total assignment, in the case of 2, rectifying an earlier proposal. The temperature dependence of the NMR spectra of 2 and 3 clearly shows that the E‐ and Z‐isopropyl groups rotate with very different rates, thus providing experimental evidence for the stepwise nature of the conformational interchange.
Structural assignment of the isomeric 2‐ and 4‐endo‐ iodobicyclo[3.3.1]non‐6‐ene‐3‐endo‐ carbonitriles by two‐dimensional 1H and 13C NMR spectroscopy
Authors: Duddeck Helmut , Kaiser Manfred , Brosch Dino 
Published: May 2005

AbstractThe structural assignment of 2‐ and 4‐endo‐iodobicyclo[3.3.1]non‐6‐ene‐3‐endo‐carbonitriles was accomplished by evaluation of their COSY spectra. All 1H and 13C signals were identified unequivocally. Vicinal 1H‐1H coupling constants. NOESY experiments and iodine substituent effects on the 13C chemical shifts show that these molecules prefer the chair conformation.
Determination of the E,Z configuration of alkenephosphonates by the use of vicinal 13C31P coupling constants
Authors: Spassov S. L. , Markova L. , Mondeshka D. M. , Tancheva Ch. N. , Angelov Ch. M. 
Published: May 2005

AbstractThe vicinal 13C31P couplings in the CCCP fragment of alkenephosphonates (∼8 Hz for a cis‐ and ∼22 Hz for a trans‐orientation of the respective nuclei) are a reliable and convenient parameter for the determination of the EZ configuration of these and analogous compounds.
SIMPLE 1H NMR observation of cooperative hydrogen bonding in O‐3′‐sucrose derivatives
Authors: Christofides John C. , Davies David B. 
Published: May 2005

AbstractApplication of the SIMPLE NMR method (secondary isotope multiplet NMR of partially labelled entities) to O‐3′‐sucrose derivatives in DMSO‐d6 solution reveals the presence not only of the 1‐OH Fru…︁‐2‐OH Glu intramolecular hydrogen bond in 3,3′,4′,6′‐tetra‐O‐acety Isucrose, but also of an extensive hydrogen bond network in the glucose residue of 3′,6′‐di‐O‐benzoylsucrose, i.e. 2‐OH…︁3‐OH…︁4‐OH…︁6‐OH.
13C NMR Spectra of 1‐Amino‐1,2,3‐triazole Derivatives. 2—Identification of 4,5‐Unsymetrically Substituted 1‐(N,N‐Diaroyl)amino‐1,2,3‐triazotes
Authors: Rodios Nestor A. 
Published: May 2005

AbstractThe13C NMR spectra of some 1‐(N,N‐diaroyl)amino‐1,2,3‐triazole derivatives are reported. The shifts of the methyl carbons attached to the triazole ring and those of C‐4 and C‐5 of the ring were used to distinguish between 4,5‐unsymmetrically substituted derivatives. The location of a methyl group on the 4‐or 5‐position of the ring can be also deduced from the 1J CH3 value. A complete assignment of the aroyl carbons of the imide moiety is given.
Steric influences on spin‐lattice relaxation rates of methyl protons in substituted aromatic molecules
Authors: Chazin Walter J. , Colebrook Lawrence D. 
Published: May 2005

AbstractProton spin‐lattice relaxation rates (R1 values) have been measured at 400 MHz for a series of substituted aromatic compounds to determine the steric effects of ortho substituents on the R1 values of the methyl groups. These values have been interpreted on the basis of differences in the barriers to methyl group rotation caused by the substituent, resulting in changes in the contributions from the dipolar and the spin‐rotation relaxation mechanisms. A significant dynamic range of methyl R1 values has been observed, showing that these measurements are sensitive to the steric environment.
Conformation‐activity relationships in diethylmethyl‐2‐[p‐(o‐alkyloxy‐benzamido)benzoyloxy]ethylammonium bromides in solution as detected by one‐ and two‐dimensional 1H NMR spectroscopy
Authors: Sega Alessandro , Gaggelli Elena , Valensin Gianni 
Published: May 2005

AbstractThe relative conformation of the aromatic rings and the amide bridge of a series of diethylmethyl‐2‐[p‐(o‐alkyloxybenzamido)benzoyloxy]ethylammonium bromides has been established by a combined analysis of non‐selective, single‐selective and double‐selective pulse experiments. Relevant details of the main conformation adopted in solution by the alkyloxy and the diethylmethyl‐2‐benzoylosyethylammonium side‐chains have been obtained by 1H{1H} NOE and 1H two‐dimensional NMR analysis. Molecular Dreiding models were used as a basis of comparison.
Re‐investigation of the conformational interconversion of the 1,2,3,6,7,8‐hexahydropyrene cation radical by EPR, ENDOR and TRIPLE spectroscopy
Authors: Mäkelä Reijo , Vuolle Mikko 
Published: May 2005

AbstractThe conformational interconversion of the 1,2,3,6,7,8‐hexahydropyrene cation radical has been re‐examined by EPR, ENDOR and TRIPLE spectroscopy, and the Arrhenius plot is presented for a wider temperature range than that used earlier. The EPR spectra were measured from 143 to 369 K and the ENDOR spectra from 143 to 263 K. The thermodynamic constants of the conformational interconversion of the cation radical were determined on the basis of the temperature‐dependent spectra. The high‐resolution spectra clearly show that there are two overlapping spectra at low temperature, and this is confirmed by simulation.
Synthetic applications of N–N linked heterocycles. Part 18—substituent effects on the 13C NMR spectra in N‐(4‐Aryliminio‐2,6‐dimethylpyridin‐1‐yl)pyridinium bistetra‐fluoroborates, and some variable‐temperature 1H NMR measurements
Authors: Sammes Michael P. , Ho King‐Wah , Katritzky Alan R. 
Published: May 2005

AbstractThe 13C and 1H NMR spectra have been recorded and fully interpreted for a series of N‐(4‐Aryliminio‐2,6‐dimethylpyridin‐1‐yl)pyridinium bistetrafluoroborates having a variety of phenyl para substituents. Correlations between 13C chemical shifts and both Hammett and Taft dual‐substituent parameters for the aryl substituents were found for C‐2, C‐6, C‐3 and C‐5 of the iminiopyridinyl ring (but not for C‐4), and also for the aryl carbon atom attached to the imino group. Data from variable‐temperature 1H NMR spectra suggest that isomerization about the iminium CN bond is by the little known deprotonation‐imine isomerization‐reprotonation mechanism.
Solute molecular structure determination by NMR: Furan in liquid crystal mixtures
Authors: Jokisaari Jukka , Hiltunen Yrjö , Heikkilä Helena 
Published: May 2005

AbstractThe rα structure of furan dissolved in various thermotropic nematogens and in their mixtures was studied. The results indicate that the structure is not very sensitive to the solvent, contradicting the observations made earlier on the structure of thiophene. The distance ratios and bond angles are observed to be in fair agreement with the results derived from a microwave spectrum.
A 1H and 13C NMR conformational study of methyl‐substituted isochromanes
Authors: Pihlaja K. , Mattinen J. , Kleinpeter E. , Meusinger R. , Duscheck Ch. , Borsdorf R. 
Published: May 2005

AbstractThe 1H and the noise‐decoupled 13C NMR spectra of isochromane and 13 of its methyl‐substituted derivatives were recorded and analysed. The collected data were used to assign the configurations and to determine the position of the conformational equilibria based on the vicinal 1H coupling constants of the aliphatic moiety of the ring system. In some cases the substitution site‐dependent conformational energies of the methyl substituents were also used to estimate the conformer ratios. The primary and some vicinal methyl substituent effects on the 13C chemical shifts of the oxane ring carbons were derived and compared with those of 1,3‐dioxanes. Their usefulness in conformational analysis is demonstrated for 1‐methylisochromane.
Anisotropic solvent‐induced shifts of the trimethylsiloxy group
Authors: Parsonage J. R. , Vidgeon E. A. 
Published: May 2005

AbstractPolyorganosiloxanes of the QxMy type [Q = SiO4/2; M = (CH3)3SiO1/2] have been quantitatively analysed by 1H NMR in the presence of aromatic solvents. This has been achieved by integrating the signals due to the separation of the chemically equivalent trimethylsilyl protons. This separation is a further example of the ASIS effect (anisotropic solvent‐induced shift). The inverse relationship between observed shift and solute molar volume has been confirmed, and has been extended to include non‐limiting cases. Some evidence for solvent ordering and structure is also presented.
Binuclear lanthanide(III)–silver(I) NMR shift reagents: Investigations of new achiral and chiral analogs
Authors: Wenzel Thomas J. , Ruggles Anne C. , Lalonde Daniel R. 
Published: May 2005

AbstractA series of new achiral binuclear complexes formed from a ytterbium(III) tris‐beta‐diketonate and silver(I) beta‐diketonate have been evaluated as NMR shift reagents for olefins. The effectiveness of the new reagents was compared with that of similar binuclear reagents that have already been reported. Some unexpected behavior in the form of ‘wrong way’ shifts was observed in the NMR spectrum of substrates in the presence of certain binuclear reagents. Possible explanations for this observation are discussed. A series of new chiral binuclear reagents were evaluated; certain of the complexes with praseodymium(III) resulted in enhanced enantiomeric resolution when compared with previously reported examples. Binuclear complexes formed from Pr(III) tris chelates with the ligands d,d‐dicampholylmethane and 1,1‐difencholylmethane do not appear to be suitable for chiral binuclear shift reagent applications.
Deuterium isotope effects on 13C NMR chemical shifts in 7,12‐dimethylbenz[a]anthracene
Authors: Jones D. W. , Shaw J. D. 
Published: May 2005

AbstractThe 100.6 MHz 13C off‐resonance‐decoupled and polarization‐transfer NMR spectra of 7,12‐dimethylbenz[a]anthracene and its 5‐deuteriated analogue in deuteriated chloroform solution enabled assignments of the shifts of C‐3 and C‐5 to be revised, and other spectral ambiguities to be reduced. Negative, i.e. upfield, deuterium‐induced secondary isotope shifts, Δδ = δ(C…︁D) – δ(C…︁H), were evident over one, two, three and four bonds and, also, small apparently significant positive shifts to the methyl carbons at the 7‐ and 12‐positions, i.e. over five and six bonds, respectively. 13C1H coupling constants were unaffected by the deuteriation.
Differences and sums of traces within, COSY spectra (DISCO) for the extraction of coupling constants: ‘Decoupling’ after the measurement
Authors: Kessler H. , Müller A. , Oschkinat H. 
Published: May 2005

AbstractA procedure is proposed for obtaining coupling constants from phase‐sensitive H,H‐COSY spectra. For this purpose, firstly pseudo‐one‐dimensional spectra are created by co‐addition of individual traces of cross‐peaks, and by a similar addition of diagonal peaks in a spectrum which is phase corrected to pure‐absorption line shapes. The sum and difference of the pseudo‐one‐dimensional spectra of a cross‐peak and its diagonal peak give two spectra, with a pattern in which the active coupling ceases to exist (‘spin decoupling’) but is shifted by half the value of the same. If diagonal peaks are not available owing to overlapping signals, sums and differences of the pseudo‐one‐dimensional spectra of two cross‐peaks can be applied to simplify spectral patterns for the evaluation of J values. The procedure is demonstrated with the example of the AMXY spin system of a tyrosine, and the complex pattern of the Pro8 spin system of the cyclic decapeptide antamanide. The conformation of the Pro8 ring, derived from the coupling constants thus obtained, is of the γE type.
Hydrogen‐bonded 2‐hydroxybenzalazines: Complete assignment of 1H and 13C NMR spectra
Authors: Meléndez Enrique , Serrano José Luis , Sánchez‐Ferrando Francisco 
Published: May 2005

AbstractThe 80 MHz 1H NMR and 20 MHz 13C NMR spectra of eleven substited benzalazines (subsituenst: α‐methyl, α,α′‐dimethyl, 2‐hydroxy, 2,2′‐dihydroxy, 4‐n‐octyloxy, 4,4′‐di‐n‐octyloxy) possessing mesogenic acivity have been assigned using a variety of one‐dimensional techniques. These include homonuclear NOE measurements, selective heteronuclear 13C{1H} NOE difference spectroscopy, singlefrequency off‐resonance decoupling, spin—echo multiplicity sorting (SEFT) and long‐range heteronuclear coupling constant determintion via both gated decoupling and selective excitation (DANTE).
Configuration and conformation of some 4‐hydroxy‐cis‐ and ‐trans‐1‐oxadecalins
Authors: Dolmazon René , Gelin Suzanne 
Published: May 2005

AbstractThe configuration and conformation of some diastereomeric 4‐hydroxy‐cis‐ and ‐trans‐1‐oxadecalins were inferred by 1H and 13C NMR spectroscopy. The results obtained indicate that the cis‐fused compounds are conformationally homogeneous, having the oxygen atom attached to the cyclohexyl ring in the axial position. In the 13C NMR spectra, the magnitude of the α and γ substituent effects of the hydroxy group is rationalized in terms of steric deformations of the tetrahydropyran ring.
Intrinsic ASIS of the methyl protons of camphor
Authors: Bertran Jose Fernández , Rodriguez Mario rodríguez 
Published: May 2005

AbstractThe intrinsic ASIS of the C‐8, C‐9 and C‐10 methyl protons of camphor in 14 hydrocarbon solvents have been calculated using intrinsic ASIS values of the TMS protons. The intrinsic ASIS of the methyl groups show excellent correlation among themselves and, therefore, can be factored into independent solute and solvent factors UiVα. The solute factors, Ui, depend on the position of the methyl group with respect to the polar carbonyl group. The solvent factors, Vα, correlate with the benzene ring concentration of the aromatic solvents measured by d/M, which is in accordance with a general solvation mechanism but not with the formation of specific solute‐solvent complexes.
NQR and NMR study of pseudorotation in solids
Authors: Kibrik G. E. , Kjuntsel I. A. , Kozlov E. S. , Mokeeva V. A. , Soifer G. B. 
Published: May 2005

AbstractNuclear quadrupole resonance and nuclear magnetic resonance methods have been used to study the pseudorotation process in solids. In crystalline dimeric (Hal3PNR)2phosphazo compounds, where Hal = CI or F, and R contains protons, the temperature dependences of the35CI,19F and1H spectra and the relaxation times indicate intramolecular exchange of the ‘trigonal twist’ type between one axial and two equatorial halogen atoms attached to the pentacoordinated phosphorus. The activation energy,Ea, for the exchange process is obtained from theT1temperature dependence of the35CI nuclei and from theT1etemperature dependence of the19F and1H nuclei. In the case of chlorinated phosphazo compounds,Ea, lies in the 59‐105 kJ mol−1range, whereas in solid (F3PNCH3)Ea, is about 38 kJ mol−1.
Carbon‐13 and mercury‐199 NMR data for methyl‐substituted bisaryl mercury compounds
Authors: Rowland K. E. , Thomas R. D. 
Published: May 2005

Abstract13C and 199Hg NMR data are reported for seven bisaryl mercury compounds (aryl = phenyl, o‐tolyl, m‐tolyl, p‐tolyl, 2,5‐xylyl, 2,6‐xylyl and mesityl) and two unsymmetrically substituted compounds, phenyl(o‐tolyl)‐and phenyl(m‐tolyl)‐mercury, in deuteriochlorform. Also presented are carbon chemical shift substituent parameters due to mercury substitution on the aromatic ring.
13C NMR spectra of wyosine, a hypermodified nucleoside of transfer RNAs, and related compounds
Authors: Golankiewicz Bożenna , Folkman Wojciech 
Published: May 2005

AbstractComplete 13C NMR spectral assignments were made for wyosine, 4,9‐dihydro‐4,6‐dimethyl‐9‐oxo‐3‐(β‐D‐ribofuranosyl)imidazo [1,2‐a]purine, a hpermodified, fluorescent nucleoside of transfer RNAs, and its isomers methylated at N‐5 and at N‐1. The influence of the position of N‐methylation on the 13C chemical shifts of the tricyclic nucleoside is discussed. In relation to the parent N‐unsubstituted compound, the most pronounced changes of chemical shifts appear in wyosime. Chemical shift data for the sugar moiety suggest that the population of the anti conformer in wyosine is higher than in the other tricyclic nucleosides.
13C NMR Spectra and the stereochemistry of the adducts of enaminones with P‐benzoquinone
Authors: Kozerski Lech 
Published: May 2005

Abstract1‐Alkylamino‐2‐alkyloylpropenes give, with ρ‐benzoquinone, derivatives of 2H‐1,5‐benzodioxepine, 2‐phenylenamine and 2,3‐dihydrobenzo[b]furan. 13C NMR spectra were used to establish the primary structures and stereochemistry of the reaction products, which were verified by x‐ray analysis for several (Z)‐2,3‐dihydrobenzofurans. The data show the usefulness, for diastereomeric distinction, of the low‐frequency shifts induced for the chemical shifts of aliphatic or aromatic 13C nuclei by an eclipsed nitrogen in a 1,4‐arrangement.
Carbon‐13 NMR study of acridine derivatives: 13C chemical shifts of some new 9‐alkylthioacridines and 9‐alkylthio‐1,2,3,4‐tetrahydroacridinium salts
Authors: Faure R. , Poulallion P. , Galy J. P. , Giovanangelli G. , Soyfer J. C. , Barbe J. 
Published: May 2005

AbstractThirty‐five new 9‐alkylthioacridines and 9 ‐ alkylthio ‐ 1,2,3,4 ‐ tetrahydroacridinium salts were studied by 13C NMR spectroscopy and their chemical shifts are reported.
Calculation of 1H chemical shifts of conjugated alternant hydrocarbons with (4m) rings
Authors: Vogler H. 
Published: May 2005

AbstractThe 1H chemical shifts of the polycyclic alternant hydrocarbons bicyclo[6.2.0]decapentaene, cycloocta[def]biphenylene, dicycloocta[1,2,3,4‐def: 1′,2′,3′,4′‐jkl]biphenylene and cycloocta[1,2,3,4‐def]benzo[3,4]cyclobuta[6,7]biphenylene, which contain an 8‐membered ring, are calculated by means of a semi‐empirical approach. The agreement between experimental and calculated shifts is good if geometries are determined by a self‐consistent resonance integral, or even better by a π‐SCF force field procedure. Predictions are made for the as yet unknown dianions of these hydrocarbons.
Multidimensional spectroscopy
Authors: Bremser Wolfgang , Fachinger Winfried 
Published: May 2005

AbstractIntelligent programs for structure elucidation should be able to predict structural features, or even complete structures, for an unknown compound. This can be accomplished by substructure analysis of the topological matrices corresponding to the most similar reference spectra detected by a library search. A comparison of the results from different spectroscopic techniques (1H NMR, 13C NMR, IR, MS) reflects the content of the individual data bases, and also the sensitivity of the specific physical experiment to structural changes. The results can be combined to yield multidimensional information on the probability of any given substructure, even without crosslinked libraries from varying sources. In connection with the structure generator and the 13C NMR spectrum estimation in ACCESS, a prediction of novel structures is routinely possible, as exemplified by the analysis of the spectra of 3′‐methylacetophenone and genipin. The great advantages of this approach lie in its high flexibility in omitting or adding information and the absence of hand‐encoded rules, because knowledge of the system simply stems from its experience, i.e. the structure‐oriented spectral data bases.
Solid‐state tin‐119 NMR spectroscopy: The first observations of (Tin‐119, tin‐117) coupling constants
Authors: Harris Robin K. , Mitchell Terence N. , Nesbitt Geoffrey J. 
Published: May 2005

Abstract(Tin‐119, tin‐117) coupling satellites are visible in the CP/MAR spectra of tetrakis(trimethylstannyl)methane and of a series of tetrastannacyclohexanes, the values in the solid and solution states being equal within experimental error. The single signal from the former compound has a line width of only 28 Hz. The broad lines (Δν1/2 320 Hz) obtained for 1,4‐bis(trimethylstannyl)benzene precluded the observation of 5J(SnSn).
1H and 13C chemical shift data of two sulphonaphthoimidazoles
Authors: Parrilli M. , Pastore A. , Temussi P. A. 
Published: May 2005

Abstract1H and 13C chemical shifts are reported for the condensation products of 1‐amino‐2‐phenylazonaphthalene‐4‐sulphonic acid with benzaldehyde and trans‐cinnamaldehyde, two model compounds for sweetening agents. Assignments, based on several two‐dimensional techniques, confirm the naphthimidazole skeleton for both compounds.
Electron spin resonance of some nitro‐ and fluoro‐substituted triphenylmethyl radicals
Authors: Kulkarni Shrikant V. , Trapp Charles 
Published: May 2005

AbstractThe electron spin resonance spectra of the tris(4‐nitrophenyl)methyl and tris(2,3,5,6‐tetrafluoro‐4‐nitrophenyl)methyl radicals in toluene solution have been obtained and their 14N, 19F and 1H hyperfine splitting constants have been determined. Analysis of the data indicates that fluorine substituents in this system are appreciably electron attracting. This is in contrast to the fluorinated nitrobenzene radical ions, where the data suggest that fluorine may be weakly electron donating. The present results on the fluoro‐ and nitro‐substituted radical also lead to the conclusion that no steric interaction between the NO2 group and ortho‐fluorine atoms occurs, and that the group remains coplanar with the aromatic rings. The nitro group in these radicals is less electron attracting than in the nitrobenzene anions and their protonated analogs.