bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR spectra of seleninium and 1‐ and 2‐benzoseleninium cations
Authors: Boccuzzi Flora Catti , Fochi Rita 
Published: May 2005

AbstractThe analysis of the NMR spectra of seleninium and 1‐and 2‐benzoseleninium cations, recorded in deuterotrifluoroacetic acid, is reported. The effects of condensation on the spectral parameters of the protons of the seleninium ring were examined with particular reference to the shift to higher values of δ: this was consistent with the q values calculated by the HMO method. The 3J(HH) and 4J(HH) variations, including an interesting variation regarding the through‐selenium 4J coupling, are also discussed.
Spectre RMN 1H et 13C de tous les mono‐ et diacétoxynaphtalènes. Increments de déplacement chimique pour le proton et le carbone‐13. Cas de quelques autres dérivés du naphtalène
Authors: Granger P. , Maugras M. 
Published: May 2005

AbstractL'étude complète de cette série permet de justifier l'emploi des systèmes d'incréments pour l'identification des raies de résonance du proton et du carbone 13. Ces incréments peuvent être obtenus en première approximation par l'étude des dérivés monosubstitués ou par comparaison avec les dérivés du benzène.
The 14N NMR linewidth versus pH profiles for several amino acids
Authors: Cohen E. A. , Shiller A. M. , Chan S. I. , Manatt S. L. 
Published: May 2005

AbstractA spectrometer for recording 14N NMR spectra is described. The 14N NMR linewidth versus pH dependences of several amino acids and related molecules are presented. It appears that the linewidth pH profile of each amino acid is unique. Linewidth minima occur between pH 6 and 8. A discussion on how 14N NMR linewidths of amino acids might give information on weak association is given.
Group IV organometal derivatives of pyridine. I—A 1H and 13C NMR investigation of trialkylmetal derivatives of pyridine
Authors: Mitchell Terence N. 
Published: May 2005

AbstractThe proton and carbon‐13 NMR spectra of thirteen trialkylmetal derivatives of pyridine, several of which were previously unknown, have been recorded and analysed. The proton NMR spectra show variations in proton chemical shifts but not in proton‐proton coupling constants when the metal substituent is changed; the ring proton‐metal coupling constants nJ(MH) in the tin and lead derivatives correspond closely with the corresponding proton‐proton couplings nJ(HH) in pyridine. The carbon‐13 chemical shifts of the carbons bound to the metal can apparently be correlated with the electron‐donating ability of the trialkylmetal group. In the trimethylstannylpyridines the value of 1J(SnCring) varies greatly with the position of the Me3Sn group.
Double inversion de fréquences de protons méthyléniques par interaction 1‐3 syn‐diaxiales. Mise en évidence par RMN haute résolution
Authors: Grenier‐Loustalot M. F. , Lectard A. , Metras F. 
Published: May 2005

AbstractL'étude par RMN à haut champ de deux trihalogéno‐2,3,6 méthyl‐2 cyclohexanones nous a permis de mettre en évidence une double inversion de fréquences de protons méthyléniques par interaction 1‐3 syn‐diaxiales.
A computer system for structural identification of organic compounds from 13C NMR data
Authors: Schwarzenbach R. , Meili J. , Könitzer H. , Clerc J. T. 
Published: May 2005

AbstractA computerised library search system for 13C NMR data is described. Given the spectral data of an unknown compound, the system will retrieve from the library those reference compounds exhibiting similar spectra. For comparison the spectral data are converted into a binary code, designed to reflect the underlying structure rather than exact values for chemical shifts. Thus, the ability of the system to retrieve compounds similar to the unknown (as opposed to identical) is greatly enhanced. A sophisticated search strategy adapting itself automatically to the problem at hand makes the system highly efficient.
Concerning some unusual trimethylsilyl proton chemical shifts
Authors: Shapiro B. L. , Proulx T. W. 
Published: May 2005

AbstractProton and 13C NMR data are presented for six different compounds containing the fragment C6H5CCH2SiMe3. In a number of instances it was observed that, in the 1H NMR spectrum, the SiMe3 groups had a chemical shift significantly upfield from internal tetramethylsilane (δ = −0·14 to −0·36). These unexpected upfield chemical shifts of the SiMe3 groups are suggested to result from the predominance, on a time averaged basis, of conformations which place the methyl groups attached to silicon in the face of an aromatic ring. The preference for such conformations is, in turn, the result of rotational preferences exhibited by the ‘flat’ aromatic ring. These results suggest that conformational analysis of systems containing a phenyl ring should take more explicit account of the fact that the preferred orientation of this phenyl ring can have a profound influence on the conformation adopted by the remainder of the molecule. In addition, the preferred conformation of the phenyl ring can have a significant effect upon the observed 1H NMR chemical shifts, while the 13C chemical shifts are relatively insensitive to conformational factors and can be explained by well‐known substituent effects previously delineated for all‐carbon systems.
Complete analysis of the 1H NMR spectra of acetylated glycals—a conformational study
Authors: Rico M. , Santoro J. 
Published: May 2005

AbstractThe complete analysis of the 1H NMR spectra of the six acetylated glycals as well as that of tetra‐O‐acetyl‐2‐hydroxy‐D‐glucal has been carried out. The conformation of these compounds, as determined from the proton couplings (±0.05Hz) obtained, has been interpreted in terms of a rapid interconversion equilibrium between the two possible dihydropyran half‐chair conformations. A computer treatment of all observed couplings has been carried out to obtain optimized values for the populations and couplings characteristic of the two alternative half‐chair conformations. The rotamer populations of the acetoxy–methyl group are discussed on the basis of the measured 5J16 and 5J36 couplings.
Etude des formes fermées et ouvertes de spiropyrannes benzothiazoliniques en RMN 13C et 1H par transformée de Fourier
Authors: Samat A. M. , Guglielmetti R. J. , Martin G. J. 
Published: May 2005

AbstractUne étude comparative en RMN 13C et 1H par transformée de Fourier a été réalisée sur des spiropyrannes, des mérocyanines et des photomérocyanines hautement stabilisées thermiquement, en série benzothiazolinique. Les résultats obtenus mettent en évidence la polarité des formes ouvertes (mérocyanines et photomérocyanines stables), de façon générale leur configuration trans, la répartition alternée des densités électroniques sur le pont diméthinique reliant les parties ‘benzothiazolinique’ et ‘phénolate’ de ces molécules, l'existence d'une configuration privilégiée dans le cas de photomérocyanines où un groupement alkoxy ou aryloxy occupe la position 3.
Carbon‐13 chemical shifts of bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives
Authors: Lippmaa E. , Pehk T. , Belikova N. A. , Bobyleva A. A. , Kalinichenko A. N. , Ordubadi M. D. , Platé A. F. 
Published: May 2005

Abstract13C chemical shifts of more than fifty bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives (hydrocarbons, alcohols, ketones and esters) have been determined. The usefulness of ethyl derivatives for the assignment of close 13C chemical shifts in bicyclic methyl derivatives is shown both for the bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane series. Comparison of substituent effects on α‐, β‐, γ‐ and δ‐carbons in both series of compounds shows remarkable differences in steric interactions. In contrast to the rigid bicyclo[2.2.1]heptane system, both chair and boat conformations can be predominant in the bicyclo[3.2.1]octane series with the conformationally flexible 6‐membered ring.
13C NMR study of N‐unsubstituted aziridines: I—steric effects, pseudoconjugation
Authors: Mison P. , Chaabouni R. , Diab Y. , Martino R. , Lopez A. , Lattes A. , Wehrli F. W. , Wirthlin T. 
Published: May 2005

Abstract13C chemical shifts for twenty‐nine alkyl and phenyl substituted N‐unsubstituted aziridines have been measured. Additivity parameters for methyl, phenyl and aziridyl carbons have been derived with the aim of testing the consistency of the assignments made on the basis of chemical shift considerations and off‐resonance decoupling information. The observed chemical shifts are discussed in terms of steric and pseudoconjugation effects.
Hindered rotation and electronic distribution in thiocarbamates
Authors: El Migirab Saadeddin , Jadot Joseph , Laszlo Pierre , Stockis Armel 
Published: May 2005

AbstractWe wish to report here the isolation of methyl N‐(p‐methoxybenzyl)thiocarbamate, a natural product extracted from Pentadiplandra brazzena Bailli, and the synthesis of its homologue, benzyl N‐(2‐phenylethyl)thiocarbamate. The barrier to internal rotation calculated from a complete lineshape analysis of the temperature dependent 1H n.m.r. spectra is discussed. The extent of delocalization on the three N, S and O substituents on the central trigonal carbon atom is gauged from a double labelling experiment.
Chemically‐induced dynamic nuclear polarisation. Photoreactions of organomercury compounds
Authors: de Kanter F. J. J. 
Published: May 2005

AbstractThe photolysis of symmetric and asymmetric organomercury compounds has been studied by CIDNP. No indications of the existence of RHg· radicals have been found. Depending on the solvent, reactions occur from excited states with different spin multiplicities.
Proton magnetic resonance spectra of monosubstituted naphthalenes
Authors: Lucchini Vittorio , Wells Peter R. 
Published: May 2005

AbstractThe chemical shifts and coupling constants for the ring protons of fourteen monosubstituted naphthalenes in carbon tetrachloride solution have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Studies at several concentrations have enabled shifts extrapolated to infinite dilution to be obtained and concentration effects arising from solute–solute interactions to be determined.
1H NMR spectra and structures of some bicyclic compounds oriented in nematic phases
Authors: Diehl P. , Zimmermann H. 
Published: May 2005

AbstractThe 1H n.m.r. spectra of 1,4,5‐triazanaphthalene, benzothiazole and quinoline oriented in nematic liquid crystalline phases have been analysed and the parameters used to determine the interproton distance ratios.
13C and 19F chemical shifts of bridgehead halogenated adamantanes
Authors: Perkins Robert R. , Pincock Richard E. 
Published: May 2005

AbstractThe 13C chemical shifts of the sixteen bridgehead substituted mono‐, di‐, tri‐ and tetrahaloadamantanes (halo = F, Cl, Br, I) and four mixed 1,3‐dihaloadamantanes are reported. The effect of bridgehead halogens on the shift values of carbons in β and δ positions is well correlated by the simple additivity relationship based on substituent shifts of 1‐monohaloadamantanes. A substituted α‐carbon is shifted upfield with an increase in the number of halogens at other bridgehead positions and this shift is relatively greater in the order F < Cl < Br < I. This observed upfield shift of α‐carbons is opposite to the downfield shift expected from additivity. An unsubstituted bridgehead γ‐carbon is moved to lower fields by one, two and three bromines (or iodines) at other bridge‐heads while, in contrast, a third fluorine weakly shields the remaining unsubstituted γ‐carbon. Some special noncumulative effects of halogens operating across the 1,3‐bridgehead positions of adamantane are indicated by the data. The 19F chemical shifts of 1‐fluoro‐, 1,3‐difluoro‐, 1,3,5‐trifluoro‐ and 1,3,5,7‐tetrafluoroadamantanes are contrary to expectations based on inductive effects in that they move progressively upfield. Other 1‐fluoroadamantanes with chloro, bromo, or methyl groups present also show substituent‐induced chemical shifts which shield the fluorine.
A 13C NMR study of actinomycin D and related model peptides
Authors: Booth H. , Mauger A. B. , Rzeszotarski W. J. 
Published: May 2005

Abstract13C n.m.r. pulsed Fourier transform spectra were measured and interpreted for actinomycin D and for two related peptide derivatives: BOC‐Pro‐Sar‐OCH3 and BOC‐Sar‐Meval‐OCH3. Actinomycin D, specifically enriched with 13C in the chromophoric C‐methyl and in the peptide N‐methyl carbons, was produced biosynthetically. Enrichment of specific N‐methyl carbons in the model peptides was effected synthetically. Spectral assignments relied on the use of the enriched samples and particularly on off‐resonance and selective low power 1H decoupling experiments. Poor correlation was observed between some of the 13C chemical shifts in the model compounds and those of the analogous carbons in actinomycin D. Ten of our 13C assignments for actinomycin D differ from those published by Hollstein, Breitmaier and Jung.
13C n.m.r. spectra of some polychloroalkenes
Authors: Chukovskaya E. C. , Dostovalova V. I. , Vasil'eva T. T. , Freidlina R. Kh. 
Published: May 2005

Abstract13C n.m.r. spectra have been measured for thirty‐two polychloroalkenes including (i) monosubstituted compounds CH2CHCClnH2−nX, where X stands for H, Cl, alkyl, and trisubstituted alkenes CCl2CHAlk, none of which form geometric isomers; (ii) disubstituted compounds RCHCHR′; (iii) and (iv) trisubstituted compounds of the types RCClCHR′ and CHClCClR, respectively. Compounds (ii) to (iv) represent either individual isomers or mixtures of the Z and E forms. In the case of compounds (ii) and (iii), the ordering of chemical shifts is δE > δZ for the sp2‐carbon atoms and δE < δz for the adjacent tetrahedral ones. On the contrary, the signals of the sp2‐carbon atoms of compounds (iv) obey the rule δE < δz. The effect of vinyl and allyl groups as substituents on the 13C chemical shifts of chlorine‐containing groups is discussed. The dependence of the sp2‐carbon spin–spin coupling constants J(13C1H) on the number of chlorinated substituents in the molecule is also considered.
19F n.m.r spectra of polyfluoroquinolines. Long range inter‐ring 19F19F coupling constants and 19F chemical shifts
Authors: Matthews R. S. 
Published: May 2005

AbstractThe signs and magnitudes of every fluorine–fluorine coupling constant in perfluoroquinoline (1), 2,4‐dichloropentafluoroquinoline (2) and 2‐bromohexafluoroquinoline (3) have been determined by 19F n.m.r. These provide an unambiguous assignment of the spectrum of the first compound and its derivatives. Inter‐ring fluorine–fluorine coupling constants were found to be positive over an odd number of bonds and negative over an even number of bonds, similar to that observed in proton–proton coupling constants in multicyclic systems.The 19F chemical shifts of perfluoroquinoline and its protonated salt are reported and directly correlated with SCF MO calculated π‐electron densities at both fluorine and bonded carbon atoms.
1H‐NMR‐Spektroskopische Untersuchungen an isomeren Alkendiinen
Authors: Hiller A. , Kleinpeter E. , Schulze K. 
Published: May 2005

AbstractDie 1H‐NMR‐Spektren einer Reihe aliphatisch und phenylsubstituierter Alkendiine werden vorgestellt und, unter Berücksichtigung einiger literaturbekannter Verbindungen, chemische Verschiebungen und Kopplungskonstanten diskutiert.Die chemischen Verschiebungen der Protonen der untersuchten isomeren Alkendiine RCCCCCHCH2, RCHCHCCCCH und RCHCHCCCCCH3 (R = H, Alkyl, C6H5, C6H4OCH3‐p,) lassen sich hinsichtlich cis/trans‐Isomerie und Substitution an der Doppelbindung befriedigend mit elektronischen Effekten und molekularen Magnetfeldern der Mehrfachbindungen erklären. Die Kopplungs‐konstanten erweisen sich als kaum abhängig von der Substitution an der Doppelbindung. Über die Diacetylengruppierung hinweg können Kopplungen über maximal acht Bindungen beobachtet werden.
NMR studies of sulphur heterocycles: III—13C spectra of benzo[b]thiophene and the methylbenzo[b]thiophenes
Authors: Clark P. D. , Ewing D. F. , Scrowston R. M. 
Published: May 2005

AbstractAll carbon resonances in the title compounds have been unequivocably assigned. Steric effects in the peri substituted compounds have been compared with analogous effects in naphthalene and benzo[b]furan. The observed effects are not explained by current theory. Unusual deshielding steric shifts are observed at some carbons. Methyl substituent effects are not additive at any position in the sterically crowded 2,3‐disubstituted compounds.
Effects of molecular asymmetry on 13C chemical shifts in some O‐ and N‐glycidyl compounds
Authors: Everatt B. , Haines A. H. , Stark B. P. 
Published: May 2005

AbstractIn the 13C{1H} n.m.r. spectra of certain organic compounds containing two or three glycidyl (2,3‐epoxyprop‐1‐yl) groups, chemical shift nonequivalence has been observed, between diastereoisomers, for chemically similar carbon atoms in the glycidyl groups. Nonequivalence was only apparent when the glycidyl groups were linked through a single atom. In three derivatives of diglycidylaminobenzene, 13C chemical shift nonequivalence was also observed for aromatic carbon atoms ortho to the nitrogen substituent.
13C n.m.r. studies of organosilanes: II—substituent chemical shift parameters for alkoxysilanes
Authors: Rakita P. E. , Worsham L. S. , Srebro J. P. 
Published: May 2005

AbstractThe 13C n.m.r. spectra of forty alkoxysilanes of the general type XnSi(OR)4–n (X = CH3, C6H5, H; R = CH3, C2H5, n‐C3H7, i‐C3H7, n‐C4H9, i‐C4H9, s‐C4H9, n‐C5H11, CH(CH3)(C6H5), C6H5) have been recorded and assigned. The chemical shifts of the α‐carbon resonances of the alkoxy groups are shown to depend on both the nature of the alkoxy group and the number and type of substituents on the silicon. Regression analyses of the data give empirical substituent chemical shift (SCS) parameters for the silyl substituents. The β‐carbon resonances are shown to be dependent on the presence of the silyl group, but not the specific silyl substituents.
Proton n.m.r. spectra of furo[3,2‐c] and furo[2,3‐c]thiapyrylium cations, compared with their thieno homologues. Correlations between chemical shifts and charge densities from CNDO/2 and PPP calculations
Authors: Boccuzzi Flora Catti 
Published: May 2005

AbstractSignificant variations of thiapyrylium chemical shifts, by comparison with their thienohomologues, are shown by 1H n.m.r. spectra of furo[3,2‐c]thiapyrylium and furo[2,3‐c]thiapyrylium perchlorates. The observed changes can be ascribed to a different distribution of the electron charge (mainly caused by participation of the 3d orbitals of sulphur in the thienohomologues) and to a different contribution of the ring current; this is shown by MO calculations performed by the CNDO/2 and the coupled Hartree–Fock methods, respectively.
Determination of conformation of halomethyl ketones from the temperature dependence of Geminal H,H coupling constants
Authors: RamaRao M. , Bothner‐By A. A. 
Published: May 2005

AbstractThe temperature dependence of the geminal H,H coupling constant in solutions of α‐chloroacetophenone, α‐bromoacetophenone, 1‐bromo‐3‐chloro‐1‐phenylpropan‐2‐one and 1,3‐dibromo‐1‐phenylpropan‐2‐one has been determined at temperatures between 230 and 404 K. The values indicate that in the chloromethyl ketones the conformer with halogen and oxygen eclipsed is favored over that with hydrogen and oxygen eclipsed, while in the bromomethyl ketones the two conformers are of more nearly equal energy. The use of geminal coupling constants to indicate conformational preferences in substituted ketones appears promising.
Proton spin coupling constants in methylcyclopentadienes
Authors: Mstislavsky V. I. , Korenevsky V. A. , Sergeyev N. M. , Solkan V. N. 
Published: May 2005

AbstractA detailed procedure for analysing the 1H n.m.r. spectra of two isomeric methylcyclopentadienes, two dimethylcyclopentadienes and 3‐methylindene is reported. Finite perturbation INDO calculations are used to discuss the conformational features of the long range proton coupling constants.
The dilution behaviour of chlorophyll derivatives possessing α‐hydroxyethyl groups
Authors: Brockmann Hans , Trowitzsch Wolfram , Wray Victor 
Published: May 2005

AbstractThe dilution behaviour of 2(R, S)‐α‐hydroxyethyl‐2‐desvinylpyromethylphaeophorbide a (1), observed by 1H n.m.r. spectroscopy, leads to the conclusion that the doubling of many of the lines in the spectra of 1 at high concentrations in CDCl3 arises from intermolecular diastereoisomerism caused by aggregate formation.
Variable temperature n.m.r. behaviour of 1,5‐benzodiazepinones and 1,5‐benzodiazepinthiones
Authors: Benassi Rois , Lazzeretti Paolo , Taddei Ferdinando , Nardi Dante , Tajana Alberto 
Published: May 2005

AbstractThe n.m.r. variable temperature behaviour of the 7‐membered ring in 1,3‐dihydro‐2H‐1,5‐benzodiazepin‐2‐one derivatives and in the corresponding 2‐thiones has been investigated. The results indicate that the ring inversion barrier is higher in the thiones and dependent on substituents bonded at N‐1. The activation parameters are obtained and discussed.
Hétérocycles contenant du phosphore: XXVIII—Etude par Résonance Magnétique Nucléaire et analyse conformationnelle de quelques oxazaphosphorinanes‐1,3,2 (II)
Authors: Roca Claude , Kraemer Raymond , Majoral Jean‐Pierre , Navech Jacques , Brault Jean François , Savignac Philippe 
Published: May 2005

AbstractLes spectres de RMN du proton de quelques nouveaux oxazaphosphorinanes‐1,3,2 sont analysés. La stéréochimie et la conformation du cycle sont précisées. La valeur de l'enthalpie libre conformationnelle et de l'angle de torsion des liaisons C‐4C‐5 et C‐5C‐6 est calculée pour quelques uns de ces oxazaphosphorinanes‐1,3,2.
13C chemical shifts of some model olefins
Authors: Couperus P. A. , Clague A. D. H. , van Dongen J. P. C. M. 
Published: May 2005

AbstractAn extensive carbon‐13 nuclear magnetic resonance study of selected model olefins dissolved in deuteriochloroform has been carried out under standardized conditions. Assignments of the chemical shifts have been made. The influence of the nature of the solvent and the effect of changing the concentration of the solute have been investigated. The results are intended to provide a practical aid for the analysis of olefinic materials.
Diastéréotopies dans la série du benchrotrène
Authors: Tirouflet Jean , Besancon Jack , Mabon Francoise , Martin Maryvonne L. 
Published: May 2005

AbstractL'analyse des spectres RMN 1H et 13C d'une série de benchrotrènes mono‐et disubstitués a permis de discuter l'influence des substituants et spécialement les diastéréotopies associées à plusieurs types de chiralité. La forme racémique (pseudosymétrique) et les deux formes meso (pseudoasymétriques) des glycols (OC)3CrC6H4(CHOHCH3)2 sont comparées. Les implications stéréochimiques des résultats sont examinées.
13C n.m.r. of organosulphur compounds: II—13C chemical shifts and conformational analysis of methyl substituted thiacyclohexanes
Authors: Barbarella Giovanna , Dembech Pasquale , Garbesi Anna , Fava Antonino 
Published: May 2005

Abstract13C n.m.r. spectra of methyl substituted thianes and thianium cations have been determined. The magnitude of the 13C substituent effects of an equatorial methyl group or of a gem‐dimethyl grouping appear to depend in a systematic way on whether the carbon atom concerned is adjacent to, or removed from, the heteroatom. The shieldings are discussed in relation to the conformational properties of the thiane ring. Moreover, the average 13C substituent parameters obtained from conformationally biased systems are applied to potentially mobile systems to assess the position of the conformational equilibrium.