bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton magnetic resonance spectra and conformation of some trisubstituted cyclopropane compounds
Authors: Bednar R. , Herzig U. , Schuster I. , Schuster P. , Wolschann P. 
Published: May 2005

AbstractThe n.m.r. spectra of some 1,2,2‐trisubstituted cyclopropanes are reported. Coupling constants and chemical shifts of the cyclopropane protons and their dependence on substituent effects are discussed. Conformations of benzylcyclopropane derivatives are investigated by long range magnetic shielding. The concentration dependence of the n.m.r. spectra of some 1,3‐diols is explained by inter‐ and intramolecular hydrogen bonding.
Calculation of the diamagnetic component of the nuclear screening constant for C, N, O and F
Authors: Ebraheem K. A. K. , Webb G. A. , Witanowski M. 
Published: May 2005

Abstract‘Local’ and ‘nonlocal’ contributions to σd are calculated by INDO molecular orbital methods. It is demonstrated, by means of Pople's approach5 using ‘gauge dependent’ atomic orbitals, that σ is effectively constant for C, N, O or F in a number of chemically different environments and that σ is negligible. The use of Flygare's method12 produces a significant and variable ‘nonlocal’ contribution, which renders σd in this formulation comparable to the gauge dependent term in Ramsey's expression.
Isobenzopyryliumsalts: VII—13C n.m.r. shifts of 1‐arylisobenzopyrylium salts and correlation with Hammett parameters
Authors: Vajda Miklos , Voelter Wolfgang 
Published: May 2005

AbstractThe signal identifications of isobenzopyrylium salts has been achieved on the basis of proton broad‐band and off‐resonance decoupled 13C n.m.r. spectra of twelve different 1‐arylisobenzopyrylium salts and eight model compounds. From the 13C shifts valuable information about pK values, the aromatic character and the conjugative effects of isobenzopyrylium salts was obtained.
Constantes de couplage 203Tl13C et 205Tl13C
Authors: Lallemand J. Y. , Duteil M. 
Published: May 2005

AbstractLes constantes do couplage 1J (203Tl13C) et 1J (205Tl13C) dans le trifluoroacétate de phenylthallium (III) ont été mises évidence.
Structural studies by 1H and 13C d.n.m.r.: I—barrier to trans‐cis isomerization in aliphatic enamino ketones of the type RCOCHCHNHR1
Authors: Czerwińska E. , Kozerski Lech , Boksa J. 
Published: May 2005

AbstractD.n.m.r. studies have been performed involving the measurement of rates of trans‐cis isomerization of aliphatic enamino ketones of the type RCOCHCHNHR1, by means of equilibration experiments and the method of finding the coalescence temperature. Simultaneous observation of the rates of dynamic NH proton exchange and isomerization processes by the latter method has facilitated the assignment of the rate‐determining reaction step in the title compounds studied in aprotic solvents. Thermodynamic parameters are discussed and the dipolar transition state to isomerization in a nonpolar solvent indicated. The dynamic behaviour of all protons undergoing exchange between the possible sites in the molecule are discussed in the light of our own experiments and other recent data.
Shift reagent spectra. The automatic determination of relative bound shifts and the automatic assignment of signals in the parent spectrum. Effects of concentration, temperature and solvent on relative bound shifts
Authors: ApSimon John W. , Beierbeck Helmut , Fruchier Alain 
Published: May 2005

AbstractIn the use of a shift reagent as an aid in the structural elucidation of organic compounds, it is shown that accurate measurements of the shift reagent and substrate concentrations are not needed to determine the relative bound shifts of the substrate and the chemical shifts of the free substrate spectrum with good precision. This is possible whenever the induced shift ratios of nuclei of a given molecule are independent of the shift reagent concentration. This independence has been verified for all the monofunctional compounds described in this paper. The effect of absolute substrate concentration, solvent, temperature and the presence of water on the relative bound shifts is studied using the eight methyl group signals of β‐amyrin. The method is demonstrated by its use for structural determinations in the ketoandrostane series.
19F coupling constants and chemical shifts in some dimethylamino and alkoxy derivatives of tellurium hexafluoride, cis TeF4XY
Authors: Dalton John , McFarlane William , Wickens Clive R. , Fraser George W. , Millar James B. 
Published: May 2005

AbstractThe spectra of A2BC spin systems provided by the 19F nuclei in cis (RO) (MeO)TeF4 and (RO) (Me2N)TeF4 (R = Me, Et, Pr, i‐Pr) have been recorded and analysed. The geminal coupling constants 2J(F,F) range from 137–174 Hz and trends in the 19F chemical shifts permit complete assignment of the resonances. Stereospecific coupling between 19F and the protons of the N‐methylamino groups is also observed.
Stereochemical aspects of proton chemical shifts—V: The cumulative nature of the proton shift by vicinal substitution
Authors: Danneels Dirk , Anteunis Marc 
Published: May 2005

AbstractIt is shown that the proton chemical shift may be predicted with fairly good precision for a proton in an ethano fragment carrying a (long) vicinal substituent. Caution must be used however in calculating geminal effects.
Phosphoranes par fermeture trans‐annulaire: III—Conformation—configuration—labilité
Authors: Devillers Jean , Houalla Doureid , Mouheich Touhama , Wolf Robert 
Published: May 2005

AbstractL'analyse des spectres de résonance magnétique nucléaire des deux isomères du triméthyl‐1,6,6 phényl‐3 dioxa‐2,8 aza‐5 phosphav‐1 bicyclo [3.3.0]octane permet de proposer une conformation pour chacun des cycles pentagonaux d'une part, et une configuration de l'atome de phosphore d'autre part. La mobilité du proton HP, révélée par des expériences à haute température et par l'échange PH ⇌ PD, est sensiblement différente d'un isomère à l'autre.
A carbon‐13 n.m.r. study of sulfur‐donor ligand ortho‐metalated iron carbonyl complexes
Authors: Alper Howard 
Published: May 2005

AbstractCarbon‐13 n.m.r. data are reported for a series of sulfur‐donor ligand ortho‐metalated iron carbonyl complexes derived from thiobenzophenones. The chemical shift δ153·5–161·4 for the aromatic carbon σ‐bonded to iron is readily identified, and occurs in the same region as the signal for the corresponding carbon in a related nitrogen‐donor ligand complex. The benzylic carbon gives a signal at δ62·8–63·3, subject to the nature of the complex.
Formation of a carboxyl group satellite line in the n.m.r. spectra of solid carboxylic acids
Authors: Kimtys L. 
Published: May 2005

AbstractThe structural factors resulting in the formation of the carboxyl group satellite line on the low field side of the 1H n.m.r. spectra of carboxylic acids in the solid state have been determined from the temperature dependences of the carboxyl proton chemical shifts of acetic, dimethylacetic, ethylacetic, phenylacetic, benzoic, o‐methylbenzoic, p‐methylbenzoic and adamantyl carboxylic acids. The carboxyl group low field satellite forms at temperatures near the melting point only in the case of carboxylic acids with bulky hydrocarbon radicals (o‐methylbenzoic and adamantyl carboxylic acids).
13CC13 coupling constants in dimethyl phthalate and phthalic anhydride. Determination of signs—III
Authors: Hansen P. E. , Berg A. 
Published: May 2005

AbstractRelative signs of 13C13C coupling constants between ring carbons and carbonyl carbons in dimethyl phthalate and phthalic anhydride, 13C‐labelled in both carbonyl groups, have been determined. The two‐and three‐bond coupling constants are shown to be positive, whereas four‐bond coupling constants are negative. Substituent effects on carbon‐carbon couplings due to a carboxyl group have been determined and effects of 5‐membered ring formation in phthalic anhydride have been observed.
Etudes par la RMN du carbone‐13 de quelques dérivés cyclopropaniques: Déplacements chimiques et paramètres structuraux
Authors: Monti J. P. , Faure R. , Vincent E.‐J. 
Published: May 2005

AbstractL'étude des déplacements chimiques de 13C des dérivés monosubstitués du cyclopropane (C3H5X, X = CH3, Br et CCH) permet la détermination des paramètres directs d'additivité qui ne dépendent que de la nature du substituant. Dans le cas de substitutions multiples, à ces effets directs se superposent des effets complémentaires dus à des interactions croisées entre les substituants. L'étude systématique des dérivés polysubstitués par des atomes de brome et des groupements méthyle et ethynyle, met en évidence ces différentes contributions, et nous permet de proposer pour la plupart des cas une interprétation simple. Ces interactions font appel, soit à des transferts électroniques, soit à des interactions stériques, symétriques ou dissymétriques, entre les différents substituants ainsi que le montre la comparaison entre valeurs théoriques et mesures expérimentales des déplacements chimiques.
Carbon‐13 spin–lattice relaxation in strongly associated molecules: Carboxylic acids
Authors: Levy George C. , Terpstra Dan 
Published: May 2005

Abstract13C spin–lattice relaxation times determined for the protonated carbons of carboxylic acids and methyl esters give indications of solution dimerization with the free acids. Since isopthalic and fumaric acids have two carboxyl functions they are able to polymerize in solution. Unlike the case for molecular aggregation due to weak hydrogen bonding in solution (e.g. alcohols, phenols), the 13C T1 values of mono carboxylic acids are not significantly affected by dilution to c. 10−2 M. Variable temperature T1 measurements of both the mono and dibasic acids gave activation energies for molecular reorientation of the order of 2 kcal mol−1, considerably lower than Ea for hydrogen bonded alcohols and comparable with Ea for the unassociated methyl esters of propionic and benzoic acids.
Polymerization of 1,1,1‐trifluoroacetone with aliphatic secondary amines. A proton and fluorine magnetic resonance investigation
Authors: Dhingra M. M. , Tatta K. R. 
Published: May 2005

AbstractThe polymerization of 1,1,1‐trifluoroacetone with aliphatic secondary amines is reported. The polymerization product is found to be a mixture of four diastereoisomers of the cyclic trimer, the structure of which has been determined using proton and fluorine magnetic resonance spectroscopy. The proportions of the isomers have been estimated to be 70:19:8:3 from the 19F resonance spectrum. A comparative study of the reaction products of trifluoroacetone with metallic sodium and diethylamine is also discussed.
13C n.m.r. investigation on the nitrogen methylation of some azabenzenes
Authors: Van De Weijer Peter , Mohan Chandra 
Published: May 2005

AbstractThe 1H and 13C n.m.r. spectra of N‐methylated pyridine, pyridazine, pyrimidine and pyrazine and N,N‐dimethylated pyrimidine and pyrazine have been recorded and analysed. The change in the 13C chemical shifts under the influence of N‐methylation (Δδ) in the diazabenzenes could be predicted by the Δδ values of pyridine. A comparison of the Δδ values of N‐methylation with those of N‐protonation showed that both reactions have a similar effect.
1H‐ und 13C‐NMR‐untersuchungen an dibromoxabicyclo[n.2.1]alkanen
Authors: Kleinpeter E. , Haufe G. , Mühlstädt M. , Graefe J. 
Published: May 2005

AbstractDie 1H‐NMR‐Spektren einer Reihe von Dibromoxabicyclo[n.2.1]alkanen werden zur Bestimmung der Konfiguration und Konformation herangezogen. Die 13C‐NMR‐Spektren bestätigen die ermittelte Stereochemie. Mit zunehmender Ringgröße verlagern sich die 13C‐chemischen Verschiebungen der heteroatomsubstituierten C‐Atome kontinuierlich nach niederem Feld.
13C n.m.r. spectra of rotameric dimethyl 1‐isopropyldibenzo[b,e]bicyclo[2.2.2]octatriene‐7,8‐dicarboxylate: Non‐equivalency of carbons along the rotational axis
Authors: Nakanishi Hiroshi , Kitagawa Yukio , Yamamoto Osamu , Ōki Michinori 
Published: May 2005

Abstract13C n.m.r. spectra of dimethyl 1‐isopropyldibenzo[b,e]bicyclo[2.2.2]octatriene‐7,8‐dicarboxylate disclose the existence of both dl and meso isomers, whereas 1H n.m.r. spectra were interpreted by the sole existence of the former. Characteristic chemical shifts for the rotamers were found, among others, for carbons along the rotational axis. The non‐equivalence is most probably attributed to the difference in geometry about the carbons in question. An unusual fact was also that the more compressed methyl carbon of the isopropyl group gives a signal at higher field.
1H n.m.r. study and conformation of 3,3‐dimethyl‐3‐sila‐1‐heterocyclohexanes and derivatives (heteroatom SiCl2, SiMe2, O, NMe, S, Se, Te)
Authors: Anteunis Marc J. O. , Dedeyne Raymond 
Published: May 2005

AbstractIt is found that the basic form of the 3,3‐dimethyl‐3‐sila‐1‐heterocyclohexane family (heteroatom X = O, NMe, S, Se, Te, SiMe2, SiCl2) is the chair, having ring torsion angles in the aliphatic region tending to be somewhat more puckered (up to 7°) than in cyclohexane, except next to Si when the other heteroatom is relatively small. The 5‐tertiarybutyl‐, 6‐methyl‐ and 2‐phenyl derivatives are all anancomeric, except for the latter two derivatives when X = NMe. A 5‐tertiarybutyl group causes an additional deformation, e.g. an increased puckering of the aliphatic C‐4C‐5C‐6 region (buttressing effect). Other 1H n.m.r. features are discussed in detail, and the behaviour of the 3‐sila‐1‐heterocyclohexanes is compared with other 1,3‐diheterocyclohexanes.
Analysis of the 1H n.m.r. spectrum of 4‐methyl‐1,3‐oxathiolane. An interestingly coupled ABXM3‐case
Authors: Pihlaja Kalevi , Keskinen Raimo 
Published: May 2005

AbstractThe 220 MHz proton magnetic resonance spectrum of 4‐methyl‐1,3‐oxathiolane was recorded and analysed. The methyl and ethanic protons form an ABXM3 system, the analysis of which was carried out through several ‘trial‐and‐error’ attempts. This part of the spectrum is an interesting example of second‐order effects which, in the past, have been mistakenly associated with ‘virtual coupling’. The results are compared with those presented earlier for several alkyl substituted 4‐methyl‐1,3‐oxathiolanes.
Transmission of substituent effects through unsaturated systems. I—relative magnitudes of proton and carbon substituent chemical shifts in ethylenes, butadienes, α‐enones and benzenes
Authors: Azzaro Marcel , Gal Jean‐François , Géribaldi Serge , Novo‐Kremer Nicole 
Published: May 2005

AbstractThe carbon‐13 shifts of C‐1, C‐2 and C‐3 are determined in a series of 1‐cyclohexen‐3‐ones substituted in position 1. Linear relationships are demonstrated between the substituent chemical shifts of corresponding carbons in substituted ethylenes, butadienes, α‐enones and benzenes. The substituent chemical shifts of proton H‐2 are also reported and correlated with those of corresponding protons in ethylenes and benzenes. The slopes of the lines for the carbons directly linked to the substituent are close to unity, showing a relative independence of the substituent effect for this nucleus from the variation of the unsaturated framework. In contrast to this, the transmission of the substituent effect through one double bond (nuclei β to the substituents) decreases as the number of conjugated π bonds in the whole structure increases. This relationship is interpreted as being due to the ability of an unsaturated system to spread the variation of π electron density induced by the substituent.
77Se n.m.r. studies of organoselenium compounds: III—substituent effects in 4,4′‐disubstituted diphenyl selenides and 4,4′‐disubstituted diphenylmethanes studied by 1H, 13C and 77Se spectroscopy
Authors: Gronowitz S. , Konar A. , Hörnfeldt A.‐B. 
Published: May 2005

Abstract77Se N.m.r. spectra of 4,4′‐disubstituted diphenyl selenides have been obtained. The chemical shifts could be correlated with substituent constants of the Hammett type or with Swain and Lupton two‐parameter equations. No correlations were observed between these 77Se shifts and the 13C shifts of the CH2 group of 4,4′‐disubstituted diphenylmethanes, the latter shifts showing no correlation with substituent constants. On the other hand linear correlation was observed between the 77Se shifts of the 4,4′‐disubstituted diphenyl selenides and the 1H shifts of the CH2 group of the diphenylmethanes, the 13C shifts of their 1‐carbons and the 19F shifts of 4‐substituted fluorobenzenes.
1H n.m.r. spectra of some bicyclic compounds: I—relative configurations of the diastereomeric endo‐α‐methyl‐5‐norbornene‐2‐methanols, the corresponding saturated analogues, and their cyclization ether products
Authors: Mihailović M. Lj. , Milosavljević S. , Jeremić D. , Milovanović J. 
Published: May 2005

AbstractThe configurational and conformational relationship at C‐2 and C‐α in the two racemic diastereomeric endo‐α‐methyl‐5‐norbornene‐2‐methanols and the corresponding saturated endo‐α‐methyl‐2‐norbornanemethanols were determined by first‐order analysis of the 1H n.m.r. spectra of these compounds and of their cyclization ether products, i.e. 3‐methyl‐2‐oxatricyclo[4.2.1.04,8]nonanes and 5‐methyl‐4‐oxatricyclo[4.3.0.03,8]nonanes. In addition, the conformational preference of the hydroxyl group in the unsaturated and saturated alcohols was confirmed by the lanthanide induced shift technique, using Eu(fod)3 as shift reagent, combined with a computer program involving various conformations of the –CHOHMe group.
N.m.r. studies in the heterocyclic series: XVI—determination of the structure of 3‐azidoindazole by 1H and 13C n.m.r. spectroscopy
Authors: Fruchier Alain , Alcalde Ermitas , Elguero José 
Published: May 2005

AbstractThe 1‐NH structure for 3‐azidoindazole has been demonstrated by the observation of 1H1H and 13C1H couplings involving the hydrogen atom attached to nitrogen. A comparison between 3‐azidoindazole and indazole shows that both compounds have the same tautomeric structure.
NMR‐Untersuchungen an Dicyclopentadienderivaten. IV—1‐Syn/anti‐Epimere von endo‐Dicyclopentadienderivaten
Authors: Kleinpeter E. , Kühn H. , Mühlstädt M. 
Published: May 2005

AbstractDie syn/anti‐Stellung einer Reihe Substituenten R in 1‐Stellung am endo‐Dicyclopentadien wird mit 1H‐ und 13 C‐NMR‐Spektroskopie untersucht. Die HH‐Kopplungskonstanten der epimeren Alkohole 2 und 3 werden durch Experimente unter Zuhilfenahme von paramagnetischen Verschiebungsreagenzien[Eu(fod)3] bestimmt und die beobachteten relativen paramagnetischen Verschiebungen ΔEu gleichzeitig zur Konfigurations‐bestimmung herangezogen. Die bei syn‐Anordnung der Substituenten zunehmende sterische Spannung im Molekül spiegeln 1 H‐ und 13C‐chemische Verschiebungen sehr gut wider.
Carbon‐13 nuclear magnetic resonance spectra of isomeric oxaziridines. Effects of the nitrogen lone pair on carbon‐13 chemical shifts
Authors: Jordan Guy J. , Crist DeLanson R. 
Published: May 2005

AbstractThe carbon‐13 n.m.r. spectra of several oxaziridines were measured. Aliphatic and aromatic ipso carbon atoms trans to the lone pair of nitrogen in oxaziridines were shifted upfield by c. 9 ppm, and 3.4 ppm, respectively, in comparison with isomers of inverted configuration. The results suggest that the nitrogen lone pair is partially responsible for the observed upfield shifts.
15N and 13C n.m.r. study of azimines and azoxybenzenes
Authors: Schwotzer W. , Leuenberger Ch. , Hoesch L. , Dreiding A. S. , von Philipsborn W. 
Published: May 2005

Abstract15N chemical shifts, 1J(NN), 1J(NC) and 2J(NC) coupling constants have been used to prove the open chain structure and configuration of cis‐ and trans‐2,3‐diphenyl‐1‐phthalimidoazimines. For comparison, the corresponding data of the iso‐π‐electronic cis‐ and trans‐azoxybenzenes are also reported and discussed.
Configurational assignment of some isomeric 1,4‐diacetoxy‐2,3‐dialkylcyclopentanes from 1H‐n.m.r. spectral parameters
Authors: De Clercq P. , Samson M. 
Published: May 2005

AbstractFrom the study of the 1H n.m.r. spectral parameters of differently functionalized 1,4‐diacetoxy‐2,3‐dialkylcyclopentanes it is shown that the magnitude of those parameters allows an easy configurational assignment within a set of four different configurations.
Versuche zur Berechnung der chemischen Verschiebung von 1H, 13C und 19F Atomen in Aliphaten, Olefinen und Acetylenen
Authors: Sterk H. , Fabian W. , Suschnigg J. J. , Janoschek R. 
Published: May 2005

AbstractDie Vorhersage der chemischen Verschiebung für 1H, 13C und 19F Atome wird auf der Basis von SCF‐LCGO‐MO‐rechnungen versucht. Der 〈1/R〉 Erwartungswert als Maß für den Diamagnetismus wird exakt berechnet, der Paramagnetismus durch 〈1/R3〉 sowie Werte der Ladungsbindungsordnung angenähert. Der Einfluß der Nachbaratome wird über die Elektronendichte p(r) auf einem kugelförmigen Raster ermittelt. Die Terme ermöglichen in Form eines linear funktionalen Ansatzes die Berechnung von 1H und 13C Verschiebungen an Fluoracetylen, Fluoräthylen und Fluoräthan wobei die Regressionsrechnung für 1H einen Standardfehler von 0,39 ppm und für 13C einen Standardfehler von 1,6 ppm ergibt. Die 19F Verschiebungen werden direkt durch Festlegung des σdia:σpara Verhältnisses berechnet.
Vicinal 13C13C spin–spin coupling constants of 1‐butanols. Conformational and substituent effects
Authors: Marshall James L. , Conn Shareen A. , Barfield Michael 
Published: May 2005

AbstractA series of (>90% isotopic purity) 13C‐labeled aliphatic alcohols of the general structure CCC13COH were synthesized and studied by 13C n.m.r. to obtain all 13C13C couplings involving the labeled carbon. The 2J(CC) values were small (<0.5 Hz) and contrast with the large (up to 2.7 Hz) 2J(CC) values obtained in a previous study for 2‐butanols. The 3J(CC) values, however, were strikingly similar in the two classes of compounds with respect both to magnitude and to conformational dependency. Thus, the effect of the hydroxyl substituent on 3J(CC) values is small.
13C n.m.r. spectra of steroids —a survey and commentary
Authors: Blunt J. W. , Stothers J. B. 
Published: May 2005

AbstractThe literature on 13C n.m.r. examinations of steroids has been reviewed and the shielding data for over 400 examples are tubulated. The assignments for each compound have been considered and, where necessary, revised in the light of more recent evidence and for consistency throughout each series. The methods available for assignments are reviewed and, in many cases, illustrated with specific examples. The major practical features concerning 13C studies of steroids are discussed as a guide to the use of the technique. From the main body of shielding data, an extensive set of substituent effects has been generated to aid the examination of new systems. The utility and the limitations of these effects are described.
Quantitative analysis by nuclear magnetic resonance using precision coaxial tubing
Authors: Hatada Koichi , Terawaki Yoshio , Okuda Hiroshi 
Published: May 2005

AbstractQuantitative analysis by n.m.r. using precision coaxial tubing is described. A solution of the intensity standard is placed in the central capillary and the sample of interest in the surrounding annulus. By this method the contamination of the sample by the standard compound can be avoided and an accurate determination can be carried out by using solutions of correct concentrations of the intensity standard. Applications to several types of quantitative problems are given. In order to get a higher accuracy and precision the experimental conditions were also studied.
Étude des Paramètres de Résonance Magnétique Nucléaire et de la Stéréochimie de Thiono‐2 R‐2 Dithiaphosphorinanes‐1,3,2
Authors: Martin J. , Robert J. B. 
Published: May 2005

AbstractLes spectres de résonance magnétique nucléaire (1H, 13C, 31P) de onze R‐2 thiono‐2 dithiaphosphorinanes‐1,3,2, portant au niveau du phosphore divers restes R, ont été enregistrés et analysés. Pour les composés avec R = Cl, OMe et magnified image, la molécule adopte une forme chaise rigide, le groupement R étant axial; quand magnified image la molécule adopte une forme chaise rigide à groupement R équatorial. Les molécules avec R=phényl, Me, N(Me)2 et NHt‐Bu montrent un équilibre conformationnel chaise–chaise. L'étude de la rotation autour de la liaison PN est également examinée dans le cas du dérivé où magnified image.