bluuebunny/crossref_metadata_2025_split huggingface dataset:
The NMR spectra of the carbanions of xanthene and thioxanthene. Evidence for paratropism
Authors: Vos H. W. , Bakker Y. W. , MacLean C. , Velthorst N. H. 
Published: May 2005

AbstractThe proton NMR spectra of the carbanions of xanthene [XH]− and thioxanthene [TxH]− have been recorded and interpreted. Paratropism in the central rings of [XH]− and [TxH]− is inferred from a comparison of the chemical shifts with those of the carbanion of 9,10‐dihydroanthracene [AH]−. The contributions to the chemical shifts arising from n‐electron excess charges, local dipoles and magnetic anisotropies are discussed. Numerical values for the various ring currents have been estimated by a least squares analysis of the observed chemical shifts after applying corrections for the excess charge effect. The results point to a strongly increasing paramagnetic ring current in the central ring in the order [AH]−, [TxH]−, [XH]−.
Studies of 13CH coupling constants: III—the conformational dependence of 1J(13CH) for the formyl proton in aromatic aldehydes
Authors: Ewing D. F. 
Published: May 2005

Abstract1J(13CH) and 2J(13CH) involving the aldehydic proton in ortho‐alkylbenzaldehydes have been examined for evidence of a hyperconjugative contribution from the aromatic π‐electrons. The expected hyperconjugative effect is obscured by changes in the coupling constants resulting from steric inhibition of resonance.
NMR experiments on acetals. 300 MHz spectrum and conformational aspects of the 1‐aza‐4,6‐dioxabicyclo[3.3.0]octane system
Authors: Anteunis Marc , Gelan J. , Van Cauwenberghe R. 
Published: May 2005

AbstractComplete analyses of the 300 MHz 1H NMR spectra of 1‐aza‐4,6‐dioxabicyclo[3.3.0]octane (1a), the 5‐Me‐ (1b), and both the cis‐ and trans‐3,5‐diMe‐ derivatives (1c and 1t), as well as most of the corresponding methiodides are reported. Spectral data suggest probable conformations to be 11 (1a, 1b and 1c) and 13 (1t), respectively. The corresponding methiodides adopt slightly different forms, having flattened NC‐2C‐3 moieties (12 for 2a, 2b and 2c).
A study of 5‐membered ring conformations by the temperature dependence of the vicinal spin–spin coupling constants. Conformations of cis‐ and trans‐isomers of 4‐benzoylamino‐3‐acetoxythiophane
Authors: Lavrukhin B. D. , Filippova T. M. , Fedin E. I. 
Published: May 2005

AbstractConformational equilibrium in cis‐ and trans‐4‐benzoylamino‐3‐acetoxythiophanes has been analysed on the basis of the temperature dependence of the vicinal spin–spin coupling constants. The conformations of the compounds have been established. It has been shown that in problems of this kind the real accuracy of the experiments corresponds to a wide range of spin‐spin coupling constant values and differences between the conformer energies. To narrow the range, additional data have been used, such as the temperature dependence of other vicinal coupling constants in the same molecule, angular dependence of the vicinal constants, etc.
Long range carbon—carbon coupling in olefins. 4‐13C‐4‐propyl‐3‐heptene and 1‐13C‐1‐methylcyclohexene
Authors: Marshall James L. , Miller Denis E. 
Published: May 2005

AbstractAll 13C—13C splittings involving the C‐4 carbon of 4‐propyl‐3‐heptene and the C‐1 carbon of 1‐methylcyclohexene were determined from the appropriately labeled (> 90%‐13C) derivatives. The observed trends in coupling constants continue to offer additional means of carbon chemical shift assignments and to provide mechanistic information regarding the nature of long range carbon—carbon coupling.
Carbon‐13 nuclear magnetic resonance spectroscopy IX—monosubstituted ethylenes
Authors: Miyajima Goh , Takahashi Kensuke , Nishimoto Kichisuke 
Published: May 2005

AbstractCarbon‐13 chemical shifts of sixteen monosubstituted ethylenes were obtained. In order to explain the chemical shifts, σ and π electron densities of these compounds are calculated by the σ‐included ω‐HMO method.See Ref. 8.
A linear relationship exists between carbon‐13 chemical shifts and the calculated electron densities, and also between substituent constants and electron densities. A slope of unity is obtained between the chemical shifts of α carbons of monosubstituted ethylenes and those of carbons adjacent to the substituents in monosubstituted benzenes. On the other hand, a plot of chemical shifts of Cortho of benzene derivatives against that of the β carbon in ethylene derivatives gives a slope of 3. These slopes can be explained by the calculated electron densities. A slope of 4/3 is obtained between the direct coupling constant 1J(CH) of the α carbon in monosubstituted ethylenes and that in the corresponding substituted methanes.
Das 13C‐NMR‐Spektrum von β‐Carotin und die Ladungsverteilung in der Polyenkette von Apocarotinalen
Authors: Bremser W. , Paust J. 
Published: May 2005

AbstractEine Zuordnung der 13‐Resonanzfrequenzen von β‐Carotin gelingt als Grenzwert einer Serie von Apocarotinalen mit wachsender Kettenlänge. Dadurch erhält man genauen Einblick in die abklingende Polarisierung der Doppelbindungen mit wachsendem Abstand von der Carbonylgruppe und mit Hilfe der Relaxationszeiten in die Beweglichkeit des Moleküls.
Conformational analysis of the tropane analogue of pethidine and related compounds by 1H NMR spectroscopy
Authors: Casy A. F. , Coates J. E. 
Published: May 2005

AbstractThe preferred solute conformation of ethyl 3α‐phenyltropane‐3β‐carboxylate hydrochloride, the tropane analogue of pethidine, is shown to be a piperidine chair with an axial 3‐phenyl substituent by analysis of its 1H NMR characteristics and spectral comparisons with model compounds. Conformational studies of synthetic intermediates are also reported and favoured boat forms identified for 3α‐diphenylhydroxymethyl‐3β‐tropanol and 3α‐phenyl‐3β‐tropanyl phenyl ketone. In the hot‐plate test for analgesia performed on mice, ethyl 3α‐phenyltropane‐3β‐carboxylate is about 1·5 times as effective as pethidine.
Assignment of carbon‐13 NMR spectra and sign determination of long range carbon‐13—proton coupling constants with SPI
Authors: Chalmers A. A. , Pachler K. G. R. , Wessels P. L. 
Published: May 2005

AbstractThe application of selective population inversion (SPI) to the assignment of 13C resonances and to the determination of the relative sign of 13C1H coupling constants is demonstrated for 1‐phenyl‐1,2‐dibromo‐2‐nitroethane. A negative sign for the geminal C‐2H‐1 coupling constant has been determined from the 13C spectra. The relationship between SPI and TSI is discussed.
Carbon‐13 NMR spectra of retinal1 and its related compounds
Authors: Inoue Yoshio , Takahashi Akio , Tokitô Yasuo , Chûjô Riichirô , Miyoshi Yasuhiro 
Published: May 2005

AbstractCarbon‐13 NMR spectra of all‐trans retinal1 and vitamin A1 were measured by the pulse Fourier transform method in CCl4. All peaks in these spectra were assigned from considerations of chemical shifts, half proton‐decoupled spectra, spin‐lattice relaxation times and induced chemical shift by the addition of shift reagent. The carbon‐13 NMR spectrum was also measured for all‐trans retinal1 which had been exposed to the sunlight for three hours, and the induced isomer was proposed to be 11‐s‐cis retinal1.
Substituent effects on long range proton–proton couplings in 4‐substituted bornanones
Authors: Morris D. G. , Murray A. M. 
Published: May 2005

AbstractLong range proton–proton coupling constants between H3exo and H5exo have been measured in a series of 4‐substituted bornanones. Correlation between the magnitudes of 4J3exo–5exo and the inductive linear free energy σI has been obtained. 4‐Substituted bornanone nitrimines exhibit diminished values of 4J3exo–5exo with respect to the parent ketone.
Solvent effects on the NMR spectra of heterocyclics
Authors: Rao G. Venkoba , Balakrishnan M. , Subramanian N. Venkata 
Published: May 2005

AbstractThe NMR spectra of pyridine, pyrazine and imidazole are examined in acetone‐d6. The differential shifts of the ring protons are accounted for in terms of an interaction between the lone pair on the ring nitrogen atom and the carbonyl group of acetone.
Epoxydes cyclopentaniques conformationnellement homogènes. II—Détermination des configurations au moyen des déplacements chimiques induits par compléxation a l'Europium
Authors: Vidal Jean‐Pierre , Girard Jean‐Pierre , Rossi Jean‐Claude , Chapat Jean‐Pierre , Granger Robert 
Published: May 2005

AbstractLa configuration de divers époxydes conformationnellement homogènes en série bicyclo‐(n.3.0) alcanique trans est établie par compléxation progressive avec avec Eu(dpm)3. Les exemples décrits mettent en évidence l'importance de cette technique qui est très supérieure à tous les autres procédés physico‐chimiques déjà mis en oeuvre pour déterminer la configuration des époxydes en série cyclopentanique.
Détermination des configurations Z et E d'imines par RMP. Combinaison de l'étude directe et en présence d'Eu(fod)3
Authors: de Savignac Alain , Lattes Armand , Bon Mme Maryse 
Published: May 2005

AbstractLa combinaison de l'étude directe des spectres de RMN du proton et des déplacements induits par le complexe Eu(fod)3 a permis d'étudier les phénomènes d'isomérie syn‐anti (Z‐E) dans un certain nombre d'imines cycliques et acycliques. Un cas d'équilibration syn ⇌ anti par addition d'Eu(fod)3 a pu être mis en évidence.
Structure du propyne par RMN en phase nématique. Utilisation des satellites du carbone‐13
Authors: Haloui Ezzeddine , Canet Daniel 
Published: May 2005

AbstractLe spectre protonique ainsi que les satellites du carbone‐13 du propyne orienté dans un solvant nématique permettent d'accéder à la structure complète de cette molécule. L'accord avec les résultats obtenus par spectroscopie micro‐onde est excellent.
Carbon‐13 NMR spectra of some tetra‐ and pentacyclic triterpenoids
Authors: Knight S. A. 
Published: May 2005

AbstractThe carbon‐13 NMR spectra of lanosta‐8‐en‐3β‐ol, lanosta‐8, 24‐dien‐3β‐ol, lanosta‐7,9(11)‐dien‐3β‐ol, lanostan‐3β‐ol, eupha‐8‐en‐3β‐ol, eupha‐8,24‐dien‐3β‐ol, ursa‐12‐en‐3β‐ol (α‐amyrin) and oleana‐12‐en‐3β‐ol (β‐amyrin) have been obtained and completely assigned. The results of this study provide chemical shift data for methyl, methylene, methine and quaternary carbon atoms in tetra‐ and pentacyclic triterpenoid spectra. The carbon‐13 NMR spectrum of a triterpenoid provides a unique fingerprint for the molecule.
Proton and 13C NMR spectra of substituted methyl cyanopropionates: Effects of molecular asymmetry
Authors: Schwarz Meyer , Bradley Robert B. , McIntyre H. Michael , Becker Edwin D. 
Published: May 2005

AbstractThe proton NMR spectra at 220 MHz of two series of substituted cyanopropionates,
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have been investigated. In addition the 13C spectra at 15 MHz of the series I were also studied. In I, where the R groups are diastereotopic, differences are observed in the proton chemical shifts of the CH3 groups in R for R = CH3, C2H5, n‐C3H7, i‐C3H7, n‐C4H9, n‐C5H11 and n‐C6H13. In II [R′ = n‐C3H7, CH(CH3)2, CH2CH(CH3)2 and C(CH3)3] diastereoisomers are found with substantial differences in chemical shifts between corresponding protons. Coupling constants are interpreted in terms of conformational preferences for certain molecules in both series.
Etude par Résonance Magnétique Nucléaire de dioxaphosphorinanes‐1,3,2 à liaison PN extracyclique. Exemple de changement d'orientation de la liaison PN
Authors: Cogne André , Guimaraes Afonso G. , Martin Jean , Nardin Robert , Robert Jean‐Bernard , Stec Wojciech J. 
Published: May 2005

AbstractLe spectre de résonance magnétique nucléaire du proton de divers dioxaphosphorinanes‐1,3,2, qui portent au niveau du phosphore une liaison PN extracyclique a été analysé. Cette étude confirme que, pour une disposition géométrique donnée des atomes P, O, C et H, le couplage 3J(POCH) dépend fortement de l'orientation des liaisons au niveau du phosphore. Suivant la nature des restes attachés à l'atome d'azote, le cycle dioxaphosphorinane adopte une forme du type chaise rigide à liaison PN axiale ou équatoriale, ou au contraire une forme chaise qui s'inverse rapidement pour le temps d'observation de la RMN.
Etudes conformationnelles par Résonance Magnetique Nucléaire et variations de températures d'éthanes di‐ et trisubstitués
Authors: Rouvier Emile , Pastor Raphaël , Musso Jean , Cambon Aimé 
Published: May 2005

AbstractNous présentons dans ce travail l'étude conformationnelle de divers éthanes di‐ ou trisubstitués par des groupements N‐dialkyle, thioalkyl, alcoxy, N‐pyrrolidino, N‐benzyl, nitrile ou methoxycarbonyle. Les spectres ont été analysés par une méthode basée sur les déplacements chimiques. La stabilité relative des isomères de rotation est discutée en fonction des paramètres structuraux accessibles (géométriques et électroniques).
Carbon‐13 NMR spectra of monosubstituted pyrazines
Authors: Turner C. J. , Cheeseman G. W. H. 
Published: May 2005

AbstractCarbon‐13 NMR chemical shifts and one‐bond carbon–hydrogen coupling constants have been obtained at 15·09 MHz. The trends in the carbon chemical shifts obtained for the pyrazines parallel those of monosubstituted benzenes and 2‐substituted pyridines, except for the direct effect of substitution where the pyrazines resemble pyridines not benzenes. The substituent effects on the 13C NMR spectra are generally quite similar to those in the 1H NMR spectra. The 13C NMR spectrum of the tautomeric hydroxypyrazine has been compared with the 13C NMR spectra of 2‐, 3‐ and 4‐hydroxypyridines. Hydroxy compounds that can exist as a cyclic amide show a large meta substituent effect on the chemical carbon shift.
NMR determination of the enantiomer composition of penicillamine using an optically active europium shift reagent
Authors: Cockerill Anthony F. , Davies Geoffrey L. O. , Harrison Roger G. , Rackham David M. 
Published: May 2005

AbstractAn NMR method is described for assaying the enantiomer composition of the pharmacologically active material penicillamine (1), using tris‐(3‐heptafluorobutyryl‐d‐camphorato)europium. The L enantiomer can be detected at levels of 0·4 to 0·5% in DL mixtures. Problems due to the insolubility of penicillamine in nonpolar solvents can be overcome by a two step derivatisation procedure.
Interactions intramoleculaires. XXI—Constantes de couplage et interactions gauches avec un groupement t‐butyle (molécules cyclohexaniques deutériées)
Authors: Aycard Jean‐Pierre , Bodot Hubert 
Published: May 2005

AbstractUne ou plusieurs modifications isotopiques sont mises en évidence par l'analyse des spectres RMN des produits de deutériation du t‐butyl‐1 méthoxycarbonyl‐4 cyclohexène (d4‐3,3,6,6), des méthyl‐3 cyano‐4 cyclohexène (d3‐3,6,6) cis et trans, des t‐butyl‐3 méthoxycarbonyl‐4 cyclohexènes (d3‐3,6,6) cis et trans et des t‐butyl‐3 cyano‐4 cyclohexènes (d3‐3,6,6) cis et trans. D'après la comparaison des constantes de couplage 3J et 4 J des molécules modèles et des molécules à fortes interactions gauches, il est prouvé que ces dernières sont en conformation chaise avec des déformations de cycle relativement modérées.
Proximity effects in pyridines. Proton chemical shifts in substituted methyl pyridinecarboxylates
Authors: Deady L. W. , Harrison P. M. , Topsom R. D. 
Published: May 2005

AbstractRing and ester proton chemical shifts in six series of substituted methyl pyridinecarboxylates have been measured. Results for ring protons ortho and para to the substituent can generally be accounted for by additive substituent, ester and nitrogen effects. Shifts for protons meta to the substituent, when compared with analogous shifts in monosubstituted benzenes, provide evidence of substituent–nitrogen interactions. In particular, a special effect is noted for series where both the proton and substituent are adjacent to the nitrogen. The origin of this effect is discussed. The ester proton results lead to essentially the same conclusions. Although this probe is much less sensitive to substituent effects, the same special effect is evident for the methyl 6‐X‐picolinate series.
NMR spectral analysis of 1,3,2‐dithiaphosphorinanes and 1,3‐dithianes
Authors: Martin J. , Robert J. B. 
Published: May 2005

AbstractThe full set of NMR spectral parameters (1H, 13C, 31P) are reported for 2‐phenyl‐1,3,2‐dithiaphosphorinane and 2‐phenyl‐1,3‐dithiane. The stereochemical dependence of the coupling constants is discussed.
The solvent‐induced shift in the proton NMR of some quinolizidine substituents
Authors: Lalonde Robert T. , Donvito Thomas N. , Tsai Amy I‐M. , Wong Chunfook 
Published: May 2005

AbstractThe proton chemical shift values for the methyl groups in the nine monomethylquinolizidines are determined in deuterochloroform and benzene solutions. This solvent change results in the shielding of all the methyl groups except those in 1(a)‐and 3(a)‐methylquinolizidine which become deshielded. These results are compared with those obtained earlier for equatoral and axial methyl and methylene groups attached to the quinolizidine systems in Nuphar alkaloids and related compounds.
Hochauflösungs‐13C‐NMR‐Spektroskopie. I—Analyse der Spektren des 1,2,4‐ und 1,3,5‐Triazins sowie ihrer Methyl‐ und Phenylderivate
Authors: Braun S. , Frey G. 
Published: May 2005

AbstractMit Hilfe der Puls‐Fourier‐Transform‐Technik wurden die Hochauflösungs‐13C‐NMR‐Spektren des 1,2,4‐ und 1,3,5‐Triazins sowie ihrer Methylderivate aufgenommen, ferner auch die 1H‐breitbandentkoppelten 13C‐Spektren von phenyl‐ und methyl‐phenyl‐substituierten Triazinen. Die chemischen Verschiebungen der mehrfach substituierten 1,2,4‐Triazine verhalten sich weitgehend additiv; Abweichungen bei Phenylderivaten werden sterischen Ursachen zugeschrieben. Die 13CH‐Kopplungskonstanten werden mit denen im Benzol, im Pyridin, in den Diazinen sowie in disubstituierten Äthylenen verglichen. Der starke Einfluß von Anzahl und Position der Stickstoffatome auf die Kopplungskonstanten läßt sich daran erkennen, daß im 1,2,4‐Triazin, entgegen der üblichen Reihenfolge, geminale Kopplungen größer als vicinale sind.
Interactions intramoleculaires: XXII—Constantes de couplage, équilibres conformationnels et interactions gauches avec un groupement t‐butyle (molécules cyclohexéniques deutériées)
Authors: Aycard Jean‐Pierre , Bodot Hubert 
Published: May 2005

AbstractLes paramètres RMN d'une série de cyclohexènes disubstitués (R = CH3, (CH3)3C; X = COOCH3, CN) et spécifiquement deutériés sont déterminés. A partir des valeurs des constantes de couplage 3J(HH), 3J(HD), 4J(HH) et 5J(HH), les équilibres conformationnels sont évalués. Trois des cinq composés ayant un groupement t‐butyle en position allylique sont conformationnellement hétérogènes; les équilibres correspondants et les équilibres entre stéréoisomères permettent une analyse de ce phénomène dans le cadre de l'hypothèse de l'additivité des enthalpies libres conformationnelles et des interactions gauches.
Studies of the kinetics of the interaction between N‐trifluoroacetlyl‐D‐tryptophan and α‐chymotrypsin by pulsed nuclear magnetic resonance
Authors: Gerig J. T. , Stock A. D. 
Published: May 2005

AbstractThe Carr‐Purcell experiment first used by Allerhand and Gutowsky for the determination of chemical exchange rates has been applied to the study of an enzyme inhibitor complex. Chemical shift and relaxation time data obtained by analysis of pulsed fluorine NMR data collected at 51 MHz are shown to be consistent with high resolution results assembled at 94° 1 MHz. The rate constants for dissociation of the N‐trifluoroacetyl‐D‐tryptophan‐α‐chymotrypsin complex were determined to be 1 × 104 s−1 at 26°C and 2 × 103 s−1 at 6·5°C. The resonance position of the fluorine nuclei of the inhibitor is shifted downfield ∼1 ppm upon complexation to the enzyme, and the trifluoromethyl group suffers some restriction of molecular motion in the bound state as indicated by T1 and T2 data.
NMR study of catechol and some catecholamines
Authors: Lambert Françoise , Ellenberger Michel , Merlin Louis , Cohen Yves 
Published: May 2005

AbstractThe proton magnetic resonance spectra of catechol, epinephrine, dopamine, synephrine, tyramine and amphetamine have been analysed by computer simulation. The chemical shifts and coupling constants are discussed, with their molecular implications. Convenient parameters are introduced for the additivity of substituent effects on chemical shifts of aromatic protons. The additivity rule of coupling constants is extended to these compounds.
Alcoxyflurophosphoranes. II—Monoalcoxyfluorophosphoranes possédant un centre d'asymétrie; diastéréotopie des fluors apicaux
Authors: Robeert Dominique U. , Costa D. Jean , Riess Jean G. 
Published: May 2005

AbstractVingt‐six monoalcoxyfluorophosphoranes comportant un group asymétrique et appartenant aux types R1PF3(OR2*) (1), R1*PF3(OR2) (2), R1R3PF2(OR2*) (3) et R21PF2(OR2*) (4) ont été préparés. La non‐équivalence des fluors occupant les sites apicaux de la bipyramide trigonale est mise en évidence par RMN de 19F pour les types 1 (δFa) – δF′a ∼ 0,5 à 3,8 ppm. J(FaFa′) ∼ (10 Hz), 2 δFa – δF′a ∼ 1,1 à 1,5 ppm, J(FaFa)′ ∼ 14 Hz et 3 δFa ‐ δF′a ∼ 0,2 ppm J(FaFa′) ∼ 10 Hz, mais non pour les types 4 R12PF2(OR2*) Elle est attribuée à la diastéréotopie de ces fluors apicaux. La possibilité d'une gěne à la rotation des substituants est exclue. La synthèse de sec‐BuPF4 et EtPhPF est également décrite.
Etude par RMN du proton d'hétérocycles voisins de l'oxazaphospholane‐1,3,2. I—La phényl‐3 oxo‐2 oxathiazolidine‐1,3,2
Authors: Devillers Jean , Cornus Martine , Navech Jacques , Cazaux Louis 
Published: May 2005

AbstractL'analyse complète du spectre de résonance du proton du composé du titre est mise à profit pour une étude conformationnelle de la molécule au niveau C‐4—C‐5. La position relative des protons vis à vis de la liaison S=O est fixée grâce à l'utilisation du complexe de l'Europium Eu(fod)3. Les résultats obtenus sont tout à fait cohérents avec ceux trouvés pour des composés similaires contenant, ou non, un atome de phosphore.
Constantes de couplage de vinylallènes
Authors: Lefèvre F. , Martin M. L. , Le Bail H. , Odiot S. 
Published: May 2005

AbstractAfin de préciser l'influence d'une conjugaison de type allénique les spectres RMN du vinylallène et de plusieurs de ses dérivés méthylés ont été analysés et les signes des constantes de couplage ont été déterminés. Ces composés présentent une structure s‐trans plane des deux doubles liaisons non cumulées. Une discussion des paramètres et no amment de l'influence des substitutions méthylées fait ressortir une forte prédominance des contributions de type π. Cette interprétation est corroborée par les calculs théoriques des constantes de couplages, effectués par la méthode de perturbations finies CNDO et INDO.
NMR studies on benzaldehydes. III—Rotational isomerism and torsional barriers in stable protonated o‐ and m‐substituted benzaldehydes
Authors: Jost R. , Sommer J. M. , Drakenberg T. 
Published: May 2005

AbstractProton and carbon‐13 NMR spectroscopy have been used to obtain the torsional barrier in some protonated ortho and meta substituted benzaldehydes, and the relative populations of the O‐cis and O‐trans rotamers have been determined. The results are compared with earlier data on free benzaldehydes.
Three chlorinated bipyridine compounds: Quantum calculations and their relationship to the molecular structure and physicochemical properties of the molecules considered
Authors: Redshaw Mavis 
Published: May 2005

AbstractThe Cl35 nuclear quadrupole resonances were measured for three chlorinated bipyridine compounds. The number of resonances obtained is explained in terms of the position of one ring of the compound with respect to the other. Quantum chemical calculationsDetails of the computer programs used are available from the author on request.
confirm the explanation given.