bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear magnetic resonance in structure determination—VII: Stereochemistry of the epoxides of the adducts of cyclopentadiene with α‐methyl‐β‐acetyl acrylic acid lactone
Authors: Sánchez‐Obregón Rubén , Salmón Manuel , Walls Fernando 
Published: May 2005

AbstractBy double and triple nuclear magnetic resonance experiments performed at 100 MHz the stereochemistry of the epoxides of Cyclopentadiene with α‐methyl‐β‐acetyl acrylic acid lactone, were determined to have the exo position.
Hammett correlation and chemical shift parameters of the methine proton in some 9‐phenyl octahydroxanthenes
Authors: Salmón M. , Jiménez A. , Zawadzki R. 
Published: May 2005

AbstractThe Hammett σ values for para E (−) Substituents in 9‐Phenyl octahydroxanthene outweigh the inductive and resonance effects acting on the methine proton.
The proton magnetic resonance spectrum of 4‐t‐butyl‐5, 6‐dihydro‐4H‐pyran
Authors: DeBoer Andrew 
Published: May 2005

AbstractThe proton magnetic resonance spectrum of 4‐t‐butyl‐5,6‐dihydro‐4H‐pyran has been analyzed with the aid of the paramagnetic shift reagent Eu(fod)3. All hydrogen‐hydrogen spin‐spin coupling constants are reported and a conformation is suggested which is consistent with these data.
Electron spin resonance spectrum of the diphenylcyclobutene anion radical
Authors: Goldberg Ira B. 
Published: May 2005

AbstractThe anion radical of 1,2‐diphenylcyclobutene was studied by electron spin resonance. The hyperfine splittings were found to be 0·47 and 0·74 G for the meta‐positions, 2·23 and 2·69 G for the ortho‐positions and 4·21 G for the para‐positions of the phenyl rings. The methylene proton splittings were 4·27 G, which would imply that the value of Q is 27 G, much lower than that of other cyclobutene anions. It was also estimated that the angle between the axis of the p‐orbitals of the ethylene group and that of the phenyl group is about 30°, in agreement with that found for the tetraphenylethylene anion.
Etude par Résonance Magnétique Nucléaire de dérivés phosphores. Etude de dithiaphospholanes‐1,3,2
Authors: Albrand Jean‐Pierre , Gagnaire Didier , Martin Jean , Robert Jean‐Bernard 
Published: May 2005

AbstractLes spectres de résonance magnétique du proton de huit dithiaphospholanes‐1,3,2 qui diffèrent par la nature du substituant attaché au niveau du phosphore ont été analysés. Les spectres du type AA′BB′X (X atome de phosphore) montrent que les deux couplages 3J(PSCH) sont faibles en valeur absolue et de signe opposé. Une étude de la torsion autour de la liaison C4—C5 est faite en examinant les valeurs des constantes de couplage 3J(HH). Les conformations des deux isomères du phényl 2, méthyl‐4 dithiaphospholane‐1,3,2 sont également discutées.
Nuclear magnetic triple resonance studies on formamide‐14N
Authors: Barboiu V. , Petrescu V. 
Published: May 2005

AbstractThe magnitudes of the two spin‐spin coupling constants J(N1H …︁ 13C), and all relatives signs of the couplings J(1H …︁ 1H) and J(1H …︁ 13C) of formamide‐14N, were determined by triple resonance experiments of the types 1H—{13C}—{14N} and 1H—{1H}—{14N}.
Proton magnetic resonance spectra of the atropisomers of ortho‐hexaphenylene
Authors: Ernst Ludger , Mannschreck Albrecht , Rümpler Klaus‐Dieter 
Published: May 2005

AbstractThe structures of the atropisomers of o‐hexaphenylene are confirmed by their proton magnetic resonance spectra. The centrosymmetrical isomer 1a gives rise to an AA′BB′ spectrum, whereas the helical isomer 1b displays an AA′BB′ spectrum for two of its aromatic rings and an ABCD for the remaining four rings. Long‐range coupling between the AA′BB′ and ABCD parts of 1b leads to a tentative assignment of the protons. An analysis of the spectrum of o‐tetraphenylene (2) is also given.
NMR‐Untersuchungen an Piperidinen—IV.13C‐NMR‐Messungen an stereoisomeren Dimethylpiperidinen
Authors: Wendisch Detlef , Feltkamp Herbert , Scheidegger Mitarbeit von Ueli 
Published: May 2005

AbstractEs wird über die 13C‐Spektren der 12 isomeren Dimethylpiperidine berichtet. Die chemischen Verschiebungen der verschiedenen 13C‐Kerne werden diskutiert, speziell in Hinblick auf konfigurative und konformative Effekte.Auszugsweise vorgetragen auf dem ‘Colloquium Spectroscopicum Internationale XVI’, Heidelberg, Germany, Oktober 1971.
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Concerning the angular dependence of the Vicinal31P1H coupling constants of phosphonate and of hydroxy‐phosphonate derivatives
Authors: Evelyn L. , Hall L. D. , Steiner P. R. , Stokes D. H. 
Published: May 2005

AbstractA series of organic phosphonate and hydroxy‐phosphonate derivatives have been synthesised and their NMR spectra fully analysed. The vicinal 31P1H coupling constants of these derivatives give evidence of a regular angular dependence.
Configurations and conformations in acyclic, unsaturated hydrocarbons. A 13C NMR study
Authors: de Haan J. W. , Van de Ven L. J. M. 
Published: May 2005

Abstract13C NMR (CMR) spectra of a number of di‐ and trisubstituted ethylenes have been measured. Very consistent values are found for the differential shieldings of allylic carbons in a number of linear, (Z)‐ and (E)‐disubstituted ethylenes. The discrepancies between the several structural elements are explained tentatively by assuming different rotational preferences in the (Z)‐isomers, the (E)‐isomers, or both. The results obtained for some branched olefins are qualitatively in agreement with conclusions reached in previous 1H NMR (PMR) investigations, with the possible exception of 2,5‐diMe‐3‐hexene.Differential shieldings in trisubstituted ethylenes are larger than in disubstituted ethylenes, probably as a consequence of steric interaction between geminal substituents.It is confirmed, that API's recent relabelling of the isomers of 3‐Me‐2‐hexene was justified. Furthermore, the (E)‐configuration is assigned to the high‐boiling isomer of 3,4,4‐triMe‐2‐pentene. On the other hand, the high‐boiling isomer of 3‐Et‐4‐Me‐2‐pentene is shown to be the (Z)‐isomer. For the isomeric pair of geraniol and nerol, the (E)‐configuration is assigned to the former and the (Z)‐configuration to the latter, in agreement with our recent PMR investigations.
Note on the relative magnitudes of substituent effects on 1H‐chemical shifts in olefinic and aromatic systems
Authors: Beeby Jane , Drake Linda , Duffin R. , Sternhell S. , Pretsch E. , Simon W. 
Published: May 2005

AbstractA regular relationship was noted between the influence of substituents on the chemical shifts of the ortho protons in mono‐substituted benzenes and the influence of the same substituents on the protons in the cis relationship in monosubstituted ethylenes.
1H‐NMR‐Spektroskopische Untersuchungen an methylsubstituierten Cyclohexen‐(4)‐dicarbonsäure‐(1,2)‐anhydriden
Authors: Werner H. , Kleinpeter E. , Zschunke A. , Mann G. 
Published: May 2005

AbstractEs wurden die chemischen Verschiebungen und Kopplungskonstanten von methylsubstituierten Cyclohexen‐(4)‐dicarbonsäure‐(1,2)‐anhydriden bestimmt. Die NMR‐Daten beweisen die Bootkonformation der cis‐Anhydride. Die Orientierung des cis‐Anhydridringes relativ zum Cyclohexenboot wird durch die Konstitution und Konfiguration der Verbindungen bestimmt und kann von den Kopplungskonstanten und den δ‐Werten der H1‐ und H2‐Protonen abgeleitet werden. Methylgruppen in Nachbarschaft zu diesen Protonen verschieben die Resonanzfrequenzen in Abhängigkeit von der konformativen Anordnung.
NMR study of the influence of β‐substituents on the intramolecular hydrogen bond in β‐dicarbonyl compounds
Authors: Shape'ko N. N. 
Published: May 2005

AbstractThe hydroxyl proton chemical shifts of β‐dicarbonyl compounds involving various β‐substituents have been studied. An additive influence of β‐substituents on the δOH shift values has been found. The results obtained suggested the existence of only one potential proton energy minimum in the intramolecular hydrogen bond of the enol forms of the β‐diketones. It has been shown that the enol forms of β‐keto esters do not follow the additivity of the δOH values for the same substituents, which may be due to a change in the proton distribution potential function in the intramolecular hydrogen bond.
Chemically induced polarisation in the decomposition of 2‐methyltetrahydrofuran hydroperoxide
Authors: Ignatenko A. V. , Kessenikh A. V. , Glukhovtsev V. G. , Nadtochii M. A. 
Published: May 2005

AbstractThe CIDNP effects observed during thermal decomposition of 2‐hydroperoxide‐2‐methyltetrahydrofuran at 150° in C6H5COH are described.An A/E multiplet effect is observed on the CH3‐propyl protons of the propylacetate formed as a result of decyclisation of the methylfuryl radical.
FT‐NMR investigation of 13C11B coupling
Authors: Axelson D. E. , Oliver A. J. , Holloway C. E. 
Published: May 2005

AbstractThe 13C FT‐NMR spectrum of sodium tetraphenylboron obtained with proton decoupling has a line‐shape which suggests the operation of a magnetic‐dipole relaxation mode. Coupling constants between 11B and the ring carbons are reported.
Ionen‐VI: Das Tetraphenyloborat‐Ion als Kernresonanz‐Verschiebungsreagens bei Anilinium‐Kationen
Authors: Schiemenz G. P. 
Published: May 2005

AbstractB(C6H5)4⊖ ist ein nützliches NMR‐Verschiebungsreagens für Anilinium‐Kationen. Die Signale von N⊕CH‐Protonen werden um 1,1 bis 2,5 ppm zu höherem Feld verschoben. Weiter entfernte Protonen werden weit schwächer beschirmt. Innerhalb gewisser Grenzen kann die Signallage frei gewählt werden. Der Nutzen von Salzmischungen für die Auflösung zufälliger Signalkoinzidenzen und die Signalzuordnung wird dargelegt.
Recherches sur la stéréochimie des diènes fonctionnels—X: Etude par Résonance Magnétique Nucléaire d'alcoxybutadiènes 1,3
Authors: Dorie J. P. , Martin M. L. , Odiot S. , Tonnard F. 
Published: May 2005

AbstractLes paramètres RMN d'alcoxybutadiènes 1,3 dépendent fortement de la configuration cis ou trans du motif éthylénique. Une discussion des différents types de constantes de couplage et des effets d'additivité de substituants sur les déplacements chimiques tente de dégager les facteurs électroniques ou stéréochimiques influencés par un changement de configuration. L'équilibre conformationnel au niveau des liaisons CC et CO est discuté en faisant appel notamment aux effets de solvant aromatique et de température.
NMR experiments on acetals—XXXIX: Conformational insights through NMR studies at 300 MHz of 2‐methyl‐4‐halogenomethyl‐1,3‐dioxolanes
Authors: Borremans F. , Anteunis M. , Ketelaere F. Anteunis‐De 
Published: May 2005

AbstractNMR spectra of cis‐ and trans‐2‐methyl‐4‐halogeno‐methyl‐1,3‐dioxolanes have been analysed at 300 MHz. Some of the extracted parameters facilitate easy distinction between these 1,3‐dioxolanes and the corresponding structurally isomeric 2‐Methyl‐5‐halogeno‐1,3‐dioxanes. Criteria enabling configurational assignments to be made for the cis‐trans isomers of the dioxolane series are tested. The Me‐2 group causes an upfield shift (0·2 to 0·3 ppm) of a trans proton at position 5, but the reversed shift for the corresponding cis proton. This competes with, or even overwhelms the effect of the CH2X‐4 substituent, which by virtue of its pronounced preferential rotameric orientation and in comparison with a simple Me‐group, has no large upfield effect on the shift of the syn‐adjacent proton. Shift criteria and coupling constants JH‐4, H‐5 in cis‐ and trans derivatives allow further conformational insights into these 1,3‐dioxolanes.
Rotational isomerism—XVI: The AA′BB′X NMR spectrum and rotational isomerism of 2‐fluoroethyl trichloroacetate
Authors: Abraham R. J. , Monasterios J. R. 
Published: May 2005

AbstractThe complete AA′BB′X analysis of the 1H and 19F NMR spectrum of CH2F.CH2OCO·CCl3 (1) as a neat liquid and in various solvents is given and considered in detail. The differentiation of the two conjugate solutions is obtained both from the X spectrum and by analysis at two field strengths. The coupling constants obtained show that the compound exists almost entirely in the gauche rotamer in all solvents.
Studies in nuclear magnetic resonance—XII: Complete analysis of the proton spectra of tert‐butylcyohexane‐3,3,4,4,5,5‐d6 and ‐3,3,5,5‐d4
Authors: Haddon Virginia R. , Jackman L. M. 
Published: May 2005

AbstractAccurate parameters for the two title compounds have been obtained by the aid of a spectral subtraction technique in conjunction with analysis by LAOCN3. It is observed that J1eq, 6eq and J1ax, 2ax are abnormally large and small, respectively, and the significance of these and other coupling constants are discussed in terms of the probable geometry of tert‐butylcyclohexane. The tert‐butyl group affects the chemical shifts of the 4‐protons, indicating that tert‐butylcyclohexyl derivatives are poor models for fixed conformers of monosubstituted cyclohexanes. The deuterium isotope effects on proton chemical shifts appear to be influenced by the same factors as proton‐proton coupling constants.
Interactions intramoléculaires—XIX: Constantes de couplage vicinales, équilibres conformationnels et interactions gauches (séries cyclohexanique et cyclohexénique)
Authors: Aycard Jean‐Pierre , Geuss Reinhart , Berger Jeanne , Bodot Hubert 
Published: May 2005

AbstractLes paramètres RMN ont été déterminés et identifiés pour les quatre stéréoisomères du diméthyl‐3,4 méthoxycarbonyl‐cyclohexane (d6‐2,2,3,4,5,5) et pour les deux stéréoisomères du méthyl‐2 méthoxycarbonylcyclohexane (d5‐2,3,4,5,5) et des méthyl‐3 X‐4 cyclohexènes (d3‐3,6,6) (X = COOCH3, CH2OH, CH2Cl). Pour le composé cyclohexanique à COOCH3 axial, la déformation du cycle est confirmée par les valeurs des constantes de couplage vicinales. Plusieurs équilibres conformationnels sont estimés et discutés, en particulier en fonction de l'inégalité des interactions gauches entre deux substituants vicinaux cis.
13C and 1H NMR spectroscopic studies on the structure of N‐methyl‐3‐pyridone and 3‐hydroxypyridine
Authors: Vögeli U. , von Philipsborn W. 
Published: May 2005

AbstractCarbon and proton NMR spectra of 3‐hydroxypyridine and its O‐methyl and N‐methyl derivatives have been analysed, and are compared with the spectra of the corresponding 2‐ and 4‐substituted pyridines. It is shown, that contrary to quantum chemical predictions and in agreement with chemical experience, 3‐hydroxy‐pyridine has a phenolic structure in solution. For the N‐methyl derivative, however, carbon and proton NMR data clearly demonstrate that this compound should be formulated as N‐methyl‐3‐pyridone. The general problem of the 3‐pyridones is discussed on the basis of calculated π‐electron densities, IR and NMR data.
Zur Interpretation 29Si‐NMR‐chemischer Verschiebungen
Authors: Engelhardt G. , Radeglia R. , Jancke H. , Lippmaa E. , Mägi M. 
Published: May 2005

AbstractZusammenfassung‐die 29Si‐NMR‐chemischen Verschiebungen δ(29Si) einer größeren Zahl von Verbindungen des Typs (CH3)4−nSiXn sowie δ(13C) einiger analoger Kohlenstoffverbindungen werden mit Hilfe von relativen paramagnetischen Abschirmungskonstanten σ* diskutiert, die nach einem vereinfachten Berechnungsverfahren bestimmt werden. Für die Berechnung von σ* werden nur p‐Orbitale berücksichtigt, als Ausgangsgrößen sind lediglilch die Elektronegativitäten von Si, C und X sowie ein einziger empirischer Korrekturfaktor erforderlich. Die berechneten Änderungen von σ* befinden sich in guter Übereinstimmung mit dem Gang der experimentellen Verschiebungen, die in den (CH3)4−nMXn‐Verbindungen in Abhängigkeit von Zahl und Art der Substituenten X beobachtet werden. Die erhaltenen Ergebnisse zeigen, daß δ(29Si) und δ(13C) im wesentlichen durch die σ‐Ladung am Si‐bzw. C‐Atom bestimmt werden und daß (p—d)π Wechselwirkungen am Si‐Atom nur eine untergeordnete Bedeutung besitzen.
Direct and indirect substituent effects on 1J(CH) in vinyl derivatives and related compounds
Authors: Ewing D. F. 
Published: May 2005

AbstractThe variation in the one–bond couplings 1J(CH) in vinyl derivatives with substituent has been examined. For the geminal proton 1J correlates very badly with substituent electronegativity but extremely well with σI, if conjugating substituents are excluded. In the case of halogen substituents the marked stereospecificity of 1J(CH) for the cis and trans protons can be rationalised in terms of an intrinsic dependence of πCH on the dihedral angle between the coupling atoms and the perturbing substituent, with an additional positive increment to the cis coupling due to direct interaction of the substituent non‐bonding electrons or to orbital circulation of the substituent electrons. The intrinsic specificity of β‐substituent effects on 1J(CH) is also found in analogous compounds containing CN and CO bonds.
1H NMR spectra of oxiranes. cis‐Arylmethyl oxiranes substituted in the phenyl ring
Authors: Villa L. , Schenetti L. , Taddei F. 
Published: May 2005

AbstractThe 1H NMR parameters for a number of cis‐arylmethyl oxiranes are reported and discussed in comparison with those of trans derivatives and styrene oxides substituted in the phenyl ring. While the macroscopic behaviour of the results is in agreement with a perturbative mechanism through the oxirane ring that is mainly electrostatic in character, a small contribution due to conjugative interaction is not excluded. It seems likely that the effect of substituents in the phenyl ring is mainly transmitted through bonds rather than through space, and that the different polarisation of the CH bonds in the oxirane ring is mainly responsible for the different behaviour of the protons in cis‐ and trans‐ arylmethyl oxiranes towards the effect of substituents.
Etude par Résonance Magnétique Nucléaire du carbone 13 de complexes du cobalt (III) et de la diméthylglyoxime
Authors: Bied‐Charreton C. , Septe B. , Gaudemer A. 
Published: May 2005

AbstractLa mesure des spectres de résonance magnétique nucléaire de 13C de plusieurs alcoylcobaloximes RCo(DMG)2B (DMG = anion diméthylglyoximate, B = amine) a permis de déterminer les effets α, β et γ du groupement Co(DMG)2B sur les déplacements chimiques des carbones du radical alcoyle R. Les déplacements chimiques des carbones des ligands diméthylglyoximates et de l'amine B sont peu dépendants de la nature du radical R. Les valeurs de δ dans les benzylcobaloximes XC6H4CH2Co(DMG)2B sont en accord avec un effet donneur du radical CH2Co(DMG)2B. Les constantes de couplages 1J(13CH) mesurées dans les méthylcobaloximes enrichies en 13C sur le méthyle ont une valeur constante lorsque B varie (J13CH = 137 ± 1 Hz) et voisine de celle trouvée dans la méthylcobalamine.
Hindered rotation in thioureas: Steric effects and conformations
Authors: Sullivan Richard H. , Price Elton 
Published: May 2005

AbstractThe temperature dependent spectra of several mono‐, di‐ and trialkylthioureas have been recorded. Free energy barriers to internal rotation about the CN bonds have been calculated. In thioureas that were unsymmetrically substituted, free energy barriers were found to be different for each CN bond with the more substituted amino group exhibiting the higher barrier. The monosubstituted thioureas showed different rotational barriers for the NH2 groups of the cis and trans isomers, respectively. The free energy barriers for the trans isomers were found to be substituent dependent and substantiate the reassignment of the high and low field substituent signals to the trans and cis isomers, respectively. The spectrum of 1‐methyl‐3‐t‐butylthiourea indicates restricted rotation of the t‐butyl group at temperatures below 200 K.
1H NMR spectra and stereochemistry of cis‐ and trans‐5,6‐dimethyl‐2‐oxo‐1,4‐dioxans
Authors: Äyräs Pertti 
Published: May 2005

AbstractThe 1H NMR spectra of isomeric 5,6‐dimethyl‐2‐oxo‐1,4‐dioxans have been recorded and the pertinent chemical shifts and coupling constants determined. The parameters indicate that both isomers exist as an equilibrium mixture of interconverting half chair ring conformations.
Addition de l'Hexafluoroacétone sur les Acides Carboxyliques—Mise en Évidence par RMN 1H et 19F. Application à l'Analyse d'un Mélange d'Acides
Authors: Pellissier N. 
Published: May 2005

AbstractLa formation réversible d'un composé, résultant de l'addition de l'hexafluoroacétone sur les acides carboxyliques, a été mise en évidence par RMN 1H, 19F et infrarouge. Ce composé, magnified image, est le résultat d'une addition nucléophile de l'acide sur le carbonyle de l'hexafluoroacétone. Cette addition est favorisée par un abaissement de la température et la présence de substituants R donneurs d'électrons.D'autre part, le déplacement chimique des groupes CF3 (ou du groupe OH) de ce composé dépend de la nature du substituant R, il est possible d'en déduire une méthode d'analyse de mélange d'acides.
Diamagnetic contribution and substituent effects on 13C n.m.r. spectra
Authors: Shahab Y. A. 
Published: May 2005

AbstractCorrection of measured chemical shifts by subtracting the diamagnetic contributions caused by certain substituents on various carbons of a molecule leads to data that allow a reasonable interpretation of substituent effects on chemical shifts in 13C n.m.r. spectroscopy. It is shown that both paramagnetic and diamagnetic terms increase on all carbons of a molecule when the atomic number of a substituent increases down the same group of the periodic table. An explanation of α‐, β‐, and γ‐ effects for methyl substitution using the same procedure is attempted.
A carbon‐13 nuclear magnetic resonance study of the cobalt (II)–Nicotinamide adenine dinucleotide complexes
Authors: Torreilles Jean , De Paulet André Crastes , Platzer Nicole 
Published: May 2005

AbstractThe addition of Co2+ to D2O solutions of Nicotinamide Adenine Dinucleotide induces modifications of the 13C n.m.r. signal line widths of these coenzymes. Analysis of the observed paramagnetic effects shows that both states (reduced and oxidized) and both conformations (folded or unfolded) of these coenzymes always allow two types of interactions between the cobalt ion and the nucleotide, namely where Co2+ is linked to the phosphate groups and to nitrogen‐7 of the adenine nucleus. Moreover, the metal ion also interacts with the adenine NH2 in the NAD+ folded conformation. These natural abundance 13C n.m.r. experiments allowed a fairly precise description of the Nicotinamide Adenine Dinucleotide—Co2+ interactions.
Carbon‐13–fluorine‐19 coupling constants in benzotrifluorides
Authors: Newmark Richard A. , Hill James R. 
Published: May 2005

AbstractThe carbon–fluorine coupling constants in 33 different substituted benzotrifluorides (trifluoromethyl‐benzenes) have been determined. The 3J(CF) to the ortho aromatic ring carbons varied between 1.7 and 5.6 Hz and, in a given molecule, were always larger than the 5J(CF) to the para carbon, which ranged between 0.7 and 1.7 Hz. Coupling to the meta carbons, 4J(CF), was not observed and is under 0.3 Hz.
Carbon‐13 n.m.r. characterization of indenyllithium in solution
Authors: Edlund Ulf 
Published: May 2005

Abstract13C N.m.r. chemical shifts obtained for indenyl‐ and cyclopentadienyllithium in several, mostly ethereal, solvents are presented. The chemical shift changes induced by varying the solvent are assumed to probe the actual π‐electron density distribution, thus providing an insight into the structure of the ion‐pair. The increase in the estimated π‐electron densities obtained for the protonated aromatic carbons of indenyllithium by increasing the coordinating ability of the solvent gives evidence of a change of the ion‐pair equilibrium towards solvent‐separated species. The average chemical shifts for indenyl‐ and cyclopentadienyllithium were independent of the choice of solvent, a fact which supports the ion‐pair model in all studied media.