bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon‐13 n.m.r. and CNDO/S study of 1,2‐indandione and heterocyclic analogues
Authors: Galasso Vinicio , Pellizer Giorgio , Pappalardo Giuseppe C. 
Published: May 2005

Abstract13C n.m.r. spectra are reported for 1,2‐indandione, coumarandione and thionaphthenequinone in CDCl3 solution and for isatin in dimethyl sulphoxide solution. The chemical shifts are assigned and discussed in connection with the influence of the heteroatom on the dicarbonyl group and the aromatic ring. The 13C shieldings have also been calculated by means of Pople's perturbation theory using CNDO/S wave functions.
13C n.m.r. studies of some phenanthrene and fluorene derivatives
Authors: Stothers J. B. , Tan C. T. , Wilson Nancy K. 
Published: May 2005

AbstractThe 1H and 13C spectra of fluorene, fluorenone, phenanthrene and their 4‐methyl and 4,5‐dimethyl derivatives have been examined. To complete the analyses for fluorenone and 4‐methylfluorenone, 1H spectra were recorded at 270 MHz. The results from the 1H spectra permitted unequivocal assignments for the protonated aryl carbons by selective proton decoupling. A consistent set of assignments for the quaternary carbons was obtained through consideration of the dominant relaxation processes operative at these centres. This series of compounds was examined to investigate the shielding effects produced by the close approach of methyl groups separated by five bonds for comparison with the contrasting trends found for methyl carbons separated by three and four bonds. The results indicate that the relative orientation of the methyl groups is an extremely critical factor governing their shieldings and those of neighboring centres.
Carbon‐13, proton spin–spin coupling constants in some 2‐substituted propanes
Authors: Wasylishen Roderick E. , Chum Kalvin , Bukata John 
Published: May 2005

AbstractCarbon‐13, proton coupling constants have been measured in eighteen different 2‐substituted propanes. 1J(C‐2,H) shows variations similar to those observed previously for monosubstituted methanes. 2J(C‐2,H) is essentially independent of the substituent at C‐2, while 2J(C‐1,H) varies over a range of at least 5 Hz. The latter coupling constant becomes more positive as the electronegativity of the substituent increases while 3J(CH) decreases as the electronegativity of the substituent increases. The observed trends in nJ(CH) are compared with those calculated using semi‐empirical molecular orbital theory at the INDO level of approximation.
Nuclear magnetic resonance studies of 1,3‐butadienes. IX—The 1H spectra of isoprene and related compounds
Authors: Harris R. K. , Cunliffe A. V. 
Published: May 2005

AbstractFull analyses of the five‐spin 1H n.m.r. spectra for the diene protons of isoprene, ethylbutadiene and β‐myrcene under conditions of decoupling the sidechain α‐protons are reported. The data are discussed in terms of spin–spin coupling mechanism and molecular conformation. The fully‐coupled spectra of the compounds were also examined and coupling information obtained.
Carbon‐13 n.m.r. studies of flavanone 5,3′,4′‐trihydroxy‐7β‐glucoside from Juelia subterranea (Balanophoraceae)
Authors: Desalbres X. , Duteil M. , Lallemand J. Y. , De Groot‐Pfleiderer W. , Veraloza C. 
Published: May 2005

AbstractThe complete structure and stereochemical elucidation of flavanone 5,3′,4′‐trihydroxy‐7β‐glucoside has been achieved by the aid of 13C n.m.r.
Zur Konformation von 3‐Chlormethylsubstituierten 2,3‐Dihydro‐1,4‐benzoxathiinen
Authors: Kleinpeter Erich , Mühlstädt Manfred , Kuhl Peter 
Published: May 2005

AbstractDie Vorzugskonformation einer Reihe 3‐substituierter 1,4‐Benzoxathiane wird mit Hilfe der 1H‐NMR‐Spektroskopie bestimmt.
Iterative least‐squares analysis of dynamic n.m.r. spectra. Hindered rotation of the N‐nitroso group in N‐nitroso‐N‐cyanomethylmethylamine
Authors: Szymański S. , Stefaniak L. , Witanowski M. , Ejchart A. 
Published: May 2005

AbstractIterative analysis of dynamic n.m.r. (d.n.m.r.) spectra by the least‐squares method was applied to the entire proton spectrum of N‐nitroso‐N‐cyanomethylmethylamine and, separately, to the CH3 and CH2CN sub‐spectra. Resulting differences in the estimated rates of rotation of the NO group are discussed in terms of systematic errors which may be involved in determining spin exchange rates by d.n.m.r. methods. The most probable explanation is that quadrupolar broadening and then unresolved 14N1H spin–spin splitting may appear on increasing the temperature. Estimated entropies of activation indicate that the methyl sub‐spectrum gives more reliable results.
N.m.r. studies in the heterocyclic series: XVII—carbon‐13 spectra of indazole derivatives
Authors: Bouchet Philippe , Fruchier Alain , Joncheray Gérard , Elguero Jose 
Published: May 2005

AbstractThe 13C chemical shifts of 17 indazole derivatives are discussed as a function of substituent effects and the N‐1—H or N‐2—H structure of indazole. The presence in solution of the N‐1—H tautomer is confirmed.
II. Etude de l'Influence de la Nature et de l'Orientation d'un Substituant (Cl, CO) sur les Déplacements Chimiques en Série Tertiobutyl‐4 Cyclohexanonique par RMN Protonique à Haut Champ
Authors: Grenier‐Loustalot M. F. , Lectard A. , Metras F. , Forchioni A. 
Published: May 2005

AbstractA partir des spectres de RMN protonique à 250 MHz d'une série homogène d'α chloro tertiobutyl‐4 cyclohexanones, nous montrons qu'il est possible d'évaluer les incréments ΔδCl eq et ΔδCl ax pour tous les protons du cycle; ils sont comparés à ceux trouvés par Anteunis pour le groupe OH. A partir des incréments publiés par Jackman pour le groupe tertiobutyle, nous tentons une détermination des incréments du groupe carbonyle.
Proton magnetic resonance spectra of some disubstituted naphthalenes
Authors: Lucchini Vittorio , Wells Peter R. 
Published: May 2005

AbstractThe chemical shifts and coupling constants for the ring protons of nine disubstituted naphthalenes (mainly halogenonitre compounds) in carbon tetrachloride solutions have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Substituent effects are essentially additive except when a strong π‐donor group is in direct conjugation with a strong π‐acceptor group.
Carbon‐13 n.m.r. studies of methylquinolines and methylisoquinolines
Authors: Su Ja‐An , Siew Ernest , Brown Ellis V. , Smith Stanford L. 
Published: May 2005

AbstractSpectra are reported for all seven methylquinolines, nine dimethylquinolines, six methylisoquinolines and one dimethylisoquinoline. Substituent effects for the α, ortho, meta, para, vinylogous para and peri positions are reported for the monomethylcompounds. Additivity of these substituent effects is demonstrated for the dimethyl compounds which also exhibit a vicinal dimethyl steric effect.
Carbon‐13 NMR spectra of heterocycles. Sultones and sultams.
Authors: Kausch M. , Dürr H. , Doss S. H. 
Published: May 2005

AbstractThe 13C NMR spectra of 1,3‐propanesultam, 2,4‐butanesultam, 1,4‐butanesultam, 1,3‐propanesultone and 1,4‐butanesultone, as well as some of their unsaturated analogs 2,4‐dimethylbuta‐1,3‐diene‐1,4‐sultone and 2,4‐dimethylbuta‐1,3‐diene‐1,4‐sultam, have been recorded. The observed chemical shift data for the sultams and sultones can be explained mainly on the basis of inductive effects. The δ values of the dienesultone and the dienesultam are mainly affected by M‐effects. 1H NMR as well as mass spectra have.
Application of carbon‐13 n.m.r. Spectroscopy to the structural investigation of ezomycins
Authors: Sakata Kanzo , Uzawa Jun , Sakurai Akira 
Published: May 2005

AbstractEzomycins A1, A2, B1, B2, C1, C2, D1 and D2, antifungal antibiotics, are anhydrooctose uronic acid nucleosides. Their novel structures were confirmed by studying their natural abundance 13C n.m.r. spectra in detail from gated proton‐decoupled, long‐range selective proton‐decoupled and selective proton‐decoupled spectra. The J(CH) value of the anomeric carbon signal (C‐1″) supports the β‐configuration.
17O NMR: 2J(17O1H) coupling constants by line shape analysis
Authors: Delseth C. , Kintzinger J. P. , Nguyên T. T. Tâm , Niederberger W. 
Published: May 2005

AbstractTwo bond spin‐spin coupling constants 2J(17O1H) are determined for the oxygen in ether, aldehyde, acid, ester and amide groups by line shape analysis of the corresponding 17O NMR spectra.
A Karplus‐type relationship for the vicinal coupling 3J(CCCP) in phosphonates
Authors: Thiem Joachim , Meyer Bernd 
Published: May 2005

AbstractThe complete assignment of the 13C NMR spectrum of a conformationally rigid camphane phosphonate derivative leads to a Karplus‐type function for the vicinal 3J(CCCP) coupling constants in phosphonates. The general applicability of this relationship is demonstrated.
Determination of substituent chemical shifts in the proton resonance spectra of the porphyrins
Authors: Abraham Raymond J. , Eivazi Fahimeh , Nayyir‐Mazhir R. , Pearson Harry , Smith Kevin M. 
Published: May 2005

AbstractReproducible proton chemical shifts in the porphyrin series are obtained when the spectrum is measured in chloroform using the zinc (II) complex of the porphyrin in the presence of an excess of pyrrolidine. This method is specifically demonstrated for the case of 2,4‐dicyanodeuteroporphyrin‐IX dimethyl ester which, as the free base, shows dramatic effects due to aggregation phenomena. The shifts obtained using the zinc (II) complex plus pyrrolidine method, which allow compilation of substituent chemical shifts in the porphyrin series, are shown to be the same as the less easily accessible infinite dilution shifts of the porphyrin free bases.
13C‐NMR‐spektren von bicyclo[n.1.0]alkenen
Authors: Dürr Heinz , Albert Karl‐Heinz 
Published: May 2005

AbstractDie 13C‐NMR‐Spektren einiger Bicyclo[3.1.0]hex‐3‐en‐2‐ole und Bicyclo[3.1.0]hex‐3‐en‐2‐one werden beschrieben. Die Bindungsparameter des Bicyclo[3.1.0]hex‐3‐en‐2‐ons werden aus der Kristallstruktur des endo‐6‐Methoxy‐1,3,6‐triphenylbicyclo[3.1.0]hex‐3‐en‐2‐ons abgeleitet. Mit der EHT‐Methode wird die Elektronendichte berechnet und mit den 13C‐Verschiebungen korreliert. Als Vergleichsspektrum wird das 13C‐NMR‐Spektrum eines Bicyclo[4.1.0]hepta‐1,5‐dionderivats analysiert. Die Einflüsse des an den Fünfring und an den Sechsring annellierten Cyclopropansystems werden miteinander verglichen. Während am Fünfring eine Konjugation zwischen der Carbonylgruppe und dem Cyclopropansystem auftritt, wird sie am Sechsring nicht beobachtet. Die Erklärung dafür wird auf die besonders starre Struktur des Fünfringsystems zurückgeführt.
Carbon‐13, 1H coupling constants for benzene and the tropylium ion
Authors: Günther Harald , Seel Horst , Günther Maria‐Eugenia 
Published: May 2005

AbstractThe 13C, 1H spin–spin coupling constants for benzene and tropylium fluoroborate have been measured from the 13C NMR spectra of [D5]benzene and the [D6]tropylium ion using a new experimental technique which employs highly deuterated compounds and 2D‐decoupling. For benzene the new data are in good agreement with earlier results. For the tropylium ion we find 1J = 166.79, 2J ≃ 0, 3J = 9.99 and 4J = (−)0.64 Hz. Secondary isotope effects for 13C chemical shifts, including one over four bonds, are reported.
Carbon‐13 NMR studies of thyroid hormones and model compounds. The conformational analysis of diphenyl ethers
Authors: Mazzocchi Paul H. , Ammon Herman L. , Colicelli Elena 
Published: May 2005

AbstractThe 13C spectra of a series of thyroid hormones and derivatives including thyroxine (T4) sodium salt, T4‐N‐acetyl methyl ester, triiodothyronine (T3), T3‐sodium salt, T3‐methyl ester hydrochloride, sodium triiodothyroacetate and ethyl triiodothyropropionate were assigned using chemical shift trends from model compounds, coupling constants and relaxation times. The 13C spectra of a series of diphenyl ethers were assigned and the chemical shift trends observed were analyzed on the basis of conformational changes engendered by mesomeric or steric effects.
Carbon‐13 NMR spectra of some pentacyclic triterpenoids with the olean‐12‐ene and 18α‐olean‐12‐ene skeleton
Authors: Ricca Giuliana Severini , Danieli Bruno , Palmisano Giovanni , Duddeck Helmut , Elgamal M. Hani A. 
Published: May 2005

AbstractThe 13C NMR spectra of some pentacyclic triterpenoids, 3β‐acetoxy‐11‐oxo‐olean‐12‐ene‐30‐oic acid methyl ester, 3β‐acetoxy‐11‐oxo‐olean‐12‐ene‐29‐oic acid methyl ester, the corresponding 11‐desoxo methyl esters, 3β‐acetoxy‐11‐oxo‐18α‐olean‐12‐en‐30‐oic acid methyl ester and 3β‐acetoxy‐11‐oxo‐18α‐olean‐12‐en‐29‐oic acid methyl ester are discussed. The shielding data are interpreted in term of the different orientation of the carbomethoxy group and of the change in configuration at the D/E ring junction and are diagnostically valuable for the differentiation of the mentioned compounds.
The interaction of metallophthalocyanines with electron‐acceptor metal chlorides
Authors: Białkowska Ewa , Graczyk Alfreda 
Published: May 2005

AbstractIt has been found that interactions of metallophthalocyanines with chlorides having electron‐acceptor properties results in the formation of charge transfer complexes of an ion‐pair nature. The electronic structure of these complexes and the mechanism of the interaction were studied by the EPR method. Spin‐Hamiltonian parameters were determined and the effect of the complex‐forming substance on the nature of the EPR spectrum was analysed. The experimental EPR results were correlated with the effective magnetic moments determined from measurements of magnetic susceptibility by the NMR method.
Chemical shifts for tritons in the ortho, meta and para positions of toluene as determined by tritium NMR spectroscopy
Authors: Calvert D. , Martin R. W. , Odell A. L. 
Published: May 2005

AbstractChemical shifts for tritons in ortho, meta and para positions in toluene have been determined using a 64 MHz tritium NMR spectrometer. The order of shift is meta>para>ortho, whereas the calculated shift order for protons is meta>ortho>para.
Carbon‐13 spectra of polycyclic systems Tricyclo[3.2.1.02,7]octanes as models for some tetracyclic sesquiterpenes and pentacyclic diterpenes. Ishwarane and trachylobane derivatives
Authors: Cory R. M. , Stothers J. B. 
Published: May 2005

AbstractThe 13C spectra of tricyclo[3.2.1.02,7]octane, its 1,5‐dimethyl derivative and ten tricyclo[3.2.1.02,7]octan‐6‐ones have been recorded as model compounds to aid the interpretation of the spectra of the naturally occurring polycyclic terpenes, ishwarane, ishwarone, ishwarol and methyl trachylobanate. The assignments for specific carbons in this series are based on the internal consistency of the observed shielding trends together with the effects of shift reagent on the shieldings of some of these derivatives.
13C13C spin coupling constants in phenanthrene derivatives
Authors: Berger Stefan , Zeller Klaus Peter 
Published: May 2005

AbstractThe synthesis of six 1‐X‐ (X = OH, OCH3, OCOCH3, CH3, CHO and CN) phenanthrene derivatives with a 13C label at C‐1 is described. An analysis of the 13C13C spin coupling constants shows the importance of π‐interaction for the coupling constant transmission. Small 13C13C spin coupling constants over 6 bonds are reported.
Carbon‐13 nuclear magnetic resonance spectroscopy of naturally‐occurring substances‐ LVII Triterpenes related to lupane and hopane
Authors: Wenkert Ernest , Baddeley G. Vernon , Burfitt Ivor R. , Moreno Louis N. 
Published: May 2005

AbstractThe 13C NMR spectra of lupeol and related triterpenes were recorded and all carbon shifts assigned. Their analysis aided in the shift assignment of the structurally related hopane‐like triterpenes.
Analyse Conformationnelle de Pseudoprotoberbérines Naturelles. II. Etude Structurale par RMN de 13C des Tétrahydropseudoprotoberbérines provenant de I'Isopyrum thalictroïdes
Authors: Moulis Claude , Stanislas Edouard , Rossi Jean‐Claude 
Published: May 2005

AbstractLes quatre pseudoprotoberbérines extraites de l'Isopyrum thalictroïdes L. ont été réduites par NaBH4 en tétrahydropseudoprotoberbérines correspondantes. La confrontation de leurs données de RMN de 13C avec celles de protoberbérines de synthèse permet d'une part d'attribuer une configuration du type trans‐1 à ces quatre bases réduites et d'autre part de mettre en évidence pour cette configuration trans‐1 un critère sǔr de différenciation, basé sur le déplacement chimique du carbone C‐8, entre tétrahydroprotoberbérines (sub‐stituées en 9, 10) et tétrahydropseudoprotoberbérines (substituées en 10, 11).
1H, 13C, 31P NMR and conformational study of 7‐membered ring organophosphorus compounds. 1,3,2‐dioxaphosphepanes
Authors: Guimaraes A. C. , Robert J. B. , Taieb C. , Tabony J. 
Published: May 2005

AbstractThe 1H, 13C and 31P NMR data of several 2‐R‐2‐thiono‐1,3‐dioxa organophosphorus molecules with 7‐membered rings [R = Cl, OC6H5, C6H5, CH3, N(CH3)2] are reported. The conformation of the 7‐membered ring is discussed by reference to the 3J(POCH) coupling constants which are compared with those observed in 6‐membered 1,3,2‐dioxaphosphorinanes. It is shown that caution must be exercised in using the 3J(POCH) angular dependence as a stereochemical tool. The 31P spin lattice relaxation times of some of these 7‐membered rings have been measured and the values are discussed.
Carbon‐13 nuclear magnetic resonance spectroscopy of methyl‐substituted piperidines and their hydrochloride salts
Authors: Beguin Claude G. , Deschamps Marie‐Noëlle , Boubel Véronique , Delpuech Jean‐Jacques 
Published: May 2005

AbstractCarbon‐13 chemical shifts and 1J(CH) coupling constants of piperidine, 4‐t‐butylpiperidine, five C‐methyl substituted piperidines and of the corresponding N‐methyl compounds have been measured. These NMR parameters have also been determined for the fourteen corresponding hydrochlorides. The N‐methyl‐C‐methyl piperidinium salts showed two stereoisomers on the positive nitrogen atom. The effect of protonation is discussed in relation to charge and steric effects and the methyl substituent effects are compared with those of methyl‐substituted cyclohexanes. Deviations from the general tendencies in the series are correlated with changes in ring conformations around the highly crowded substituted carbons.
15N nuclear magnetic resonance spectroscopy. Natural‐abundance 15N spectra of aliphatic oximes
Authors: Botto Robert E. , Westerman Philip W. , Roberts John D. 
Published: May 2005

Abstract15N chemical shifts of the Z and E isomers of twenty‐two ketoximes and fourteen aldoximes have been determined at the natural‐abundance level of 15N, using Fourier transform methods. The influences of π delocalization, methyl substituents and solute concentration on the oxime nitrogen shielding have been determined. The 15N shifts for oximes of several cycloalkanones have been measured and the influence of ring size on the chemical shifts is discussed.
A carbon‐13 NMR study of some alkyl‐substituted indenes. An experimental study of the baker‐nathan order of hyperconjugation in the neutral ground state
Authors: Edlund Ulf 
Published: May 2005

AbstractCarbon‐13 NMR spectra of several alkyl‐substituted indenes have been assigned and analysed. For structures having an alkyl substituent in the C‐2 position an increased shielding was observed for the remote conjugated positions C‐4 and C‐6, an alternating trend similar to that found for the 2‐cycloaminoindenes. The hyperconjugative behaviour was slightly more pronounced for the methyl group compared with an isopropyl or tert‐butyl substituent, a fact which supports a model where CH σ–π interactions are more efficient than those involving CC bonds.
NMR investigations on alanyl‐[15% 13C, 95% 15N]‐proline: 15N chemical shifts and 13C15N coupling constants
Authors: Blomberg F. , Rüterjans H. , Lintner K. , Toma F. , Fermandjian S. 
Published: May 2005

AbstractThe dipeptide alanylproline has been prepared with the proline residue both 13C (15%) and 15N (95%) enriched. 15N NMR spectra of alanylproline reveal signals for both possible conformations—cis and trans—of the dipeptide backbone in solution. Different pK values for both conformers are obtained from the pH dependence of the 15N chemical shifts using a least square programme based on the Henderson–Hasselbach equation. These different values are discussed in terms of interaction between the α‐amino group and the carboxylate group and between the carboxylate oxygen and the carbonyl oxygen of the dipeptide via hydrogen bonding. Further evidence for these interactions is obtained from the pH dependence of the ratio of the 15N NMR signal intensities of the two conformers. One, two or three bonded 13C15N coupling constants measured in the 13C NMR high resolution spectra have different values in the cis and trans isomers of alanylproline and thus indicate different geometry in the pyrrolidine ring.
Etude par RMN 13C de Dérivés Aromatiques Phénylés: Observation de Substituants Phényles en Rotation Restreinte
Authors: Caspar A. , Altenburger‐Combrisson S. , Gobert F. 
Published: May 2005

AbstractLa rotation restreinte de substituants phényles a été directement observée chez plusieurs dérivés aromatiques phénylés. Les barrières de rotation apparaissent en général supérieures à 14 kcal mol−1. Des critères utiles pour l'analyse structurale des dérivés aromatiques phénylés ont été dégagés.
13C NMR: Substituent effects on one‐bond 15N13C coupling constants in anilines and anilinium ions
Authors: Axenrod T. , Wieder M. J. , Khin Tun , Webb G. A. , Yeh H. J. C. , Bulusu S. 
Published: May 2005

Abstract1J(15N13C) values obtained from FT 13C NMR spectra were measured for a number of 15N‐enriched aniline derivatives and are found to exhibit varying degrees of dependence on the nature of the ring substituent. Theoretical calculations of 1J(15N13C) values for representative members of the systems examined were made using INDO parameters and a ‘sum‐over‐states’ perturbation approach. The calculated coupling constants are generally in fair agreement with experimental values when the integral products SN2(o)SC2(o) and (r−3)N(r−3)C have values of 34.437 au−6 and 2.770 au−6, respectively.
The complete analysis of the 1H NMR spectra of quinoline and two of its derivatives. sign determinations of inter‐ring coupling constants by means of the INDOR technique
Authors: Attimonelli M. , Sciacovelli O. 
Published: May 2005

AbstractThe complete 1H NMR spectral analyses of quinoline and two of its derivatives (4,7‐dichloroquinoline and 8‐nitroquinoline) have been performed. All the long‐range coupling constants were determined both in magnitude and sign. In determining the signs the INDOR technique was very useful and successful, allowing the resolution of transitions as close as a few hundredths of a Hz. The signs of the inter‐ring coupling constants alternate with the number of intervening bonds, according to McConnell's rule, except the all‐trans6J couplings. A linear relationship has been found between the 1H−1H and 19F−19F inter‐ring coupling constants for which the spin polarization is transmitted almost exclusively via the π‐electron system.