bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrimination of two methylene groups in non‐symmetric succinate esters in sesquiterpene dimers by heteronuclear 13C{1H}NOE spectroscopy
Authors: Fukushi Eri , Kawabata Jun , Mizutani Junya 
Published: May 2005

AbstractIn the assignment of the non‐equivalent methylene group of an asymmetric succinate residue in the macrocyclic lactone ring of shizukaols B and F, isolated from Chloranthus japonicus, distinction of two‐bond C—H and three‐bond C—H was needed. The steady state and transient 13C{1H}NOE was used to detect two‐bond C‐H. One pair of non‐equivalent methylene protons was saturated simultaneously by quasi‐simultaneous irradiation. Inversion of two protons whose chemical shifts were close was carried out by a squared pulse, and inversion of two protons whose chemical shifts were far from each other was performed using a double DANTE pulse train.
13C NMR chemical shifts of unbranched alk‐2‐yn‐1‐ols, ω‐alkyn‐1‐ols and ‘internal’ alkyn‐1‐ols
Authors: Poleschner Helmut , Heydenreich Matthias 
Published: May 2005

Abstract13C NMR chemical shifts of three types of unbranched alkyn‐1‐ols were measured and assigned: alk‐2‐yn‐1‐ols, ω‐alkyn‐1‐ols and ‘internal’ alkyn‐1‐ols. The derived OH shift increments depend on the number of CH2 groups between the triple bond and the OH group.
NMR spectroscopy of steroidal sapogenins and steroidal saponins: An update
Authors: Agrawal Pawan K. , Jain Dharam C. , Pathak Ashish K. 
Published: May 2005

AbstractThe 13C NMR chemical shifts of 126 Steroidal sapogenins published between 1983 and 1993 are listed and critical spectral features and advances made in the NMR characterization of these compounds are discussed as a guide for the identification of the parent skeleton and the determination of substitution patterns. The NMR spectroscopic methods applicable to deduce the complete structure of the oligosaccharide moiety and its linkage to the sapogenin residue are also presented to elucidate the structure of steroidal saponins.
Novel NMR aspects of tertiary phosphine complexes of Ru(II) etioporphyrin I
Authors: Licoccia Silvia , Paci Maurizio , Paolesse Roberto 
Published: May 2005

AbstractThe synthesis and characterization of hexacoordinated ruthenium complexes of etioporphyrin I (EP) of general formula [(EP)RuL2] (L = teriary phosphine) and of the pentacoordinated complex [(EP)Ru(PPh3)] are reported. The multiplicity observed in the 1H NMR spectra of complexes is discussed on the basis of the steric interactions between the axial ligands and the macrocycle.
Carbon‐13 and proton magnetic resonance studies of some carbonyl‐bis‐(amino acid esters)
Authors: Lochmüller C. H. , Souter R. W. 
Published: May 2005

AbstractA number of carbonyl‐bis‐(amino acid esters) have been examined by proton and carbon‐13 nuclear magnetic resonance techniques. All but one of the compounds were synthesized with two chiral centers of like‐configuration. In one series, the diastereotopic nonequivalence of isopropyl methyl groups attached to the asymmetric centers is apparent in both the proton and the carbon spectra, and the relative magnitude of the observed nonequivalence increases slightly with increasing ‘bulk’ of the neighboring ester groups. Carbon‐13 chemical shifts are reported, and a linear correlation of Taft σ* inductive constants with ester carbonyl carbon chemical shifts and with amide proton chemical shifts (for a series in which only variation of the ester substituent occurs) is presented. In addition, the effect in terms of chemical shift differences of keeping the same ester group at the asymmetric centers while varying the other substituent group, is examined.
Résolution de spectres RPE par régression non linéaire. Application à des radicaux anions dérivés de thiazoles substitués
Authors: Humm Françoise , Romanetti Robert , Tordo Paul , Bouscasse Lue , Phan‐Tan‐Luu Roger 
Published: May 2005

AbstractUne méthode de résolution des spectres RPE par régression non linéaire est décrite. On ajuste le modèle théorique avecle spectre expérimental. Le calcul de l'erreur sur chaque paramètre est décrit. On applique cette méthode à la résolution des spectres anions nitro‐2‐méthyl‐4‐thiazole, p‐nitro phényl‐4‐thiazole et p‐nitro phényl‐5‐thiazole.
The NMR spectra and conformations of cyclic compounds—VII: The conformations of β‐pinene, pinocarvone and the cis‐ and trans‐pinocarveols
Authors: Abraham R. J. , Cooper M. A. , Indyk H. , Siverns T. M. , Whittaker D. 
Published: May 2005

AbstractThe proton magnetic resonance spectra of β‐pinene pinocarvone and the cis‐ and trans‐pinocarveols have been completely assigned at 220 and 300 MHz. On the basis of the proton‐proton spin‐spin couplings derived, conformations have been deduced for these molecules with greater certainty than has hitherto been possible. Pinocarvone is Y‐shaped, while in all the other compounds the conformation is intermediate between a Y‐shape and a bridged chair, with the C3 atom bent away from the gem dimethyl groups. These conformations are discussed in terms of the steric interactions in these systems and are compared with related molecules.
Beiträge zur Chemie der Phosphinalkylene—VII: NMR‐Daten von Dimethylamino‐methylen‐phosphoranen
Authors: Issleib K. , Lischewski M. , Zschunke A. 
Published: May 2005

AbstractEs Werden die 1H‐ und 31PNMR‐Spektren der Dimethylamino methylen‐phosphorane
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mitgeteilt und ein einfaches Herstellungsverfahren für 4 beschricben.
Chemical polarisation of 13C and 15N nuclei in the thermal decomposition of diazoaminobenzene (1,3‐diphenyltriazene)
Authors: Lippmaa E. , Saluvere T. , Pehk T. , Olivson A. 
Published: May 2005

AbstractChemical polarisation of 13C and 15N nuclei in the thermal decomposition of diazoaminobenzene has been investigated. Most of the polarised products with the exception of benzene result from cage recombination processes, and both the 13C and 15N true nuclear polarisation coefficients are rather high, up to 10000 and more. 13C CIDNP has been shown to provide a new and useful technique for the measurement of 13C spin‐lattice relaxation time T1.Free radical reactions of organic compounds and the corresponding CIDNP mechanisms can be studied very successfully using proton spectra. Since the hyperfine coupling constants with 13C and 15N nuclei can, however, be considerably larger, the nuclear relaxation times longer and the spectra generally much simpler and easier to interpret in detail, the study of heavier nuclei provides many advantages over 1H‐CIDNP, particularly in the case of σ‐radicals.
A 13C‐NMR and IR study of isocyanides and some of their complexes
Authors: Stephany R. W. , de Bie M. J. A. , Drenth W. 
Published: May 2005

Abstract13C chemical shifts and 1J(14N13C) coupling constants as well as stretching frequencies of the isocyano group are reported for some representative aliphatic, unsaturated and aromatic isocyanides and for two copper(I) isocyanide complexes. The results are discussed in terms of the inductive and mesomeric substituent effects on the polarisation and charge density of the CNC bonds. The marked solvent effect on the chemical shifts of the isocyano carbon hampers comparison of our data with previously reported data. The hydrogen bonding shift of this carbon in water or methanol is much smaller than previous data suggest.
Determination of the 1H—31P coupling parameters in triphenylphosphine
Authors: Radics L. , Baitz‐Gács E. , Neszmélyi A. 
Published: May 2005

AbstractFrom the single and double resonance 1H NMR spectra of triphenylphosphine, magnitudes and relative signs of the proton–proton and proton–phosphorus spin coupling constants were calculated. The values of these parameters were found to be nearly equal to those of the respective 1H—1H couplings in benzene. Results show that inter‐ring proton–proton couplings are negligibly small.
Analyse conformationnelle par l'étude de RMN d'oximes de systèmes figés: Corrélation Δδ = f (angle dièdre)
Authors: Durand Robert , Geneste Patrick , Moreau Claude , Pavia André Armand 
Published: May 2005

AbstractL'étude RMN des systèmes syn–anti d'oximes cyclaniques figés nous a permis de mettre en évidence une relation entre le déplacement chimique d'un proton voisin du groupement hydroximino et l'angle dièdre constitué par la liaison CH du carbone en α de la fonction et le plan constitué par le groupe NOH. La correlation Δδ = f (angle dièdre), établie par l'étude de modèles conformationnellement connus permet alors d'évaluer les angles dièdres de molécules cycliques dont l'étude géométrique n'avait pas été faite. La géométrie de l'oxime reste identique à celle de la cétone, sauf, toutefois, dans le cas de modèles stériquement encombrés.
Zur 13C‐NMR‐Spektroskopie von Oxepinen
Authors: Berger St. , Rieker A. 
Published: May 2005

AbstractDie 13C‐chemischen Verschiebungen von 6 substituierten Oxepinen wurden vermessen und zugeordnet. Für die mit den entsprechenden valenztautomeren Benzoloxiden im Gleichgewicht stehenden Oxepine 1a (unsubstituiert) und 1d (2,5‐Dimethyl‐oxepin) wurden die Mittelwertsignale durch ihre Verschiebung bzw. Verbreiterung in Abhängigkeit von der Temperatur bestimmt. Schließlich werden Vergleiche zum Cycloheptatriensystem gezogen.
The use of 13CH satellite NMR spectra in structure determination: (Chlorovinyl) dichlorophosphine
Authors: Sheer M. Lana 
Published: May 2005

Abstract13CH satellite NMR spectra have been employed in the analysis of an unknown reaction product. Observation of the deceptively simple 1H NMR spectrum did not, in this instance, yield sufficient information for identification of the compound. However, with the aid of the satellite parameters the reaction site became clearly defined and the structure was assigned as α‐(chlorovinyl)‐dichlorophosphine. These unique spectral parameters are discussed and compared to those of similar ethylenic species.
Beziehungen zwischen chemischer Verschiebung und Ladungsdichte
Authors: Sterk H. , Holzer H. 
Published: May 2005

AbstractEs ist gezeigt worden, daß von den in dieser Arbeit untersuchten Beziehungen zwischen den chemischen Verschiebungen δ von Protonen und deren Ladungsdichten q die Beziehung δH = a + bqH + cqC (qC ist die Ladungsdichte des mit dem Proton in Bindung stehenden C‐Atoms) für eine Voraussage der δ‐Werte aus gerechneten Ladungsdichtewerten am geeignetsten ist. Der Standardfehler der Voraussage der δ‐Werte wird dabei am kleinsten, wenn die in die Beziehung einzusetzenden Ladungsdichtewerte nach der CNDO‐ oder INDO‐Methode berechnet werden.
Barriers to internal rotation in 1,3,5‐trineopentylbenzenes: V—conformational studies by carbon‐13 magnetic resonance
Authors: Nilsson Bertil , Drakenberg Torbjörn 
Published: May 2005

AbstractThe temperature dependence of the carbon‐13 NMR signals in three completely substituted 1,3,5‐trineopentylbenzenes has been studied by the Fourier transform technique. The assignment of all peaks was based on studies of 1,3,5‐trineopentylbenzene and some of its mono‐ and disubstituted derivatives. Nearly all carbon signals showed a splitting into several peaks at low temperature, which gave information about the existing rotamers in the completely substituted compounds. Spectra for one compound were studied in a narrow temperature interval in order to test the reliability of rate constants obtained from 13C FT spectra. Good agreement was found between previously reported values obtained from 1H NMR and those obtained in this investigation.
Carbon‐13 nuclear magnetic resonance spectra of some 2‐substituted tetrahydropyrans
Authors: de Hoog A. J. 
Published: May 2005

AbstractFourier transform carbon‐13 nuclear magnetic resonance spectra have been obtained and interpreted for some 2‐substituted tetrahydropyrans. The effects of the substituents on α, β, γ and δ‐carbon atoms are discussed. Using suitable reference compounds the γ‐parameter can be used for quantitative conformational analysis.
Lanthanide chemical shift reagents as tools for determining isomer distributions in 2,4‐hexadienoates and related compounds
Authors: MacMillan John H. , Washburne Stephen S. 
Published: May 2005

AbstractQuantitative analysis of geometrical isomers of unsaturated esters and alcohols is facilitated with Eu(fod)3. Commercial sorbic acid exists in the all‐trans form, while sorbyl alcohol contains c. 10% of the cis‐4,5 isomer.
The NMR identification of the ring A protons of C‐3 oxygenated steroids using the lanthanide paramagnetic shift technique
Authors: Rodig Oscar R. , Roller Peter P. 
Published: May 2005

AbstractThe lanthanide induced chemical shifts and coupling constants have been determined for ring A protons of steroids having a keto, hydroxyl, or acetate functional group at C‐3. The assignments were made with the aid of suitably deuterated compounds and should prove useful in steroidal stereochemical and conformational studies.
1H NMR studies on thioamides: Barriers to internal rotation
Authors: Lepoivre J. A. , Desseyn H. O. , Alderweireldt F. C. 
Published: May 2005

AbstractThe barrier to the internal rotation of the dimethylamino group in thioamides of structure RCSN(CH3)2, R being (CH3)2,NCS, CH3O2C or NC, is studied by proton magnetic resonance, using the lineshape analysis method of Nakagawa. In the solvents o‐dichlorobenzene, naphthalene and nitrobenzene all ΔG≠ values are in the range of 23 to 24 kcal/mol. In these solvents the Ea and ΔS≠ values of each product are linearly related to the dielectric constants.
Carbon‐13 assignments in 1‐ and 2‐naphthyl compounds: Extensive benefits of deuterium substitution
Authors: Kitching William , Bullpitt Maxwell , Doddrell David , Adcock William 
Published: May 2005

AbstractThe natural abundance, proton‐decoupled carbon‐13 spectra of 1‐methylnaphthalene, 1‐fluoronaphthalene, l‐naphthonitrile and their 4‐deutero analogues, as well as 2‐naphthol and its 6‐deutero analogue, have been recorded. Careful comparisons of the spectra of the deuterated and undeuterated compounds allow assignment, not only of the deuterated carbon, but also of the two ortho carbons (based on an upfield ‘two‐bond’ deuterium isotope effect), as well as the two meta carbons (based on a significant J(CCCD) of ∼1 Hz) which causes substantial broadening). In the 1‐naphthyl compounds, significant coupling between the deuterium (at C4) and C5 allows assignment of this latter carbon. Thus, the consequences of the introduction of one deuterium atom, together with results from off‐resonance noise decoupling, permits assignment of most of the spectra. Tentative, but very likely assignments of the few remaining signals, can be made on the bases of chemical shifts and compressional effects. This approach could allow indirect assignment of an aryl carbon to which direct attachment of deuterium is difficult, due to directive effects of an existing substituent.
Conformational analysis: IX–a 300 MHz study of 4‐vinylbutyrolactone
Authors: Pihlaja Kalevi , Riddell Frank G. , Jalonen Jorma , Rinta‐Panttila Pirkko , Anteunis Marc 
Published: May 2005

AbstractThe 300 MHz 1H NMR spectrum of 4‐vinylbutyrolactone has been recorded and analysed. The results showed that the compound is a mixture of two rapidly interconverting envelope forms in which (C‐3) is the flap atom. The vinyl group favours the pseudo‐equatorial orientation by 1·9 ± 0.3 kJ mol−1, as shown by the dependence of the vicinal coupling constants on temperature.
NMR studies of bridged ring systems: XIX—13C1H spin coupling and 13C chemical shift of the bridge methylene in benzonorbornene and benzonorbornadiene
Authors: Tori Kazuo , Tsushima Tadahiko , Tanida Hiroshi , Kushida Katsuhiko , Satoh Shiroh 
Published: May 2005

AbstractData on 13C chemical shifts and 13C1H spin coupling constants of norbornane (1), norbornene (2), norbornadiene (3), benzonorbornene (4) and benzonorbornadiene (6) are reported. The non‐equivalence in J(13CH) values determined from the two bridge methylene proton signals in 2,2,3,3‐tetradeuteriobenzonorbornene (5) and 6 is briefly discussed. The extraordinary deshielding of the bridge methylene carbon in 6 has been noted.
Stéréochimie en pentacoordination. Apport des réactifs inducteurs de déplacement chimique à l'etude de spirophosphoranes à liaison PH
Authors: Houalla D. , Sanchez M. , Wolf R. , Bois M. , Gagnaire D. , Robert J. B. 
Published: May 2005

AbstractLe spectre de Résonance Magnétique Nucléaire de huit spirophosphoranes à liaison PH a été enregistré en présence de chélate d'europium. L'addition du complexe d'europium amène la levée partielle ou totale de dégénérescence des spectres. Les modifications observées dans les déplacements chimiques permettent de proposer une attribution de position endo ou exo de certains signaux. L'addition du complexe d'europium entraîne, dans certains cas, une modification de l'équilibre entre les formes phosphites et spirophosphoranes.
Long range H,H coupling constants in cycloheptatrienes
Authors: Günther Harald , Görlitz Manfred 
Published: May 2005

AbstractThe 1H NMR spectra of 1,6‐dicarbomethoxycyclohepta‐1,3,5‐triene (2) and 3,4‐benzocyclohepta‐1,3,5‐triene (3) have been analysed in terms of chemical shifts and coupling constants. A method for the assignment of δ(AA′) and δ(BB′) in AA′BB′ systems, based on the observation of 13C satellites in the 1H NMR spectrum, is described. For J(1,5) in 3, a negative sign was established. Spin tickling experiments were used to determine the positive sign for J(2,5) in 2 and the negative sign for J(2,7) in 3. The conformation of 3 is discussed.
Relative signs and conformational dependence of H,H coupling constants in cyclohepta‐1,3,5‐trienes
Authors: Günther Harald , Görlitz Manfred , Meisenheimer Hermann 
Published: May 2005

AbstractThe 1H NMR spectra of 7,7‐dimethyl‐3‐carbomethoxy‐cyclohepta‐1,3,5‐triene (thujic acid methyl ester), 3,7,7‐trimethylcyclohepta‐1,3,5‐triene and 7,7‐dimethoxycyclohepta‐1,3,5‐triene have been analysed in terms of chemical shifts and coupling constants. Extensive spin tickling experiments were performed to determine the relative signs of the H,H coupling constants in cycloheptatrienes. The conformational dependence of these parameters is discussed and calculated within the framework of the Pople‐Santry theory using the extended Hückel method.
Radikale aus Polymethincyanin‐Farbstoffen. I—Polymethincyanine mit Indolenin‐Endgruppen
Authors: Baer F. , Oehling H. 
Published: May 2005

AbstractDie ESR‐Spektren von Radikalen in Lösung, die durch elektrolytische Reduktion dinuclearer und trinclearer Polymethincyanin‐Farbstoffe erhalten wurden, werden interpretiert. Aus den Werten der Kopplungskonstanten lassen sich Aussagen über die Konformation der Radikale gewinnen.
The 13C NMR spectra and structure of 2,1,3‐benzoxadiazole,‐benzothiadiazole and ‐benzoselenadiazole
Authors: Cheeseman G. W. H. , Turner C. J. 
Published: May 2005

AbstractThe 13C NMR chemical shifts and one‐bond carbon–hydrogen coupling constants have been obtained for the title compounds in carbon disulphide as solvent. There appears to be little solvent effect on the 13C chemical shifts. The results suggest the order of release of electrons into the ring is O ≫ S > Se.
Interpretation of the asymmetrical ESR hyperfine spectrum of sodium pyrazine [Na P] in DME in the low temperature region. Evidence for the triple ion [Na P Na]+
Authors: Gooijer C. , Oosterbeek W. , Velthorst N. H. , MacLean C. 
Published: May 2005

AbstractThe ESR spectrum of Na pyrazine in DME, at temperatures below −50°C, has been studied in detail. It is shown that two paramagnetic species with slightly different g values are present in the solution, i.e. the sodium pyrazine ion pair [Na P] and the iriple ion [Na P Na]+. The interpretation is based on the concentration dependence of the spectrum.
Identification of isomeric amides of itaconic acid by proton magnetic resonance spectroscopy
Authors: Kyung Jai Ho , Cha Sungman , Clapp Leallyn B. 
Published: May 2005

AbstractTwo half amides of itaconic acid, (1) and (2), have been synthesized and identified by proton magnetic resonance spectroscopy as a preliminary to an interpretation of the mechanism of action of succinate thiokinase on guanosine triphosphate substrates.
Processus de rotation empêchée autour de plusieurs liaisons dans les sels de (N,N‐diméthylamino‐1 propényl‐1‐ylidène‐3) diméthylammonium
Authors: Filleux‐Blanchard Marie‐Louise , le Botlan Denis , Reliquet Alain , Reliquet‐Clesse Françoise 
Published: May 2005

AbstractLes études réalisées par spectrographies RMN et ultraviolette permettent l'identification structurale des sels de (N, N‐diméthylamino‐1 propényl‐1‐ylidène‐3) diméthylammonium. Plusieurs processus de rotation gênée autour des liaisons CN et CC sont mis en évidence. Les enthalpies libres d'activation sont déterminées et discutées en fonction des effets de substituant, d'anion, de solvant.
Analyse conformationnelle de cétones cyclopropaniques par RMN à l'aide des déplacements paramagnétiques induits par Eu(dpm)3
Authors: Andrieu Claude G. , Lemarié Bernard , Paquer Daniel 
Published: May 2005

AbstractLes déplacements paramagnétiques induits par le tris (dipivalométhanato) Europium Eu(dpm)3 sont décrits pour plusieurs cétones cyclopropaniques. La conformation du groupe cyclopropanoyle est étudiée par comparaison avec les déplacements observés pour deux composés dont les conformations sont nécessairement s‐cis: la dispiro[2.1.2.2]nonanone‐4 et s‐trans: la triméthyl‐4,4,5 bicyclo[3.1.0]hexanone‐2.
Etudes des sélénophènes mono et bisubstitués par Résonance Magnétique de 1H et de 13C
Authors: Garreau M. , Martin G. J. , Martin M. L. , Morel J. , Paulmier C. 
Published: May 2005

AbstractUne série de sélénophènes mono‐ et bisubstitués est étudiée en résonance de 1H et 13C. Les déplacements chimiques protoniques sont analysés en termes d'effets d'anisotropie et de champ électrique des substituants et utilisés à une discussion des équilibres conformationnels. Les relations entre δ1H et δ13C et les charges π calculées par la méthode PPP sont examinées. Les couplages 1J(13CH), nJ(13C ∼ H) et 1J(13C77Se) se révèlent de bonnes caractéristiques structurales et des relations d'additivité sont dégagées pour δ13C.
13C RMN: Non‐équivalences d'ammoniums quaternaires diastéréoisoméres
Authors: Solladié‐Cavallo A. , Solladié G. 
Published: May 2005

AbstractLes spectres de 13C de six couples d'ammoniums quaternaires ont été étudiés. L'attribution des signaux des carbones non‐aromatiques et la détermination des non‐équivalences ont conduit au dosage des diastéréoisomères ainsi qu'à la mise en évidence d'un effect β déblindant et γ blindant lors de la quaternarisation.
Spectres RMN et analyse conformationnelle de germa‐4 dioxannes‐1,3
Authors: Cazaux Louis , Barrau Jacques , Massol Michel 
Published: May 2005

AbstractLes méthodes de calcul de l'angle de torsion de la liaison CC sont appliquées à quelques germa‐4 dioxannes‐1,3. On montre ainsi que le diéthyl‐4,4 trichlorométhyl‐2 germa‐4 dioxanne‐1,3 adopte dans CCl4 et C6D6 une conformation chaise à groupe CCl3 équatorial déformée par la présence du germanium: l'angle de torsion du fragment GeCH2CH2O est de 45°. Les dérivés alkylés en 6 les plus stables (isomères cis) existent dans la měme conformation, l'isomére tertiobutylé trans le moins stable préférant une forme croisée compatible avec un angle de torsion d'environ 60°.
Etudes RMN en série hétérocyclique. XV—Résonance Magnétique Nucléaire de 1H et de 19F de quelques fluoro‐2 benzothiazoles
Authors: Calafell M. , Elguero J. , Fruchier A. 
Published: May 2005

AbstractOn donne les valeurs des déplacements chimiques et des constantes de couplage de cinq fluoro‐2 benzothiazoles substitués en position 6 par Me, H, F, Cl et NO2. La constante de couplage J26 dans le difluoro‐2,6 benzothiazole est trouvée égale à 10,4 Hz, ce qui représente en très grand couplage ‘cross‐ring’.