bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron spin resonance studies of the anions of some azulene derivatives: 1‐tert‐butyl‐, 1,3‐di‐tert‐butyl‐ and 4,6,8‐trimethylazulene
Authors: Waltman R. J. , Bargon J.
Published: May 2005

Hyperfine splitting constants are reported for radical anions of the azulene derivatives 1‐tert‐butyl‐, 1,3‐di‐tert‐butyl‐ and 4,6,8‐trimethylazulene. Radical anion geometries are optimized at the Hartree‐Fock level of theory using 3–21G and 3–21 + G* basis sets. The perimeter bond lengths are all approximately 1.40–1.44 Å except for the C‐4C‐5 (and C‐7C‐8) bond which, at 1.36 Å, is best described as a double bond. The singly occupied antibonding molecular orbitals are computed to be symmetric with respect to the mirror plane perpendicular to the molecular plane, consistent with the ESR data.
61Ni NMR spectroscopy of di‐ and tricarbonylnickel complexes
Authors: Behringer Klaus D. , Blümel Janet
Published: May 2005

Di‐ and tricarbonylnickel phosphine complexes (22) were prepared and their liquid‐state 61Ni NMR spectra were recorded with the use of special solenoid glass sample tubes and a solenoid probehead, which are described. The acquired chemical shifts δ(61Ni), linewidths v1/2(Ni), relaxation times T1 and coupling constants 1J(61Ni,31P) are discussed with reference to the electronegativity of the substituents at the phosphine ligands and the Tolman angle θ of the latter.
Dynamic NMR: A new procedure for the estimation of mixing times in the 2D EXSY experiments. A four‐site exchange system studied by 1D and 2D EXSY spectroscopy
Authors: Dimitrov Valentin S. , Vassilev Nikolay G.
Published: May 2005

A procedure for the estimation of the mixing time between the last two 90° pulses in the classic three‐pulse sequence NOESY/EXSY is proposed and tested and some considerations for the treatment of the two‐dimensional (2D) 1H NMR exchange spectra are given. The rate constants are thus obtained with reasonable precision. This procedure was followed to obtain the 2D spectra of the model compound α‐[bis(dimethylamino)methylene]‐4‐nitrophenylacetonitrile, which represents a four‐site exchange system. The barriers to restricted rotations found in this compound were also determined from one‐dimensional (1D) 1H NMR spectra, which were processed with the iterative complete lineshape analysis (CLSA) method. The double‐fit approach was incorporated in the CLSA method. It is shown that the results from the 2D dynamic NMR spectral studies corroborate those obtained by the CLSA double‐fit method.
Carbon and proton NMR assignments for 6,7‐dimethoxycoumarin
Authors: Reinecke Manfred G. , Minter David E. , Jia Qi
Published: May 2005

The carbon and proton NMR spectra of 6,7‐dimethoxycoumarin are completely assigned from XCORFE and HETCOR studies.
Preparation of exo‐ and endocyclic aminoxyl radicals of 2‐Amino‐substituted quinazolin‐4(3H)‐ones
Authors: Omelka Ladislav , Světlik Jan
Published: May 2005

2‐Amino‐substituted quinazolin‐4(3H)‐ones were oxidized with RO2· radicals and 4‐nitroperoxybenzoic acid. Two types of radical products, i.e. exo‐ and endocyclic aminoxyl radicals, were observed. Their differentiation was carried out on the basis of ESR parameters.
33S NMR spectroscopy: Substituent γ‐effect. Halogen derivatives of tetrahydrothiophene 1,1‐dioxide
Authors: Rozhenko A. B. , Bzhezovsky V. M. , Polovinko V. V. , Makarenko A. G.
Published: May 2005

A series of halogen‐substituted tetrahydrothiophene 1,1‐dioxides (sulpholanes) were investigated by 13C, 17O and 33S NMR spectroscopy. It was shown that successive replacement of hydrogen atoms in positions 3 and 4 of the sulpholane ring led to an increase in 33S nuclei shielding. The 33S NMR chemical shift range exceeded 39 ppm. The variation of the 33S nuclei shielding with increasing number of chlorine or bromine atoms was caused by an electrostatic through‐space effect of the halogen atoms and the strongly polarized CHal bonds.
17O NMR studies of diaryl α‐diketones. The case of 2,2′,4,4′,6,6′‐hexa‐tert‐butylbenzil
Authors: Cerioni Giovanni , Plumitallo Antonio , Frey Joseph , Rappoport Zvi
Published: May 2005

Natural abundance 17O NMR spectra of eleven diaryl α‐diketones are reported. An excellent correlation was found between 17O shifts and σp+. Conformations and π character of the intercarbonyl CC bond are discussed.
Differentiation of meso isomers from racemic mixtures with the combined use of chiral shift reagents and two‐dimensional heteronuclear correlation NMR spectroscopy
Authors: Henrichs P. Mark , Rodger Charles A. , Caulfield Thomas , Guo Peng
Published: May 2005

In the presence of chiral shift reagents the enantiotopic nuclei of a pair of enantiomers become diastereotopic and have the potential to give resolved NMR signals. Similarly, the enantiotopic nuclei within a meso isomer become diastereotopic in the presence of a chiral shift reagent and may give resolved NMR signals. However, the diastereotopic nuclei of a meso isomer mixed with a chiral shift reagent, unlike those of a racemic mixture, are located in the same molecule. Their intramolecular character can be established experimentally by detection of spin‐spin splitting between them or to a common third nucleus. Comparison of the correlation peaks in a two‐dimensional, heteronuclear, multiple‐quantum correlation (HMQC) spectrum with those of a heteronuclear multiple‐bond correlation (HMBC) spectrum is an effective means of detection of coupling to a third nucleus. Two‐dimensional NMR spectroscopy was used to identify the meso form of di‐(trans‐2‐aminocyclohexyl)amine.
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

In 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

13C 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

The 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

The 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

A 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

Une 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

The 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

Es 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

Chemical 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

13C 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

From 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

L'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

Die 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

13CH 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.
Carbon‐13 chemical shifts and coupling constants in cis‐ and trans‐1,2‐di‐tert‐butylethylene
Authors: Garratt Dennis G. , Tidwell Thomas T.
Published: May 2005

The spectral parameters of the title compounds were redetermined to resolve discrepancies between data reported in the literature.
Beziehungen zwischen chemischer Verschiebung und Ladungsdichte
Authors: Sterk H. , Holzer H.
Published: May 2005

Es 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 some dimethylamino substituted azoles
Authors: Liljefors Tommy
Published: May 2005

Activation parameters for the hindered rotation in some dimethylamino substituted azoles are reported and the effects of various ring systems and substituents on the barrier are discussed. Possible errors in ΔH≠ and ΔS≠ are investigated.
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

The 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.
INDOR study of long range cross‐ring couplings in heptahelicene: XX
Authors: Defay Nicole
Published: May 2005

INDOR experiments on heptahelicene have revealed the existence of positive 5J (epi), negative 4J (peri) and |4J| (peri) cross‐ring couplings.
Carbon‐13 nuclear magnetic resonance spectra of some 2‐substituted tetrahydropyrans
Authors: de Hoog A. J.
Published: May 2005

Fourier 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

Quantitative 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

The 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

The 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

The 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

The 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

Data 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

Le 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

The 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

The 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

Die 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

The 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

The 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

Two 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

Les 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

Les 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.
Comparison and evaluation of some available methods for the analysis of lanthanide induced shift data
Authors: Cawley John J. , Petrocine David V.
Published: May 2005

Some available methods for the analysis of lanthanide induced shift data have been examined. These methods are compared and evaluated using the data gathered from substituted phenyl tert‐butyl carbinols.
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

Une 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

Les 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

Les 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

On 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’.
Three rotational isomers of se‐methyl N,N‐di‐isopropyldiselenocarbamate and the sulphur analogue found in low temperature 1H NMR spectra
Authors: Takeda Yu‐ichi , Tanaka Toshio
Published: May 2005

Variable temperature 1H NMR spectra of Se‐methyl N,N‐di‐isopropyldiselenocarbamate, CH3SeC(Se)N (C3H7‐i)2, in CS2 have indicated that internal rotations around both the carbamate CN and isopropyl–nitrogen bonds are restricted below −40°C; the compound exists as three rotational isomers with respect to the isopropyl‐nitrogen bond with mol ratios of approximately 0·54:0·31 :0·15. The corresponding dithiocarbamate, CH3SC(S)N(C3H7‐i)2, has also been found to exist as three isomers with ratios of about 0·71:0·27:0·02 under similar conditions. Possible conformations of both carbamate esters are proposed, together with the assignments of each proton signal.
Long range 13C1H coupling constants IV—methoxy‐, amino‐ and hydroxypyridines
Authors: Takeuchi Yoshito , Dennis Nicholas
Published: May 2005

One bond and long range 13C1H coupling constants for some methoxy‐, amino‐ and hydroxypyridines are described. An unambiguous assignment of carbon‐13 resonances is carried out based on the analysis of the fine splitting caused by long range couplings. J values for compounds other than 2‐ and 4‐hydroxy‐pyridines are explainable in terms of the values previouly obtained for cyano‐ and methylpyridines. The hydroxypyridine‐pyridone tautomerism affects 2J(Hα), i.e. 2J associated with the α proton. This effect can be used to differentiate pyridones from hydroxypyridines.
Vicinal interproton couplings through two heteroatoms. II—Coupling 3J(HNOH) occurring in m‐Nitrophenylhydroxylamines
Authors: Bouchet Philippe , Coquelet Claude , Elguero José
Published: May 2005

The proton NMR spectra of certain arylhydroxylamines in DMSO‐d6 show a vicinal coupling through nitrogen and oxygen. The assignment of OH and NH signals was made using a 15N labelled derivative.
Conformational Analysis of cyclotrisilazanes by the NMR method
Authors: Lavrukhin B. D. , Andrianov K. A. , Fedin E. I.
Published: May 2005

1H NMR spectra of substituted cyclotrisilazanes are discussed in terms of conformational analysis. Experimental spectra are consistent with an equilibrium involving chair conformers, following from simulating the effect of phenyl substituents and the temperature dependence of methyl proton chemical shifts. The barrier to chair‐chair interconversion in hexamethyl‐cyclotrisilazane is estimated. An analysis is carried out of the shielding of non‐equivalent methyl groups in substituted cyclotrisilazanes.
Proton NMR determination of the 2,4–/2,6–isomer ratio in commercial toluene di‐isocyanates
Authors: Platten M. R.
Published: May 2005

The CH3‐proton resonances for the 2,4‐ and 2,6‐isomers of toluene di‐isocyanate separate when hexafluorobenzene is used as a solvent. Integration of these absorptions over an expanded sweep scale gives the isomer ratio with an accuracy of ±0.5% over the range normally encountered with commercial samples.
NMR study of 4‐membered rings. VIII—The sign of the four‐bond couplings in adducts of cyclopentenone with vic‐dichloroethylenes
Authors: Bongini A. , Lamartina L. , Mondelli R. , Tagliabue G.
Published: May 2005

The proton spectra of the four stereoisomers prepared by photocycloaddition of 2‐cyclopentenone to cis and trans dichloroethylene have been analysed using tickling and INDOR techniques in order to obtain the sign of the cross‐ring four‐bond coupling constants in the cyclobutane ring. These parameters are correlated with the relative orientation of the protons involved. The complete NMR analysis of the seven‐spin system of the cycloadduct endo‐7‐phenoxybicyclo[3.2.0]hept‐2‐en‐6‐one has been carried out and all the four‐bond coupling constants have been obtained and discussed. The sign of the cross‐ring coupling in the cyclobutanone ring has been determined.
Etude théorique des déplacements chimiques du phosphore en RMN
Authors: Rajzmann Michel , Simon Jacques‐Claude
Published: May 2005

La méthode des perturbations est appliquée aux fonctions d'onde CNDO/S pour calculer les déplacements chimiques du phosphore de quelques phosphines, phosphites, phosphonates et phosphates. Nous montrons la nécessité d'introduire les orbitales 3d du phosphore et de considérer Zeff3d comme un paramètre à déterminer pour chaque famille de composés. Les valeurs calculées sont alors en bon accord avecl' expérience.
Stereochemical aspects of proton chemical shifts. III—Configurational assignments in pentacyclic systems without recourse to a karplus equation
Authors: Anteunis Marc , Danneels Dirk
Published: May 2005

It is shown that in contrast to the use of coupling constants, chemical shift criteria may lead to unambiguous structural elucidations in pseudorotational frameworks (pentacycles, heptacycles, etc.).
Long range HH couplings and bond fixation in 2‐pyrones
Authors: Sardella D. J. , Holak T. , Vogel G.
Published: May 2005

We have determined the magnitudes of all possible four‐, five‐ and six‐bond HH couplings in four 2‐pyrone derivatives. Substituents exert a negligible effect on the couplings. The allylic couplings are position‐specific (J34 = 1·2; J45 ≤ 0·2; J56 = 0.8) and the observed pattern of alternating magnitudes is indicative of π‐bond fixation. The allylic couplings can be translated into π‐bond orders which agree well with results of recently published SCF‐MO calculations on 2‐pyrone. Finally, comparison of long range coupling constant data for 4,6‐dimethyl‐2‐pyrone with those for related cyclic anhydrides and trans‐1,3‐pentadiene further supports the picture of 2‐pyrone as a slightly perturbed butadiene, in agreement with extensive chemical and physical evidence.
Exemple d'une transposition dyotropique à l'état solide Mise en evidence par RMN haute résolution
Authors: Grenier‐Loustalot M. F. , Lectard A. , Metras F.
Published: May 2005

L'analyse des spectres RMN à 250 MHz de tribromo‐2,3,6 méthyl‐4 cyclohexanones a permis de déterminer avec précision les constantes de couplage J(HH) de ces composés. La validité des attributions a été contrôlé en reconstituant les spectres par calcul électronique. Les résultats observés ont été interprétés en terme de déformation géométrique.
Influence de la substitution sur la structure de la benzophenone. X.—Etude conformationnelle de benzaldehydes, acetophénones et benzophénones substitués par complexation avec les lanthanides
Authors: Grimaud Marcel , Pfister‐Guillouzo Geneviève
Published: May 2005

La résonance magnétique nucléaire du proton à basse température s'est révélée peu fructueuse dans l'étude conformationnelle des benzophénones substituées. Cependant, l'analyse des déplacements induits par les lanthanides nous a permis de recouper de façon très satisfaisante les résultats obtenus par diffusion Rayleigh dépolarisée et dipolemétrie pour les benzophénones meta et ortho substituées. L'existence en solution d'un équilibre conformationnel pour ces composés est confirmée.
An NMR study of some N‐arylaminopropenylylidenearylammonium salts
Authors: Richards C. P. , Webb G. A.
Published: May 2005

The preparation, characterisation and 1H NMR spectra of some N‐arylaminopropenylylidenearylammonium salts are reported. The NMR data show that in DMSO the cations exist as conjugated amino–imines, generally as the ‘all‐trans’ geometrical isomer. An exception is found in the case of the 4‐nitrophenyl derivative which produces a mixture of the ‘all‐trans’ and ‘cis‐trans’ isomers with slow exchange between them at room temperature. The relative stability of the ‘all‐trans’ isomer increases as the salt becomes more ionic. By varying the temperature, pH and nature of the anion it is found that exchange of the NH protons on the cation controls the appearance of spin‐spin coupling between the NH and 1,3‐propene protons.
Determination of relative signs of 13C13C coupling constants in doubly labelled compounds
Authors: Hansen P. E. , Poulsen O. K. , Berg A.
Published: May 2005

Analysis of the noise decoupled 13C spectra of doubly 13C labelled compounds where the two labelled carbons are identical, makes the determination of reltive signs of 13C13C coupling constants possible in a very simple way. The involved carbon form AA'X or AA'B spin systems.
13C NMR: Stereochemical dependence of the one‐bond coupling constant 1J13CH in α‐halogenoketones
Authors: Cantacuzene J. , Jantzen R. , Tordeux M. , Chachaty C.
Published: May 2005

The one‐bond coupling constant 1J 13CH for the halogenated carbon in α‐halogenocyclohexanones is more important when the CH bond is in the equatorial then in the axial position. When a conformational equilibrium is present, the resulting coupling is a linear function of the equilibrium constant.
Solvent effects upon the proton NMR linewidth in dimethylformamide
Authors: Herres W. , Ziessow D.
Published: May 2005

The NMR linewidth of the formyl proton in dimethylformamide has been studied in the neat liquid and twelve organic solvents. It varies by more than one order of magnitude which is referred to solvent viscosity changes and to the protonation of dimethylformamide. The data do not allow the distinction between N‐ and O‐protonation without further knowledge of the solvent dependence of either the nitrogen‐14 spin lattice relaxation time or the spin‐spin coupling 2J(NH).
Etude par RMN protonique d'heterocycles voisins de l'oxazaphospholane‐1,3,2. II—Le diméthylamino‐2 méthyl‐3 oxazaarsolane‐1,3,2
Authors: Devillers Jean , Cornus Martin , Navech Jacques , Wolf Jean‐Gérard
Published: May 2005

Le spectre de résonance magnétique protonique du diméthylamino‐2 méthyl‐3 oxazaarsolane‐1,3,2 est très sensible à la température et à la nature du solvant. L'analyse complète du spectre protonique à −48 °C dans le toluène deutérié montre que la molécule est dans une conformation privilégiée au niveau C‐4C‐5. Dans le nitrobenzène à +31 °C, le spectre de type A2X2 indique un mouvement de libration autour de cette liaison. A température plus élevée un nouveau phénomène de coalescence peut être expliqué par l'inversion de l'atome d'arsenic.
Study of rotation barriers in N,N‐dimethylnicotinamide and quaternary salt derivatives by proton NMR. A correlation of rotation barriers of N,N‐dimethylamides with carbon‐13 chemical shifts
Authors: Lepoivre J. A. , Dommisse R. A. , Alderweireldt F. C.
Published: May 2005

The rotational barrier in the N,N‐dimethylamide group is studied by proton NMR for N,N‐dimethylnicotinamide and two quaternary salts in aqueous solution. The carbon‐13 NMR spectra of a number of aromatic N,N‐dimethylamides are discussed. A roughly linear correlation is found between the ΔG≠ values of the rotation barriers and the chemical shifts of the carbon atom substituted by the amide group.
13C‐NMR‐Spektren von Monoterpenen
Authors: Bohlmann F. , Zeisberg R. , Klein E.
Published: May 2005

Die 13C‐NMR‐Spektren von fast 100 Monoterpenen zeigen, daß sie zur Charakterisierung derartiger Verbindungen sehr brauchbar sind. Besonders wertvoll ist diese Methode zur Klärung stereochemischer Probleme. Bis auf wenige Fälle folgen die beobachteten chemischen Verschiebungen den allgemeinen Regeln. Die Probleme der Messungen mit Verschiebungsreagenzien werden diskutiert.
Structure and protonation study of the imidazo [1,2‐a]‐pyrimidine system in 1H nuclear magnetic resonance
Authors: Marchetti Leonardo , Pentimalli Luciano , Lazzeretti Paolo , Schenetti Luisa , Taddei Ferdinando
Published: May 2005

The 1H NMR spectra of imidazo [1,2‐a]pyrimidine derivatives have been analysed to study the aromatic character and protonation behaviour of this system. By employing the ‘ring currentn’ model and calculations based on the coupled Hartree‐Fock method it can be deduced that a large π‐electron delocalisation exists in this heterocyclic system and affects the screening constant of the protons. Charge density schemes obtained by SCF techniques agree with the reactivity behaviour of these molecules.

A detailed study of protonation carried out by following the 1H NMR spectra both in trifluoroacetic acid and in aqueous hydrochloric acid shows that the most probable site of protonation is N‐1, but leaves open the possibility of a rapid exchange of one proton between N‐1 and N‐8.
Substituent effects on 13C13C coupling constants and chemical shifts in 13C labelled polycyclic aromatic hydroxy compounds
Authors: Hansen P. E. , Poulsen O. K. , Berg A.
Published: May 2005

The effects of an hydroxy substituent on 13C13C coupling constants and 13C chemical shifts have been measured in 1‐hydroxynaphthalene‐2‐13C and 1‐hydroxypyrene‐1‐13C. The changes observed in the 13C13C couplings show the effect of a substituent attached directly to the labelled carbon or to a carbon ortho to this. In both situations the effect is a decrease in the numerical magnitude of most of the long range 13C13C coupling constants.
Application des mesures de couplages 15NH à la détermination de configurations d'oximes
Authors: Crépaux Danielle , Lehn Jean‐Marie
Published: May 2005

Plusieurs oximes, enrichies en 15N, d'aldéhydes hétérocycliques ont été préparées dans les formes syn et anti. La forme la moins stable peut être obtenue par irradiation UV de l'autre. Le couplage géminal 15NH dans le fragment RCH15NOH permet une attribution non ambiguë de la configuration; il est de 13 à 16 Hz et de 2 à 3 Hz pour les formes anti et syn, respectivement. Les oximes 1 à 4 sont préférentiellement anti, alors que la forme stable des oximes des aldéhydes de N‐méthyl pyridinium (8 à 11) est syn et non pas anti comme cela avait été admis. Cette réattribution présente un intérêt spécial puisque 2‐PAM (8), qui est un excellent antidote réactivant l'acétylcholinestérase inhibée par phosphorylation, a été utilisée pour étudier la géometrie du site actif de l'enzyme.
Evaluation of limiting‐induced shifts of disubstituted adamantane derivatives on the basis of shift additivity
Authors: Hájek M. , Vodička L. , Hlavatý J.
Published: May 2005

A quantitative interpretation of 1H NMR spectra of symmetrically disubstituted adamantane derivatives (2,4‐adamantanedione, 2,6‐adamantanedione and 2,4‐adamantanetdiol) with shift reagents is reported. Assumptions are made of shift additivity and an average coordination of one molecule of the shift reagent to both functional groups. A much better fit between the experimental and the calculated set of limiting‐induced shifts was obtained for calculations based on shift additivity.
1H and 13C NMR study of the enol–enolic tautomerism of some cyclic β‐ketoaldehydes
Authors: Shapet'ko N. N. , Radushnova I. L. , Bogachev Yu. S. , Berestova S. S. , Potapov V. M. , Kiryuschkina G. V. , Talebarovskaya I. K.
Published: May 2005

Aldehyde (δCH) and enolic (δOH) proton chemical shifts, the corresponding spin–spin coupling constants (JCH,OH) and the 13C chemical shifts (δC) have been measured for three cyclic β‐ketoaldehydes as a function of temperature. A tautomeric equilibrium has been shown to exist between the aldo–enol (A) and hydroxymethylene ketone (B) forms. The chemical shifts δCH δOH and δC for the two pure tautomeric forms A and B have been calculated. The enthalpy changes ΔH in the tautomeric process A⇄B and the percentages of the tautomeric forms have been determined.
Détermination de la forme la plus stable de l'ortho‐dichlorofluorure de benzyle par RMN en phase nématique
Authors: Gout E. , Béguin C. , Canet D. , Marchal J. P.
Published: May 2005

La valeur des couplages directs dans l'ortho‐dichlorofluorure de benzyle, obtenus par RMN en phase nématique, permet d'affirmer que la position la plus stable du CH2F est telle que le fluor se trouve dans un plan perpendiculaire au cycle benzénique. L'interprétation complète de ces couplages en fonction de la géométrie de la molécule laisse cependant supposer une modification de l'orientation intervenant en même temps que la rotation du groupement CH2F.
3J(PCNH) in phosphorus substituted thioformamides as a configurational probe
Authors: Dahl Otto , Laursen Svend Aage
Published: May 2005

Coupling between P and (N)H has been observed in the 1H{14N}NMR spectra of a series of phosphorus substituted thioformamides, R12/P(X)C(S)NHR2. For R2 = H one of the two couplings constants 3J(PCNH) is much larger than the other. The larger constant is assumed to be 3J(PCNH) (trans) and the magnitude of 3J(PCNH) for several compounds with R2 = Me or Ph is used to assign the configuration about the C(S)N bond.
Amines α et β acétyléniques. Couplages J(15NH), J(15N13C) et hybridation de l'azote
Authors: Bottin‐Strzalko T. , Pouet M. J. , Simonnin M. P.
Published: May 2005

Les trois amines 15N‐méthylaniline, 15N‐méthylphénylpropargylamine et 15N‐méthylphénylpropynylamine ont été étudiées par RMN du 1H et 13C. Les grandeurs des couplages 1J(15N13C) et 1J(15N13C) indiquent que l'hybridation de l'azote est intermédiaire entre sp3 et sp2 dans le 15N‐méthylaniline et la 15N‐méthylphénylpropargylamine mais est sp2 dans l'amine α‐acétylénique. La valeur du couplage 1J(15N13Csp), calculée à l'aide de la relation de Binsch, est plus faible que la valeur expérimentale, ce qui suggère que les mécanismes orbitalaire et dipolaire apportent une contribution non négligeable à ce couplage.
Dynamic NMR: A new intensity ratio for evaluation of lifetime in paripartite A ⇌ B systems
Authors: Dimitrov Valentin S.
Published: May 2005

A simple formula for evaluation of rates of exchange in paripartite A ⇌ B systems is introduced. It is concerned only with the intensity ratio in a two‐site system in much the same way as that of Rogers and Woodbrey, but the new formula is also applicable above the coalescence point of the spectrum. The formula has been applied to the classical case of N,N‐dimethyltrichloroacetamide. An error analysis demonstrates that the approximations inherent in the derivation of the new formula lead to smaller errors than do those of Rogers and Woodbrey.