bluuebunny/crossref_metadata_2025 huggingface dataset:
Aminophosphines: Influence des Substituants lies au Phosphore sur la Barriere a la Rotation Autour de la liaison PN et sur la Nucleophilie de L'atome D'azote
Authors: Simonnin Marie‐Paule , Charrier Claude , Burgada Ramon
Published: May 2005

L'étude par RMN de la rotation autour de la liaison PN dans diverses aminophosphines permet de mettre en évidence l';influence des substituants liés au phosphore sur les valeurs de ΔG*. Le parallélisme observé entre la barrière à la rotation et la grandeur des couplages 3J(PNCH) montre que les variations de ΔG* reflètent principalement l'importance du recouvrement pπ—dπ.

Une étude de la nucléophilie de l'azote, par réaction d'échange aprotique entre le trifluoroacétate de méthyle et diverses aminophosphines, confirme ces conclusions.
Conformational studies by nuclear magentic resonance—II: The effect of steric factors on hindered rotation in enamino aldehydes and ketones
Authors: Dabrowski J. , Kozerski L. J.
Published: May 2005

Rotational barriers of the dimethylamino group in different enamino aldehydes and ketones have been applied for evaluation of their conformation. It has been maintained that repulsion between bulky substituents causes twisting of the molecule rather than planar deformations. Arguments for and against these alternative concepts based on the analysis of JHH and J(13CH) coupling constants in different fragments of the molecule have been discussed.
13C, 14N, 15N and 17O NMR spectra of nitropyrroles and nitroimidazoles
Authors: Lippmaa E. , Mägi M. , Novikov S. S. , Khmelnitski L. I. , Prihodko A. S. , Lebedev O. V. , Epishina L. V.
Published: May 2005

Carbon, nitrogen and oxygen NMR spectra of some nitro derivatives of pyrrole and imidazole have been investigated. The 13C chemical shifts of para‐carbons and the 17O chemical shifts of the nitro group correlate qualitatively with the electron densities on these carbon and oxygen atoms, which in turn depend upon the degree of conjugation of the nitro groups with the heterocyclic ring. Conjugation of several nitro groups with the benzene ring is in most cases not impaired by mutual interactions and the 13C shifts show good additivity. Such additivity is much worse in pyrrole and imidazole derivatives. Taken together with the diamagnetic nature of these deviations from additivity, this leads to a possible conclusion about the less pronounced conjugation of the nitro groups with the heterocyclic ring in heterocyclic dinitro derivatives.
Heteronuclear multiple magnetic resonance studies of quaternary ammonium salts derived from heterocyclic bases
Authors: McFarlane H. C. E. , McFarlane W.
Published: May 2005

14N tickling experiments performed with simultaneous decoupling of substituent protons are used to show that 2J(14NHortho) and 3J(14NHmeta) are both positive in the N‐methyl pyridinium ion and related species. Long range coupling extending over as many as five bonds is observed between N‐methyl protons and ring protons in 14N‐decoupled spectra. Triple resonance decoupling is used to permit an analysis of the AA′MM′ spin system given by the ring proton of N‐methyl pyrazinium iodide.
4J(HH)‐Kopplungen und Magnetisch Nichtäquivalente Methylenprotonen in Einigen 1,3‐oxathiolan‐5‐on‐Derivaten
Authors: Brink Maud
Published: May 2005

4J(HH)‐Kopplungen und magnetisch nichtäquivalente Methylenprotonen in einigen 1,3‐Oxathiolan‐5‐on‐ Derivaten wurden in vershiedenen Lösungsmitteln studiert.
Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XVIII Configurational and conformational studies with derivatives of hexahydroindolizin‐2(3H)‐one
Authors: Cahill R. , Crabb T. A.
Published: May 2005

A series of substituted hexahydroindolizin‐2(3H)‐ones and some related ketones have been prepared by Dieckmann condensation of the appropriate diesters. Utilising spectral data, the configurations of these compounds have been assigned, and their conformations discussed with particular reference to the magnitude of the geminal coupling constant (Jgem) for the NCH2C(O) protons. With the exception of tetrahydropyrrolizin‐2(3H)‐one, all the ketones in this study are shown to exist in predominantly trans‐fused conformations. In the case of hexahydroindolizin‐2(3H) one and hexahydro‐2H‐quinolizin‐3 (4H)‐one, the separate contributions to Jgem from the adjacent N lone pair and the carbonyl π electrons are discussed.
Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XIX Configurational and conformational studies with derivatives of hexahydropyrido [2,1‐c][1,4]oxazin‐4(3H)‐ones
Authors: Cahill R. , Crabb T. A.
Published: May 2005

A series of substituted hexahydropyrido [2,1‐c][1,4]oxazin‐4(3H)‐ones has been prepared by reaction of the sodio derivative of the appropriate piperidyl carbinol with ethyl chloroacetate. From a study of their NMR spectra the configurations of these compounds have been assigned and the conformation of the perhydro‐1, 4‐oxazinone moiety shown to be that with the ring oxygen atom and the angular hydrogen on the same side of the plane defined by C3C(O)N. The synthesis and NMR spectra of hexahydro‐2H‐pyrido [1,2‐d][1,4]oxazepin‐5(4H)‐one, 1,6,11,11a‐tetrahydro [1,4]‐oxazino [4,3‐b]isoquinolin‐4(3H)‐one and of hexahydropyrido [2,1‐c][1,4]thiazin‐4(3H)‐one are also discussed. cis‐6,9a‐H‐6‐Methyl‐hexahydropyrido[2,1‐c][1,4]oxazin‐4(3H)‐one is shown to exist in a conformation containing a deformed perhydropyridine ring.
Benzene dilution shifts and steric interactions in N,N‐dialkylamides
Authors: Graham Laurine L. , Miller Michael R.
Published: May 2005

The NMR spectra of ten disubstituted amides have been recorded at 0°C in carbon tetrachloride and in benzene solutions. The benzene dilution shifts (ASIS) and proton spin decoupling were used to make the chemical shift assignments. A time‐averaged solvent cluster model for the association between the amide and benzene is consistent with the observed ASIS values. The assignments for the N‐methine and N‐methyl resonance peaks in RCON[CH(CH3)2]2, where R is methyl, ethyl or propyl are inverted from the assignments for N,N‐diisopropylformamide (R  H).
Natural abundance 13C NMR investigation of substituted bromobenzene using noise decoupling of proton resonances
Authors: Hinton J. F. , Layton B.
Published: May 2005

The natural abundance 13C NMR spectra of bromobenzene and ten derivatives have been obtained using the technique of noise modulated decoupling of the proton resonances. Assignments have been made for all 13C resonance signals using an additivity rule. The chemical shifts of the aromatic carbon nuclei in the para‐substituted compounds are discussed in terms of the Taft parameters (σR, σI) and the electronegativity of the substituent.
An NMR study of the conformational equilibrium of 5‐fluoro‐1,3‐dioxan in solution. Dependence on solvent
Authors: Hall L. D. , Johnson R. N.
Published: May 2005

The 1H and 19F NMR parameters of 5‐fluoro‐1,3‐dioxan (1) dissolved in a number of solvent systems are interpreted on the basis of fast inversion between two chair conformations. In cyclohexane solution the two chair conformations are almost equally populated, whereas in more polar solvents, such as chloroform, the conformation having the fluorine substituent in an axial position is strongly preferred. Addition of acetic acid to a solution of 1 in cyclohexane increases the preference of the fluorine substituent for the axial orientation. Possible reasons for these observations are discussed.
Determination Empirique de l'Effet d'Anisotropie Diamagnetique Exerce sur les Protons Aliphatiques en Resonance Magnetique Nucleaire—II
Authors: Gouverneur P. , Nagy O. B. , Soumillion J. Ph. , Burton T. , Bruylants A.
Published: May 2005

La corrélation empirique δ =
equation image
est étendue à un grand nombre de composés halogénés et de nouvelles corrections d'anisotropie diamagnétique sont déterminées. La signification de ces corrections est discutée et une analyse soignée des données permet de fixer les limites de la méthode.
Anisochronism of large geminal groups in the 1H and 13C nuclear magnetic resonance spectra
Authors: Biernacki Wladyslaw , Da̧browski Janusz , Ejchart Andrzej
Published: May 2005

The role of steric factors in magnetic non‐equivalence anisochronism of complex geminal groups and of their fragments in compounds of the general formula RCH(Ph)CH(COOR′)2 has been investigated. CMR anisochronism is more sensitive to conformational and other steric changes than is PMR.
An NMR study of phenol self‐association
Authors: Bogachev Yu. S. , Vasianina L. K. , Shapet'ko N. N. , Alexeeva T. L.
Published: May 2005

This paper presents a study of the chemical shift of the phenol hydroxyl group as a function of concentration and temperature in cyclohexane, methylcyclohexane and carbon tetrachloride solutions. The chemical shift of monomeric phenol has been found. For these solutions monomertrimer equilibrium is observed within the entire temperature range and within a wide concentration range. At low phenol concentrations, from 1 to 3 mole‐%, the monomer‐dimer equilibrium is observed in cyclohexane, methylcyclohexane and carbon tetrachloride solutions. Chemical shift of the hydroxyl group of trimeric phenol is temperature‐dependent.

From the experimental data the association constants and thermodynamic functions of the systems under study have been determined. The association constants differ for the above systems at the same temperatures. Association entropy ΔS changes from one system to another, while ΔH is the same for all systems.
Conformation et Spectrometrie de RMN
Authors: Wylde Renée , Cerveau Geneviéve
Published: May 2005

L'examen des spectres de RMN des quatre diméthylamino‐3‐décalols‐2‐trans et des iodures d'ammonium quaternaires correspondants permet d'envisager pour ces composés une déformation de l'un des cycles de la décaline trans habituellement double chaise.

Cette déformation est apparente specialement dans le cas de l'isomère cis à groupements hydroxyle equatorial et diméthylamino axcial, pour lequel on propose une conformation ‘chaise aplatie'. Le passage à l'ammonium quaternaire accentue entre deformation jusqu’à la conformation chaise‐bateau ou préférentiellement chaise croisée.
The NMR spectra and conformations of cyclic compoundsV: Proton couplings and chemical shifts in bridged cyclobutanes
Authors: Abraham R. J. , Cooper M. A. , Salmon J. R. , Whittaker D.
Published: May 2005

The PMR spectra of twelve pinene derivatives are reported, analysed and assigned.

The proton couplings in the bridged cyclobutane group are compared with those of other strained cyclobutanes, and the relationship between 2JHH and the C.CH2.C angle is shown to be anomalous in these systems, suggesting unusually small H. C. H. angles in cyclobutanes.

The very large values of 4JHH (eq‐eq) in buckled cyclobutanes are interpreted in terms of current M. O. theory and also given a simple geometric rationalisation based on the direct mechanism.

The various couplings in the pinene skeleton are discussed in terms of present theories and minor conformational effects in these molecules. Substituent chemical shift (SCS) values for Me and OH groups around the pinene skeleton are obtained, and shown not to agree with calculations based on present theories of chemical shifts.
Interpretation du Spectre RMN de l'Octaacetate de Cellobiose a 250 MHz. Application au Triacetate de Cellulose
Authors: Dunand J. , Gagnaire D. , Odier L. , Vindendon M.
Published: May 2005

Nous avons interprété totalement le spectre de RMN de l'α octaacétate de cellobiose en effectuant le spectre à 250 MHz et en utilisant la technique de double irradiation. Les 14 protons des deux cycles ont été attribués.

L'octaacétate de cellobiose étant le premier modèle du triacétate de cellulose, cette interprétation nous a permis d'attribuer à L'extrémité anomère du triacétate tous les protons se trouvant à champ faible dans son spectre RMN.
Analysis of the PMR spectrum of 1,4‐naphthoquinone in a nematic solvent
Authors: Dereppe Jean‐Marie , Degelaen Jacques , van Meerssche Maurice
Published: May 2005

The analysis of the PMR spectrum of 1,4‐naphthoquinone dissolved in the nematic phase of pp′‐di‐n‐hexyloxyazoxybenzene showed that the naphthoquinone molecule is planar. The ratios of the various interprotonic distances were determined.
13C‐NMR‐chemische Verschiebungen von Polymethinen. Elektronenstruktur und Lösungsmitteleinfluss
Authors: Radeglia R. , Engelhardt G. , Lippmaa E. , Pehk T. , Nolte K.‐D. , Dähne S.
Published: May 2005

Die 13C‐NMR‐chemischen Verschiebungen von einfachsten Polymethinen bestätigen die alternierende Elektronendichteverteilung bei diesen Verbindungen. Die Verschiebungen polarer Merocyanine sind von der Polarität des Lösungsmittels abhängig und beweisen damit eine lösungsmittelinduzierte Veränderung der Elektronenstruktur.
Confirmation of the E and Z attribution to the isomers of 3‐ethylidene‐1‐azabicyco‐[2,2,2]octane by CMR spectroscopy
Authors: Van Binst G. , Tourwe D.
Published: May 2005

CMR spectra of the following bicyclo[2,2,2]octane compounds were measured: 1‐azabicyclo[2,2,2]octan‐3‐one (3), 2‐azabicyclo[2,2,2]octan‐3‐one (5), bicyclo[2,2,2]octaone (4), 3‐ethyl‐1‐azabicyclo[2,2,2]oct‐2‐ene (6) and of the Z and E isomers of 3‐ethylidene‐1‐azabicyclo‐[2,2,2]octane (1 and 2). The attribution of the signals and confirmation of the Z and E configuration of isomers (1) and (2) is described.
The structure of 2‐arylamino‐2‐thiazolines, analogous thiazines and their amides—X. An IR and NMR investigation of the N‐methyl derivatives
Authors: Sohár P. , Toldy L.
Published: May 2005

The isomer‐pairs of the 2‐arylamino‐2‐thiazolines and ‐thiazines, carrying a methyl substituent on the nitrogen atom of the ring and outside the ring were synthesised by unambiguous routes. An IR and NMR investigation of these compounds revealed the fact that the NMR signal of the 2,6‐symmetrically substituted aryl group can be used advantageously for the determination of the isomeric structures. The AB2 multiplet of the aromatic protons is shifted towards the AX2 pattern in the b isomer—containing a conjugated CN bond outside the ring—as compared to the a isomers. The structure of this multiplet does not depend on the size of the hetero‐ring.
Studies of polarised ethylenes—IV: Barriers to rotation around formal double bonds and formal single bonds in 1, 1‐bis‐dimethylaminoethylenes
Authors: Wennerbeck I. , Sandström J.
Published: May 2005

1, 1‐Bis‐dimethylaminoethylenes with electron attracting substituents on C2 show rotations around the CC and CN bonds, the rates of which are in most cases measurable by the NMR line shape method. The temperature‐dependent four‐and eight‐site NMR spectra have been analysed and the barriers to rotation around the different bonds have been evaluated by a complete line shape treatment based on the Bloch formalism. Assignment of sites to methyl groups has been made with the aid of aromatic solvent induced shifts and anisotropy effects.
Lanthanide‐induced shifts in proton NMR spectra—IV: Praseodymium‐induced shifts to lower applied fields and obscured chemical shifts from lanthanide‐induced shift (LIS) data
Authors: Hlubucek J. R. , Shapiro B. L.
Published: May 2005

Praseodymium(III) tris(dipivalomethanato) [Pr(DPM)3] reduces the complex overlapping aromatic absorptions in the proton NMR spectrum of a monosubstituted naphthalene, cis‐3‐(1‐naphthyl)‐1,3,5,5‐tetramethlcyclohexan‐1‐ol(1) to a virtually first‐order pattern, whereas Eu(DPM)3 at the same and higher molar concentrations does not completely resolve the aromatic proton signals. Plots of the Pr(DPM)3‐induced shifts measured in carbon tetrachloride solution versus molar equivalents of Pr(DPM)3 added may be extrapolated to provide accurate chemical shifts in the absence of added lanthanide shift reagent (LSR). The qualitative conformational conclusions from the Pr(DPM)3 shifts agree with those from the Eu(DPM)3‐induced shifts, but there are detailed differences in the relative lanthanide‐induced shifts (LIS) for different proton types in the molecule.
14N and 35Cl NQR studies of organophosphorus compounds
Authors: Osokin D. J. , Safin I. A. , Nuretdinov I. A.
Published: May 2005

14N and 35Cl NQR spectra have been investigated for 24 organophosphorus compounds using a pulse technique. The electron populations of the nitrogen lone pair orbital and the NP bond are calculated according to the Townes and Dailey method. The experimental data are interpreted assuming a partial double bond character of the NP bond due to the pπdπ interaction and pπσ conjugation of the lone pair electrons of the nitrogen atoms. The effect of the different nature of substituents X on the NP bond populations is observed in X  PRn (R2N)3‐n molecules (where X is O, S, Se, or lone pair electrons and n = 0, 1, 2). It can be seen from this dependence that the effective electronegativity of the phosphorus atom is largest in selenophosphoramidates and falls in the sequence PSe > PS > PO > P.
An NMR study of spatial arrangements in natural alkaloids—I: Indor spectra and conformations of pachycarpine (d‐sparteine), lupanine and 13‐hydroxylupanine
Authors: Sadykov A. S. , Kamayev F. G. , Korenevsky V. A. , Leon'ev V. B. , Ustynyuk Yu. A.
Published: May 2005

The INDOR homonuclear PMR spectra of three quinolizidine alkaloids—pachycarpine (d‐sparteine), lupanine and 13‐hydroxylupanine—have been studied. The molecular conformations including the boat‐structure of the ring C have been established.
Analyse des Effets de Substituant du Noyau Benzenique EN RMN du Fluor: Application aux Fluoro‐2 Alcools Phenylethyliques
Authors: Aranda G. , de Luze H.
Published: May 2005

Les déplacements chimiques du fluor de différents phényls‐1 et 2 fluoro éthanols ont été mesurés; les valeurs obtenues ont été extrapolées à dilution infinie en soluté et référence interne. Les corrélations linéaires ou non, obtenues entre ces déplacements chimiques et les constantes de substituant σ donnent lieu à une discussion générale relative à la validité des relations d'enthalpie libre étendues aux données de la RMN; les limites et les possibilités de telles relations sont précisées.
Zur Kenntnis des Chinoiden Zustandes—XX:13CMR‐Untersuchungen an Cyclohexadienonen
Authors: Rieker Anton , Berger Stefan
Published: May 2005

Die 13C‐chemischen Verschiebungen von 19 para‐und 5 ortho‐Cyclohexadienonen werden durch 13C‐Fourier‐Transform‐Spektroskopie ermittelt und zugeordnet. Der Substituenteneinfluß auf die chemische Verschiebung der Signale der Ringkohlenstoffatome wird diskutiert. Durch die Aufstellung von Regressionsgeraden wird gezeigt, daß die Resonanzlagen der olefinischen Ringatome und des allylischen C‐Atoms im para‐chinoliden Ring wechselseitig voneinander abhängen. Eine Korrelation zwischen 1H‐NMR‐ und 13C‐NMR‐Daten wird am Beispiel der Cyclohexadienone überprüft.
Nuclear magnetic resonance in structure determination—VII: Stereochemistry of the epoxides of the adducts of cyclopentadiene with α‐methyl‐β‐acetyl acrylic acid lactone
Authors: Sánchez‐Obregón Rubén , Salmón Manuel , Walls Fernando
Published: May 2005

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

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

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

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

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

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

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

Es wird über die 13C‐Spektren der 12 isomeren Dimethylpiperidine berichtet. Die chemischen Verschiebungen der verschiedenen 13C‐Kerne werden diskutiert, speziell in Hinblick auf konfigurative und konformative Effekte.

Auszugsweise vorgetragen auf dem ‘Colloquium Spectroscopicum Internationale XVI’, Heidelberg, Germany, Oktober 1971.

.
Concerning the angular dependence of the Vicinal31P1H coupling constants of phosphonate and of hydroxy‐phosphonate derivatives
Authors: Evelyn L. , Hall L. D. , Steiner P. R. , Stokes D. H.
Published: May 2005

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

13C NMR (CMR) spectra of a number of di‐ and trisubstituted ethylenes have been measured. Very consistent values are found for the differential shieldings of allylic carbons in a number of linear, (Z)‐ and (E)‐disubstituted ethylenes. The discrepancies between the several structural elements are explained tentatively by assuming different rotational preferences in the (Z)‐isomers, the (E)‐isomers, or both. The results obtained for some branched olefins are qualitatively in agreement with conclusions reached in previous 1H NMR (PMR) investigations, with the possible exception of 2,5‐diMe‐3‐hexene.

Differential shieldings in trisubstituted ethylenes are larger than in disubstituted ethylenes, probably as a consequence of steric interaction between geminal substituents.

It is confirmed, that API's recent relabelling of the isomers of 3‐Me‐2‐hexene was justified. Furthermore, the (E)‐configuration is assigned to the high‐boiling isomer of 3,4,4‐triMe‐2‐pentene. On the other hand, the high‐boiling isomer of 3‐Et‐4‐Me‐2‐pentene is shown to be the (Z)‐isomer. For the isomeric pair of geraniol and nerol, the (E)‐configuration is assigned to the former and the (Z)‐configuration to the latter, in agreement with our recent PMR investigations.
Note on the relative magnitudes of substituent effects on 1H‐chemical shifts in olefinic and aromatic systems
Authors: Beeby Jane , Drake Linda , Duffin R. , Sternhell S. , Pretsch E. , Simon W.
Published: May 2005

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

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

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

The CIDNP effects observed during thermal decomposition of 2‐hydroperoxide‐2‐methyltetrahydrofuran at 150° in C6H5COH are described.

An A/E multiplet effect is observed on the CH3‐propyl protons of the propylacetate formed as a result of decyclisation of the methylfuryl radical.
FT‐NMR investigation of 13C11B coupling
Authors: Axelson D. E. , Oliver A. J. , Holloway C. E.
Published: May 2005

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

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

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

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

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

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

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

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

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

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

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

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

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

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

La formation réversible d'un composé, résultant de l'addition de l'hexafluoroacétone sur les acides carboxyliques, a été mise en évidence par RMN 1H, 19F et infrarouge. Ce composé, magnified image, est le résultat d'une addition nucléophile de l'acide sur le carbonyle de l'hexafluoroacétone. Cette addition est favorisée par un abaissement de la température et la présence de substituants R donneurs d'électrons.

D'autre part, le déplacement chimique des groupes CF3 (ou du groupe OH) de ce composé dépend de la nature du substituant R, il est possible d'en déduire une méthode d'analyse de mélange d'acides.
Diamagnetic contribution and substituent effects on 13C n.m.r. spectra
Authors: Shahab Y. A.
Published: May 2005

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

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

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

13C N.m.r. chemical shifts obtained for indenyl‐ and cyclopentadienyllithium in several, mostly ethereal, solvents are presented. The chemical shift changes induced by varying the solvent are assumed to probe the actual π‐electron density distribution, thus providing an insight into the structure of the ion‐pair. The increase in the estimated π‐electron densities obtained for the protonated aromatic carbons of indenyllithium by increasing the coordinating ability of the solvent gives evidence of a change of the ion‐pair equilibrium towards solvent‐separated species. The average chemical shifts for indenyl‐ and cyclopentadienyllithium were independent of the choice of solvent, a fact which supports the ion‐pair model in all studied media.
Nitrogen‐15 n.m.r. studies of 13C, 15N labeled arginine
Authors: London R. E. , Walker T. E. , Whaley T. W. , Matwiyoff N. A.
Published: May 2005

15N n.m.r. spectra of [13C‐2, 3‐15N2‐guanidino]arginine and [13C, 15N2] urea were obtained in D2O and H2O at a variety of pH values both with and without proton decoupling. The effects of the proton exchange rate are readily observable in the proton coupled 15N spectra. When the guanidino group is deprotonated (pK = 12.5), the terminal nitrogens give a single resonance 6.6 ppm downfield of the protonated species, indicating a rapid tautomeric exchange. The observed NH and CN couplings are compared with calculated values, and good agreement is found for 1J(CN) using a Blizzard–Santry type calculation. The ramifications of the proton exchange on 15N n.m.r. spectra of amino acids and peptides are discussed.
INDOR study of 1H1H inter‐ring couplings in naphthalene derivatives
Authors: Attimonelli M. , Sciacovelli O.
Published: May 2005

The 1H n.m.r. spectra of two naphthalene derivatives have been completely analysed. The advantages of the INDOR technique have been illustrated in the determination, magnitudes and signs, of small couplings in complex spin systems. A splitting of 0.07 Hz has been resolved in the 100 MHz spectrum of 1,2‐dichloro‐3 nitronaphthalene. The signs of the inter‐ring coupling constants alternate with the number of intervening bonds.
Etude Stéréochimique par RMN 1H de Tetrahydropyrannes β‐Chlorés α‐Substitués
Authors: Delaunay Jacques , Lebouc Alain , Riobé Olivier
Published: May 2005

L'étude RMN 1H des alkyl‐2 chloro‐3 tétrahydropyrannes, préparés par action des réactifs de Grignard sur le mélange des dichloro‐2,3 tétrahydropyrannes cis et trans, indique la présence de deux isomères cis et trans, dans lesquels les groupements alkyles sont en position équatoriale; le chloro‐3 phényl‐2 tétrahydropyranne n'existe que sous la forme trans (éq‐éq). L'étude RMN 1H des alcoxy (aryloxy)‐2 tétrahydropyranne n'existe que sous la forme trans (éq‐éq). L'étude RMN 1H des alcoxy (aryloy)‐2 chloro‐3 tétrahydropyrannes cis et trans, obtenus par action d'alcools et du phénol sur les měmes dérivés dichlorés, montre que le groupement alcoxyle (ou aryloxyle) est toujours en position axiale.
The stereochemical dependence of the vicinal 13C14N coupling constant as a constitutional probe
Authors: Valckx Ludo A. , Borremans Frans A. M. , Becu Chris E. , De Mar Robert H. K. , Anteunis Marc. J. O.
Published: May 2005

The magnitudes of 13C14N coupling constants have been measured in 12 rigid or anancomeric (biased) tetraalkylammonium iodides. The one‐bond coupling is typical for the degree of substitution of the carbon atom and the geminal coupling is very small. Vicinal couplings depend on the dihedral angle and other factors.
Self‐consistent Perturbation Theory of 13C magnetic resonance parameters in pyridines
Authors: Galasso Vinicio
Published: May 2005

The 13C chemical shifts for pyridine and 22 of its monosubstituted derivatives, the 13C19F couplings for fluoropyridines and the 13C15N couplings for pyridine, the pyridinium cation and pyridine‐N‐oxide have been calculated using the SCF‐INDO Finite Perturbation Theory. Experimental 13C chemical shifts show only modest correlation with calculated shieldings; trends and magnitudes are, however, reasonably reproduced in some cases. Theory yields a correct account of the magnitudes, signs and trends for the various couplings except for 2J(CF). Addition of an empirical correction of + 33.5 Hz to the Fermi contact term leads also to excellent reproduction of this coupling.
13C NMR spectra of non‐labelled and 15N‐mono‐labelled azo dyes
Authors: Lyčka Antonín , Šnobl Dobroslav , Macháček Vladimír , Večeřa Miroslav
Published: May 2005

13C NMR spectra of four types of azo coupling products from benzenediazonium chloride have been measured and interpreted, viz. hydrazo compounds with an intramolecular hydrogen bond (3‐methyl‐1‐phenylpyrazole‐4,5‐dione 4‐phenylhydrazone), azo compounds without an intramolecular hydrogen bond (4‐hydroxyazobenzene), azo compounds with an intramolecular hydrogen bond (2‐hydroxy‐5‐tert‐butylazobenzene) and an equilibrium mixture of both the tautomers of 1‐phenylazo‐2‐naphthol. The absolute values of the J(15N13C) coupling constants have been determined by recording the spectra of the 15N isotopomers, and have been used, in some cases, for 13C signal assignment. A relationship has been found between the chemical shifts of the C‐1′ to C‐4′ carbons of the phenyl group (from the benzenediazonium ion) or the 1J(15N13C) coupling constant, and the composition of the tautomeric mixture.
Nuclear magnetic resonance spectra of psychotherapeutic agents. V*—conformational analysis of 1,3,4,5‐tetrahydro‐2H‐1,5‐benzodiazepin‐2‐ones
Authors: Aversa M. C. , Giannetto P. , Romeo G. , Ficarra P. , Vigorita M. G.
Published: May 2005

The conformational analysis of biologically active lofendazam (7‐chloro‐5‐phenyl‐1,3,4,5‐tetrahydro‐2H‐1,5‐benzodiazepin‐2‐one) is carried out by means of lanthanide shift reagent assisted 1H NMR spectroscopy: the lanthanide induced shift computer simulation suggests that in deuteriochloroform the heterocyclic ring of lofendazam assumes a cycloheptene‐like chair conformation, where 1‐N moves away from trigonal stereochemistry to a very flattened pyramidal structure. At room temperature the conformational equilibrium is markedly shifted (85%) towards the conformer showing pseudoaxial H‐1 and 5‐Ph. The remarkable influence of steric requirements in controlling conformation, and the importance of 3‐ and/or 4‐methyl groups in hindering the ring inversion at room temperature, have been verified by conformational analysis of suitable analogous 1,3,4,5‐tetraydro‐2H‐1,5‐benzodiazepin‐2‐ones.