bluuebunny/crossref_metadata_2025 huggingface dataset:
PMR studies on the cyclitol mytilitol
Authors: Sangster A. W. , Thomas Shirley , Johnson LeRoy F.
Published: May 2005

The PMR spectra of mytilitol at 60, 100 and 220 MHz are presented; the latter confirms the structure 1.
Geminal coupling constants in methylene groups α to nitrogen in indolizidine, quinolizidine and related systems
Authors: Cahill R. , Crabb T. A. , Newton R. F.
Published: May 2005

Values of J(5a—5e) for indolizidine and related systems show that, contrary to results described in an earlier communication, these couplings do not differ markedly from the corresponding geminal coupling constant in quinolizidine.
An interpretation of 1H and 13C chemical shifts in substituted benzenes on the basis of M.O. charge densities
Authors: Lazzeretti P. , Taddei F.
Published: May 2005

The results of an MOLCAO calculation on both σ and π electron systems of several substituted benzenes are reported. The charge densities obtained reproduce the dipole moments of the molecules examined, provided that substituents with strong mesomeric effects are not present. It is shown that there is a satisfactory agreement between 13C and 1H chemical shifts and the trend of total charge densities for all positions of substituted benzenes.
Etude par RMN d'une Serie d'Indoanilines et d'Indophenols
Authors: Canet D. , Granger P. , Bugaut A. , Estradier F.
Published: May 2005

Nous rapportons les résultats de l'étude RMN de 25 indoanilines et indophénols. Ces mesures nous permettent de préciser les formes tautomères stables et de donner la position des différents substituants sur les cycles.
Protonenresonanzuntersuchungen an Tellur‐, Schwefel‐ und Sauerstoff‐substituierten Benzolderivaten
Authors: Müllen Klaus
Published: May 2005

Die Protonenresonanzspektren von o‐Phenylen‐bis[p‐äthoxy‐phenyltellurid], o‐Dimercapto‐benzol und p‐Hydroxy‐mercapto‐benzol sind vollständig analysiert worden. Die Einflüsse der TeR‐, SR‐ und OR‐Gruppen in den analogen Benzolderivaten (1) bis (4) werden anhand spezifischer Substituenten‐Inkremente diskutiert.
Proton magnetic resonance spectra of methylacridines. The relative signs of the inter‐ring coupling constants
Authors: Sciacovelli O. , von Philipsborn W.
Published: May 2005

High‐resolution proton spectra of acridine and the five monomethyl derivatives have been analyzed using multiple resonance and computer techniques. It was possible to determine the magnitudes and relative signs of the inter‐ring coupling constants between H‐C(9) and all the protons of the adjacent rings. Positive signs have been obtained for 5J29 and 5J49, negative signs for 4J19 and 6J39. The coupling constants are discussed in terms of σ‐ and π‐contributions and as a function of the geometry of the pathway.
Chemical polarization of nuclei. PMR spectra of decomposition products of dimethyl peroxydiphthalate
Authors: Kessenikh A. V. , Rykov S. V. , Starostin E. K. , Nikishin G. I.
Published: May 2005

Chemical polarization of protons was observed in methyl benzoate formed during the thermal decomposition of dimethyl ester of peroxydiphthalic acid. The polarization pattern of methyl benzoate aromatic protons was very different in this case from that observed during the thermal decomposition of acetyl benzoyl peroxide. The unpolarized products formed from the methoxy radical, CH2O and CH3OH, were found in the mixture of decomposition products of this peroxide and were identified by means of PMR spectroscopy.
NMR parameters of sulphur heterocycles: Solvent and concentration effects for thiophen and related systems
Authors: Ewing D. F. , Scrowston R. M.
Published: May 2005

Infinite dilution data for six sulphur heterocycles have been obtained from second order analyses of their NMR spectra in CS2, CDCl3, CD3COCD3, or C6D6. Use of LAOCOON3 leads to accurate chemical shifts, but substantial errors remain in some of the coupling constants. Evidence is presented of specific association of chloroform with the sulphur heterocycles and of the interaction of acetone with the sulphur atom. An apparently anomalous geometry for the complex of benzene with thiophen and with other solutes is discussed. Dilution effects are considered in relation to the formation of solute dimers.
Synthesis and NMR analysis of 2,4‐dichloro‐1‐pentene and of 2,4‐dichloro‐1‐pentene‐1‐d1
Authors: Gurato Giorgio , Rigo Adelio
Published: May 2005

The compound 2,4‐dichloro‐1‐pentene‐1‐d1 (1) was synthesized starting from and CHCNa. In the last stage of the synthesis on activated carbon‐HgCl2 catalyst), (3) were formed together with (1).

The NMR parameters of (1), its cis and trans isomers and (2) were obtained in C6D6 solution at 100 MHz. Theoretical spectra of (1) at 60 MHz were simulated with the aid of a computer, using as input the NMR parameters obtained at 100 MHz and good agreement with the experiment was obtained.
The NMR spectrum and conformation of 2,3‐difluoropropionic acid ethyl ester
Authors: Hägele G. , Harris R. K. , Sartori P.
Published: May 2005

The 1H and 19F NMR spectra of the CH2FCHF group in FCH2CHFCO2C2H5 were analysed on the basis of an ABCXY spin system. The non‐equivalence of the methylene protons is discussed in terms of rotational isomerism. It is concluded that the dominant rotamer is probably considerably distorted from a perfectly staggered orientation. The variation of 3JHF with substituent electronegativity is reviewed.
Conformation of substituted five‐membered rings
Authors: Dradi Emanuele , Gatti Giuseppe
Published: May 2005

Proton magnetic resonance chemical shifts and coupling constants for some 5‐substituted dihydrofurans, dihydrofuran and dihydrothiophene fused rings are reported, the substituents being methyl, ethyl and phenyl.

The observed coupling constants are consistent with buckled rings, in which it appears that a conformation with pseudo‐equatorial substituents is predominant.
Proton magnetic resonance spectra of thenyl derivatives—II. Chloromethylthiophenes and some dithienylmethanes
Authors: Sone Tyo , Takahashi Kensuke
Published: May 2005

PMR spectra of thirty‐eight chloromethylthiophene and seven dithienylmethane derivatives were observed at 60 or 40 MHz. The chemical shifts of methylene protons were 4·63 to 5·25 ppm for monosubstituted 2‐chloromethylthiophenes and 4·37 to 4·56 ppm for monosubstituted 3‐chloromethylthiophenes, respectively, with reference to TMS. Those for 2,2′ ‐dithienylmethanes, which have one substituent in each ring, were 4·12 to 4·34 ppm. These shifs are useful for determination of the positions of the methylene groups in the related compounds. The long‐range coupling constants observed for methylene proton signals are also useful for the determination of the positions of substituents.
Pentafluorobutane; an example of long‐range five bond HF coupling
Authors: de Marco A. , Gatti G.
Published: May 2005

The complete analysis of the spectrum of 2,2,4,4,4‐pentafluoro‐n‐butane is reported. From the sum of the vicinal proton‐fluorine coupling constants an estimate of the conformational energy has been obtained and successively the long‐range coupling of the individual conformers has been calculated.
NMR studies on the interaction of ethyl‐aluminium chlorides with some methyl‐substituted pyridines
Authors: Matsubayashi Gen‐Etsu , Wakatsuki Kizuku , Tanaka Toshio
Published: May 2005

The interaction of triethylaluminium, diethylaluminium chloride and ethylaluminium dichloride with some methyl‐substituted pyridines has been investigated in 1,2‐dichloroethane or dichloromethane by means of NMR spectroscopy. 2,6‐Dimethyl‐ and 2,4,6‐trimethyl‐pyridine have been found to form three types of complexes with diethylaluminium chloride and ethylaluminium dichloride in solution. In addition, the configurations of the complexes in solution have been estimated from proton NMR chemical shifts of the methyl‐substituted pyridines and the conductivity measurements.
The difference in the barrier heights for internal rotation between amides and thioamides
Authors: Walter Wolfgang , Schaumann Ernst , Voss Jürgen
Published: May 2005

Evidence is presented which shows, contrary to the opinion expressed by Moriarty et al., that for electronic reasons internal rotation is substantially more hindered in thioamides than in amides.
Protonenresonanz‐spektroskopische Untersuchungen an substituierten Cyclobutenen. Ein Beitrag zur Kenntnis der Bindungsverhältnisse im komplex‐gebundenen Cyclobutadien
Authors: Hüther Hans , Brune Hans Albert
Published: May 2005

Die vollständigen Protonenresonanz‐Spektren—einschließlich aller beobachtbaren 13CH‐Kopplungen wurden für eine Reihe substituierter Cyclobutene, Methylen‐cyclobutene und Bismethylen‐cyclobutene aufgenommen und zugeordnet. Die Meßergebnisse werden im Hinblick auf die Bindungsverhältnisse im durch Komplexbildung stabilisierten‐Cyclobutadien diskutiert.
PMR spectra of dimers of cyclopentadienyl compounds
Authors: Sergeyev N. M. , Avramenko G. I. , Korenevsky V. A. , Ustynyuk Yu A.
Published: May 2005

The PMR spectra of cyclopentadine endo‐dimer, its 1y‐acetoxy‐derivative and the dimer of spiro‐heptadiene have been thoroughly studied. The assignment is proved by the use of spindecoupling experiments and the INDOR‐technique. The relative signs of several coupling constants were found and used for the assignment. General trends in the proton chemical shifts and coupling constants are discussed for the derivatives of the cyclopentadiene dimer and for the substituted cyclopentadiene dimers.
Determination Rapide de la Configuration Cis Trans des Alcenes CHCHCH Utilisation des Complexes de Terres Rares
Authors: Martin G. J. , Naulet N. , Lefevre F. , Martin M. L.
Published: May 2005

Dans les composés de structure
equation image
Z CHCHCHY la complexité du spectre rend souvent difficile l'obtention du couplage J(HCCH) et donc l'identification de la configuration. L'étude de nombreux dérivés de ce type préparés par des méthodes stéréospécifiques montre qu'à de rares exceptions près, le déplacement chimique δ CH(Z) de l'isomère cis est supérieur à δCH(Z) de l'isomére trans. Dans le cas des alcools R CHCH CHOH R′ les isoméres configurationnels ont des comportements différents en présence de complexes d'europium ou de praseodyme, holmium et dysprosium. Si le spectre des isoméres trans reste fortement couplé en présence de complexe l'obtention de 3J(HCCH) devient aisée dans les composés cis.
Magnetic non‐equivalence in carbinols of the general formula R1R2C(OH)CH2OR (1H and 13C NMR)
Authors: Dabrowski Janusz , Ejchart Andrzej
Published: May 2005

Several compounds of the general formula R1R2C(OH)CH2OR containing different geminal group systems have been investigated in proton and carbon magnetic resonances at variable temperatures. The role of steric factors, viz. of the size of substituents and the distances between different parts of the molecules, have been discussed.
Resonance des Phospholes—Reaction Avec le n‐Butyl Lithium
Authors: Mathey F. , Mankowski‐Favelier R.
Published: May 2005

Sept phospholes ont été préparés par une méthode en deux étapes précédemment décrite. Sur la base de données de RMN du proton et du phosphore, on a essayé de classer ces phospholes suivant leur degré d'aromaticité. On a fait réagir deux d'entre eux avec le n‐butyl lithium. On a observé une attaque nucléophile sur le phosphore et sur les doubles liaisons. Ces faits sont expliqués par un accroissement des conjugaisons p—π et pπ—dπ entre le phosphore et le système diénique par comparaison avec les vinyl phosphines.

Les données RMN semblent en accord avec cette façon de voir. Les influences de la substitution et de la délocalisation du doublet du phosphore sur le δ 31P ont été interprétées dans le cadre du formalisme de Letcher et Van Wazer.
New tables of ‘ring current’ shielding in proton magnetic resonance
Authors: Haigh C. W. , Mallion R. B.
Published: May 2005

A new theory6 for ‘ring current’ effects on the chemical shifts of protons in or out of the plane of a benzene ring is summarized, and pictorially compared with the predictions of the earlier semi‐classical theory of Johnson and Bovey.1 In the Appendix are presented extensive numerical tables of the predicted shieldings.
NMR studies of viomycin
Authors: Viglino P. , Franconi C. , Lai A. , Brosio E. , Conti F.
Published: May 2005

The 1H and 13C NMR spectra of antibiotic Viomycin sulphate and its constituent aminoacids in H2O and D2O were examined in a wide range of pH values. The spectra were analysed by proton spin‐spin decoupling experiments and measurements of the relative intensities of the resonance and chemical shift values. Exchange experiments were also carried out and an almost complete assignment of the resonances of the spectra was possible. The data obtained are discussed in terms of possible structures for Viomycin and the presence of intramolecular hydrogen bonds. Some information about the conformation of the molecule is also given. A tentative assignment of the 13C spectrum of Viomycin is given and the experimental 13C chemical shift values compare well with the theoretical ones evaluated by Grant's rule.
The proton chemical shifts of polychlorinated biphenyls
Authors: Welti D. , Sissons D.
Published: May 2005

A 220 MHz NMR spectrometer has been used to identify the structure of polychlorinated biphenyls (PCBs). The proton chemical shifts and approximate coupling constants of PCBs fractionated from Aroclor 1254 are given in the text. The spectra of model compounds are included in the supplement. The chemical shifts are also tabulated according to the ring substitution pattern, when it can be seen that the shifts change systematically with the degree of both the total ring substitution and the substitution in the positions ‘ortho’ to the bridging bond between the rings.
A PMR investigation of organic cations—II: Mixed p‐tolyl‐thienyl carbonium ions
Authors: Lazzeretti P. , Schenetti L. , Taddei F. , Spagnolo P. , Tiecco M.
Published: May 2005

The PMR spectra of isomeric p‐tolyl‐thienyl carbonium ions and the corresponding carbinols were studied in order to compare the relative abilities of 2‐thienyl, 3‐thienyl and p‐tolyl groups to stabilize a carbonium ion. The low field shifts in the ions relative to the neutral molecules are discussed in terms of positive charge delocalisation, as seen by a comparison with calculated π charge densities. Additionally, vicinal coupling constants fit a correlation with π bond order, but this applies only to the thienyl groups in the ionic species.
The NMR spectra and conformations of dihydropyran derivatives—II: The conformational energies of carbomethoxy, hydroxymethyl and acetoxymethyl groups at c‐6 of the 5,6‐dihydro‐α‐pyran ring
Authors: Achmatowicz O. , Chmielewski M. , Jurczak J. , Kozerski L. , Zamojski A.
Published: May 2005

The sum of coupling constants of proton H‐6 for conformations H1 and 1H of the 6‐substituted 5,6‐dihydro‐α‐pyran derivatives have been determined with the aid of appropriate, conformationally biased compounds. With the use of these values and the PMR spectra of the title compounds, thermodynamic values of their conformational equilibria and the conformational preferences of the carbomethoxy, hydroxymethyl and acetoxymethyl groups, have been evaluated.
1H and 13C NMR spectra of benzyl compounds
Authors: Zetta L. , Gatti G.
Published: May 2005

Proton and carbon‐13 spectra of benzyl compounds of the general formula (C6H5CH2)nX with a large variety of X substituents have been measured. While a linear relationship between the CH2 chemical shift and the substituent electronegativity was found both for 1H and 13C, large deviations from linearity were observed for transition metals such as titanium and zirconium. These later results are correlated with the X‐ray studies of the latter compounds.
Transferts Protoniques de Sels d'Ammonium Substitues—VIII: Sels de Pyridinium 4‐Substitues
Authors: Delpuech Jean‐Jacques , Serratrice Guy
Published: May 2005

La vitiesse de déprotonation 1/τ de sels de pyridinium [4 – R –PyH]+, où R  NH2, t‐Bu, Me, Cl, Br or CN, est mesurée par la coalescence du spectre RMN des protons α‐pyridiniques dans un mélange CF3COOH/H2O/HCLO4, d'acidité variable Ho, à 38°C. 1/τ est une fonction linéaire kho de l'acidité 1/ho. La constante k est approximativement proportionnelle à la teneur en eau, et indépendante de la concentration en sel, ce qui semble prouver un échange sur un hydrate de pyridine intermédiaire, selon:
equation image
.

Après une étape d'ionisation très rapide:
equation image
La constante k vérifie, comme KA, une corrélation de Hammett (ρ = 5,05), à l'exception de la 4‐aminopyridine. Elle varie done grandement avec la nature de R (de 3,44 × 102 à 3,14 × 102 M−1 s−1 pour R  NH2 et CN), trandis que kH (de l'ordre de 1010 s−1) y est peu sensible.
A study of the 220 MHz proton resonance spectra for a series of biologically important acridine‐type heterocycles
Authors: Angerman Neil S. , Danyluk Steven S.
Published: May 2005

The high resolution proton magnetic resonance spectra of acridine, phenazine, phenoxazine and phenothiazine have been measured at 220 MHz in various solvents and at several temperatures. Spectra for all four molecules were analyzed iteratively and good agreement was obtained between observed and calculated spectra.

Significant differences are noted between the coupling constants and chemical shifts of acridine and phenazine on the one hand and phenoxazine and phenothiazine on the other. These differences are attributed to a nonplanar heterocyclic ring conformation for phenoxazine and phenothiazine in solution. Moreover, it is concluded from the temperature measurements that the heterocyclic rings of phenoxazine and phenothiazine are conformationally flexible in the range covered. Possible mechanisms are suggested for the chemical shift and coupling constant changes.
C‐13 magnetic resonance studies of some papaveraceae alkaloids
Authors: Nakashima Thomas T. , Maciel Gary E.
Published: May 2005

The natural abundance 13C magnetic resonance spectra of some Papaveraceae alkaloids have been determined at 22·628 MHz employing the pulse Fourier transform technique. Several techniques were employed to aid in spectral assignments and it has been possible to make self‐consistent assignments for all the resonances for these alkaloids. Evidence is presented for trans‐annular interaction between the amino group and the carbonyl group situated across the ten‐membered ring.
Proton and boron‐11 magnetic resonance studies of some potassium tetraarylborates
Authors: Vandeberg John T. , Moore Carl E. , Cassaretto Frank P.
Published: May 2005

Proton and boron‐11 magnetic resonance spectra for several potassium para‐substituted tetraarylborate compounds [KB(C6H4‐pX)4, where X is H, OCH3, CH3, Br, Cl, F, CF3] have been obtained. The chemical shift between the centers of the AA′ and XX′ multiplets for the ring proton multiplets, relative to a reference chemical shift of 0·39 ppm for potassium tetraphenylborate, correlated with the corresponding Hammett σ values for the para‐substituent. Additionally, the boron‐11 chemical shifts gave a good correlation with corresponding σ values for the substituents. Electronegativities of para‐substituted phenyl rings were calculated and found to be approximately 2·70 for all compounds studied. It was shown that electronic substituent effects do not greatly influence the electron density surrounding the central boron atom in the tetraarylborate ions.
Conformations of highly hindered aryl ethers—XVII. Hindered rotation and carbon–halogen bond magnetic anisotropy in benzyl phenyl ethers
Authors: Lehmann F. Pedro A.
Published: May 2005

The PMR spectrum of 3,5‐dibromo‐4‐methoxybenzyl 2′,6′‐dibromo‐4′‐methylphenyl ether shows two aromatic proton
equation image
signals at δ = 7·33 and 7·71. Comparison with related benzyl ethers and anisoles led to assignment of the upfield signal to the phenyl‐ring protons (H3′ and H5′) and the downfield signal to the benzylic aromatic protons (H2 and H6). In view of the nearly identical inductive effects to which they are subjected, their large shift difference must be due to long‐range effects in preferred conformations. Analysis showed that the anomalous shift observed for the benzylic aromatic protons is due to deshielding by both the other aromatic ring and by the carbon‐halogen bonds. The relation of this work to related biphenyls and diphenyl ethers is discussed.
Magnetic nonequivalences in 2,2,4‐trimethylpentane‐1,3‐diol diisobutyrate and diacetate
Authors: Fantazier Richard M.
Published: May 2005

2,2,4‐Trimethylpentane‐1,3‐diol diisobutyrate (1) and diacetate (2) exhibit magnetic nonequivalence for both sets of geminal‐dimethyl groups adjacent to the asymmetric center, and nonequivalence of the methylene protons three bonds removed. Solvent and temperature studies indicate that one geminal‐dimethyl moiety is affected only by intramolecular influences, while the other is also subject to solvent effects. The behavior is rationalized in terms of a preferred conformation in which steric effects prevent the interaction of one moiety with solvent. An inverse temperature dependence for methyl nonequivalence is observed for 2 and an absence of a temperature dependence is noted for 1. The unusually large methylene nonequivalences, 23 Hz in 1 and 34 Hz in 2, are attributed to the proximity of an ester carboxylate.
On the alleged correlations between simple LCAO‐MO reactivity indices and proton chemical shifts in planar, condensed, benzenoid hydrocarbons
Authors: Mallion R. B.
Published: May 2005

Previous investigations into the proposed correlations between proton chemical shifts in conjugated hydrocarbons and the various LCAO‐MO ‘reactivity indices’ (at the corresponding carbon atoms to which the peripheral protons are bonded), are here reassessed in the light of more‐recently acquired experimental data, for the case of the planar, alternant, condensed, benzenoid hydrocarbons. A correlation coefficient of 0·73, statistically ‘significant’ at less than the ½% level, is obtained. Nevertheless, there are several unsatisfactory features of such proposed correlations (which are discussed), and, in the final analysis, no causative relation is expected between proton chemical shifts and reactivity indices in these molecules. Furthermore, the relative chemical shifts of the sterically unhindered protons in planar, alternant, benzenoid hydrocarbons can be accounted for by the ‘ring current’ effect alone, without the need to postulate a dependence of the proton chemical shifts on reactivity indices, which is in any case considered to be unlikely on physical grounds.
PMR configurational analysis of pinitol with the aid of lanthanide shift reagents and the homonuclear INDOR technique
Authors: Cavagna F. , Groebel A.
Published: May 2005

The PMR spectrum of the peracetylated O‐methyl‐chiro‐inositol (pinitol) could be analysed by employing lanthanide shift reagents and performing spin‐decoupling and INDOR experiments. The 100 MHz theoretical spectrum has been simulated and good agreement with the experiment has been achieved. Analysis of the vicinal HH‐couplings yields the relative configuration.
Etude de la Barrière de Rotation et du Couplage 5J d'α‐Formylpyrroles Stériquement Encombrés
Authors: Jaureguiberry C. , Fournie‐Zaluski M. C. , Roques B. , Combrisson S.
Published: May 2005

Les α‐formylpyrroles substitués sur l'azote par des groupements d'encombrement croissant ne montrent aucune modification sensible dans la valeur du couplage stéréospécifique 5J. Dans les i.Pr‐1 et s.Bu‐1 formyl‐2 pyrroles on met en évidence l'existence d'une conformation préférentielle plane. L'examen des barrières de rotation des dérivés étudiés indique une torsion dans le seul cas du t.Bu‐1 formyl‐2 pyrrole. L'absence de modification de la valeur du couplage 5J dans ce dernier composé est interprêtée par un relais du mécanisme σ—σ par une transmission σ—π.
Transmission of substituent effects in 1,2,3‐selenadiazole derivatives—I
Authors: Caplin G. A.
Published: May 2005

Chemical shifts are reported for the heterocyclic ring hydrogen of a series of para‐substituted 4‐aryl‐1,2,3‐selenadiazoles and substituent effects are evaluated statistically by means of the Swain‐Lupton multiple correlation analysis. A satisfactory understanding of the various substituent effects is obtained by this approach. Excellent correlations were obtained for a number of varying aliphatic solvents, no serious hindrances to correlation being encountered. An approach was also made towards an understanding of aliphatic‐ and aromatic‐induced solvent shifts, as far as these are modified by substituents.
A comparison of classical and quantum‐mechanical ‘ring‐current’ theories
Authors: Rose P. I.
Published: May 2005

The proton resonance spectra of a series of 2,7‐disubstituted‐4,5‐bis(2‐pyridyl)phenanthrene‐3,6‐diols are examined with emphasis on the shielding effects produced by aromatic ‘ring currents.’ In this series, two pyridine rings are rigidly held less than 3.4 Å apart and with considerable overlap. The ‘ringcurrent’ shieldings found for above‐the‐plane positions are in good agreement with the Johnson‐Bovey theory, whereas a recently proposed quantum‐mechanical theory underestimates the shieldings by a factor of nearly three.
Über die Struktur der Thioamide und ihrer Derivate—XXIII:14N‐Entkoppelte H‐NMR‐Spektren und Messung der Rotationsbarrieren bei primären Amiden und Thioamiden
Authors: Walter W. , Schaumann E. , Rose H.
Published: May 2005

Durch Sättigung der 14N‐Resonanz lässt sich in den H‐NMR‐Spektren der primären Amide (1a bis 1d) und der Thioamide (2a bis 2g) die behinderte Rotation um die CN‐Bindung des (Thio)Amid‐Systems nachweisen. Mit Hilfe von Kopplungskonstanten und der Benzolverdünnungsmethode gelingt es, die Signale der Amino‐Gruppe dem cis‐ und dem trans‐NH‐Proton zuzuordnen. Aus der Koaleszenz wird die freie Aktivierungsenthalpie der behinderten Rotation ermittelt und ihre Abhängigkeit von sterischen und elektronischen Effekten sowie vom Lösungsmittel diskutiert.
Diazoalcanephosphonates. Etude par RMN du proton de la configuration de Δ1‐pyrazolines dérivées du norbornadiène
Authors: Cohen Huguette , Benezra Claude
Published: May 2005

Les spectres de RMN de onze pyrazolines 1 à 11 dériveés du norbornadiène sont interprétés et discutés. Les configurations des pyrazolines sont déduites du couplage vicinal PCCH10: celui‐ci est de ∼20 Hz dans les dérivés anti et de ∼6,0 Hz dans les dérivés syn. Le couplage à longue distance P,H9 est stéréospécifique, il est maximum pour les épimères syn.
Carbon‐13carbon‐13 coupling constants of 13C‐methyl labeled o‐ and p‐substituted toluenes
Authors: Marshall James L. , Ihrig Arthur M.
Published: May 2005

From 13C‐7 labeled toluene the following 13C‐methyl o‐ and p‐substituted toluenes were synthesized: o‐NO2, ‐NH2, ‐I and CN; p‐NO2 and ‐NH2. Each of these labeled compounds was studied by carbon magnetic resonance to determine all carbon‐13carbon‐13 splittings involving the methyl carbon.
Electron spin emission phenomena
Authors: Atkins P. W.
Published: May 2005

A brief review of a method that has been used to observe transient ESR signals from short‐lived radicals generated photolytically is presented. At short intervals emission spectra are observed, which in the cases studied (aromatic carbonyls in paraffins) show virtually no multiplet effect. One application of this observation is to the direct determination of electron spinlattice relaxation times in liquids. Some of the theoretical problems connected with the polarisation process are described, with particular reference to the role of radical re‐encounters. Some simple analytical expressions for the polarisation are presented.
Quantitative theory of chemically induced dynamic nuclear polarisation in high magnetic fields
Authors: Buchachenko A. L. , Markarian Sh. A.
Published: May 2005

Further development of the diffusional model of the radical pair is suggested. A function is proposed for the exponential distribution of the diffusional trajectories of the radicals in a radical pair. By this function, the differences in the populations of nuclear spin levels in the molecules are calculated for the S, T and U precursor pairs.

The equations which express the relationship between the theoretically calculated population differences and the experimentally determined enhancement coefficients are derived.
Carbon‐13 chemical shifts of substituted nortricyclenes
Authors: Lippmaa E. , Pehk T. , Paasivirta J.
Published: May 2005

13C NMR spectra of a series of substituted nortricyclene derivatives have been measured, and the 13C chemical shifts interpreted in terms of α, β, γ and δ‐effects. The nature of these substiuent shifts is discussed together with some analytical possibilities. The substituent shifts provide valuable data about the steric effects in strained molecules and can be used as increments for structural analysis, particularly for the determination of orientations of substituent groups.
Nuclear magnetic resonace spectra of substituted oxazoles and oxazolidinones
Authors: Deavenport Dennis L. , Harrison C. H. , Rathburn D. W.
Published: May 2005

During the synthesis of 2,5‐disubstituted oxazoles and 4‐oxazolidinones, NMR spectroscopy was utilized to obtain information on the structure, bonding and geometric isomerism in the various compounds. Long range couplings between substituents attached at C2 and C5 in both ring systems was of particular utility in this respect. The aromaticity of the oxazole ring is substantiated by the ability of the π system to transmit long range coupling through the ring and by the chemical shifts of the ring protons. Geometric isomers of the 4‐oxazolidinones are identified by observing long‐range cis and trans couplings of the order of 1·8 to 2·4 Hz.
The effect of solute concentration on the chemical shift of aromatic compounds. Some studies using 1‐iodonaphthalene as a model compound
Authors: Ewing D. F.
Published: May 2005

The change in chemical shift with solute concentration (dilution effect) has been determined for a model compound—1‐iodonaphthalene—in cyclohexane and carbon tetrachloride. The data and assignments for this compound differ from those of previous work. A simple model is proposed to account for dilution shifts in aromatic solutes and their sensitivity to proton position. Solvent shifts are also discussed.
Chemical polarisation of electrons in redox reactions
Authors: Shuvalov V. F. , Stunzhas P. A. , Moravskii A. P.
Published: May 2005

In the system Ti(III)H2O2RH (RH is isobutyric acid or isopropanol) the concentration and polarisation of the β‐radical decreases during the reaction, while the polarisation of the α‐radical increases with the decrease of the α‐radical concentration. The second fact is not in accordance with Adrian's model of inducing the polarisation in redox systems during the radical recombination process.
Conformational studies by nuclear magnetic resonance—V:13C spectra and structural problems of enamino carbonyl compounds
Authors: Kozerski Lech , Dabrowski Janusz
Published: May 2005

A 13C magnetic resonance investigation of 22 compounds of the general formula OC1(R1)C2(R2)C3(R3) NR4R4′ has been carried out in order to confirm the conformational assignments estimated previously by PMR and IR spectroscopy. The effects of nonplanarity and hindered rotation have been discussed based on chemical shifts and shapes of the C1, C2 and C3 signals.
Sur les conditions de formation des complexes des chloroalkylgallium (ClnR3−nGa) avec diverses bases de Lewis (R2O, R2S, R3N et R3P): étude par spectroscopie de RMN (1H)
Authors: Haran Raymond , Laurent Jean‐Pierre , Commenges Gérard
Published: May 2005

Une étude des conditions de formation des complexes résultant de l'addition des bases de Lewis usuelles (R2O, R2S, R3Net R3P) sur les chloroalkylgallium (ClnR3−nGa) a été réalisée à l'aide de la spectroscopie de RMN.

Il apparaǐt que les seuls composés à se former à la température ambiante sont des complexes mettant en jeu 1 mole de base et 1 mole d'acide. Leur stabilité est gouvernée par le nombre d'atomes de chlore fixés sur le gallium et par la nature de l'atome donneur.
An NMR study of some substituted 1,3‐ and 1,4‐bistrifluoromethylbenzenes
Authors: Bartle K. D. , Hallas G. , Hepworth J. D.
Published: May 2005

Contrary to an earlier report, the metallation of 1,3‐bistrifluoromethylbenzene with n‐butyllithium is found to take place at the 4‐ and 2‐positions. Lithiation of 1,4‐bistrifluoromethylbenzene and subsequent carboxylation gives exclusively the 2‐carboxylic acid. Structures are assigned on the basis of PMR data (100 and 220 MHz). The effects of coupling between aromatic protons and trifluoromethyl groups and the aromatic chemical shifts brought about by esterification are discussed for a series of bistrifluoromethylbenzoic acids.
Some aspects of anisochronism of geminal methyl groups in quaternised α‐dimethylamino esters (1H and 13C NMR)
Authors: Da̧browski Janusz , Ejchart Andrzej , Kamieńska‐Trela Krystyna
Published: May 2005

The magnitude of chemical shift nonequivalence (Δδ) in compounds having the general formula R1CH(COOR2)N+R3Me2X− is discussed from the viewpoint of selective shielding of one of the geminal groups by the ester group in the preferred rotamer. In addition, a novel example of the increase of Δδ with rise in temperature has been observed.
31P CIDNP in the reactions of phosphoranyl radicals
Authors: Levin Ya. A. , Il'yasov A. V. , Goldfarb E. I. , Vorkunova E. I.
Published: May 2005

The polarisation of phosphorus nuclei (31P CIDNP) during the free radical reactions of triakyl and triaryl phosphites proceeding via intermediate phosphoranyl radicals is discussed.
Etude par Résonance Magnétique Nucléaire de la thiamine (vitamine B1). Site de protonation‐équilibre de tautomérie
Authors: Fournier J. , Vincent E. J. , Chauvet A. M. , Crevat A.
Published: May 2005

Nous mettons en évidence l'existence d'un équilibre de tautomérie dans la thiamine et ses esters phosphoriques. Et nous évaluons la position relative de l'équilibre dans ces différents composés. Le calcul permet de relier un grand nombre d'observations expérimentales.
Cyclodimerisation reactions of conjugated dienes with aldehydes—I: Formation of tetrahydropyrans and their 300 MHz 1H NMR spectra
Authors: De Smet A. , Anteunis M.
Published: May 2005

The palladium catalysed reaction of butadiene with aldehydes yields 2‐substituted 3,6‐divinyl‐tetrahydropyrans.1–4 The reaction has been extended to isoprene and myrcene. With formaldehyde only 2,5‐substituted pyrans have been isolated. The isomeric tetrahydropyrans obtained were fully characterised by 1H NMR, and representative 300 MHz spectra are given. Attempts to react aldehydes with 2‐methoxybutadiene were unsuccessful.
Chemically induced dynamic nuclear polarisation in some SE and SN reactions
Authors: Beletskaya I. P. , Rykov S. V. , Buchachenko A. L.
Published: May 2005

CIDNP has been found for the methylene protons in Ph3CR (R = C6H5CH2) from the reaction of RHg with Ph3CX. A weak CIDNP effect was observed in the product (CH3O)2C6H3CPh3 of alkylation of veratrol by Ph3CCl (an aromatic SE substitution) and in the Meisenheimer complex resulting from the reaction of (CH3COCH2)2Hg with trinitrobenzene in DMSO in the presence of iodide ions (an aromatic SN substitution).
CIDNP effects in various magnetic fields during the reaction of substituted benzyl chlorides with n‐butyllithium
Authors: Sagdeev R. Z. , Molin Yu. N. , Salikhov K. M. , Leshina T. V. , Kamha M. A. , Shein S. M.
Published: May 2005

We detected and studied CIDNP effects in the reaction of substituted benzyl chlorides with n‐butyllithium in hexane (Scheme 1) in various magnetic fields (from 0·5 Oe to about 25,000 Oe). The polarisation of 19F nuclei in the reaction of p‐F‐benzyl chloride in strong fields has been observed by Rakshys.1 We succeeded, however, in finding the CIDNP effects for both 19F and 1H in all the reactions investigated. The CIDNP effects observed offer a number of remarkable features; therefore, a detailed analysis of these effects can be useful for a better understanding of the nature of CIDNP.
Conformational studies of monoterpenes. II–conformational studies of bicyclo[3.1.1]heptane derivatives by 13C NMR
Authors: Holden Collette M. , Whittaker David
Published: May 2005

The carbon‐13 spectra of seventeen bicyclo[3.1.1]‐heptane derivatives have been recorded and assigned. Study of the C‐6 and C‐7 chemical shifts permits the conformations to be assigned to the bridged chair, Y‐shaped, or bridged boat conformations. The spectrum of verbenone is anomalous and is compared to that of umbellulone recorded earlier.
Mesomere Kationen. IV—13C‐NMR‐Spektren von Uronium‐, Thiouronium‐ und Guanidiniumsalzen, sowie einigen Guanidinen
Authors: Kalinowski Hans‐Otto , Kessler Horst
Published: May 2005

Die 13C‐NMR‐chemischen Verschiebungen von Uronium‐, Thiouronium‐ und Guanidiniumsalzen werden mit den entsprechenden ungeladenen Harnstoffen, Thioharnstoffen und Guanidinen verglichen. Die chemischen Verschiebungen der aromatischen Kohlenstoffatome geben in Zusammenhang mit den entsprechenden Phenolen und Thiophenolen einen Einblick in die Ladungsverteilung in diesen Systemen.
Etude conformationnelle d'acyl‐2 et acyl‐3 furannes par RMN
Authors: Fournié‐Zaluski M. C. , Roques B. P. , Chatain‐Cathaud C.
Published: May 2005

Les déplacements chimiques des protons d'aroyl‐2 et ‐3 furannes (α‐thénoyle, α‐furoyle, benzoyle) 1 et 2 ont été interprétés en termes de conformations préférentielles et ont permis de comparer les énergies de conjugaison de ces différents groupements. Le groupe thénoyl‐2 conserve toujours une disposition OS cis alors que le groupe furoyl‐2 ne possède aucune préférence conformationnelle.
A NMR study of trimethylacetic acid self‐association
Authors: Kimtys L.
Published: May 2005

The carboxyl proton chemical shifts of neat trimethylacetic acid and its solutions in cyclohexane have been measured as a function of temperature. Formation, at the melting point, of a carboxyl group satellite line on the low field side has been found. The intensity of this satellite line rises with decreasing temperature, whereas the intensity of the main line decreases. The chemical shifts of the monomer (δm = 4·9 ± 0·6 ppm) and dimers, the equilibrium constants, enthalpy (ΔH = −(11·3 ± 0·6) kcal/mol) and entropy (ΔS = −(13·5 ± 0·7) cal/mol. degree) changes have been calculated using the concentration dependence of the chemical shifts of trimethylacetic acid in cyclohexane solutions at various temperatures. The chemical shift of the satellite line has been shown to correspond to the chemical shift of the cyclic dimers of the acid.
1H NMR spectra and ring shapes of the 4,5,8‐trimethyl and 4‐methyl derivatives of 1‐tetralone
Authors: Cook Michael J. , Hock Teh Kim
Published: May 2005

The 220 MHz spectra of the title compounds are reported and values for the internal ring dihedral angle, Ψ, formed between the C‐2C‐1 and C‐3C‐4 bonds, calculated using the R‐value method. The trimethyltetralone exists in a conformer having Ψ = 51° and the 4‐methyl group in the axial position. 4‐Methyl‐1‐tetralone exists in a conformational equilibrium where the mean value of Ψ for the conformers adopted is 56°.
Etude par RMN du Proton et du Carbone‐13 de Pyrimidines Substituées. I—Effets de Substituant dans les Dérivés Méthylés et Aminés
Authors: Riand J. , Chenon M. T. , Lumbroso‐Bader N.
Published: May 2005

Les effets de substituant des groupes méthyle et amino sur les déplacements chimiques de la pyrimidine ont été étudiés par RMN du proton et du carbone‐13 et comparés à ceux observés pour le benzène et la pyridine. Compte‐tenu des interactions mutuelles des substituants, les déplacements chimiques calculés à l'aide d'un schéma d'additivité sont en très bon accord avec les déplacements chimiques observés, sauf dans quelques cas concernant des pyrimidines encombrées. Cette étude des effets de substituant a permis l'attribution sans équivoque des spectres du carbone‐13 de pyrimidines trisubstituées.
Assignment of juvabione diastereomers by 13C nuclear magnetic resonance spectroscopy
Authors: Manville John Fieve , Bock Klaus
Published: May 2005

The determination of structures and partial assignments of stereochemistry of juvabione and some of its analogues can be made on the basis of 13C nuclear magnetic resonance studies. The complete 13C n.m.r. spectral assignments for juvabione and five analogues are reported.
J(23)cis and J(23)trans of 2‐carbonyl substituted 2,3‐dihydrobenzofurans
Authors: Croce Piero Dalla , Stradi Riccardo
Published: May 2005

The J(23)cis and J(23)trans values in several 2‐carbonyl substituted 2,3‐dihydrobenzofurans were measured. Although J(cis)>J(trans), the values found disagree with the Karplus rule.
An instrumental modification for rapid‐scan deuterium magnetic resonance spectroscopy
Authors: Bloxsidge James P.
Published: May 2005

A modification of a Bruker WH‐90 spectrometer is reported, enabling acquisition of rapid‐scan (Fourier transform correlation) deuterium magnetic resonance spectra, using the D‐lock frequency source and a computer generated field sweep. This modification is not suited to high sensitivity or high precision studies, but does avoid the considerable expense or extensive rebuilding required for a 19F lock channel and 2H pulsed Fourier channel.
Indirect 13C13C couplings in benzene and the contribution of their anisotropies to the direct couplings in the oriented molecule
Authors: Diehl P. , Bösiger H. , Jokisaari J.
Published: May 2005

The indirect ortho and para carbon‐carbon coupling constants in benzene were determined utilizing the deuterium isotope effect on the carbon chemical shifts in 1‐d1‐ and 1,3,5‐d3‐benzene. The measurements gave for J(CC, ortho) and J(CC, para) the values of 55.3 ± 0.5 Hz and 10.08 ± 0.10 Hz, respectively. The ratios of the direct dipolar CC coupling constants were calculated using the previous results of 1‐13C‐benzene in an oriented phase. These ratios differ from the theoretical ones obtained assuming the benzene ring to be hexagonal, showing significant indirect contributions in the D values.
Etude par RMN du 13C d'Hydroxy‐4 Coumarines Substituées en 3. Analyse par Corrélation des Effets de Substituants
Authors: Rabaron A. , Didry J.‐R. , Kirkiacharian B. S. , Plat M. M.
Published: May 2005

Les déplacements chimiques du 13C et les constantes de couplage 13C‐1H d'hydroxy‐4 coumarines et d'hydroxy‐4 méthoxy‐7 coumarines substituées en 3 sont déterminés. Une corrélation à 3 paramètres: ℱ et ℛ de Swain et Lupton et Q de Schaefer appliquée à ces deux séries établit les relations linéaires qui permettent de prévoir les déplacements chimiques à partir des paramètres des substituants.
C,H coupling constants of propene
Authors: Dubs R. V. , Von Philipsborn W.
Published: May 2005

The proton coupled 13C NMR spectrum of propene has been analysed at 100.6 and 25.2 MHz and a complete set of C,H coupling constants is reported. In particular, vicinal and one‐bond coupling constants are discussed with respect to substituent effects of alkyl groups. An incremental method allows us to predict 1J(CH) in more highly methyl‐substituted alkenes.
Carbon‐13 NMR of cephalosporins
Authors: Schanck A. , Coene B. , Van Meerssche M. , Dereppe J.‐M.
Published: May 2005

The 13C spectra of five cephalosporins have been recorded and interpreted.
Carbon‐13 NMR spectra of N‐methylimidazole‐substituted sterol esters
Authors: Wilk Manfred , Schmitt Karlheinz
Published: May 2005

The 13C NMR spectra of two N‐methylimidazole‐substituted sterol esters are discussed. The calculated shifts are compared to those obtained experimentally. For one of the sterol esters the experimental and calculated data show good agreement, and the substituent increments can be evaluated. This does not apply in the case of the second sterol ester, where the steric and/or electronic effects of a further substituent—a hydroperoxy group in close proximity to the N‐methylimidazole group—prohibits the additive calculation of substituent increments.
13C{1H} single frequency off‐resonance decoupling of secondary carbons
Authors: Roth Klaus , Bauer Hans
Published: May 2005

13C{1H} single frequency off‐resonance decoupled spectra of secondary carbons with two chemically non‐equivalent protons are analysed theoretically and experimentally. By a careful analysis of the frequencies of all six transitions all spectral parameters, including the geminal proton‐proton coupling constant, can be determined very accurately.
Asymmetric NMR spectra of weakly coupled nuclei: A common characteristic in the 13C NMR spectra of [U‐13C]‐labeled molecules and in natural abundance protoncoupled 13C spectra
Authors: London R. E. , Walker T. E.
Published: May 2005

Typically encountered proton‐decoupled spectra of [U‐13C]‐labeled molecules or proton‐coupled spectra of natural abundance or singly labeled molecules contain many nuclei which satisfy the weak coupling approximation. The spectra of such nuclei are frequently highly asymmetric and often appear to exhibit the skewed intensity distribution characteristic of strongly coupled spins. Analysis of typical cases indicates that such effects arise in the presence of at least one moderately strong coupling interaction in the spin system (Jδν ∼ 1/3), and the apparent intensity asymmetry reflects small differences in the spacing of unresolved components of the observed resonance. This effect is analogous to the case of ‘virtual coupling’ in which weakly coupled spins cannot be analyzed as first order spectra; however; the ABX spin system which generally serves as a model for such systems does not predict the existence of spectral asymmetry for the X resonances. Prediction of this asymmetry requires a spin system of at least four spins with at least ABMX complexity, and can be treated generally using the effective Hamiltonian approach of Poeple and Schaefer.
Assignment of stereochemistry to cyclohexenylidenecyanoacetates by 1H NMR spectroscopy
Authors: Bardakos Vassilios , Sandris Constantine
Published: May 2005

The stereochemistry of various pairs of isomeric 2‐cyclohexen‐1‐ylidenecyanoacetates was assigned using 1H NMR spectroscopy. The isomers with the γ‐methylene or the γ‐vinyl protons cis to the carbalkoxy group were found to have the signals of these protons at approximately 0.3 ppm and 1 ppm, respectively, downfield relative to their geometrical isomers or the corresponding 2‐cyclohexen‐1‐ylidenemalononitriles. The observation regarding the γ‐vinyl proton proved useful for the assignment of configuration to cyclohex‐enylidenecyanoacetates derived form cholest‐4‐en‐3‐one. The large and constant downfield shift (c. 1 ppm) of the γ‐vinyl proton when cis to the ester group results from the rigid cyclohexenylidenecyanoacetate system, in which the vinylic proton can approach more closely to the magnetically anisotropic ester carbonyl group.
15N chemical shifts and one bond 15N1H coupling constants in simple amides
Authors: Marchal J. P. , Canet D.
Published: May 2005

An indirect method is employed for determining the 15N parameters at the natural abundance level in a series of simple acyclic and cyclic amides. The one bond coupling constant, 1J(15N1H), and the 15N chemical shift are measured as a function of the carbonyl substituent group or the ring size and the nature of the solvent (CCl4 or H2O). These 15N parameters are related to the amide bond structure, the nitrogen configuration and possible intermolecular hydrogen bonding (amide‐amide or amide‐water).
Carbon‐13 nuclear magnetic resonance spectra. XVI—lanthanide induced signal shifts of diastereotopic 13C nuclei as a probe for a conformational equilibrium
Authors: Duddeck Helmut , Wiskamp Volker
Published: May 2005

The 13C NMR signals of the two methyl groups in 4‐hydroxy‐1‐isopropyl‐2‐oxaadamantane are anisochronous in the presence of Yb(fod)3. This is interpreted in terms of the different populations of three rotational conformers.
Stereochemical substructure codes for 13C spectral analysis
Authors: Gray N. A. B. , Nourse James G. , Crandell Christopher W. , Smith Dennis H. , Djerassi Carl
Published: May 2005

Computer programs for encoding canonical representations of stereochemical substructural environments are presented. Applications of these substructure codes in the study of relationships between molecular structure and chemical shifts observed in 13C NMR spectra are described, using natural products as examples. The utility of the codes for the detection of erroneous spectral assignment is illustrated.