bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen hyperfine splitting of nitroxide solutions: Differently structured and charged nitroxides as probes of environmental properties
Authors: Ottaviani M. Francesca , Martini Giacomo , Nuti Laura
Published: May 2005

The dependence of the nitrogen isotropic coupling constants, aN, on the structure and charge of the radicals, temperature and solvent polarity was analysed for solutions containing the following nitroxides: 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (Tempol); 4‐trimethylammonium‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl, iodide salt (TempTMA+); 2,2,5,5‐tetramethylpyrrolin‐1‐oxyl‐3‐carboxamide (Tempyo); and 2,2,5,5‐tetramethylpyrrolin‐1‐oxyl‐3‐carboxylate, sodium salt (Tempyca−). Polar hydrogen bond acceptor solvents and hydroxylic solvents were used. In each solvent used, Tempol and Tempyca− showed aN values which were higher, respectively, than those of TempTMA+ and Tempyo due to inductive, structural and charge effects. Such effects were analysed on the basis of the proton and 13C coupling constants. Non‐hydroxylic solvents gave temperature coefficients for aN that were almost independent of solvent polarity. Lower daN/dT values were found for charged radicals. A gradual decrease of temperature coefficients with decreasing hydrogen bond donor (HBD) properties were related to free volume changes of radical molecules. The analysis of the aN dependence on polarity parameters gave the best fitting using a simplified form of the Wertheim reaction field. Tempyca− was greatly affected by changes in polarity. A parameter to account for HBD abilities was also analysed.
Selenium‐77 NMR of coordination compounds with unsaturated selenium ligands and/or selenium (II) central ions
Authors: Dietzsch Wolfgang , Olk Ruth‐Maria , Hoyer Eberhard , Meiler Wolfgang , Robien Wolfgang
Published: May 2005

77Se NMR spectra of coordination compounds containing unsaturated dithio, thioseleno or diseleno ligands are reported. NiII, ZnII, SeII and TeII were used as central ions. The shielding of the Se donor atoms of the same ligands depends on the central ion, following the series SeII < ZnII < TeII < NiII. The greater is the concentration of selenium atoms in the coordination sphere of identical central ions, the more their signals are shifted to lower field. Comparisons are made between mixed ligand complexes and the corresponding selenium containing parent compounds.

The chemical shifts found for the selenium donor atoms in the planar NiII complex {Ni[Se2 CC(CN)2]2}2‐ and the octahedral NiIV complex {Ni[Se2CC(CN)2]3}2‐ differ by 265 ppm. The most downfield shifts of all the investigated compounds were found for donor atoms in 1,2‐diselenolene compounds.
Solvent dependence of 13C relaxation times and reorientational dynamics in tribromobenzene
Authors: Chen A. F. T. , Wang S. P. , Schwartz M.
Published: May 2005

The 13C spin–lattice relaxation times and nuclear Overhauser enhancements of protonated carbons in 1, 3, 5‐tribromobenzene were measured in a number of solvents of widely varying viscosity, Derived reorientational correlation times were found to increase approximately linearly with solution viscosity, as predicted by hydrodynamic theories of rotational diffusion.

Rotational correlation times calculated from the perrin stick model were two to three times longer than the measured τc values. Similarly, correlation times predicted by the Hu–Zwanzig slip model were too small by a factor of two. On the other hand, application of the newer Hynes–Kapral–Weinberg theory furnished reorientational correlation times that were in virtually quantitative agreement with the experimental results.
Comparison of substituent‐induced proton NMR shift in steroids and decalins
Authors: Schneider Hans‐Jörg , Jung Marion
Published: May 2005

The proton shifts of trans‐decalin and of its 9‐hydroxy derivative were determined by 2D NMR methods, supported in the latter case by lanthanide‐induced shifts. Based on these shifts and on literature data, substituent (X)‐induced chemical shifts (SCS) were obtained for the 9‐X‐trans‐decalins for X = OH, Cl, Br, I and Ch3. Comparisons with corresponding secondary cyclohexyl derivatives, derived from androstane measurements, usually showed good correlations; 38 SCS values out of 40 (for X = Hal, OH) deviate by < ±0.08 ppm and are in line with earlier linear electric field effect calculations. Only two literature values for Br and I on the antiperiplanar tertiary H‐10 exhibit unusual upfield shifts which, however, cannot be related to dihedral angle changes.
Configurational assignment of β‐phenylaspartic acids in solution by 1H and 13C nuclear magnetic resonance
Authors: Barrelle M. , Gey C. , Béguin C. G.
Published: May 2005

Vicinal 3J(HH) and 3J(13CH) coupling constants are reported for the two diastereoisomers of β‐phenylaspartic acid at various pH values. A comparison between these coupling constants and those expected from the possible conformations of these molecules allows configurational assignments to be made. In strong acidic medium we observed intermediate values for 3J(HH) for both isomers, for one isomer two intermediate values for 3J(Co‐α, H‐β) and 3J(Co‐β, H‐α), and for the other isomer a very small value for 3J(CO‐α, H‐β) and an intermediate value for 3J(Co‐β, H‐α). The discussion shows that the former has the RR/SS configuration and the latter the RS/SR configuration.
Configurational assignment of 2‐alkylsulphinyl‐1‐arylethanol diastereomers by 13C NMR
Authors: Alcudia F. , Fernández I. , Llera J. M. , Trujillo M. , Zorrilla F.
Published: May 2005

The relative configurations of erythro‐ and threo‐2‐alkylsulphinyl‐1‐phenyl(or 2‐thiophen or 2‐furyl)ethanol have been correlated with 13C NMR data. A general rule for determining the configuration of this type of compound is presented.
EPR and ENDOR investigation of daunomycin and adriamycin semiquinones
Authors: Jülich Thomas , Scheffler Klaus , Schuler Paul , Stegmann Hartmut B.
Published: May 2005

Electron spin resonance and ENDOR spectra of semiquinones from daunomycin, adriamycin, their derviatives and model compounds are reported. Hyperfine coupling constants were assigned with the help of TRIPLE resonance and partial deuteration. In contrast to published results, the data obtained were interpreted on the basis of a rapid conformational interconversion of ring A with participation of half chair and boat conformers.
13C NMR chemical shift assignments for some 1‐aminopyrrole derivatives
Authors: Attanasi Orazio A. , Grossi Mario , Perrulli Francesca R. , Santeusanio Stefania , Serra‐Zanetti Franco , Bongini Alessandro , Tugnoli Vitaliano
Published: May 2005

The 13C NMR spectra of various 1‐aminopyrrole derivatives are reported and the chemical shift assignments are discussed. The NMR assignments were confirmed by MNDO calculations.

13C NMR chemical shifts 1‐Aminopyrrole derivatives.
Structure of two stereoisomers of Pt(trans‐MeO2CCHCHCO2Me)2[P(cyclohexyl)3]: Complete assignment of the 11 non‐equivalent tricyclohexylphosphine protons using DQF‐COSY and 13C, 1H two‐dimensional methods
Authors: Rüegger Heinz
Published: May 2005

The 1H NMR spectrum of the Pt(0) complex Pt(trans‐MeO2CCHCHCO2Me)2[P(cyclohexyl)3] was measured and the structures of the two isomeric forms, which differ with respect to olefin coordination, were assigned. The structural study made use of a complete analysis of the 11 non‐equivalent protons of the P(cyclohexyl)3 in one isomer, and this was accomplished via DQF‐COSY and 13C,1H inverse heteronuclear correlation methods.
17O NMR spectroscopic study of substituted 9‐fluorenones
Authors: Boykin D. W. , Nowak‐Wydra Barbara
Published: May 2005

The 17O NMR chemical shift data for 23 9‐fluorenones in acetonitrile at 75°C are reported. 17O NMR data for the 3‐substituted 9‐fluorenones are correlated with 17O NMR data for 4‐substituted acetophenones. Chemical shift data for 1‐halogeno‐9‐fluorenones are deshielded relative to the 3‐isomers, suggesting important repulsive van der Waals interactions. The keto carbonyl signal for 9‐fluorenone‐1‐carboxylic acid is substantially shielded, as expected, from intramolecular hydrogen bonding. The data for several multi‐substituted 9‐fluorenones demonstrate that substituent effects are additive for the 9‐fluorenones.
Determination of dynamic parameters in amino acids from 17O NMR line width measurements
Authors: Tritt‐Goc J. , Fiat D.
Published: May 2005

The viscosity and temperature dependence of the 17O NMR line width of glycine, alanine, proline, leucine, histidine and phenylalanine were investigated at pH 2, 7 and 12.5. The observed viscosity/temperature (η/T) dependence of the reorientation correlation time, τc, is compared with that given by hydrodynamic models. It was found that for amino acids the Gierer–Wirtz model is superior to the Stokes–Einstein–Debye and Hu–Zwanzig models. The 17O quadrupole coupling constant for glycine, alanine and histidine was determined in water solution; the activation energies for molecular tumbling were evaluated, and the hydration of the amino acids in their cationic zwitterionic and anionic ionization states is discussed.
Analysis of low‐resolution, low‐field NMR relaxation data with the Padé‐Laplace method
Authors: Tellier Charles , Guillou‐Charpin Marion , Le Botlan Denis , Pelissolo François
Published: May 2005

An integral transform technique, the Padé‐Laplace method, was adopted to calculate the number of discrete exponential components and the corresponding parameters from NMR spin relaxation decay curves. The results thus obtained can be improved by injection into an iterative program. This ‘Padé‐Laplace plus iterative’ method was tested on simulated data of up to five relaxation times and then on experimental data obtained with a tube containing four manganese chloride‐doped water samples. The results extracted from the low‐resolution, low‐field NMR signals of complex chemical and biological products are discussed.
EPR and ENDOR investigations of chrysazin and aclacinomycin A semiquinones
Authors: Jülich Thomas , Stegmann Hartmut B. , Krohn Karsten , Eickhoff Astrid
Published: May 2005

Different assignments of the coupling constants to distinct positions of chrysazin are given in the literature. Several methyl derivatives, particularly the hitherto unknown 1,8‐dihydroxy‐2,3‐dimethyl‐9,10‐anthraquinone, were prepared, and their radical anions were investigated by EPR and ENDOR spectroscopy to achieve a reliable attribution of these values. The data obtained show a remarkable solvent dependence of the spin density distribution. Thus, the discrepancy mentioned above can be explained in terms of intermolecular hydrogen bond formation. Therefore, the requirements for an investigation of the semiquinones of the antitumour drug aclacinomycin A and 7‐deoxyaklavinone are fulfilled. The splitting constants of the radical anions are assigned using model compounds, TRIPLE experiments and the solvent dependence. In contrast to the results obtained for daunomycin radicals, the data can be interpreted in terms of an almost rigid half‐chair conformation of the A ring.
Studies of the π‐electron distribution in push–pull alkenes by 1H and 13C NMR spectroscopy—II
Authors: Kleinpeter E. , Thomas St. , Uhlig G. , Rudorf W.‐D.
Published: May 2005

A wide variety of push–pull alkenes were studied by means of variable‐temperature 1H and 13C NMR spectroscopy with respect to the configuration/conformation and the barriers to rotation about partial CC and CN double bonds. For the assignment of the 13C NMR spectra especially the semi‐selective INEPT pulse sequence and an incremental system for estimating the 13C chemical shift values of aromatic carbon atoms proved useful. The influence of thioether, sulphone and sulphoxide moieties in the acceptor part of the push–pull system on the π‐electron distribution is critically considered.
Reinvestigation of 1H and 13C NMR spectra of 1,8‐bis(dimethylamino)naphthalene complexes with mineral acids
Authors: Dega‐Szafran Zofia , Nowak‐Wydra Barbara , Szafran Miroslaw
Published: May 2005

Hydrogen and carbon‐13 NMR chemical shifts of five complexes of 1,8‐bis(dimethylamino)naphthalene with strong acids were measured in acetonitrile‐d3 and nitromethane‐d3 and identified by 2D, NOE difference and long‐range enhanced COSY spectra. The assignments of the resonances corresponding to H‐2,7, H‐4,5, C‐3,6 and C‐4,5 obtained in this study differ from those reported previously.
Quantitative silicon‐29 NMR investigations of highly concentrated high‐ratio sodium silicate solutions
Authors: Harris Robin K. , Bahlmann Elke K. F. , Metcalfe Kenneth , Smith Edward G.
Published: May 2005

In concentrated alkaline sodium silicate solutions a consistent decrease in the amount of silicate monomer Q0, end‐groups Q1, cyclic trimer Q groups and middle groups Q2, and also branching groups in ring formations Q, is observed with increasing molar ratio of SiO2 to Na2O (RM), whereas for branching groups Q3 and cross‐linking groups Q4 a consistent increase is found. The interest of this work is particularly focused on the Q4 region, which may indicate the formation of colloidal silicate particles. For this region the 29Si background signal from the NMR probe and the glass tube can cause problems, so the subtraction technique was used. Spin‐lattice relaxation times, not previously reported for silicate solutions of concentrations and molar ratios as high as those studied here, are given for all structural units, including Q4. It was found that sodium silicate solutions of RM = 2.0 do contain a Q4 region when they are extremely highly concentrated in SiO2 (38 wt% SiO2) or aged.
Structural reinvestigation of two diastereoisomeric aspidosperma–eburnea type bis‐indoles by NMR methods. Detection of a ‘hidden’ exchange partner and implications in noe analysis
Authors: Szántay Csaba , Demeter Ádám , Honty Katalin , Kolonits Pál , Szántay Csaba
Published: May 2005

Full 1H and 13C assignments are reported for two aspidosperma—eburnea type diastereoisomers. Homonuclear NOE difference measurements revealed that the previously reported configurational assignment of these compounds is in error. More interestingly, rotation about the bond connecting the two indole units is hindered in both molecules and gives a strongly biased two‐site chemical exchange system. At room temperature the exchange rates are slow on the chemical shift time‐scale with regard to certain 1H signals. In addition, the exchange rates are such that the signals due to the minor component are broadened to the extent that they escape detection in a conventional 1H spectrum, whereas only a very small amount of broadening is observed on the main signals. The presence of this ‘hidden’ exchange partner can give rise to peculiar effects in the NOE difference spectra. Such spurious effects can be the source of misinterpretation if the existence of the ‘silent partner’ goes unnoticed. Thermodynamic parameters are evaluated based on earlier work addressing the problem of the ‘hidden’ exchange partner.
NMR data for sulphur and selenium analogues of furocoumarin (psoralen)
Authors: Jakobs Andreas , Llabres Gabriel , Baiwir Marcel
Published: May 2005

1H, 13C and 77Se chemical shifts of sulphur and selenium analogues of furocoumarin are given. These data are very similar to the values obtained from benzofuran, coumarin and their sulphur and selenium analogues.
Multiple magnetic resonance studies of some para‐substituted derivatives of triphenyl phosphine
Authors: McFarlane W.
Published: May 2005

19F and 31P decoupling experiments are used to simplify the proton spectra of para‐substituted derivatives of triphenyl phosphine, prior to 1H‐{1H} tickling experiments. 3J(31P…︁H) and 4J(31P…︁H) are positive, and 5J(31P…︁19F) is negative in the trivalent phosphorus derivatives, and all become more positive as the valency of the phosphorus atom is increased. A triple resonance experiment is used to show that 7J(31P…︁H) in [p‐CH3C6H4CH2P⊕(C6H5)3] is negative. The double resonance technique is used to relate the 31P chemical shifts to the tetramethylsilane resonant frequency.
NMR‐Untersuchungen an Dialkylsubstituierten Piperidinen–I. Konfigurationsbestimmung der 2,3‐, 2,4‐ und 3,4‐Dimethylpiperidine und die Analyse Ihrer NMR‐Spektren
Authors: Feltkamp Herbert , Naegele Walter , Wendisch Detlef
Published: May 2005

Die Gemische der stereoisomeren 2,3‐, 2,4‐ und 3, 4‐Dimethylpiperidine warden durch katalytische Hydrierung der entsprechenden Lutidine dargestellt. Die einzelnen Isomeren warden durch fraktionierte Destillation getrennt. Die Konfigurationsaufklärung erfolgt kernresonanzspektroskopisch durch Analyse der 100 und 220 MHz NMR Spektren. Es gelingt eine weitgehende Zuordnung aller Protonen des Piperidinringes.
Konformative Beweglichkeit Flexibler Ringsysteme—X. Untersuchungen mit Hilfe der Protonenresonanz‐Spektroskopie. Substituentenabhängigkeit der Ringinversion bei 1.3‐Dioxanen, 1.3‐Dithianen und 1.3‐Oxathianen
Authors: Friebolin Horst , Schmid Helmut G. , Kabuß Siegfried , Faißt Wilhelm
Published: May 2005

Mittels der Temperaturabhängigkeit der Protonenresonanzsignale wurden für 1.3‐Dioxane, 1.3‐Oxathiane und 1.3‐Dithiane mit ein und zwei Paaren geminaler Methylsubstituenten Geschwindigkeitskonstante k, freie Aktivierungsenthalpie ΔG‡ und Aktivierungsenergie Eα der Sesselinversion bestimmt. Die Geschwindigkeit der Sesselinversion hängt bei den drei genannten Ringsystemen in unterschiedlicher Weise von der Zahl und der Stellung der Substituentenpaare ab:

Beim Dioxanring wird k nur dann erniedrigt, wenn ein Paar Methylgruppen in 5‐Stellung eingeführt wird; k wird jedoch erhöht, wenn die Substituenten in 2‐ oder 4‐Stellung angegliedert werden. Dieser letztere Effekt ist bei Einführung von zwei Paar Methylgruppen in 4‐ und 6‐Stellung besonders stark.

Eine ähnliche Substituentenabhängigkeit von k wird auch bei den Oxathianen beobachtet, während die Inversionsgeschwindigkeit des 1.3‐Dithianringes von Substituenten nur wenig beeinflußt wird.

Die durch 2‐ und 4‐ständige Methylgruppen verursachte Erleichterung der Sesselinversion des 1.3‐Dioxanringes kann auf die Deformation (Abflachung) des Sessels zurückgeführt werden, die bei 1.3‐Abstoßung der synaxialen Liganden auftreten muß. Ein solcher Effekt ist beim 1.3‐Dithianring infolge der langen CS‐Abstände nicht möglich. Beim Oxathiansystem ist eine eindeutige Erklärung der beobachteten Substituenteneffekte durch die Unsymmetrie des Ringsystems erschwert.
Konformative Beweglichkeit Flexibler Ringsysteme–XI Untersuchungen mit Hilfe der Protonenresonanzspektroskopie Ringinversion bei Methyl‐ und Alkoxylcyclohexanen
Authors: Friebolin H. , Schmid H. G. , Kabuß S. , Faißt W.
Published: May 2005

Mittels der Temperaturabhängigkeit der Protonenresonanzsignale wurde die sesselinversion von Cyclohexanderivaten mit ein, zwei und drei Paaren geminaler Methyl‐ und Alkoxylgruppen untersucht.

Die Geschwindigkeit der Sesselinversion hängt von der Zahl und der relativen Stellung der Ligandenpaare sowie von der Größe der Liganden ab.

Ein Paar geminaler Liganden verändert die Inversionsgeschwindigkeit nur unwesentlich.

Zwei Liganden‐Paare erschweren die Inversion, wenn sie in 1‐ und 4‐Position zueinander stehen, erleichtern sie jedoch, wenn die in 1‐ und 3‐Position zueinander angeordnet sind. Beide Effekte sind bei Methoxylgruppen kleiner als bei Methylgruppen.

Drei Liganden‐Paare erhöhen die Umklapphäufigkeit besonders stark, wenn sie in 1‐, 3‐ und 5‐ Position zueinander stehen, vermindern sie hingegen, wenn sie in 1‐, 2‐ und 4‐Position angeordnet sind.

Der Effekt 1,3‐ständiger Substituenten wird auf Erhöhung des Energieinhaltes des Grundzustandes der Molekeln, der Effekt 1,4‐ständiger Substituenten auf Erhöhung des Energieinhaltes des Übergangszustandes der Sesselinversion zuriückgeführt.
Konformative Beweglichkeit Flexibler Ringsysteme–XII Modellrechnungen zur Ringinversion bei Methylsubstituierten Cyclohexanen
Authors: Schmid H. G. , Jaeschke A. , Friebolin H. , Kabuß S. , Mecke R.
Published: May 2005

Zur Interpretation der experimentell bestimmten Werte der Aktivierungsenergie bzw. der freien Aktivierungsenthalpie der Ringinversion wurden für Cyclohexan, 1,1‐Dimethyl‐, 1,1,3,3‐ und 1,1,4,4‐Tetramethyl‐ sowie 1,1,3,5,5‐Hexamethylcyclohexan Modellberechnungen des ‘relativen’ Energieinhalts von Grund‐, Zwischen‐ und Übergangskonformationen durchgeführt. Dazu wurde das Hendrickson'sche Rechenmodell so erweitert, daß mit molekülinternen Variablen (Bindungsabständen, Valenz‐ und Torsionswinkeln) die Topographie und der ‘relative Energieinhalt’ jeder beliebigen unsymmetrischen Konformation berechnet warden können.

Zur optimalen Anpassung der berechneten Daten an die experimentellen Ergebnisse wurden insgesamt 17 verschiedene Kombinationen von Potentialfunktionen für Deformation von Valenzund Torsionswinkeln und HH‐Wechselwirkung verwendet.

Bei Anwendung des erweiteren Rechenverfahrens auf die Cyclohexanmolekel ergab sich, daß die halbsesselähnliche Konformation nicht, wie bisher angenommen, einzige Übergangskonformation der Sesselinversion ist, vielmehr gibt es außerdem unendlich viele unsymmetrische Übergangskon‐formationen gleichen Energieinhalts. Die Rechnungen ergaben für die Methylcyclohexane, daß bei Molekülen mit synaxialer Anordnung von Methylgruppen der relative Energieinhalt des Sessels zwar stark angehoben ist, der Sessel ist jedoch in allen Fällen selbst bei den Molekeln des 1,1,3,3,5,5‐Hexamethylcyclohexans die stabilste Konformation. Die günstigsten Twistkonformationen sind um 2,6 bis 6,5 kcal/mol energiereicher. Bei der Berechnung der Aktivierungsenergie wurde gefunden, daß bei synaxialer Stellung von mindestens zwei Methylgruppen der relative Energieinhalt der Übergangskonformation weniger stark angehoben ist als derjenige der Sesselform, wodurch die Aktivierungsenergie im Vergleich zum Cyclohexan erniedrigt wird; bei 1,4‐Stellung der Substituenten wird dagegen der relative Energieinhalt der Übergangskonformation stärker angehoben als der des Grundzustandes, die Aktivierungsenergie wird erhöht.
Determination des taux de deuteriation de molecules organiques par resonance magnetique nucleaire
Authors: Martin Gérard J. , Quemeneur Marie‐Thérèse , Martin Maryvonne L.
Published: May 2005

Les précisions de différentes méthodes de détermination du taux de deutériation de molécules organiques par RMN sont évaluées. On compare successivement les méthodes de changement de tube‐échantillon et les méthodes utilisant un étalon interne. Ces méthodes sont ensuite appliquées au dosage du deutérium dans plusieurs molécules et les résultats sont comparés à des mesures de spectrographie de masse.
Substituent effect in aromatic proton NMR spectra—IV Proton NMR spectra of monosubstituted (poly) methylbenzenes
Authors: Nomura Yujiro , Takeuchi Yoshito
Published: May 2005

Proton NMR spectra of 1‐substituted 2,4‐dimethylbenzenes (2), 1‐substituted 2,6‐dimethylbenzenes (3) and 1‐substituted 2,4,6‐trimethylbenzenes (4) were determined and the SCS values compared with those of monosubstituted benzenes (1). SCS of 1 are assumed to be primarily due to the effects of π‐electron charge density, substituent electric field and substituent diamagnetic anisotropy, and the van der Waals interaction: thus

When, however, the substituent is sterically hindered, then:

where cπ∼V may be constants predictable from the theories associated with each component. By estimating SCSπ∼V or cπ∼V, a quantitative separation of SCS into their components was attempted. It is shown, however, that the data available, as well as the nature of this approach, cannot necessarily be sufficient for this purpose.

Various effects which might also contribute to the proton NMR chemical shifts of sterically hindered molecules are also discussed.
The NMR spectrum of pentafluorothiophenol
Authors: Lustig E. , Hansen E. A. , Ragelis E. P.
Published: May 2005

High‐precision line measurements and tickling were shown to yield information, often not accessible, on the assignment and signs of spin coupling constants. For pentafluorothiophenol‐d, this information was obtained for the three meta‐JFF's. Relative to C6F5SH, the 19F resonances in C6F5SD experienced an upfield ‘isotope’ shift.
NMR studies of complex formation between N‐methyl morpholine and sulphur dioxide
Authors: Harris R. K. , Spragg R. A.
Published: May 2005

Proton magnetic resonance spectra of methylene dichloride solutions containing N‐methyl morpholine and sulphur dioxide have been studied as a function of temperature. Complex formation reduces the rate of interchange of magnetic sites via inversion at nitrogen but increases the rate of ring inversion. The conformational preference of the complex is discussed. It is suggested that interaction with SO2 may be a useful general method of studying nitrogen inversion.
Application des relation de Mislow et Raban a la determination de configuration (mesothreo) par resonance magnetique nucleaire
Authors: Le Goaller Raymond , Pierre Jean‐Louis , Arnaud Paul
Published: May 2005

La configuration meso ou thréo de molécules diastéréoisomères est déterminée à partir des spectres RMN respectifs xde chaque isomère. Les relations de symétrie (Raban et Mislow), qui existent entre protons ou groupes de ces molécules sont différentes par chaque diastéréoisomère d'un couple donné et ces différences se traduisent dans les déplacements chimiques et constantes de couplage mis en jeu. Des attributions de configuration sont ainsi rendues possibles.
Multipolar complexes–II The self association of ‐NO2 ‐CN and ‐COCN polar groups
Authors: Uschold R. E. , Taft R. W.
Published: May 2005

Fluorine nuclear magnetic resonance (F‐NMR) has been used to determine dissociation constants for multipolar complexes formed by several p‐substituted fluorobenzenes in CCl4 and cyclohexane at 25°. Data in CCl4 were also obtained at −20°. The results are interpreted in simplified terms as dipole‐dipole interactions which lead to a complex of net zero dipole moment. Although the dissociation constants are not of high accuracy, the values obtained do indicate that both polarity and steric effects are important in the presumed multipolar complexes.
NMR spectrum of phenylacetylene oriented in the nematic phase
Authors: Diehl P. , Khetrapal C. L.
Published: May 2005

The NMR spectrum of phenylacetylene has been studied in the nematic phase of a mixture of 50% 4‐methoxy benzylidene 4‐amino‐α‐methyl cinnamic acid‐n‐propyl ester and 50% anisole‐p‐azophenyl‐n‐capronate at 30°C. Ratios of interproton distances have been derived.
NMR spectra of some alkyl(oxinato)tin(IV) complexes
Authors: Kawasaki Yoshikane
Published: May 2005

Proton magnetic resonance spectra of a series of alkyl(oxinato)tin(IV) complexes, alkyl(oxinato)thallium(III), dimethylbis(oxinato)lead(IV), 8‐methoxyquinoline, 2‐methyl‐8‐hydroxyquinoline and 8‐hydroxyquinoline were studied. The indirect spin‐spin coupling constants J23, J34 and J24 of the oxinato ligand in the alkyl(oxinato)tin(IV) complexes and of 8‐methoxyquinoline were found to be 4.4 ± 0.2, 8.3 ± 0.2 and 1.7 ± 0.2 Hz, respectively. When the interaction between tin and nitrogen in the oxinato ligand is not strong as in trialkyl(oxinato)tin(IV), the resonance of the 2‐proton of the ligand shifts to high magnetic field relative to that of 8‐methoxyquinoline, but in the case of the strong interaction, as in dimethyl(oxinato)halogenotin(IV), the resonance is shifted to low magnetic field. The 4‐proton signals, however, shift monotonously to low magnetic field with increasing interaction. The behaviour of the 2‐proton signals was explained by a paramagnetic anisotropic effect of a nitrogen lone pair of the oxinato ligand and an intramolecular electric field effect and that of the 4‐proton by the latter effect. By comparing the change of the δ‐values of the 2‐, 3‐ and 4‐protons of the alkyl(oxinato)tin(IV) complexes and those of 8‐hydroxyquinoline by altering the solvents, from methylene chloride to benzene, it was found that the electron density around the 2‐carbon is reduced in the complexes compared with that of 8‐hydroxyquinoline.
The NMR spectra and conformations of cyclic compounds—IV: The conformation of 3,4‐cyclopropyl‐proline
Authors: Abraham R. J. , Gatti G.
Published: May 2005

The 1H magnetic resonance spectrum of the title compound has been completely analysed, using 60, 100 and 220 MHz spectrometers. The values of the chemical shifts and coupling constants obtained confirm the proposed structure and also provide information on the conformation. The molecule is slightly boat‐shaped.
Etude de la Protonation du Groupe Amide par Resonance Magnetique Nucleaire. Comportement des Anilides Substitues en Milieu Acide Concentre
Authors: de Lockerente Serge Rysman , Nagy Otto B. , Bruylants Albert
Published: May 2005

En étudiant par RMN cinq anilides de formule générale magnified image en milieu acide, les auteurs ont mis en évidence la protonation de l'atome d'azote de l'ion amidonium formé.
Semidiones—X. Radical anions derived from 1,1,2,2‐bis(1,3‐diketo‐2,2‐bindanylidene)ethane and 1,1,4,4‐bis(1,3‐diketo‐2,2‐bindanylidene)butene‐2
Authors: Neugebauer Franz. A. , Russell Glen A.
Published: May 2005

The 1,1,2,2‐bis(1,3‐diketo‐2,2‐bindanylidene)ethane radical anion (13) and 1,1,4,4‐bis (1,3‐diketo‐2,2‐binanylidene)butene‐2 radical anion (14)

We employ herein nomenclature wherein the term ‘radical anion’ means the gain of one electron of the named substrate.

representing 1,6‐ and 1,8‐conjugated semidiones have been prepared by reduction. Electron spin resonance hyperfine splitting constants have been assigned on the basis of Hückel and McLachlan calculations.
PMR studies of N‐substituted‐2,5‐dimethyl‐4‐piperidones
Authors: Hassan M. M. A. , Casy A. F.
Published: May 2005

PMR characteristics of some isomeric 1‐substituted‐2,5‐dimethyl‐4‐piperidones are reported and major isomers shown to have a trans 2,5‐dimethyl configuration. Differences between benzylic methylene signals of isomeric 1‐benzyl analogs provide evidence of the preferred conformation of the cis derivative. Evidence of the D/H exchange of α‐protons in 1,2,5‐trimethyl‐4‐piperidone base and of addition of D2O to the carbonyl group of the corresponding hydrochloride and methiodide salts is also demonstrated. The effect of a 2‐methyl substituent upon the chemical shifts of N‐methyl groups in some piperidine methiodides is discussed.
FF coupling constants in dichlorotetrafluorocyclopropanes
Authors: Cavalli Luciano
Published: May 2005

The 19F NMR spectra of the cis‐ (1) and the trans‐isomer (2) of the 1,2‐dichlorotetrafluorocyclopropane and that of the 1,1‐dichlorotetrafluorocyclopropane (3) have been investigated at different temperatures and in several solvents. magnified image From chemical shift calculations the two geminal fluorines in the cis‐isomer (1) could be assigned and on this basis the two vicinal coupling constants of 1, Jtrans (ca. 140°) and Jcis (ca. 0°), were unequivocally distinguished. By frequency sweep double resonance Jtrans has been shown to be of opposite sign to Jgem, whereas for Jcis the situation has been found to be reversed. Therefore Jtrans is presumably negative and Jcis positive. Only the N(Jcis + Jtrans) value could be extracted from the vicinal coupling constant in the fragment CFClCFCl could be evaluated. It has been noted that Jcis is more sensitive to changes in temperature than is Jtrans. The variations of Jcis and Jtrans induced by solvents are, on the contrary, small and irregular and no correlation with the dielectric constant of the medium has been noted. The different temperature dependence of Jcis and Jtrans can be useful for assigning the vicinal FF coupling constants in cyclopropane derivatives and also for defining their signs. This method was applied to the coupling constants extracted from the 13C satellite spectrum of isomer 3. The coupling constants results were compared with some literature data already known, and some rationalisation and correlations from the trends was attempted.
A new method for structure determination of trifluoroacetyl steroids by 19F‐NMR
Authors: Voelter Wolfgang , Breitmaier Eberhard , Jung Günther , Bayer Ernst
Published: May 2005

A useful method for the assignment of hydroxyl groups in steroids is described in which hydroxy‐steroids are reacted with trifluoroacetic anhydride. The δ‐values of the CF3 signals from the resulting trifluoroacetates characterize the positions of the trifluoroacetylated hydroxyl groups.
Protonenresonanz‐Untersuchungen an N,N‐Dialkylaminoboranen. Substituentenabhängigkeit der Rotationsbarriere um die NB‐Bindung 1,2
Authors: Imbery D. , Jaeschke A. , Friebolin H.
Published: May 2005

An einer Anzahl von N,N‐Dialkylaminoboranen wurde die Substituentenabhängigkeit der Rotationsbarriere um die NB‐Bindung mit Protonenresonanzen studiert. Dabei konnte (1) eine deutliche Abhängigkeit der Barriere von der Größe der Substituenten festgestellt werden, die auf eine ‘sterische Behinderung der Mesomerie’ zurückgeführt wird, und (2) eine z.T. außerordentlich große Erleichterung der Rotation, wenn Alkylgruppen am Bor durch ein Chlor bzw. eine zweite Aminogruppe substituiert werden. Die Erniedrigung der Rotationsbarriere um ca. 10 kcal/Mol in Bis‐aminoverbindungen verglichen mit den entsprechenden Monoaminoverbindungen wird durch eine Verminderung des Doppelbindungsgrades jeder NB‐Bindung infolge Beteiligung zweier N‐Atome an der Mesomerie des Grundzustandes erklärt. Dieser Effekt ist bei der Aminogruppe weit größer als bei einem Chloratom.
The solvent effect on polar compounds containing acidic hydrogens
Authors: NG Soon
Published: May 2005

The effect of aromatic and non‐aromatic solvents on the proton chemical shifts of 23 polar compounds has been determined. The protons which are activated by electron‐withdrawing groups show large highfield shifts in benzene (relative to the isotropic solvents). Based on evidence provided by infrared data, the highfield shifts of the acidic protons in benzene solution are interpreted in terms of a model involving CHπ hydrogen bonding. This model successfully interprets the data reported previously for steroidal ketones. The same model can be extended to benzene solutions of other polar compounds containing strongly electron‐deficient sites to which alkyl groups are attached. It is observed that the use of CCl4 as a reference solvent in studies of benzene induced shifts may have greater significance, since these two solvents have similar dielectric constants.
Concentration dependent chemical shifts in the NMR spectrum of 3,5‐dimethyl‐5‐nitro‐tetrahydro‐1,3‐oxazine
Authors: Crabb T. A. , Judd S. I.
Published: May 2005

The marked concentration dependence of the chemical shifts of the C2, C4 and C6 protons in 3,5‐dimethyl‐5‐nitro‐tetrahydro‐1,3‐oxazine is described.
Molecular structure of pyrimidine by NMR in the nematic phase
Authors: Khetrapal C. L. , Patankar A. V. , Diehl P.
Published: May 2005

The NMR spectrum of pyrimidine has been studied in the nematic phase of 4‐methoxy benzylidene‐4‐amino‐α‐methyl cinnamic acid‐n‐propyl ester at room temperature. The ratios of all the interproton distances are determined and found to differ significantly from those obtained from microwave data. The molecule, like other aromatics, is shown to orient preferentially with its plane in the direction of the magnetic field.
Recherches par resonance magnetique nucleaire sur les rotations empechees—IV: Determination des parametres d'activation associes a l'interconversion des isomeres de rotation autour de la liaison CC dans la serie des composes carbonyles vinyliques β‐amines
Authors: Filleux‐Blanchard Marie‐Louise , Durand Henri , Martin Gérard Jean
Published: May 2005

L'effet de la nature du substituant R sur l'équilibre conformationnel s‐cis‐s‐trans est examiné dans la série (CH3)2NCHCHCOR. L'utilisation d'un programme de calcul des courbes théoriques de l'échange permet la détermination des paramètres d'activation ΔH* et ΔS*.
NMR‐untersuchungen an dialkylsubstituierten piperidinen—II: 2.5‐, 2.6‐ und 3.5‐ dimethylpiperidine
Authors: Wendisch Detlef , Naegele Walter , Feltkamp Herbert
Published: May 2005

Die Gemische der stereoisomeren 2.5‐ und 2.6‐ Dimethylpiperidine wurden durch katalytische Hydrierung der entsprechenden Lutidine hergestellt und die einzelnen Isomeren durch fraktionierte Destillation getrennt; die beiden isomeren 3.5‐Dimethylpiperidine wurden nach einem speziellen Verfahren hergestellt. Die Konfigurationszuordnung erfolgt durch Analyse der 220 MHz (in einem Fall 100 MHz) Spektren. Alle Protonen des Piperidinringes können weitgehend zugeordnet werden. Ausserdem wird über die 13C‐Spektren der beiden isomeren 3.5‐Dimethylpiperidine berichtet. Die Protonenspektren aller 12 möglichen Dimethylpiperidine werden eingehend, speziell im Hinblick auf die abschirmende Wirkung der Methylgruppen auf benachbarte Ringprotonen, diskutiert.
Natural abundance 13C NMR studies of perezone and derivatives
Authors: Joseph‐Nathan P. , González Ma. P. , Johnson LeRoy F. , Shoolery James N.
Published: May 2005

Assignment of all 13C chemical shifts of perezone (1) and some derivatives was possible using time averaged 25·15 MHz spectra with the aid of proton noise modulated and CW decoupling. Rapid interconversion of tautomeric forms of 2,5‐dihydroxy‐1,4‐benzoquinones is deduced from the 13C spectra.
NMR studies of fluorocarbon diphosphines and oxy‐ and thio‐bisphosphines
Authors: Kang Dae‐Ki , Servis Kenneth L. , Burg Anton B.
Published: May 2005

Both the diphosphine CH3CF3PPCH3CF3 and the thio‐bisphosphine CH3CF3PSPCH3CF3 show 19F and 31P NMR spectra indicative of diastereomeric mixtures of d,l and meso isomers. The temperature‐dependent reversible interconversions of the isomers have been attributed to the inversion at the phosphorus atom. The equilibrium constants for the isomerization reactions have been measured at various temperatures. The fluorine NMR spectra of the meso and d,l isomers of CD3CF3PSPCD3CF3 have been analyzed as M3XX′M3′ spin systems. Good agreement is found between the observed and calculated spectra. The five‐bond fluorine‐fluorine coupling constant of the low‐field isomer is larger than that of the high‐field isomer. The 19F NMR spectra of (CF3)2PP(CF3)2, (CF3)2POP(CF3)2, (CF3)2PSP(CF3)2, CH3CF3PPCH3CF3 and CH3CF3PSPCH3CF3 have been examined over a wide range of temperatures in an attempt to correlate the data to the geometries of these compounds.
Charge density and NMR parameters. Aliphatic derivatives
Authors: Lazzeretti P. , Taddei F.
Published: May 2005

The charge distribution in several substituted aliphatic derivatives was determined by a parametric MOLCAO method. The charges were successfully employed to interpret NMR parameters, namely proton and carbon chemical shift and vicinal proton‐proton coupling constants in ethyl derivatives and carbon‐proton coupling constants.

The linear correlations found between NMR parameters and charge densities are restricted to substituents of the same row of the periodic system. The decay along the aliphatic chain of the perturbation induced by substituents on proton chemical shift is also reproduced by charge distribution. Some results also seem to indicate that the substituents affect the hybridization of the attached carbon atom.
Studies of the substituent effect in aromatic systems by 35 Cl‐NQR. Chloroacetanilides ClxC6H5−x NHCOCH3−y Cly
Authors: Pies W. , Rager H. , Weiss Alarich
Published: May 2005

The 35Cl‐NQR spectra of 45 chlorosubsitituted acetanilides, ClxC6H5−xNHCOCH3−yCly, were investigated and the temperature dependence of some spectra, especially of monochloroacetic acid derivatives, was measured. A preliminary assignment of the NQR frequencies is given. A correlation between NQR frequencies and substituent parameters permits the study of the substituent effect of the acetamido group, NHCOCH3−yCly. The chloro‐substitution in the side chain of the acetanilides seems to have no noticeable influence on the 35Cl‐NQR frequencies of the chlorine atoms at the benzene ring. The NQR frequencies of the chlorine atoms in the chloroacetamido group are, on the other hand, insensitive to substitutions at the benzene nucleus. The possibility of steric influences on the NQR spectrum of ortho‐chloro‐substituted acetanilides is discussed. The investigation further confirms that a crystal field effect of about ±500 kHz must be considered in the interpretation of NQR spectra of chlorobenzene derivatives.
Barrières de Rotation Autour des Liaisons CN dans la Série des Urées. Influence du Remplacement de CO par CS
Authors: Filleux‐Blanchard M. L. , Durand A.
Published: May 2005

Une barrière de rotation de faible valeur autour de la liaison NCO est mise en évidence dans les urées de formule CH3NHCONHR (R  H, CH3). Les thiourées correspondantes sont examinées afin d'étendre l'étude comparative des systèmes carbonyle‐thiocarbonyle. Les paramètres RMN et les grandeurs thermodynamiques liées au processus d'isomérisation sont discutés.
Long‐range proton‐proton interactions through epoxides
Authors: Joseph‐Nathan P. , Díaz E.
Published: May 2005

Double and triple nuclear magnetic resonance experiments performed at 100 MHz demonstrate the existence of long range 1H—1H couplings through epoxides. In a series of epoxycontaining sesquiterpenoids, interactions between protons separated by up to six sigma bonds were detected. These interactions may have origins similar to the well‐known allylic and homoallylic couplings found in carbon‐carbon double bonded compounds, although they are much smaller in the epoxy systems. We propose to name them as ‘epoallylic’ and ‘epohomoallylic’ interactions. Some couplings are observed directly, whereas in other cases only an improvement in resolution is seen during multiple irradiation experiments. Even in these latter cases the areas of the observed peak do not change upon multiple irradiation which demonstrates the absence of nuclear Overhauser effects. The stereochemistry of some asymmetric centers of the compounds studied is deduced from the spectra.
Solvent effects in nuclear magnetic resonance spectra of some pyrazines, pyrimidines and their N‐oxides
Authors: Paudler William W. , Humphrey Sharon A.
Published: May 2005

The benzene‐induced solvent effects upon the proton chemical shifts of various pyrazines, pyrimidines and their N‐oxides are described. Larger chemical shift effects, implying closer benzeneheterocycle association, are noted in the N‐oxides as compared to the non‐oxidized heterocycles.

The solvent‐induced chemical shift changes can be used to establish the site of N‐oxidation in those instances where different isomers can be formed.
A PMR study of hydration products in aqueous acetaldehyde solutions
Authors: Podo F. , Viti V.
Published: May 2005

By analysing the PMR signal CHhyd in hydrated acetaldehyde molecules, the various hydration products in water‐acetaldehyde solutions were detected and studied.
Protonenresonanz‐Spektroskopie ungesättigter Ringsysteme—XVI 7,7‐Difluor‐benzo‐cyclopropen
Authors: Günther Harald , Pawliczek Josef Bernd
Published: May 2005

Das NMR‐Spektrum von 7,7‐Difluor‐benzo‐cyclopropen (2) wurde zur Bestimmung der chemischen Verschiebungen und Spin, Spin‐Kopplungskonstanten analysiert: δAA′ = 7,6026, δBB′ = 7,4834, ppm; JAB = 6,86, JAA′ = 7,45, JAB′ = 0,34 und JBB′ = 1,89 Hz. Mit Hilfe heteronuklearer Doppelrresonanz‐Experimente wurde ein positives Vorzeichen für 4J(HF) (3,64 Hz) und ein negatives Vorzeichen für 5J(HF) (−0,33Hz) in diesem Molekül sichergestellt. Die Ergebnisse werden im Hinblick auf die Struktur von 2 und die NMR‐Daten, die für Benzo‐cyclopropen gefunden wurden, diskutiert.
A two frequency method for the interpretation of multiple NQR spectra
Authors: Grechishkin V. S. , Shishkin E. M. , Shishkin V. A. , Kjunzel I. A.
Published: May 2005

A new method for the interpretation of NQR spectra is described. The indentification of multiple lines belonging to different transitions \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{1}{2} \to \frac{3}{2}{\rm and}\frac{3}{2} \to \frac{5}{2} $\end{document}is carried out by using the ‘seizure’ of the corresponding low or high frequency transitions in a two‐frequency pulse experiment.
Wannier spin excitons in charge‐transfer complexes
Authors: Alikin A. A. , Grechishkin V. S. , Grechishkina R. V. , Gusarov V. M.
Published: May 2005

Electron spin resonance in some charge‐transfer complexes of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) with sulphanilamides and antibiotics has been investigated.

The ESR spectra are caused by two types of paramagnetic centres: the impurity type and the thermally excited type (Wannier spin excitons).
Etude RMN de l'Acetone en Solution dans une Phase Nematique
Authors: Courtieu J. , Gounelle Y.
Published: May 2005

Le spectre RMN de l'acétone orientée dans le p‐(p′ ethoxyphenyloxycarbonyl)phényl carbonate de butyle est étudié dans l' intervalle de température 48° à 58°C. La mesure des constantes de couplage direct permet de calculer les facteurs d' orientation moléculaires; ceux‐ci permettent de mettre en évidence ici l' intervention de la polarisabilité dans le phénoméne d' orientation.
Nuclear magnetic resonance studies of methyl‐5, 6‐dicarboxy‐2‐norbornene derivatives
Authors: Kamezawa Norimasa , Ueda Toyoichi
Published: May 2005

A simple procedure is provided for the quantitative analysis of Diels‐Alder adduct prepared from commercial methylcyclopentadiene and maleic anhydride by NMR spectra without further separation of its components. The adduct is considered as a mixture of endo norbornene derivatives (Cn), (Dn), (E) and (Fn) which are obtained from 1‐, 2‐ and 5‐methylcyclopentadiene and cyclopentadiene, respectively.

The quantitative analysis of the adduct can be made on a basis of the ratio of the signal intensities of the olefinic protons in the adduct. The result shows that the adduct prepared under mild conditions mainly consists of three norbornene derivatives (Cn), (Dn) and (Fn), with a negligibly small amount of (E). When the adduct prepared under mild conditions is heated, it contains the exo isomers (Cx), (Dx) and (Fx). The ratio of the endo and the exo norbornene derivatives, i.e. ((Cn) + (Dn) + (Fn)):((Cx) + (Dx) + (Fx)), may be estimated from the signal intensities of the 5‐ and 6‐protons.

As the result of the analyses of the adducts which are obtained by heating at different temperatures the adduct prepared under mild conditions, the mole fraction of 2‐methyl isomers (Dn) and (Dx), which is found to be 58 % in the adduct prepared at − 15°C, keeps on increasing with rising temperature and shows almost the same value, ∼86%, when heated above 150°C. Therefore, the equilibrium between 1‐methyl and 2‐methyl isomers does not change above 150°C. On the other hand, the isomerization from endo to exo isomers is not found below 110°C, and then exo isomers keep on increasing above 140°C.
Etudes RMN en Serie Heterocyclique—VIII: Effet des Dipivalomethanates de Nickel(II), Cobalt(II), Europium(III) et Praseodyme(III) sur les Deplacements Chimiques de quelques Derives du Pyrazoles
Authors: Claramunt Rosa‐Maria , Elguero José , Jacquier Robert
Published: May 2005

On a déterminé l'effet produit par quatre réactifs de déplacement sur les signaux de sept derivés du pyrazole et sur ceux du methyl‐ 1 imidazole. Ces effets sont discutés en fonction de leur utilité pour différencier des structures isomères.
Shielding constants of tin 119Sn nuclei
Authors: Tupčiauskas A. P. , Sergeyev N. M. , Ustynyuk Yu. A.
Published: May 2005

A number of organotin compounds have been studied using the heteronuclear double resonance H1‐{Sn119}. The tin chemical shifts have been tabulated and discussed on the basis of the concept of electronegativity. The highfield displacement is found attributable to the filling of the 5d‐orbitals of the tin atom.
The determination of aromatic substitution patterns by nuclear magnetic resonance
Authors: Zanger M.
Published: May 2005

A method is described which permits the analysis of many substituted benzene compounds. The method is useful for mono‐through tetra‐ substituted aromatics. In ideal cases, the number and disposition of the substituents and the chemical shifts of the residual protons can be accurately determined. The method assumes approximate first order couplings and is useful for roughly 50% of all aromatics. Frequently observed anomalous spectra are also discussed.