bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR‐Untersuchungen über inter‐ und intramolekulare Wechselwirkungen in substituierten Trifluormethylphenylisocyanaten, Fluorphenylisocyanaten, in Fluoranilin und Fluornitrobenzol
Authors: Kosfeld R. , Henke L.
Published: May 2005

Die chemischen Verschiebungen der Fluor‐ und Protonensignale substituierter Trifluormethylphenylisocyanate, Fluorphenylisocyanate, des Fluoranilins und des Fluornitrobenzols werden in Abhängigkeit von der Probentemperatur und der Konzentration des Lösungsmittels Tetrachlorkohlenstoff ermittelt. Der Temperatureinfluß auf die chemischen Verschiebungen der Fluorsingale ortho‐substituierter Trifluormethylphenylisocyanate wird von der intramolekularen Wechselwirkung zwischen den Trifluormethylgruppen und den ortho‐Substituenten bestimmt, die zu einem Anstieg der chemischen Verschiebungen mit zunehmender Temperatur führt.

Die Temperaturabhängigkeit der Elektronenverteilung innerhalb meta‐ und para‐substituierter Trifluormethylphenylisocyanate ist hauptsächlich auf intermolekulare Wechselwirkungen zurück‐zuführen, die eine Abnahme der chemischen Verschiebungen der Fluorsignale mit steigender Probentemperatur verursachen.

Da sich die Protonen der untersuchten Substanzen an der ‘molekularen Oberfläche’ befinden, ist der van der Waals‐Effekt für die Temperaturabhängigkeit der chemischen Verschiebungen der Protonensignale bestimmend. Das Lösungsmittel Tetrachlorkohlenstoff verursacht mit zunehmender Konzentration infolge einer Schwächung des Anisotropie‐Effektes einen Anstieg der chemischen Verschiebungen der Fluor‐ und Protonensignale aller untersuchten Substanzen.
Diazanaphthalenes: A 13C NMR investigation on the site of protonation and pKa values
Authors: van de Weijer Peter , Thijsse Hans , van der Meer Douwe
Published: May 2005

The pH dependence of the 13C chemical shifts (δ) of the diazanaphthalenes has been recorded. From this dependence the pKa values have been determined using the Henderson‐Hasselbach equation. The change in 13C chemical shifts under the influence of nitrogen protonation (Δδ) has been predicted using the Δδ values of quinoline and isoquinoline. The correlation between observed and expected Δδ values of the symmetric diazanaphthalenes is very good. Assuming these changes in chemical shifts to be of general validity, the site of protonation in the asymmetric diazanaphthalenes has been determined by comparison of the expected Δδ values for α‐ and β‐nitrogen protonation with the observed ones. The site of protonation for 1,6‐ and 1,7‐naphthyridine is the β‐nitrogen atom, whereas for cinnoline both monoprotonated species are present in a significant amount.
13C NMR spectral studies of arecoline, hordenine, strychnine and brucine
Authors: Srinivasan P. R. , Lichter R. L.
Published: May 2005

The 13C n.m.r. spectra of arecoline, hordenine, strychnine, brucine and their salts were determined and the chemical shifts reported previously for arecoline have been verified by single frequency proton decoupling techniques. Effects of protonation on the carbon resonances in aiding unambiguous assignments in strychnine and brucine are discussed. The quaternary N‐methiodide of brucine was also studied to confirm the assignments made for carbon atoms adjacent to the basic N atom.
On the structure of oxonic acid
Authors: Pike Richard K.
Published: May 2005

1H n.m.r. spectra of some derivatives of oxonic acid are described which augment the evidence that oxonic acid has a 6‐membered ring structure and indicate that allantoxaidin exists predominantly in its monoenolic form.
Modification d'une sonde de spectromètre C60 HL pour des ètudes de photo CIDNP
Authors: Caplain S. , Vermeersch G.
Published: May 2005

La photo CIDNP est une technique nouvelle permettant d'élucider le mécanisme de réactions photochimiques. Dans la majorité des cas, le problème principal pour sa mise en oeuvre est d'amener suffisamment d'énergie lumineuse au niveau de la sonde de détection.

Nous relations ici les modifications que nous avons apporté à la sonde d'un spectromètre JEOL C 60 HL de façon à pouvoir étudier les réactions photochimiques de l'acridine dans les alcools et les éthers.
NMR‐Untersuchungen an Dicyclopentadienderivaten: II.—13C‐NMR: γ‐gauche‐Effekt in Abhängigkeit von der exo/endo‐Isomerie an Dicyclopentadien diolen
Authors: Kleinpeter E. , Kühn H. , Mühlstädt M.
Published: May 2005

Die 13C‐FT‐NMR‐Spektren einer Reihe von exo‐ bzw. endo‐Dihydro‐ und Tetrahydrodicyclopentadien‐9, 10‐diolen (exo/exo bzw. endo/endo) werden aufgezeigt und die einzelnen chemischen Verschiebungen unter Verwendung von Eu(fod)3‐ Verschiebungsversuchen bzw. additiver Inkrementberechnung zugeordnet. Dabei werden besonders für die C‐Atome 4, 5, 7, 9. 10 und 1, 3 in Abhängigkeit von der exo/endo‐Stellung des angeknüpften 5‐Ringes bzw. der OH‐Gruppen am Norbornangerüst relativ starke γ‐Effekte bis 12,8 ppm beobachtet, die einen interessanten Einblick in die Geometrie dieser Norboran‐Systeme geben.
1H n.m.r. studies on intramolecular hydrogen bonding in anilides of 6‐methylpicolinic acid N‐oxide
Authors: Brzezinski Bogumil
Published: May 2005

The 1H n.m.r. spectra of eleven anilides of 6‐methyl‐picolinic acid N‐oxide in chloroform were obtained. The influence of temperature, concentration and substituents on the chemical shifts of the NH protons was investigated. The structure of the anilides is discussed.
13C n.m.r. spectra of cyclopropenes
Authors: Günther Harald , Seel Horst
Published: May 2005

13C n.m.r. chemical shifts and one bond 13C, 1H coupling constants for cyclopropene and its 1‐ and 3‐methyl derivatives as well as for methyl cyclopropane have been measured. The data for cyclopropene are 108·9 ppm and 228·2 Hz, 2·3 ppm and 167·0 Hz in the olefinic and allylic position, respectively. Substituent effects for the methyl group are discussed.
Proton magnetic resonance spectra and conformation of some trisubstituted cyclopropane compounds
Authors: Bednar R. , Herzig U. , Schuster I. , Schuster P. , Wolschann P.
Published: May 2005

The n.m.r. spectra of some 1,2,2‐trisubstituted cyclopropanes are reported. Coupling constants and chemical shifts of the cyclopropane protons and their dependence on substituent effects are discussed. Conformations of benzylcyclopropane derivatives are investigated by long range magnetic shielding. The concentration dependence of the n.m.r. spectra of some 1,3‐diols is explained by inter‐ and intramolecular hydrogen bonding.
Calculation of the diamagnetic component of the nuclear screening constant for C, N, O and F
Authors: Ebraheem K. A. K. , Webb G. A. , Witanowski M.
Published: May 2005

‘Local’ and ‘nonlocal’ contributions to σd are calculated by INDO molecular orbital methods. It is demonstrated, by means of Pople's approach5 using ‘gauge dependent’ atomic orbitals, that σ is effectively constant for C, N, O or F in a number of chemically different environments and that σ is negligible. The use of Flygare's method12 produces a significant and variable ‘nonlocal’ contribution, which renders σd in this formulation comparable to the gauge dependent term in Ramsey's expression.
Isobenzopyryliumsalts: VII—13C n.m.r. shifts of 1‐arylisobenzopyrylium salts and correlation with Hammett parameters
Authors: Vajda Miklos , Voelter Wolfgang
Published: May 2005

The signal identifications of isobenzopyrylium salts has been achieved on the basis of proton broad‐band and off‐resonance decoupled 13C n.m.r. spectra of twelve different 1‐arylisobenzopyrylium salts and eight model compounds. From the 13C shifts valuable information about pK values, the aromatic character and the conjugative effects of isobenzopyrylium salts was obtained.
Constantes de couplage 203Tl13C et 205Tl13C
Authors: Lallemand J. Y. , Duteil M.
Published: May 2005

Les constantes do couplage 1J (203Tl13C) et 1J (205Tl13C) dans le trifluoroacétate de phenylthallium (III) ont été mises évidence.
Structural studies by 1H and 13C d.n.m.r.: I—barrier to trans‐cis isomerization in aliphatic enamino ketones of the type RCOCHCHNHR1
Authors: Czerwińska E. , Kozerski Lech , Boksa J.
Published: May 2005

D.n.m.r. studies have been performed involving the measurement of rates of trans‐cis isomerization of aliphatic enamino ketones of the type RCOCHCHNHR1, by means of equilibration experiments and the method of finding the coalescence temperature. Simultaneous observation of the rates of dynamic NH proton exchange and isomerization processes by the latter method has facilitated the assignment of the rate‐determining reaction step in the title compounds studied in aprotic solvents. Thermodynamic parameters are discussed and the dipolar transition state to isomerization in a nonpolar solvent indicated. The dynamic behaviour of all protons undergoing exchange between the possible sites in the molecule are discussed in the light of our own experiments and other recent data.
Shift reagent spectra. The automatic determination of relative bound shifts and the automatic assignment of signals in the parent spectrum. Effects of concentration, temperature and solvent on relative bound shifts
Authors: ApSimon John W. , Beierbeck Helmut , Fruchier Alain
Published: May 2005

In the use of a shift reagent as an aid in the structural elucidation of organic compounds, it is shown that accurate measurements of the shift reagent and substrate concentrations are not needed to determine the relative bound shifts of the substrate and the chemical shifts of the free substrate spectrum with good precision. This is possible whenever the induced shift ratios of nuclei of a given molecule are independent of the shift reagent concentration. This independence has been verified for all the monofunctional compounds described in this paper. The effect of absolute substrate concentration, solvent, temperature and the presence of water on the relative bound shifts is studied using the eight methyl group signals of β‐amyrin. The method is demonstrated by its use for structural determinations in the ketoandrostane series.
19F coupling constants and chemical shifts in some dimethylamino and alkoxy derivatives of tellurium hexafluoride, cis TeF4XY
Authors: Dalton John , McFarlane William , Wickens Clive R. , Fraser George W. , Millar James B.
Published: May 2005

The spectra of A2BC spin systems provided by the 19F nuclei in cis (RO) (MeO)TeF4 and (RO) (Me2N)TeF4 (R = Me, Et, Pr, i‐Pr) have been recorded and analysed. The geminal coupling constants 2J(F,F) range from 137–174 Hz and trends in the 19F chemical shifts permit complete assignment of the resonances. Stereospecific coupling between 19F and the protons of the N‐methylamino groups is also observed.
Stereochemical aspects of proton chemical shifts—V: The cumulative nature of the proton shift by vicinal substitution
Authors: Danneels Dirk , Anteunis Marc
Published: May 2005

It is shown that the proton chemical shift may be predicted with fairly good precision for a proton in an ethano fragment carrying a (long) vicinal substituent. Caution must be used however in calculating geminal effects.
Phosphoranes par fermeture trans‐annulaire: III—Conformation—configuration—labilité
Authors: Devillers Jean , Houalla Doureid , Mouheich Touhama , Wolf Robert
Published: May 2005

L'analyse des spectres de résonance magnétique nucléaire des deux isomères du triméthyl‐1,6,6 phényl‐3 dioxa‐2,8 aza‐5 phosphav‐1 bicyclo [3.3.0]octane permet de proposer une conformation pour chacun des cycles pentagonaux d'une part, et une configuration de l'atome de phosphore d'autre part. La mobilité du proton HP, révélée par des expériences à haute température et par l'échange PH ⇌ PD, est sensiblement différente d'un isomère à l'autre.
A carbon‐13 n.m.r. study of sulfur‐donor ligand ortho‐metalated iron carbonyl complexes
Authors: Alper Howard
Published: May 2005

Carbon‐13 n.m.r. data are reported for a series of sulfur‐donor ligand ortho‐metalated iron carbonyl complexes derived from thiobenzophenones. The chemical shift δ153·5–161·4 for the aromatic carbon σ‐bonded to iron is readily identified, and occurs in the same region as the signal for the corresponding carbon in a related nitrogen‐donor ligand complex. The benzylic carbon gives a signal at δ62·8–63·3, subject to the nature of the complex.
Formation of a carboxyl group satellite line in the n.m.r. spectra of solid carboxylic acids
Authors: Kimtys L.
Published: May 2005

The structural factors resulting in the formation of the carboxyl group satellite line on the low field side of the 1H n.m.r. spectra of carboxylic acids in the solid state have been determined from the temperature dependences of the carboxyl proton chemical shifts of acetic, dimethylacetic, ethylacetic, phenylacetic, benzoic, o‐methylbenzoic, p‐methylbenzoic and adamantyl carboxylic acids. The carboxyl group low field satellite forms at temperatures near the melting point only in the case of carboxylic acids with bulky hydrocarbon radicals (o‐methylbenzoic and adamantyl carboxylic acids).
13CC13 coupling constants in dimethyl phthalate and phthalic anhydride. Determination of signs—III
Authors: Hansen P. E. , Berg A.
Published: May 2005

Relative signs of 13C13C coupling constants between ring carbons and carbonyl carbons in dimethyl phthalate and phthalic anhydride, 13C‐labelled in both carbonyl groups, have been determined. The two‐and three‐bond coupling constants are shown to be positive, whereas four‐bond coupling constants are negative. Substituent effects on carbon‐carbon couplings due to a carboxyl group have been determined and effects of 5‐membered ring formation in phthalic anhydride have been observed.
Etudes par la RMN du carbone‐13 de quelques dérivés cyclopropaniques: Déplacements chimiques et paramètres structuraux
Authors: Monti J. P. , Faure R. , Vincent E.‐J.
Published: May 2005

L'étude des déplacements chimiques de 13C des dérivés monosubstitués du cyclopropane (C3H5X, X = CH3, Br et CCH) permet la détermination des paramètres directs d'additivité qui ne dépendent que de la nature du substituant. Dans le cas de substitutions multiples, à ces effets directs se superposent des effets complémentaires dus à des interactions croisées entre les substituants. L'étude systématique des dérivés polysubstitués par des atomes de brome et des groupements méthyle et ethynyle, met en évidence ces différentes contributions, et nous permet de proposer pour la plupart des cas une interprétation simple. Ces interactions font appel, soit à des transferts électroniques, soit à des interactions stériques, symétriques ou dissymétriques, entre les différents substituants ainsi que le montre la comparaison entre valeurs théoriques et mesures expérimentales des déplacements chimiques.
Carbon‐13 spin–lattice relaxation in strongly associated molecules: Carboxylic acids
Authors: Levy George C. , Terpstra Dan
Published: May 2005

13C spin–lattice relaxation times determined for the protonated carbons of carboxylic acids and methyl esters give indications of solution dimerization with the free acids. Since isopthalic and fumaric acids have two carboxyl functions they are able to polymerize in solution. Unlike the case for molecular aggregation due to weak hydrogen bonding in solution (e.g. alcohols, phenols), the 13C T1 values of mono carboxylic acids are not significantly affected by dilution to c. 10−2 M. Variable temperature T1 measurements of both the mono and dibasic acids gave activation energies for molecular reorientation of the order of 2 kcal mol−1, considerably lower than Ea for hydrogen bonded alcohols and comparable with Ea for the unassociated methyl esters of propionic and benzoic acids.
Polymerization of 1,1,1‐trifluoroacetone with aliphatic secondary amines. A proton and fluorine magnetic resonance investigation
Authors: Dhingra M. M. , Tatta K. R.
Published: May 2005

The polymerization of 1,1,1‐trifluoroacetone with aliphatic secondary amines is reported. The polymerization product is found to be a mixture of four diastereoisomers of the cyclic trimer, the structure of which has been determined using proton and fluorine magnetic resonance spectroscopy. The proportions of the isomers have been estimated to be 70:19:8:3 from the 19F resonance spectrum. A comparative study of the reaction products of trifluoroacetone with metallic sodium and diethylamine is also discussed.
13C n.m.r. investigation on the nitrogen methylation of some azabenzenes
Authors: Van De Weijer Peter , Mohan Chandra
Published: May 2005

The 1H and 13C n.m.r. spectra of N‐methylated pyridine, pyridazine, pyrimidine and pyrazine and N,N‐dimethylated pyrimidine and pyrazine have been recorded and analysed. The change in the 13C chemical shifts under the influence of N‐methylation (Δδ) in the diazabenzenes could be predicted by the Δδ values of pyridine. A comparison of the Δδ values of N‐methylation with those of N‐protonation showed that both reactions have a similar effect.
1H‐ und 13C‐NMR‐untersuchungen an dibromoxabicyclo[n.2.1]alkanen
Authors: Kleinpeter E. , Haufe G. , Mühlstädt M. , Graefe J.
Published: May 2005

Die 1H‐NMR‐Spektren einer Reihe von Dibromoxabicyclo[n.2.1]alkanen werden zur Bestimmung der Konfiguration und Konformation herangezogen. Die 13C‐NMR‐Spektren bestätigen die ermittelte Stereochemie. Mit zunehmender Ringgröße verlagern sich die 13C‐chemischen Verschiebungen der heteroatomsubstituierten C‐Atome kontinuierlich nach niederem Feld.
13C n.m.r. spectra of rotameric dimethyl 1‐isopropyldibenzo[b,e]bicyclo[2.2.2]octatriene‐7,8‐dicarboxylate: Non‐equivalency of carbons along the rotational axis
Authors: Nakanishi Hiroshi , Kitagawa Yukio , Yamamoto Osamu , Ōki Michinori
Published: May 2005

13C n.m.r. spectra of dimethyl 1‐isopropyldibenzo[b,e]bicyclo[2.2.2]octatriene‐7,8‐dicarboxylate disclose the existence of both dl and meso isomers, whereas 1H n.m.r. spectra were interpreted by the sole existence of the former. Characteristic chemical shifts for the rotamers were found, among others, for carbons along the rotational axis. The non‐equivalence is most probably attributed to the difference in geometry about the carbons in question. An unusual fact was also that the more compressed methyl carbon of the isopropyl group gives a signal at higher field.
1H n.m.r. study and conformation of 3,3‐dimethyl‐3‐sila‐1‐heterocyclohexanes and derivatives (heteroatom SiCl2, SiMe2, O, NMe, S, Se, Te)
Authors: Anteunis Marc J. O. , Dedeyne Raymond
Published: May 2005

It is found that the basic form of the 3,3‐dimethyl‐3‐sila‐1‐heterocyclohexane family (heteroatom X = O, NMe, S, Se, Te, SiMe2, SiCl2) is the chair, having ring torsion angles in the aliphatic region tending to be somewhat more puckered (up to 7°) than in cyclohexane, except next to Si when the other heteroatom is relatively small. The 5‐tertiarybutyl‐, 6‐methyl‐ and 2‐phenyl derivatives are all anancomeric, except for the latter two derivatives when X = NMe. A 5‐tertiarybutyl group causes an additional deformation, e.g. an increased puckering of the aliphatic C‐4C‐5C‐6 region (buttressing effect). Other 1H n.m.r. features are discussed in detail, and the behaviour of the 3‐sila‐1‐heterocyclohexanes is compared with other 1,3‐diheterocyclohexanes.
Analysis of the 1H n.m.r. spectrum of 4‐methyl‐1,3‐oxathiolane. An interestingly coupled ABXM3‐case
Authors: Pihlaja Kalevi , Keskinen Raimo
Published: May 2005

The 220 MHz proton magnetic resonance spectrum of 4‐methyl‐1,3‐oxathiolane was recorded and analysed. The methyl and ethanic protons form an ABXM3 system, the analysis of which was carried out through several ‘trial‐and‐error’ attempts. This part of the spectrum is an interesting example of second‐order effects which, in the past, have been mistakenly associated with ‘virtual coupling’. The results are compared with those presented earlier for several alkyl substituted 4‐methyl‐1,3‐oxathiolanes.
Transmission of substituent effects through unsaturated systems. I—relative magnitudes of proton and carbon substituent chemical shifts in ethylenes, butadienes, α‐enones and benzenes
Authors: Azzaro Marcel , Gal Jean‐François , Géribaldi Serge , Novo‐Kremer Nicole
Published: May 2005

The carbon‐13 shifts of C‐1, C‐2 and C‐3 are determined in a series of 1‐cyclohexen‐3‐ones substituted in position 1. Linear relationships are demonstrated between the substituent chemical shifts of corresponding carbons in substituted ethylenes, butadienes, α‐enones and benzenes. The substituent chemical shifts of proton H‐2 are also reported and correlated with those of corresponding protons in ethylenes and benzenes. The slopes of the lines for the carbons directly linked to the substituent are close to unity, showing a relative independence of the substituent effect for this nucleus from the variation of the unsaturated framework. In contrast to this, the transmission of the substituent effect through one double bond (nuclei β to the substituents) decreases as the number of conjugated π bonds in the whole structure increases. This relationship is interpreted as being due to the ability of an unsaturated system to spread the variation of π electron density induced by the substituent.
77Se n.m.r. studies of organoselenium compounds: III—substituent effects in 4,4′‐disubstituted diphenyl selenides and 4,4′‐disubstituted diphenylmethanes studied by 1H, 13C and 77Se spectroscopy
Authors: Gronowitz S. , Konar A. , Hörnfeldt A.‐B.
Published: May 2005

77Se N.m.r. spectra of 4,4′‐disubstituted diphenyl selenides have been obtained. The chemical shifts could be correlated with substituent constants of the Hammett type or with Swain and Lupton two‐parameter equations. No correlations were observed between these 77Se shifts and the 13C shifts of the CH2 group of 4,4′‐disubstituted diphenylmethanes, the latter shifts showing no correlation with substituent constants. On the other hand linear correlation was observed between the 77Se shifts of the 4,4′‐disubstituted diphenyl selenides and the 1H shifts of the CH2 group of the diphenylmethanes, the 13C shifts of their 1‐carbons and the 19F shifts of 4‐substituted fluorobenzenes.
1H n.m.r. spectra of some bicyclic compounds: I—relative configurations of the diastereomeric endo‐α‐methyl‐5‐norbornene‐2‐methanols, the corresponding saturated analogues, and their cyclization ether products
Authors: Mihailović M. Lj. , Milosavljević S. , Jeremić D. , Milovanović J.
Published: May 2005

The configurational and conformational relationship at C‐2 and C‐α in the two racemic diastereomeric endo‐α‐methyl‐5‐norbornene‐2‐methanols and the corresponding saturated endo‐α‐methyl‐2‐norbornanemethanols were determined by first‐order analysis of the 1H n.m.r. spectra of these compounds and of their cyclization ether products, i.e. 3‐methyl‐2‐oxatricyclo[4.2.1.04,8]nonanes and 5‐methyl‐4‐oxatricyclo[4.3.0.03,8]nonanes. In addition, the conformational preference of the hydroxyl group in the unsaturated and saturated alcohols was confirmed by the lanthanide induced shift technique, using Eu(fod)3 as shift reagent, combined with a computer program involving various conformations of the –CHOHMe group.
N.m.r. studies in the heterocyclic series: XVI—determination of the structure of 3‐azidoindazole by 1H and 13C n.m.r. spectroscopy
Authors: Fruchier Alain , Alcalde Ermitas , Elguero José
Published: May 2005

The 1‐NH structure for 3‐azidoindazole has been demonstrated by the observation of 1H1H and 13C1H couplings involving the hydrogen atom attached to nitrogen. A comparison between 3‐azidoindazole and indazole shows that both compounds have the same tautomeric structure.
NMR‐Untersuchungen an Dicyclopentadienderivaten. IV—1‐Syn/anti‐Epimere von endo‐Dicyclopentadienderivaten
Authors: Kleinpeter E. , Kühn H. , Mühlstädt M.
Published: May 2005

Die syn/anti‐Stellung einer Reihe Substituenten R in 1‐Stellung am endo‐Dicyclopentadien wird mit 1H‐ und 13 C‐NMR‐Spektroskopie untersucht. Die HH‐Kopplungskonstanten der epimeren Alkohole 2 und 3 werden durch Experimente unter Zuhilfenahme von paramagnetischen Verschiebungsreagenzien[Eu(fod)3] bestimmt und die beobachteten relativen paramagnetischen Verschiebungen ΔEu gleichzeitig zur Konfigurations‐bestimmung herangezogen. Die bei syn‐Anordnung der Substituenten zunehmende sterische Spannung im Molekül spiegeln 1 H‐ und 13C‐chemische Verschiebungen sehr gut wider.
Carbon‐13 nuclear magnetic resonance spectra of isomeric oxaziridines. Effects of the nitrogen lone pair on carbon‐13 chemical shifts
Authors: Jordan Guy J. , Crist DeLanson R.
Published: May 2005

The carbon‐13 n.m.r. spectra of several oxaziridines were measured. Aliphatic and aromatic ipso carbon atoms trans to the lone pair of nitrogen in oxaziridines were shifted upfield by c. 9 ppm, and 3.4 ppm, respectively, in comparison with isomers of inverted configuration. The results suggest that the nitrogen lone pair is partially responsible for the observed upfield shifts.
15N and 13C n.m.r. study of azimines and azoxybenzenes
Authors: Schwotzer W. , Leuenberger Ch. , Hoesch L. , Dreiding A. S. , von Philipsborn W.
Published: May 2005

15N chemical shifts, 1J(NN), 1J(NC) and 2J(NC) coupling constants have been used to prove the open chain structure and configuration of cis‐ and trans‐2,3‐diphenyl‐1‐phthalimidoazimines. For comparison, the corresponding data of the iso‐π‐electronic cis‐ and trans‐azoxybenzenes are also reported and discussed.
Configurational assignment of some isomeric 1,4‐diacetoxy‐2,3‐dialkylcyclopentanes from 1H‐n.m.r. spectral parameters
Authors: De Clercq P. , Samson M.
Published: May 2005

From the study of the 1H n.m.r. spectral parameters of differently functionalized 1,4‐diacetoxy‐2,3‐dialkylcyclopentanes it is shown that the magnitude of those parameters allows an easy configurational assignment within a set of four different configurations.
Versuche zur Berechnung der chemischen Verschiebung von 1H, 13C und 19F Atomen in Aliphaten, Olefinen und Acetylenen
Authors: Sterk H. , Fabian W. , Suschnigg J. J. , Janoschek R.
Published: May 2005

Die Vorhersage der chemischen Verschiebung für 1H, 13C und 19F Atome wird auf der Basis von SCF‐LCGO‐MO‐rechnungen versucht. Der 〈1/R〉 Erwartungswert als Maß für den Diamagnetismus wird exakt berechnet, der Paramagnetismus durch 〈1/R3〉 sowie Werte der Ladungsbindungsordnung angenähert. Der Einfluß der Nachbaratome wird über die Elektronendichte p(r) auf einem kugelförmigen Raster ermittelt. Die Terme ermöglichen in Form eines linear funktionalen Ansatzes die Berechnung von 1H und 13C Verschiebungen an Fluoracetylen, Fluoräthylen und Fluoräthan wobei die Regressionsrechnung für 1H einen Standardfehler von 0,39 ppm und für 13C einen Standardfehler von 1,6 ppm ergibt. Die 19F Verschiebungen werden direkt durch Festlegung des σdia:σpara Verhältnisses berechnet.
Vicinal 13C13C spin–spin coupling constants of 1‐butanols. Conformational and substituent effects
Authors: Marshall James L. , Conn Shareen A. , Barfield Michael
Published: May 2005

A series of (>90% isotopic purity) 13C‐labeled aliphatic alcohols of the general structure CCC13COH were synthesized and studied by 13C n.m.r. to obtain all 13C13C couplings involving the labeled carbon. The 2J(CC) values were small (<0.5 Hz) and contrast with the large (up to 2.7 Hz) 2J(CC) values obtained in a previous study for 2‐butanols. The 3J(CC) values, however, were strikingly similar in the two classes of compounds with respect both to magnitude and to conformational dependency. Thus, the effect of the hydroxyl substituent on 3J(CC) values is small.
13C n.m.r. spectra of steroids —a survey and commentary
Authors: Blunt J. W. , Stothers J. B.
Published: May 2005

The literature on 13C n.m.r. examinations of steroids has been reviewed and the shielding data for over 400 examples are tubulated. The assignments for each compound have been considered and, where necessary, revised in the light of more recent evidence and for consistency throughout each series. The methods available for assignments are reviewed and, in many cases, illustrated with specific examples. The major practical features concerning 13C studies of steroids are discussed as a guide to the use of the technique. From the main body of shielding data, an extensive set of substituent effects has been generated to aid the examination of new systems. The utility and the limitations of these effects are described.
Quantitative analysis by nuclear magnetic resonance using precision coaxial tubing
Authors: Hatada Koichi , Terawaki Yoshio , Okuda Hiroshi
Published: May 2005

Quantitative analysis by n.m.r. using precision coaxial tubing is described. A solution of the intensity standard is placed in the central capillary and the sample of interest in the surrounding annulus. By this method the contamination of the sample by the standard compound can be avoided and an accurate determination can be carried out by using solutions of correct concentrations of the intensity standard. Applications to several types of quantitative problems are given. In order to get a higher accuracy and precision the experimental conditions were also studied.
Étude des Paramètres de Résonance Magnétique Nucléaire et de la Stéréochimie de Thiono‐2 R‐2 Dithiaphosphorinanes‐1,3,2
Authors: Martin J. , Robert J. B.
Published: May 2005

Les spectres de résonance magnétique nucléaire (1H, 13C, 31P) de onze R‐2 thiono‐2 dithiaphosphorinanes‐1,3,2, portant au niveau du phosphore divers restes R, ont été enregistrés et analysés. Pour les composés avec R = Cl, OMe et magnified image, la molécule adopte une forme chaise rigide, le groupement R étant axial; quand magnified image la molécule adopte une forme chaise rigide à groupement R équatorial. Les molécules avec R=phényl, Me, N(Me)2 et NHt‐Bu montrent un équilibre conformationnel chaise–chaise. L'étude de la rotation autour de la liaison PN est également examinée dans le cas du dérivé où magnified image.
Carbon‐13 n.m.r. studies of purines and 8‐azapurines in basic aqueous medium
Authors: Purnell Linda Goodrich , Hodgson Derek J.
Published: May 2005

The 13C n.m.r. spectra of a variety of purines and 8‐azapurines have been studied in aqueous basic medium; the shifts were measured using dioxane as reference, and corrected to the TMS scale. The compounds studied include adenine, hypoxanthine, 6‐mercaptopurine, guanine, xanthine, 8‐azaadenine, 8‐azahypoxanthine, 8‐azaguanine, 8‐azaxanthine, and 2‐thio‐8‐azaxanthine. Resonances were assigned using noise‐decoupling, selective deuteration at the 8‐position of purines, and coupled spectra. The general effect of changing from a purine to its 8‐aza analog is to produce a downfield shift of C‐2, C‐5, and C‐6 and an upfield shift of C‐4.
Etude dans la Série Bicyclo [2.2.2]octanique: IV—Influence de l'Anisotropie Magnétique d'un Groupement Géminé Chloro‐Nitrile sur les Déplacements Chimiques des Protons des Bicyclo[2.2.2]octènes
Authors: Rouillard M. , Geribaldi S. , Damiano‐Gal J. , Azzaro M.
Published: May 2005

L'analyse des spectres RMN 1H d'une série d'acétoxy‐1 ou 3 chloro‐6 cyano‐6 bicyclo[2.2.2]octènes‐2 et de chloro‐6 cyano‐6 bicyclo[2.2.2]octanones‐3 permet de déterminer l'anisotropie magnétique d'un groupment chloro‐nitrile géminé à l'aide de la relation de McConnell. Les résultats obtenus rendent possible l'attribution de la position endo ou exo des substituants CN et Cl par rapport à la double liaison ou au carbonyle pour ces composés et confirment les conclusions de la littérature relatives aux chloro‐5 cyano‐5 bicyclo[2.2.2]octènes‐2.
Dual substituent parameter analysis of the ethyl and ipso13C n.m.r. chemical shifts of some ring‐substituted ethylbenzenes and ethylnaphthalenes
Authors: Adcock William , Kitching William , Alberts Vince , Wickham Geoffrey , Barron Peter , Doddrell David
Published: May 2005

The natural abundance 13C n.m.r. spectra of a series of para‐substituted ethylbenzenes, 4‐substituted‐1‐ethylnaphthalenes and a limited series of 6‐substituted‐2‐ethylnaphthalenes have been examined at low dilution in deuterochloroform solvent. The ethyl carbons and Cipso in the phenyl series (i.e. have been assigned, and substituent chemical shifts for these carbons calculated and analysed by the Dual Substituent Parameter treatment. (Chemical shifts of all ring carbons have been obtained, but not assigned). Generally speaking, electron‐withdrawing substituents lead to positive (i.e. downfield) substituent chemical shifts for CH2 and negative substituent chemical shifts for CH3, i.e. ‘normal’ and ‘inverse’ behaviour respectively. Cipso in the phenyl series exhibits a ‘normal’ dependence. The dependences of the various substituent chemical shifts on inductive and resonance parameters are discussed, and compared with the behaviour of side chain carbons in other substituted benzene systems.
Stable conformations of N,N,N′,N′‐ tetraisopropylthiuram disulphide and monosulphide found in low temperature 1H N.m.r. spectra
Authors: Takeda Yu‐ichi , Matsuda Tsuneo , Tanaka Toshio
Published: May 2005

1H N.m.r. spectra of N,N,N′,N′‐tetraisopropylthiuram disulphide and monosulphide in CS2 suggested that internal rotations both around the carbamate CN and isopropyl–nitrogen bonds are restricted at low temperatures. As a result, both compounds exist as two dl pairs of isomers with respect to rotation around the isopropyl–nitrogen bond. The spectra further suggest that one pair of the isomers is subdivided into two sets of dl pairs, possibly owing to the restriction of torsion of the two carbamate planes with respect to each other. Possible conformations of these three dl pairs of isomers are proposed, and the assignments of each proton signal are described.
1H n.m.r. conformational studies of glycyl‐L‐phenylalanine and L‐phenylalanyl‐glycine dipeptides and their complexes with palladium (II)
Authors: Kozlowski Henryk , Formicka‐Kozlowska Grażyna , Jeżowska‐Trzebiatowska Boguslawa
Published: May 2005

The conformations of Gly‐Phe and Phe‐Gly dipeptides and those of their complexes with the Pd(II) ion has been established by means of 1H n.m.r. spectra over various pH ranges. In the most stable rotamer of both dipeptides the bulkiest groups, i.e. carboxylate (or carbonyl) and the aromatic ring, are in trans position to each other. In the 1:1 molar ratio complexes, the dipeptides are the tridentate ligands within the 3–10 pH region. In the predominant conformer the aromatic ring lies over the complex plane, which suggests its interaction with the metal ion. At pH above 13, the carboxyl group becomes non‐coordinated. The dipeptides are then bidentate and the most stable rotamers are the same as those found for the metal‐free ligands, i.e. the carboxyl or carbonyl group is in the trans position to the aromatic ring. The glycine chelate ring in the Pd(II) Gly‐Phe complex is planar up to pH 10 and its distortion from planarity follows when the ligand becomes bidentate.
Some INDO perturbation calculations of nJ(NC) values
Authors: Khin Tun , Webb G. A.
Published: May 2005

Standard INDO parameters are used in ‘sum‐over‐states’ perturbation calculations of nJ(NC) in a variety of molecular environments. Good agreement with the experimental data is, in general, obtained when the integral products SN2(o)SC2(o) and 〈r−3〉N〈r−3〉C assume the values of 35.167 a.u.−3 and 4.980 a.u.−3, respectively. For ‘pyridine‐type’ nitrogen atoms the major contribution to nJ(NC) usually arises from the orbital term whereas the contact term dominates the values of nJ(NC) for ‘pyrrole‐type’ and amino nitrogen atoms.
Rotational isomerism in 3‐mono‐oxygenated and 3,7‐di‐oxygenated derivatives of N‐acetyl‐17‐aza‐D‐homoandrost‐5‐ene
Authors: Dawson Philip J. , Crabb Trevor A. , Williams Roger O.
Published: May 2005

The 1H n.m.r. spectra of 3‐mono‐oxygenated and 3,7‐dioxygenated N‐acetyl‐17‐aza‐D‐homoandrost‐5‐enes show unequal populations of the amide rotational isomers in chloroform‐d1 solution. The populations are dependent upon the orientation of the C‐7 oxygen substituent but are independent of concentration. In pyridine‐d5 solution the two rotameric states for each compound are almost equally populated.
Stereochemical aspects of proton chemical shifts. VI—increments due to geminal hydroxyl, methyl substitution
Authors: Tavernier Dirk , Antunis Marc
Published: May 2005

In geminal methyl, hydroxyl substitution an axial hydroxyl, equatorial methyl arrangement has a downfield effect on a syn axial hydrogen atom which is larger by 0.3 ppm than an axial methyl, equatorial hydroxyl arrangement. It is proposed that these observations may constitute a basis for configurational assignment.
Déplacements Chimiques du Carbone 13, Constantes de Couplage 1J(CH) et 3J(CH) dans une série de dérivés trisubstitués du benzène
Authors: Nery H. , Canet D. , Azoui B. , Lalloz L. , Caubère P.
Published: May 2005

Les déplacements chimiques du 13C, les couplages 13CH à une liaison, les couplages 13CH à trois liaisons (méta) ont été déterminés pour une série de dérivés trisubstitués du benzène, les substituants étant: Cl, NH2, N(C2H5)2, N(iC3H7)2, N(C2H4)2O. Les déplacements chimiques n'obéissent que médiocrement aux lois d'additivité habituelles. Des lois d'additivité relatives aux couplages mentionnés plus haut sont proposées. A de rares exceptions près, l'écart entre valeurs prévues et valeurs observées est inférieur à 10%.
Substituent effect of the nitro group on alkanes in carbon‐13 n.m.r. spectroscopy
Authors: Ejchart Andrezej
Published: May 2005

Linear correlation coefficients were obtained for the substituent effect of the nitro group in primary nitroalkanes. The solvent effect of chloroform is also discussed, as well as the influence of the scalar relaxation on the half‐width of α‐carbons in13C n.m.r. spectroscopy.
Applications de la Résonance Dynamique du Proton et du Carbone‐13 à l'Etude d'Azines Hétérocycliques. Mécanismes de Formation et d'Isomérisation
Authors: Naulet M. , Leymarie‐Beljean M. , Martin G. J.
Published: May 2005

Ce travail présente une étude structurale par RMN 1H et 13C d'azines hétérocycliques, l'influence de l'isomerie Z/E sur les déplacements chimiques 13C est examinée. L'étude cinétique de la formation et de l'isomérisation Z/E de ces composés a été effectuée et les mécanismes de ces réactions sont discutés.
A theoretical interpretation of 13C screening data in unsaturated molecules
Authors: Jallali‐Heravi M. , Webb G. A.
Published: May 2005

Carbon‐13 screening constants are calculated within the INDO/S level of approximation to Pople's model. Satisfactory agreement is obtained in most cases between the calculated and observed screening results. An analysis of the contributions of the π → σ*, σ → π* and σ → σ* transitions to the paramagnetic term shows that a linear relationship between 13C chemical shifts and the lowest energy transition is not present. The average excitation energies are found to vary appreciably among the molecules studied.
Carbon‐13 isotope effect on proton decoupled 13C and 31P n.m.r. spectra of bis(diphenylphosphino)acetylene
Authors: Paasonen R. , Enqvist J. , Karhu M. , Rahkamaa E. , Sundberg M. , Uggla R.
Published: May 2005

High resolution proton decoupled 13C and 31P n.m.r. spectra of bis(diphenylphosphino)acetylene in (CD3)2SO and CDCl3 are analysed as ABX spectra to give the relative chemical shifts of the 13C and 31P nuclei as well as the spin–spin coupling constants 3J(PP) and nJ(PC). The differences in 31P shieldings are due to secondary 13C isotope effects which have been observed to be negligible over more than two bonds.
Assignment of the carbon‐13 chemical shifts of quinacrine, chloroquine and related compounds in D2O solution
Authors: Griggs Billy G. , Wilson W. David , Boykin David W.
Published: May 2005

The carbon resonances of quinacrine, chloroquine, acranil, 4‐aminopyridine and 9‐aminoacridine in D2O solution have been assigned. Resonance assignments were made using empirical shift parameters, partial proton decoupling, selective proton decoupling and by interpretation of the fully coupled spectra. The effect of pD on the carbon chemical shifts for quinacrine and chloroquine over the range of about 4.5 to 8.5 was observed. Characteristic chemical shifts for the aromatic ring carbons for deprotonation of the heteroaromatic nitrogen were observed.
How does the accuracy of NMR conformational analysis depend on the equilibrium constant?
Authors: Sergeyev N. M.
Published: May 2005

Analytical expressions are derived for the analysis of the accuracy of NMR determinations of conformational equilibrium constants, K. The relative error, σK/K, shows a nearly linear increase with K for two commonly used modifications of the NMR approach to conformational analysis (based on measurements of integral intensities and averaged chemical shifts).
Carbon‐13 nuclear magnetic resonance spectra. VIII—18α‐ and 18β‐glycyrrhetic acid derivatives
Authors: Duddeck Helmut , Elgamal M. H. A. , Ricca Guiliana Severini , Danieli Bruno , Palmisano Giovanni
Published: May 2005

The 13C NMR data of six pairs of 18α/18β‐glycyrrhetic acid derivatives are presented. It is shown that the configuration at C‐18 can easily be recognized by inspecting the chemical shifts of several characteristic carbons, e.g. C‐12, C‐13, C‐18 and C‐28. The shifts of these carbons originated by the change of the D/E ring junction proved to be largely independent of the substitution at C‐3 and C‐20.
On the stereochemistry of 1,4‐diheterocyclanes. IV—carbon‐13 NMR spectra and structural properties of 1,4‐dioxane‐2,3‐diols and their methyl‐substituted derivatives
Authors: Äyräs Pertti
Published: May 2005

The 1,4‐dioxane‐2,3‐diols and a number of their methyl‐substituted derivatives were synthesized and their 13C NMR spectra measured. The configurational properties were studied on the basis of the spectral data and chemical equilibration. For the parent compound the trans configuration is slightly more stable. The hydroxyl groups are predominantly axial. Introduction of a methyl group at the 2 position causes the cis configuration of the hydroxyl substituents to become more stable. The substituent effects on the chemical shifts were calculated and used to test the conformational homogeneity of the compounds. The results indicate a biased (chair) conformation for all the methyl‐substituted derivatives which were studied. Methyl groups have strongly predominating equatorial orientation in each case studied.
Effet de Solvant en RMN du Carbone‐13. III—Cas d'un Soluté Polaire: l'Acétone dans Divers Solvants et en Phase Gazeuse
Authors: Tiffon Bernard , Dubois Jacques‐Emile
Published: May 2005

Le déplacement chimique des carbones de l'acétone a été déterminé en phase gazeuse et en fonction de la concentration dans dix‐neuf solvants dans le but de séparer les différents termes de constante d'écran dus aux interactions de l'acétone avec elle‐même (autoassociation) et avec les solvants. On montre que le terme de constante d'écran σw dǔ aux interactions de van der Waals (interprété à l'aide de l'expression théorique proposée par Rummens) est prépondérant pour les groupes méthyles par rapport au terme d'interactions spécifiques soluté–solvant σH. Par contre, le terme d'interactions spécifiques σH du carbone du carbonyle est huit fois plus grand que celui des groupes méthyles et il est prédominant lorsque des interactions dipole–dipole ou des liaisons hydrogène interviennent entre le soluté et le solvant. Aucune preuve formelle d'existence d'un terme de champ électrique proportionnel au champ de réaction d'Onsager n'a pu ětre établie, mais dans le cas des interactions dipole‐dipole, le terme σH est proportionnel au champ électrique du dipole d'une molécule de solvant couplé de façon antiparallèle avec le dipole du soluté. La variation du terme σH avec la dilution dans un solvant non associant est interprétée comme résultant du déplacement de l'équilibre d'autoassociation, dont la constante K est déterminée.
Downfield γ‐gauche and γ‐antiperiplanar effects on 13C NMR chemical shifts exerted by thiophene sulphur
Authors: de Haan J. W. , van Dommelen M. E. , van de Ven L. J. M. , Corvers A.
Published: May 2005

The γ‐effects of sulphur on 13C NMR chemical shifts have been measured in a series of steroidal compounds containing the thiophene ring in different configurations with respect to the rest of the molecule. The data constitute the first example of downfield effects exerted by sulphur on both gauche and antiperiplanar γ‐carbons. The γ‐gauche effect of sulphur amounts to 1.6–1.8 ppm, the γ‐antiperiplanar effect from practically zero to almost 1 ppm.
Structure elucidation with lanthanide‐induced shifts. 4—Bound shifts vs relative shifts
Authors: Raber Douglas J. , Johnston Milton D. , Campbell Catherine M. , Janks Christopher M. , Sutton Pamela
Published: May 2005

The use of lanthanide shift reagents (LSR's) to obtain additional structural information from nuclear magnetic resonance studies has gained widespread acceptance. However, there has not been general agreement with regard to the most appropriate methodology for analysis of the shifted NMR spectra. We present arguments that only the bound shifts (Δ1) corresponding to the LS complex should be used for correlation of lanthanide‐induced shifts with molecular structure by means of the pseudocontact equation. Several examples are discussed of compounds for which the relative induced shifts are dependent on the concentration of LSR. For such cases it is not possible for both Δ1 and Δ2 (the bound shift corresponding to the LS2 complex) to correlate successfully with the correct structure. Alternative methods of obtaining bound shifts are critically evaluated.
Spectres RMN des Polysaccharides et de leurs Dérivés: Influence des Substituants sur le Déplacement Chimique 13C
Authors: Gagnaire D. , Mancier D. , Vincendon M.
Published: May 2005

L'influence des substituants méthyle et acétate sur le déplacement chimique 13C a été déterminée sur les polysaccharides liés par liaison glycosidique (α1→3), (α1→4), (β1→3) et (β1→4) suivants: pseudonigérane, β‐cyclodextrine, amylose, laminarane et cellulose. Nous avons utilisé les méthyl α et β glucopyranosides comme composés modès. La détermination de l'effet des substituants sur le déplacement chimique 13C nécessite l'attribution non ambiguë des spectres 13C des polysaccharides hydroxylés et substitués. On a utilisé pour cela la technique d'irradiation sélective hétéronucléaire et l'effet isotopique d'hydroxyle deutérié.
Carbon‐13 NMR. The analysis of the relaxation times T1 of benzofuran and of a series of its methyl derivatives. Correlations between molecular motions and structural properties
Authors: Platzer Nicole
Published: May 2005

Carbon‐13 relaxation times (T1) and nuclear Overhauser enhancements (η) have been measured for benzofuran and a series of its methyl derivatives. The contributions of dipolar (T1 DD) and spin rotation (T1SR) mechanisms have both been determined. The temperature dependence of T1 has been studied. The relationships between molecular motions and structural properties have been emphasized. The overall motional anisotropy of the benzofuran molecule is increased by substitution in positions 2 and 5. The internal rotation of a methyl group may change depending on its position in the molecule and on the influence of other methyl groups in its close neighbourhood.
Determination of the configuration of substituted 1,4:3,6‐dianhydrohexitols by 13C NMR spectroscopy
Authors: Sohár P. , Medgyes G. , Kuszmann J.
Published: May 2005

The configurations of 1,4:3,6‐dianhydro‐2,5‐di‐O‐mesyl‐D‐mannitol, 1,4:3,6‐dianhydro‐2,5‐di‐O‐mesyl‐D‐glucitol, 1,4:3,6‐dianhydro‐2,5‐di‐O‐mesyl‐L‐iditol, 1,4:3:6‐dianhtydro‐2‐deoxy‐2‐iodo‐5‐O‐mesyl‐D‐mannitol, 1,4:3:6‐dianhtydro‐2‐deoxy‐2‐iodo‐5‐O‐mesyl‐D‐glucitol, 1,4:3,6‐dianhydro‐2‐deoxy‐2‐iodo‐5‐O‐mesyl‐L‐iditol, 1,4:3,6‐dianhydro‐2,5‐dideoxy‐2,5‐diiodo‐D‐glucitol and 1,4:3,6‐dianhydro‐2,5‐dideoxy‐2,5‐diiodo‐L‐iditol were determined by 13C NMR spectroscopy, by invoking the field‐effect.