bluuebunny/crossref_metadata_2025 huggingface dataset:
The anion radical of azobispyridin N‐oxide
Authors: Eargle Dolan H. , Ventura‐Batista Maria Isabel , da Silva José Dias
Published: May 2005

The anion radical of the fully aromatic di‐N‐oxide system of azobispyridine N‐oxide was prepared and studied by ESR. Utilising computer simulation and CNDO computation the ESR spectrum was interpreted as follows:

Using appropriate equations the spin densities were calculated at

Ths semi‐quinoidal nature of the radical suggests a possible use as a spin label.
Carbon‐13 NMR spectra of coumarin and methoxycoumarins—a reinvestigation of charge density/Chemical Shift Relations
Authors: Günther Harald , Prestien Jörn , Joseph‐Nathan Pedro
Published: May 2005

The carbon‐13 NMR spectra of coumarin, 6‐, 7‐, 8‐methoxycoumarin, and 5,7‐, 7,8‐, 5,8‐ and 6,7‐dimethoxycoumarin have been measured and assigned. It is shown that substituent induced chemical shifts S(δ) in the mono‐ and disubstituted systems correlate well with the HMO atom‐atom polarisibilities πij of the parent compound: Si(δi) = 80.13 πij with a standard deviation of 1.42 ppm and a correlation factor of 0.994. Correlations between δ(13C) values and charge densities calculated by various semi‐empirical methods are less successful.
13C NMR spectra of thiophenes. III—Bromothiophenes
Authors: Sone Tyo , Fujieda Kunimi , Takahashi Kensuke
Published: May 2005

The 13C NMR spectra of all bromo substituted thiophenes have been obtained at 15·085 MHz. 13C signal assignments for monobromothiophenes have been confirmed by comparison with the spectra of their partially deuteriated derivatives; a revision is made for the assignment in 3‐bromothiophene. The substituent effect of bromine is generally additive for the 13C chemical shifts. The substituent effect on various types of 13C, 1H coupling constants is also obtained and discussed.
13C‐NMR‐spektroskopische und stereochemische Untersuchungen: XI—Konformationen von Bicyclo[3.3.1]nonanen und ihre Unterscheidbarkeit durch lanthanideninduzierte Verschiebungen
Authors: Schneider Hans‐Jörg , Lonsdorfer Michael , Weigand Eckehard F.
Published: May 2005

Ein Vergleich von gemessenen und aus stereospezifischen Inkrementen berechneten 13C‐Verschiebungen zeigt für Bicyclo[3.3.1]nonan und die entsprechende 9‐Hydroxy‐ und 9‐Oxo‐Verbindung eine dominierende Sessel‐Sessel‐Konformation CC an; einen ähnlichen Schluß ergibt das 1H‐NMR‐Spektrum des Ketons. 13C‐NMR‐Tieftemperaturmessungen sowie die Analyse der Temperaturabhängigkeit von 13C‐Verschiebungen in Bicyclo‐[3.3.1]nonan erlauben die Festlegung eines unteren Grenzwertes für den Energieunterschied zwischen der CC‐ und einer Boot‐Sessel‐Konformation BC von ΔG ≧ 5,85 kJ mol.−1 Die Möglichkeit zur Differenzierung flexibler Geometrien wie CC, BC und BB durch lanthanideninduzierte 1H‐ und 13C‐Verschiebungen wird unter Einschluß einer Fehlerbetrachtung untersucht. Das Auftreten mehrerer bzw. flacher Minima bei der computergestützten Geometrieanalyse der Pseudokontaktverschiebungen erlaubte nur den Ausschluß von BB‐Konformationen.
Eine neue Methode zur Beobachtung von Reaktionen im NMR‐Spektrometer. Oxidation von Trialkylboranen mit Luftsauerstoff
Authors: Friebolin H. , Rensch R.
Published: May 2005

Es wird ein Verfahren beschrieben, das eine Reaktion direkt im Spektrometer zu beobachten erlaubt, bei der kontinuierlich ein gasförmiger Reaktand über eine Glaskapillare in das rotierende 5 mm‐Proberöhrchen eingeleitet wird. Bei richtiger Versuchsführung werden die Signale durch die Kapillare und die aufsteigenden Gasblasen nur unwesentlich verbreitert (Halbwertsbreiten < 1 Hz). Eine Versuchsanordnung mit zwei Kapillaren gestattet, gleichzeitig zwei gasförmige Reaktanden zuzuführen and deren Reaktion zu verfolgen. Als Beispiel für die Anwendungsmöglichkeiten dieser Methode werden die bei der Autoxidation von Trialkylboranen aufgenommenen Protonenresonanzspektren gezeigt.
On the dimerization of α‐mercaptoacetone: An n.m.r. study
Authors: Cook Michael J. , El‐Khouly Abdel‐Azim
Published: May 2005

1H n.m.r. is used to show that α‐mercaptoacetone is formed as a mixture of monomer and a dimer. No evidence is found to support the previously claimed isolation of two dimeric species. The dimer dissociates to the monomer on standing as a solution in chloroform, but the monomer is dimerized by grinding. 1‐Mercapto‐3‐phenylpropan‐2‐one behaves similarly.
13C n.m.r. spectra of quercetin and rutin
Authors: Lallemand J. Y. , Duteil M.
Published: May 2005

The noise‐decoupled and gated‐decoupled 13C n.m.r. spectra of quercetin and rutin are studied and assignments are proposed. The previous assignments of carbons 2 and 4′, carbons 5 and 9, carbons 6 and 8 have been reversed.
Carbon‐13 n.m.r. spectra of branched carboxylic acids and their derivatives
Authors: Terent'ev A. B. , Dostovalova V. I. , Kh. Freidlina R.
Published: May 2005

13C n.m.r. spectra have been measured for 39 compounds with branched structures including carboxylic acids, their methyl and ethyl esters, nitriles and chlorinated esters. The results obtained indicate that the 13 C n.m.r. technique is applicable to structure assignment of acids and their derivatives containing various numbers of substituents on the chain. The dependence of the carboxylic carbon chemical shift on the number and structure of α‐positioned substituents has been determined. Calculation of the chemical shifts for branched carboxylic acids, esters and nitriles from the corresponding increments using the additivity scheme is shown to be possible in principle.
Systèmes Aromatiques à 10 Électrons π Dérivés de l'Aza‐3a‐pentalène: XXVI—Etude de quelques Dérivés Polyazapentaléniques en Résonance du Carbone‐13
Authors: Faure Robert , Vincent Emile‐Jean , Claramunt Rosa‐Maria , Elguero José
Published: May 2005

L'étude en RMN du 13C de neuf azapentalènes a été effectuée. Tous les signaux ont été attribués. Dans un cas on a mis en évidence des couplages entre les atomes de carbone et l'hydrogène porté par l'azote pyrrolique, fait exceptionnel dans le cas des hétérocycles aromatiques polyazotés. On démontre l'utilité de la RMN du 13C pour l'étude de la tautomérie annulaire.
Effets de Substituants en Série Diazolique et Diazinique‐1,3—Etude par Résonance Magnétique Nucléaire du Carbone‐13
Authors: Faure R. , Vincent E.‐J. , Assef G. , Kister J. , Metzger J.
Published: May 2005

Nous avons enregistré les spectres de RMN du carbone‐13 de thiones et de thioethers, en série diazolique et diazinique‐1,3, diversement substitués sur les atomes d'azote par des groupements alkyles, ainsi que certaines des structures oxygénées homologues. Toutes les raies de résonance ont été attribuées. Dans le cas des dérivés thiocarbonylés, nous montrons que l'équilibre thiol ⇄ thione est déplacé vers la forme thione, mais que la RMN du carbone‐13 ne peut conduire qu'à une évaluation qualitative de la position de cet équilibre. L'analyse des effets de substituant montre que, contrairement aux composés oxygénés, le groupement isopropyle adopte dans les dérivés soufrés une conformation privilégiée par suite de l'encombrement stérique dǔ à l'atome de soufre. La substitution par un groupement tertiobutyle conduit à des valeurs des effets γ inattendus. Nous attribuons ce phénomène à des déformations de cycle ou à des variations des angles valentiels de l'azote porteur du substituant, provoquées par des interactions stériques entre le substituant et le cycle correspondant. Nous relions ces modifications à certaines modalités de la réactivité, et à des résultats de spectroscopie photoélectronique.
The 13C n.m.r. spectra of polysubstituted benzenes. 1—the use of hexachlorobenzene as a reference for the structure elucidation of multisubstituted polychlorobenzenes
Authors: Heaton C. A. , Hunt M. H. , Meth‐Cohn O.
Published: May 2005

The use of 13C n.m.r. for structure elucidation of a series of products obtained by reaction of dialkylamines with 1,2‐dinitrotetrachlorobenzene has shown that the general problem of non‐additivity of substituent effects of contiguously substituted benzenes may be overcome, with these products, by the choice of a suitable standard. In this case hexachlorobenzene was used and the difference between the actual and calculated chemical shifts was small, allowing unambiguous structural assignment.
Protonenresonanz‐ und Röntgenstrukturuntersuchungen an unsymmetrisch substituierten Aminoboranen. III—Substituentenabhängigkeit der Struktur
Authors: Friebolin H. , Morgenthaler H. , Autenrieth K. , Ziegler M. L.
Published: May 2005

Eine Reihe unsymmetrisch substituierter N‐Methylaminoborane mit je einem Phenylring am Stickstoff und am Bor wurde synthetisiert und das in verdünnten Lösungen 1H NMR‐spektroskopisch bestimmte cistrans‐Isomerenverhältnis in Abhängigkeit von der Größe der aromatischen Reste und vom Zweitsubstituenten am Bor diskutiert. Die Strukturbestimmung aller untersuchter Verbindungen folgte aus der Lage des N‐Methylsignals mit Hilfe eines Zuordnungskriteriums, das durch die Röntgenstrukturanalysen von Methyl(4‐Br‐phenyl)amino‐chlorphenylboran und Methyl(2‐methyl‐4‐Br‐phenyl)amino‐chlor(2‐methylphenyl)boran erstellt wurde. Von Methylphenylamino‐chlorphenylboran ist im thermischen Gleichgewicht das Isomere mit cis‐ständigen Phenylringen stark begünstigt (90%). Beim Ersatz eines Phenylringes durch den 2‐Methyl‐ oder 2,6‐Dimethylphenylrest nimmt stets der Anteil des cis‐Isomeren ab. Substitution des Chloratoms am Bor durch Brom oder die Methylgruppe führt ebenfalls zu einer Verschiebung des Isomerenverhältnisses zum trans‐Isomeren hin. Absolut betrachtet sind jedoch nur bei den Verbindungen mit einer Methylgruppe oder mit einem 2,6‐Dimethylphenylrest am Bor, sowie bei denen mit je einem 2‐Methylphenylrest am Stickstoff und am Bor die trans‐Isomeren energetisch günstiger als die cis‐Isomeren. Für die gefundenen Substituenteneffekte werden sterische Hinderung und elektronische Abstoßung verantwortlich gemacht. Die Experimente zeigen außerdem, daß in allen Fällen das im Kristall bevorzugte Isomere auch im Lösungsgleichgewicht überwiegt.
Carbon‐13 n.m.r. studies of substituted bisalkylamino‐s‐triazines in acidic media
Authors: Tseng C. K. , Mihailovski A.
Published: May 2005

The carbon‐13 n.m.r. spectra of six substituted bisalkylamino‐s‐triazines are reported. The site of protonation of 2‐methoxy‐s‐triazines is shown to be at N‐1 or N‐3. The effect of trifluoroacetic acid on 2‐chloro‐s‐triazines is also discussed.
Long range 13C13C coupling constants. A review
Authors: Hansen Poul Erik
Published: May 2005

A large number of 13C13C coupling constants from a diversity of compounds are now available. Attempts have been made to classify this information in order to illustrate how these data are obtained, how signs are determined and how both two‐ and three‐bond couplings can lead to structural information. Coupling constants in aromatic compounds are now well documented, substituent effect trends have been established and correlations with bond orders are noticed. Comparison of 13C13C couplings with 13C1H couplings is mentioned. Theoretical calculations are dealt with, and these can now be properly evaluated as both magnitudes and signs of the experimental couplings are known. Finally, the occurrence of long range couplings in biosynthetic material is briefly surveyed.
Etude en RMN du 13C de Mérocyanines Benzimidazoliniques
Authors: Besse J‐P. J. , Samat A. M. , Le Gall J. Y. , Guglielmetti R. J. , Le Beuze A. J.
Published: May 2005

Une série de mérocyanines α‐oxo benzimidazoliniques diversement substituées sur la partie ‘phénolate’ et possédant une chaǐne grasse sur l'un des azotes hétérocycliques, a été étudiée en RMN du carbone‐ 13. Des substituants donneurs d'électrons provoquent une augmentation de la densité électronique sur le carbone méthinique C‐3 et une augmentation de l'alternance de la distribution de charge sur le pont diméthinique 3,4. Corrélativement un déplacement bathochrome de la transition électronique de plus basse énergie est observé. Par ailleurs, l'apparition de la résonance à champ faible du proton méthinique H‐3 semble due à une interaction spécifique intervenant entre ce proton et l'atome d'oxygène ‘phénolate’, ce qui suppose l'existence d'une configuration trans privilégiée pour les mérocyanines.
Carbon‐13 NMR studies of quinolines and isoquinolines. II. Chlorine–nitrogen interactions and N‐oxide effects
Authors: Su Ja‐An , Siew Ernest , Brown Ellis V. , Smith Stanford L.
Published: May 2005

Carbon‐13 chemical shift assignments are reported for four chloroquinolines, six chloroisoquinolines, one dichloroquinoline, four dichloroisoquinolines, four methylchloroquinolines, two methylchloroisoquinolines, quinoline N‐oxide, isoquinoline N‐oxide, five methylquinoline N‐oxides, two methylisoquinoline N‐oxides and three chloroisoquinoline N‐oxides. Chlorine substituent chemical shift (SCS) effects are reported for the alpha, ortho, meta, para and peri positions. Consistent patterns are observed for the para and peri positions, a vinylogous ortho pattern is reported and the additivity of these SCS effects is demonstrated. Alpha SCS effects vary widely from 1.1 ppm upfield in 1‐chloroisoquinoline to 6.7 ppm downfield in 4‐chloroquinoline. These results, together with those in the literature, permit the definition of steric and nitrogen lone‐pair contributions which modify the ‘normal’ chlorine SCS effect, and these modifying contributions are shown to be roughly additive.

Large (6–16 ppm) upfield shifts are observed for the carbons ortho and para to the N‐oxide group. The individual magnitudes of these shifts and their sum are constant and the effects are additive in substituted systems. A 9.5 ppm upfield shift is also observed for C‐8 in quinoline N‐oxides which is attributed to a space–charge interaction. Substituent chemical shift (SCS) effects for the chloro and methyl groups and the chemical shifts of the methyl carbons are essentially the same in the N‐oxides as in the parent heterocycles and are additive, except for those molecules where the substituent is adjacent to the N‐oxide moiety, in which cases substantial interactions are observed.
Carbon‐13 NMR studies of a series of benzylphenols
Authors: Nakai Yoshimi , Yamada Fukiko
Published: May 2005

Carbon‐13 NMR spectra of a series of benzylphenols and their O‐alkylated derivatives were recorded to find the substituent effects of the benzyl, hydroxybenzyl and alkoxybenzyl groups on the 13C chemical shifts. It was found that the methylene bridge carbons show signal shifts mainly due to the mesomeric effects of the OH and OCH3 substituents, and that in the case of ortho‐substituted benzyl compounds, the methylene carbon signals exhibit upfield shifts due to both mesomeric and steric effects.
Etudes d'Hétérocycles Pentagonaux Polyhétéroatomiques par RMN du 13C. Effets de Substituant, de la Benzocondensation et Etude de la Tautomèrie Prototropique en Série Benzothiazolique
Authors: Faure R. , Elguero J. , Vincent E. J. , Lazaro R.
Published: May 2005

Les spectres de résonance magnétique nucléaire due carbone‐13 de 43 benzothiazoles ont été enregistrés dans le diméthylsulfoxyde hexadeutérié. Tous les carbones ont été attribués de facon non ambiguë, grǎce aux effets de substituant sur les positions 4, 5, 6 ou 7. Nous discutons des variations des déplacements chimiques en fonction de la nature du substituant en 2 (équation triparamétrique du type: Δδ = aF+bR+cQ+d′), de l'annélation en série benzohétérocyclique et de la tautomérie prototropique en série benzothiazolique (dans le cas où le substituant en position 2 représente un groupement OH, SH ou NHR).
Some features of the 13C NMR of cephalosporins
Authors: Dereppe J. M. , Schanck A. , Coene B. , Moreau C. , Van Meerssche M.
Published: May 2005

13C NMR spectra of 4 cephalosporins have been interpreted. Some spectral characteristics are presented, allowing easy peak assignment of the 13C resonances of the cephalosporanic ring atoms. Quaternary carbon resonances were differentiated with the aid of relaxation time measurements.
Détermination de la Conformation et de la Configuration de Sulfoxydes à Sept Chainons, Intermédiaires de Synthèse d'un Analogue de la Biotine
Authors: Lacombe Liliane , Lavielle Solange
Published: May 2005

La conformation des deux sulfoxydes du diaza‐8,10 dibenzyl‐8,10 thia‐4 bicyclo[5.3.0]décanone‐9 est étudiée par RMN. L'examen des constantes de couplage permet de conclure que ces deux sulfoxydes existent sous des conformations chaises à liaison S→O axiale.
Détermination par RMN 1H et 13C de la Conformation Favorisée des Ozonides d'Acènes
Authors: Gobert F. , Altenburger‐Combrisson S. , Albouy J. P.
Published: May 2005

L'existence d'une conformation favorisée pour l'ozonide du diméthyl‐9,10 anthracène a été démontrée par RMN 1H et 13C. On retrouve cette měme conformation dans l'ozonide du diméthoxy‐9,10 anthracène et dans celui de l'anthracène qui a pu ětre observé pour la première fois en solution.
13C substituent effects in monosubstituted benzenes
Authors: Ewing David F.
Published: May 2005

A brief analysis is presnted of the current understanding of substituent perturbations in monosubstituted benzenes as determined by substituent induced carbon chemical shifts. A critical tabulation of the four substituent chemical shifts is given for c. 700 monosubstituted benzenes.
Dynamic 13C NMR studies on the internal rotation in tetraarylallyl anions
Authors: Bauer H. , Angrick M. , Rewicki D.
Published: May 2005

Proton noise decoupled 13C NMR spectra of lithium 1,1,3,3‐bis (2,2′‐biphenylylene)propenide and lithium 1,1,3,3‐tetraphenylpropenide have been studied, and complete assignments have been made based on several methods, e.g. 13C13C coupling constants of selectively labelled compounds and low‐temperature splitting of temperature dependent signals. The barriers to rotation about the partial double bonds of the allyl group have been determined by 13C DNMR resulting in the thermodynamic parameters of activation ΔG = 57 kj mol−1, ΔH≠ = 56.5 kj mol−1, ΔS≠ = −3J mol−1K−1 and ΔG = 55.5 kj mol−1, ΔH≠ = 63 kj mol−1, ΔS≠ = 26 kJ mol−1K−1, respectively. The results are discussed, including the hitherto known data about the topomerisation process.
A theoretical study of solvent effects on the 13C chemical shifts of some polar molecules
Authors: Jallali‐Heravi M. , Webb G. A.
Published: May 2005

Calculations of the dependence of 13C chemical shifts on the dielectric constant, ϵ, of the medium are reported using the INDO/S parameterized version of Pople's method together with the solvaton model. Satisfactory agreement with the available experimental data is obtained. The rather sensitive dependence of chemical shift upon ϵ suggests that polar solute—solvent interactions in aprotic media should be taken into account when considering 13C chemical shifts.
Radical reactions in the co‐ordination sphere of transition metals IX—phenoxy and cyclohexadienonyloxy radicals derived from 2,2′‐biphenyldiols and 2,2′‐thiobisphenols
Authors: Tkáč A. , Omelka L. , Jiráčková L. , Pospišil J.
Published: May 2005

From a series of antioxidants comprising 2,2′‐biphenyldiols, 2,2′‐thiobisphenols and 2,2′‐dithiobisphenol, free phenoxyls were prepared by oxidation with tert‐butylperoxyls co‐ordinated to Co(III) in non‐polar media at ambient temperature. Both the effect of extended conjugation as a consequence of the direct bond between the two aromatic nuclei and, also, the steric effect of alkyl substituents could be observed. In the presence of free tert‐butylperoxyls in excess, primary phenoxyls are transformed into cyclohexadienonyloxyls, which form stable radical complexes with Co(III). A mechanism for the formation of the cyclohexadienonyloxyls is suggested.
The rα‐structures of partially oriented 1,2,4,5‐and 1,2,3,4‐tetrachlorobenzene determined from their proton magnetic resonance spectra with natural abundance 13C‐satellites
Authors: Diehl P. , Dombi G. , Boesiger H.
Published: May 2005

By recording two spectra of the same molecule in different nematic liquid crystals, and analysing the data simultaneously, information has been obtained on the molecular structures of 1,2,4,5‐ (1) and 1,2,3,4‐tetrachlorobenzene (2). Carbon–hydrogen and carbon–carbon internuclear distance ratios, as well as bond lengths and bond angles, were computed and corrected for harmonic vibrations. Only part of the molecular structure of 2 could be derived with reasonable precision; the reasons for this limitation are discussed. The spectra of the two isomers were also analysed in isotropic solvents in order to determine the indirect coupling constants. One‐ and two‐bond 13C isotope effects on the chemical shifts of the protons were observed. The solvent effects of the different nematic liquid crystals on the structure were found to be small compared with the experimental error.
15N NMR spectroscopy 28—solvent effects on the 15N13C coupling constants of amides, imides, ureas and polypeptides
Authors: Kricheldorf Hans R.
Published: May 2005

The 15N13C coupling constants of 15N‐enriched acetamide, N‐acetylglycine anilide, phthalimide, α,α′‐bisphthalimido‐p‐xylene, N‐methyl‐N′‐phenylurea, poly‐L‐alanine and poly‐L‐valine were measured in various solvents. It was found that the 15N13C coupling constants depend largely on the nature of the solvent. Increasing acidity leads to higher one‐bond and lower two‐bond coupling constants. A change of concentration does not have any influence on the 15N13C couplings while a large increase in temperature leads to a slightly lower 1J(NC). It is concluded that solvent effects may limit the use of 15N13C coupling constants for the elucidation of solvent‐induced conformational changes.
13C NMR spectra of 1,3,4‐thiadiazole/thiadiazoline isomeric pairs
Authors: Rackham David M. , Morgan Sarah E. , Williamson W. R. Nigel
Published: May 2005

The 13C NMR spectra of four pairs of 1,3,4‐thiadiazole/thiadiazoline isomers have been recorded using broad band and off‐resonance proton decoupling techniques and in the coupled mode. Differences in the chemical shifts of the heterocyclic ring and the carbonyl carbons allow identification of the isomer present. Their IR and UV spectra are in agreement with literature reports for azole/azoline analogues.
ENDOR study on the anion radical of benzo[c]cinnoline
Authors: Fujita Hideo , Deguchi Yasuo , Ohya‐Nishiguchi Hiroaki , Ishizu Kazuhiko
Published: May 2005

The ENDOR spectrum was obtained for the benzo[c]cinnoline anion radicalin 1,2‐dimethoxyethane. The hfs constants of the protons correspond with those found by EPR spectroscopy, and also agree well with the qualitative tendency of the reported spin density distributions by HMO calculation.
Carbon‐13 NMR studies of monohydroxylated and monochlorinated derivatives of Z‐ and E‐p‐menthanes
Authors: Dauzonne D. , Goasdoue N. , Platzer N.
Published: May 2005

Carbon‐13 NMR spectra of the 18 monohydroxylated‐ and of the 18 monochlorinated‐p‐menthanes have been recorded. The data of these complete sets of isomeric compounds allow a comparison of the efficiency of the various empirical methods for the calculation of chemical shifts. The application to conformational analysis is proposed.
13C,13C coupling constants of conjugated dienes
Authors: Stöcker Michael , Klessinger Martin , Wilhelm Konrad
Published: May 2005

One bond 13C,13C‐ and 13C,1H‐coupling constants have been measured for some 1,2‐dimethylene‐cycloalkanes, as well as for 2,3‐dimethylbuta‐1,3‐diene and methylenecyclobutane. The results for 2,3‐dimethylbuta‐1,3‐diene confirm the findings for buta‐1,3‐diene, i.e. that J(C‐1, C‐2) is smaller for the diene than for the correspondingly substituted monoene. No differences have been found between the 1J(CC) exocyclic coupling constants of the dimethylene and monomethylene cycloalkanes.
Half‐chair conformations of unsaturated heterocyclic compounds
Authors: Fatheree D. M. , Deeg G. L. , Matthews D. B. , Russell J. G.
Published: May 2005

The vicinal proton coupling constants were obtained for some 6‐membered ring unsaturated heterocyclic compounds. The R values and ring dihedral angles were determined and found to be consistent with half‐chair conformations. Relative to saturated heterocyclic compounds, the effect of the sulfur atom on ring puckering was attenuated. However, an increase in ring puckering resulted from the sulfone group and was attributed to torsional energy.
Structural assignment of isomeric chain demethylated retinals by 1H NMR spectroscopy
Authors: Broek A. D. , Courtin J. M. L. , Mellema J. R. , Lugtenburg J. , Nicolay K. , Dijkstra K. , Kaptein R.
Published: May 2005

Geometric isomers of all‐trans‐9‐demethyl‐, −13‐demethyl‐ and −9,13‐bisdemethylretinal were prepared. The 360 MHz 1H NMR spectra of 13 geometric isomers of these three demethylated retinal systems have been measured. The chemical shift and coupling constant values in each case allowed an unambiguous assignment of the structure of each compound.
Carbon‐13 NMR studies. 96—carbon‐13 spectra of several polyhydroxylated 9,10‐dihydrophenanthrene and phenanthrene derivatives
Authors: Stoessl Albert , Stothers J. B.
Published: May 2005

The 13C spectra of eleven 9,10‐dihydrophenanthrene and twelve phenanthrene derivatives were recorded in order to examine the effects of hydroxy and methoxy substitution on the skeletal carbon shieldings. For each series, the parent compounds were the 2,4‐disubstituted derivatives with the others bearing 5‐, 6‐ and/or 7‐substituents, including the naturally occurring orchinol and loroglossol. The data should be helpful for examinations of related compounds. Some examples of particularly facile hydrogen‐deuterium exchange at aryl positions were encountered. Since these occur under apparently neutral conditions, suitable caution may be required in examinations of related compounds.
14N and 35Cl nuclear quadrupole resonance data for nitrogen mustards: Attempted correlations with chemical and biological activities
Authors: Buess M. L. , Bray P. J. , Sheppard D. W.
Published: May 2005

The 14N nuclear quadrupole resonance (NQR) spectra of several nitrogen mustard compounds are reported and analyzed in the framework of the Townes and Dailey theory. For the aniline derivatives, a correlation exists between l–σ (where l is the nitrogen lone pair electron density and σ the average NC sigma‐bond electron density) and the enhanced Hammett sigma constant σ−. An improved correlation is obtained between l–σ and σR−, which emphasizes the importance of resonance effects in determining l–σ. The increase of hydrolysis and alkylation rates with increasing values of l–σ is in agreement with the identification of the aziridinium ion as the intermediate in aromatic nitrogen mustard hydrolysis and alkylation. A possible correlation is noted between the 35Cl NQR spectra for some of the mustards and measures of toxic and antitumor activity.
1H NMR long‐range coupling in the assignment of stereochemistry to 4‐imidazolidinones
Authors: Połoński T.
Published: May 2005

Long‐range couplings were observed between protons attached to C‐2 and C‐5 of the 4‐imidazolidinone ring. Since 4J(25) has a measurable value only for a trans arrangement of H‐2 and H‐5, this coupling can be utilized as an easy method of identification of 4‐imidazolidinone stereoisomers.
15N NMR spectroscopy of some azines
Authors: Stefaniak L. , Roberts John D. , Witanowski M. , Webb G. A.
Published: May 2005

15N NMR shielding data are presented for 56 cyclic azines in 0.5 M dimethyl sulfoxide solutions with 0.01 M increments of Cr(acac)3 added for each nitrogen atom in the molecules. For the polyazines, the 15N signal assignments were based on 2J(NH) interactions and some INDO/S‐SOS shielding calculations. The effects of α‐, β‐ and γ‐methyl and conjugated ring substitution on nitrogen shielding are presented and discussed, as are the influences arising from fusion with alicyclic and aromatic rings at various positions. The effects of a second nitrogen atom on the shielding of the first one are shown to be critically dependent on both their relative positions and on the position of fusion of conjugated ring systems.
A 15N NMR study of some azoles
Authors: Stefaniak L. , Roberts John D. , Witanowski M. , Webb G. A.
Published: May 2005

15N NMR data are reported for 42 azoles, taken mostly at a standard concentration and in a common solvent (0.5 M dimethyl sulfoxide with a 0.01 M increment of Cr(acac)3 for each nitrogen atom present). Signal assignments were assisted by comparison with 14N line widths, the use of 2J(15N1H) couplings, and shielding calculations obtained by the INDO/S–SOS approach. The generally large differences in nitrogen‐shielding changes permitted rather facile shift assignments.
Application of NMR spectroscopy of chiral association complexes. 14—chiral recognition of terpene and cyclohexene hydrocarbons by 1H and 13C NMR
Authors: Offermann Werner , Mannschreck Albrecht
Published: May 2005

Chiral NMR recognition of terpenic and similar hydrocarbons by Ag(fod) and optically active lanthanide shift reagents is described. Twenty‐four 1H signals of eight compounds and, as a first report in the literature, eleven 13C signals of three compounds were split into signal pairs due to the respective enantiomers. Although the magnitudes of the splittings are not connected to the structure of the substrate molecules in an obvious manner, the configurations of the similar compounds camphene and epi‐β‐santalene were related empirically. All spectra were sufficiently resolved to allow separate integration of enantiomer signals; from the integrals the enantiomeric purities of seven non‐racemic mixtures were determined with good accuracy. The shift curves made several hitherto unknown assignments feasible.
Conformational studies by nuclear magnetic resonance in nematic phases: Benzyl chloride
Authors: Longeri Marcello , Chidichimo Giuseppe , Bucci Pietro
Published: May 2005

Spectra of benzyl chloride were analysed in two nematic phases (PCH and ZLI). The existence of the molecule as conformer with the CCl bond perpendicular or parallel to the benzene plane can be safely excluded. The data are consistent with a conformer with the CCl bond forming an angle of 60° with the benzene plane. A full discussion of the conformational problem was not possible owing to the small number of independent Dij couplings related to the internal motion. In addition, when dealing with low potential barriers, the LCNMR technique does not give rigorous answers.
Calculation of 13C NMR chemical shifts for aromatic carbons in polyalkylated benzenes
Authors: Sudmeijer O. , Wilson A. E. , Hays G. R.
Published: May 2005

13C NMR spectra of a large number of polyalkylated benzenes with branched and linear aliphatic chains have been studied. This resulted in the development of a general procedure that can be used for the calculation of the aromatic chemical shifts in any polyalkylated benzene.
Precise values of the 13C component vicinal coupling constants for calculating side‐chain conformations in amino acids
Authors: Reddy M. C. , Reddy B. P. Nagi , Sridharan K. R. , Ramakrishna J.
Published: May 2005

From consideration of 1H–1H vicinal coupling constants and 13C1H long‐range coupling constants in a series of amino acid derivatives, the precise values of 13C component vicinal coupling constants have been calculated for the three minimum energy staggered rotamers for the C(α)HC(β)H2 side‐chains of amino acids.
13C NMR study of some polychloro‐isobutane and ‐isobutene compounds
Authors: Pitkänen Maija , Laihia Katri , Schulze Klaus
Published: May 2005

The 13C chemical shifts and the carbon–proton coupling constants have been determined for some chlorinated isobutane and isobutene compounds. The one‐bond coupling constants in isobutane derivatives showed a regular increase with an increasing number of γ‐chlorine substituents. The three‐bond coupling constant of the methyl carbon decreased from 4.2 to 2.0 Hz as the number of chlorine substituents in the γ‐position increased. In the isobutene compounds, the vicinal coupling of C‐1 was larger to protons in a group that is trans with respect to a chlorine substituent on C‐1 than to those in the corresponding group cis to the chlorine. The vicinal coupling constants between atoms in geminal groups (on C‐2) seem to be affected by the orientation of the chlorine substituent on C‐1.
1H, 13C and 29Si NMR spectra of allylic trimethylsilanes
Authors: Alberts Vincent , Cuthbertson Matthew J. , Hawker Darryl W. , Wells Peter R.
Published: May 2005

Chemical shift and scalar coupling constant data have been obtained for the 1H, 13C and 29Si nuclei in allyl, methally, cis‐ and trans‐crotyl, cis‐2‐methyl‐2‐butenyl and 3‐methyl‐2‐butenyl derivatives of trimethylsilane.
Use of 13C isotope shifts for assignment of deuterium labelling sites in 1,3‐diphenylpropan‐1‐one
Authors: Bar Raphael , Sasson Yoel , Blum Jochanan
Published: May 2005

13C NMR spectroscopy was used for the unequivocal analysis of the mixture of products of RuCl2[P(C6H5)3]3‐catalysed transfer deuteriation of benzylideneacetophenone by (a) DCOONa/H2O, (b) HCOONa/D2O and (c) DCOONa/D2O. Signal assignments in the 13C spectra were obtained mainly from the deuterium‐induced 13C isotope shifts. The geminal 13C2H shift of the β‐carbon of deuteriated 1,3‐diphenylpropan‐1‐one is almost twice that for the α‐carbon.
Investigation of substituent effects on the 1H and 13C NMR spectra of (Z)‐N‐(arylmethylene)‐arylamine N‐oxides (α,N‐diaryl nitrones)
Authors: Arumugam N. , Manisankar P. , Sivasubramanian S. , Wilson D. A.
Published: May 2005

Substituent effects on the 1H and 13C chemical shifts of 18 differently substituted (Z)‐α,N‐diaryl nitrones [N‐(p‐X‐benzylidene)phenylamine N‐oxides (Series I) and N‐(benzylidene)‐p‐Y‐phenylamine N‐oxides (Series II)] have been obtained. A correlation has been found between the chemical shifts of the azomethine proton (H‐α) and the Hammett σ parameters and the Swain and Lupton F and R parameters. Correlations of the chemical shifts of C‐1 and C‐4′ in Series I, and of C‐α and C‐1′ in Series II, with the same parameters have been investigated. In addition, the chemical shifts of the aromatic protons and carbons of the p‐disubstituted (m‐disubstituted in one case) benzene rings correlated with the appropriate substituent increments (Zi). These correlations confirm the dual behaviour of the nitrone group and the presence of through‐resonance in these nitrones.
Electronic delocalization in NC and NN bonds
Authors: Brémond M. , Martin G. J. , Webb G. A. , Reynolds D. J.
Published: May 2005

For a series of compounds with NC or NN bonds, the CNDO/S parameterized calculations for Qπ, the electronic charge density on the nitrogen atom, and π bond orders Pπ provide evidence for the simultaneous dependence of the 15N chemical shift on both of these parameters. The multilinear regressions obtained produce high values for the regression coefficients. The results throw some light on the nitrogen lone pair delocalization mechanism.
13C NMR examination of some N‐thioaroylmorpholine–bromine adducts
Authors: Chiacchio Ugo , Corsaro Antonino , Bottino Francesco A.
Published: May 2005

The 13C NMR chemical shifts of three N‐thioaroylmorpholine–bromine adducts, previously used as synthetic intermediates, are compared and discussed in the light of the corresponding shifts of the parent thioamides and suitable model compounds. Chemical shift changes are interpreted in terms of the electronic perturbation resulting from bromine coordination at sulphur.
17O NMR spectroscopy: Effect of substituents on chemical shifts for p‐substituted benzoic acids, methyl benzoates, cinnamic acids and methyl cinnamates
Authors: Balakrishnan P. , Baumstark A. L. , Boykin D. W.
Published: May 2005

The 17O NMR spectra for a series of 17O‐enriched p‐substituted benzoic acids, methyl benzoates, cinnamic acids and methyl cinnamates in acetone at 40°C are reported. The carboxylic acids showed one signal (benzoic 250.5 ppm, SCS range p‐MeO to p‐NO2 = 10.5 ppm; cinnamic 254.1 ppm, SCS range p‐MeO to p‐NO2 = 5.4 ppm). The esters showed two signals [methyl benzoate (CO) 341.3 ppm and (OCH3) 128.0 ppm; methyl cinnamate (CO) 339.9 ppm and (OCH3) 134.2 ppm]. The SCS ranges for the carbonyls of the esters were larger than those for the corresponding acids, while those for the OCH3 groups of the esters were slightly smaller. The carbonyl data gave good correlations with σ+ constants, while the OCH3 data gave at best only a poor correlation with σ constants. Dual substituent parameter treatment improved the correlations for all the data using σR+ constants. The ratios of ρI to ρR+ were similar for all the sets of data.
Electric field effects in 13C NMR of some quaternary morphinan derivatives
Authors: Theuns Hubert G. , Janssen Richard H. A. M. , Biessels Hubertus W. A. , Salemink Cornelis A.
Published: May 2005

13C NMR chemical shifts are assigned for some quaternary morphinan derivatives, including the ‘minor isomer’ of the thebaine N‐oxides. In quaternary morphinan alkaloids having an 8.14‐double bond, electric field effects cause unusual 13C NMR shifts.
Advertising for the introduction of an age‐sensitive product
Authors: Grosset Luca , Viscolani Bruno
Published: May 2005

An age‐dependent market segmentation is often observed for real life products. We introduce a simple age‐structured model for the advertising process of a firm and the consequent goodwill evolution. The model formal structure is characterized by a first order linear partial differential equation. We formulate the advertising problem for a new product introduction as a distributed parameter optimal control problem and solve it using the suitable maximum principle conditions. Then, we discuss and solve the same problem under the assumption that a finite set of boundedly age‐selective advertising channels are available, instead of one infinitely age‐selective channel. Copyright © 2005 John Wiley & Sons, Ltd.
DNMR investigations on 3,3‐Dihalo‐2,2,4,4‐tetramethylpentanes
Authors: Kalinowski Hans‐Otto , Röcker Erwin , Maier Günther
Published: May 2005

The 1H and 13C NMR spectra of 3,3,‐diiodotetramethylpentane (2), 3,3‐dibromotetramethylpentane (3), and 3,3‐dichlorotetramethylpentane (4) are temperature dependent. The activation parameters for the tert‐butyl group rotation in 2–4 have been determined. The 13C NMR chemical shifts are discussed.
13C NMR spectral analysis of dihydrobenzofuran lignans
Authors: Agrawal P. K. , Rastogi R. P. , Osterdahl B.‐G.
Published: May 2005

The assignments of the 13C NMR shift values of the dihydrobenzofuranoid lignans cedrusin and dihydrodehydrodiconiferyl alcohol, their respective 4‐O‐β‐D‐glucosides and their acetates have been made. The furanoid stereochemistry in 8,3′‐lignans could be deduced from comparative 13C NMR data.
Stereochemistry of alkyl 3‐substituted 4‐halotetrahydro‐2‐oxo‐3‐furancarboxylates: 2—1H and 13C NMR spectra
Authors: Gryff‐Keller A. , Kołodziejek W. , Prejzner J.
Published: May 2005

The 1H NMR parameters of methyl 3‐substituted cis‐4‐halotetrahydro‐2‐oxo‐3‐furancarboxylates are reported, with assignments of the ring protons based on solvent‐induced changes in the vicinal trans coupling constants, 3J(H‐4, H‐5). Preferred conformations, ce with a pseudo‐equatorial halogen for the cis isomers and ta with a pseudo‐axial halogen for the trans isomers, have been suggested on comparison of the magnitudes of J(trans) and J(gem) in both series. The 3J(13CH3, H‐4) values measured for methyl cis‐4‐bromotetrahydro‐3‐methyl‐3‐furancarboxylate, methyl trans‐4‐bromotetrahydro‐3‐methyl‐3‐furancarboxylate and trans‐3,4‐dibromodihydro‐3‐methyl‐2(3H)‐furanone have confirmed the stereochemical assignments.
Combined 35Cl and 79Br NQR Zeeman effect study in α‐bromo‐p‐chloroacetophenone
Authors: Ramakrishna V. , Rao D. Krishna , Satyanandam G. , Murty C. R. K.
Published: May 2005

A combined nuclear quadrupole Zeeman effect study on a single crystal of α‐bromo‐p‐chloroacetophenone was carried out for 35Cl and 79Br resonances using recording and oscilloscope displays, respectively. The orientations of the principal field gradient directions, the values of the asymmetry parameter, the crystal class (orthorhombic) and the bond characters were determined and the results are discussed.
Assignment of relative configuration in cyclopentenes from proton chemical shift increments
Authors: Hunter G. , Miller J. A. , Moore M. , Ullah G. M.
Published: May 2005

The ‘syn‐upfield’ rule for vicinal shielding by methyl and chlorine substituents has been confirmed for a series of 4‐chlorocyclopentenes, and used to make configurational assignments in cases where conclusions based on vicinal proton coupling are not reliable. The methoxymethyl group should be added to those substituents whose effect on vicinal protons can be deshielding, irrespective of geometry.
13C NMR study on the methoxy carbon chemical shifts in chloro‐substituted anisoles and guaiacols
Authors: Kolehmainen E. , Knuutinen J.
Published: May 2005

The 13C NMR chemical shifts of methoxy carbons in chlorinated anisoles and guaiacols have been measured for acetone‐d6 solutions. Multiple linear regression analysis, and also ‘simple sum rule’ calculations, have been used to estimate the effects of the chlorine atoms (the position and degree of substitution) on the chemical shifts. The most important effects have shown to be due to the chlorine atoms adjacent to the methoxy and hydroxy substituents. For chlorinated guaiacols, the greatest effect is due to the chlorine atom adjacent to the methoxy group. For chlorinated anisoles, the substituents adjacent to the methoxy group (2,6‐disubstitution) cause large effects. For both groups of compounds, the chemical shifts are also greatly influenced by the number of chlorine substituents. Using the three most important independent variables, the average differences between the observed and calculated chemical shifts are ca 0.2 ppm for anisoles and 0.1 ppm for guaiacols. For chloroguaiacols, the corresponding difference was only 0.1 ppm when calculations were performed using single substituent effects.
Substituent effects on 13C and 15N chemical shifts in triazenes studied by principal components multivariate data analysis
Authors: Dunn W. J. , Lins C. , Kumar G. , Manimaran T. , Grigoras S. , Edlund U. , Wold S.
Published: May 2005

Principal components analysis was applied to the 13C and 15N chemical shift data on a series of fifteen 1‐(para‐substituted‐phenyl)‐3‐acetyl‐3‐methyltriazenes. It was found that the halogen‐substituted triazenes formed a class, based on substituent effects, which was different from the remaining eleven triazenes. A one‐component model described the halogen class, whereas a two‐component model was necessary for a description of the second class. In the second class, substituents tended to cluster to form groups depending on their electronic character.
Phosphorus‐containing groups in analyses of carbon‐13 chemical shifts of 1‐hetera‐4‐cyclohexanones
Authors: Hirsch Jerry A. , Banasiak Kenneth
Published: May 2005

The 13C NMR chemical shifts of a series of phosphorinanes and the corresponding 4‐phosphorinanones have been evaluated using ‘double difference’ plots. Most of the compounds fit the same linear relationships for the carbons alpha and beta to the hetera group previously found for the analogous sulfur, oxygen and nitrogen six‐membered heterocycles, suggesting that these phosphorus compounds possess similar chair conformations. For the carbons gamma to the hetera group, the plots suggest that there are transannular interactions between the trivalent phosphine groups and the carbonyl group, similar to that previously observed for the sulfide group. In these 1‐hetera‐4‐cyclohexanones, transannular interactions appear whenever a lone pair of electrons on a second‐row heteroatom is present in the proper conformation for interaction with the carbonyl group.
The structural dependence of vicinal 13C13C coupling constants in s‐cis‐butane and cis‐butane
Authors: Klessinger Martin , Cho Jung‐Hyuck
Published: May 2005

The dependence of three‐bond 13C‐13C couplings of cis‐butane and cis‐butene on the valence angle, the torsional angle of the methyl groups and methyl and methylene substituents is discussed on the basis of INDO‐SCPT calculations. The results support the interpretation of the experimental couplings between the bridgehead carbons of bicyclic hydrocarbons based on a multiple‐path mechanism.
A mass‐spectrometric investigation of the radiolysis of methane by reactor radiation
Authors: Scott W. M. , Wilson H. W.
Published: May 2005

An ‘on‐line’ mass spectrometer technique which permits the examination of the effects of radiation at short times has been used to study the radiolysis of methane by reactor radiation. The mass spectrometer used was the AEI MS‐10. The experiments were carried out using the UTR‐100 reactor at East Kilbride and the results using highly purified methane and methane with radical scavangers are described. With pure methane at 0·25% conversion, G‐values of 0·36, 0·24, 0·07 and 0·03 were calculated for C3H8, C4H10, C5H12 and C6H14 respectively. No pressure‐dependent reactions were observed in the pressure range 50 to 135 torr. The effects of radical scavengers were investigated and irradiation of methane containing 1 to 2% ethylene gave G‐values for C2H6, C3H8, n‐C4H10, iso‐C4H10, C5H12 plus C6H14, C2H2, C3H6, C4H8 and C5H10 of 1·33, 2·02, 2·03, 0·35, 0·34, 0·30, 0·37, 0·90 and 0·31. The effects of adding 1 to 2% propylene and 1 to 2% oxygen were also examined and the results are described in the paper. Experiments with smaller quantities of oxygen emphasize the importance of removing all oxygen from the system before radiolysis begins. The paper then goes on to discuss in some detail the processes involved in the radiolysis of methane and concludes with suggestions for future work.
The mass spectra of carboxylic acids—I: Fragmentation mechanisms in maleic and fumaric acids and related compounds
Authors: Benoit F. , Holmes J. L. , Isaacs N. S.
Published: May 2005

The mass spectra of maleic acid, maleic acid‐2,3‐d, fumaric acid and fumaric acid‐2,3‐d have been examined and fragmentation mechanisms are proposed for these compounds. The molecular ion of the cis‐acid fragments via H atom transfer from one carboxyl group to the other followed by loss of CO2. The trans acid does not fragment significantly by this route and the former effect may be characteristic of molecules containing two carboxyl groups cis‐oriented to each other. This hypothesis was successfully tested by examining the mass spectra of citraconic, itaconic and phthalic acids. Itaconic and mesaconic acids show some of the fragmentation characteristics of fumaric acid.
Electron‐impact studies—LI: Hydrogen randomization in the stilbene molecular ion
Authors: Donaghue P. F. , White P. Y. , Bowie J. H. , Roney B. D. , Rodda H. J.
Published: May 2005

Hydrozen randomization precedes the formation of M+·  H· and M+·  CH3· species from the stilbene molecular ion at 15 eV. The carbon atom involved in the M+·  CH3· elimination originates randomly from the whole molecule. The [M  15] ion (m/e 165) in the spectra of stilbene and 9,10‐dihydrophenanthrene is produced from a common ion.
Routine, accurate mass measurement up to m/e 1700 using vapor‐deposited silver bromide plates
Authors: Hignite C. , Biemann K.
Published: May 2005

The utility of photoplate recording of high resolution mass spectra for routine, accurate mass measurement is extended to mass 1700 (and probably beyond) by the use of evaporated silver bromide plates. Data illustrating the accuracy obtainable and the dynamic range are presented.
The problem of the azatropylium ion: Hydrogen elimination from the molecular ion of γ‐picoline
Authors: Neeter R. , Nibbering N. M. M. , De Boer Th. J.
Published: May 2005

Comparison of the mass spectrum of γ‐picoline with that of analogues, specifically deuterated in the methyl group, the ring or both, has shown that the molecular ion loses the α,β and methyl hydrogen atoms (ω‐hydrogen') in the ratio 1.43: 1: 1. 13. The same trend is found for the elimination of HCN from the molecular ion. Moreover, a value of 1.52 is found for the isotope effect, expressing the favoured loss of H over D, irrespective of its position.