bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen nuclear magnetic resonance spectroscopy. Nitrogen‐15 and proton chemical shifts of methylanilines and methylanilinium ions
Authors: Psota Linda , Franzen‐Sieveking Marcia , Turnier Jocelyne , Lichter Robert L.
Published: May 2005

Nitrogen and carbon electron densities of the toluidines and xylidines have been recalculated by the INDO method; previously published errors have been corrected. Although the nitrogen‐15 chemical shifts of these compounds still display the earlier suggested correlation with σ and total electron densities, the calculated inverse correlation with proton electron densities has been shown to be incorrect. Methyl proton chemical shifts of these compounds display no meaningful correlation with the nitrogen shifts. The nitrogen chemical shifts of the toluidinium and xylidinium ions correlate moderately well with the 13C chemical shifts of the analogous di‐ and tri‐methylbenzenes.
Etude par RMN du Proton de la Stéréochimie de Composés Ethyléniques Trisubstitués. Calcul Empirique et Calcul par Incréments de la Constante d'Ecran
Authors: Brémond M. , Martin G. J. , Cariou M.
Published: May 2005

Nous avons appliqué les approximations de Pascual et de Tobey pour évaluer le déplacement chimique d'un proton éthylénique dans le cas de substituants qui causent souvent des difficultés d'attribution de signaux. Les résultats des calculs empiriques de la différence d'écran entre les protons éthyléniques des deux configurations Z et E sont comparés aux valeurs expérimentales des déplacements chimiques dans une série d'aryl‐2 propène nitriles. La configuration Z s'avère correspondre au proton le moins blindé et les effets de solvants observés concordent avec cette attribution. Lorsque la configuration Z est prépondérante, sa nature est établie sans ambiguïté, car de très faibles quantités de l'autre isomère E ont pu ětre obtenues et étudiées. Les résultats de cette méthode sont satisfaisants et permettent de déterminer de nouveaux paramètres d'incréments additifs (NH2, OH, ONa).
13C‐NMR‐Spektren von Tetracyclo[4.1.0.02,4.03,5]heptanen, Tetracyclo[5.1.0.02,4.03,5]octanen und Tricyclo[4.1.0.02,7]hept‐3‐enen. Ungewöhnliche δ‐ und γ‐Substituenteneffekte
Authors: Christl Manfred , Buchner Wolfgang
Published: May 2005

13C‐NMR‐spektroskopische Daten von elf Tetracyclo[4.1.0.02,4.03.5]heptanen, zwei Tetracyclo‐[5.1.0.02,4.03,5]octanen und zwölf Tricyclo[4.1.0.02,7]hept‐3‐enen werden mitgeteilt. In den Tetracycloheptanen üben 7‐ständige Halogene große δ‐Substituenteneffekte aus, die im endo‐Fall das C‐4‐Signal um ca. 6 ppm nach tieferem Feld rücken und im exo‐Fall am C‐3‐Signal von der Natur des Halogens abhängige Hochfeldverschiebungen hervorrufen, wobei Fluor mit 9,1 ppm das Maximum erreicht. Ein Orbitalmodell zur Deutung der Hochfeld‐δ‐Effekte wird vorgeschlagen. Die fluorhaltigen Verbindungen enthüllen einen Zusammenhang zwischen den Substituenteneffekten und den zugehörigen 13C19F‐Kopplungskonstanten. 5‐Substituenten in Tricycloheptenen sind γ‐Substituenten von C‐1, C‐3 und C‐7 und verschieben die Absorptionen dieser Kerne nach tieferem Feld. Die Substituentenabhängigkeit der Effekte folgt etwa jener in 1‐substituierten Adamantanen, ihre Gröβe übersteigt aber im Fall von C‐7 die Adamantanwerte um ein Mehrfaches, wobei sich Brom mit 15,5 ppm als Spitzenreiter profiliert.
A contradistinction in the magnetic (13C NMR spectroscopy) and chemical behaviour of 4‐Oxo‐4,5,6,7‐tetrahydroindole derivatives
Authors: Ramadas S. R. , Padmanabhan S.
Published: May 2005

Carbon‐13 NMR data are reported for a series of 1,2‐diaryl‐4‐oxo‐4,5,6,7‐tetrahydroindoles, 6‐methyl‐2‐phenyl‐4‐oxo‐4,5,6,7‐tetrahydrobenzofuran and 1‐,6‐dithiaindan‐4‐one. The chemical shifts δ 193–196, δ 195.5 and δ 184 are identified for the carbonyl carbon (C‐4) in the tetrahydroindoles, tetrahydrobenzofuran and dithiaindan derivatives, respectively. These shifts are located in the same region as that reported for the corresponding carbonyl carbon in aryl conjugated ketones. An excellent correlation between the chemical shift for the carbonyl carbon and the chemical reactivity of the ketonic function is noticed in the case of the latter two series of ketones while such a correlation is typically absent in the case of the 4‐ketotetrahydroindole derivatives.
Carbon‐13 magnetic resonance spectra of aldosterone, 18‐hydroxydeoxycorticosterone and 18‐hydroxyprogesterone
Authors: Genard P.
Published: May 2005

The 13C NMR spectra of aldosterone in various solvents show the presence of only the tautomeric forms with hemi‐acetal (11–18) and hemi‐ketal (18–20) bridges. Solutions of 18‐hydroxy‐11‐deoxycorticosterone (6) and of 18‐hydroxyprogesterone in CDCl3 contain mainly the hemi‐ketal (18–20) tautomer. Solutions of 6 in more polar solvents also contain—although to a lesser extent—a second form which may be a dimer or, more probably, a form representing two retamers with appreciable populations at the 21‐CH2OH group.
Spectroscopie RMN du Carbone‐13 de Thiocétones Aliphatiques: Propanethione et Dérivés, Thiocétones Bicycliques et α Cyclopropaniques
Authors: Andrieu Claude G. , Debruyne Danièle , Paquer Daniel
Published: May 2005

Les spectres de RMN du carbone‐13 de diverses cétones et thiocétones aliphatiques ont été déterminés et expliqués. Le groupe thiocarbonyle est plus sensible à l'effet inducteur des groupes alkyles voisins que le groupe carbonyle. II n'existe pas de relation directe avec la transition π*←n. L'effet mésomère est plus grand dans le groupe cyclopropylthiocarbonyle que dans le groupe cyclopropanoyle. L'influence du thiocarbonyle sur les atomes voisins est plus importante que celle du carbonyle.
Etude en RMN de l'Association des Sels de Lanthanides avec des Phénols; Application à la Détermination de Structure de Polyphénols Naturels
Authors: Davoust Daniel , Massias Marcel , Molho Darius , Platzer Nicole , Basselier Jean‐Jacques
Published: May 2005

L'interaction des sels de lanthanide avec des phénols en solution dans le DMSO a été étudiée en RMN en vue de la détermination de structure de polyphénols naturels. Par des expériences de compétition intermoléculaire, il a étée possible de mettre en évidence des différences de réactivité en fonction de la nature et de la position des substituants. Des règles empiriques de réactivité ont été proposées; elles ont permis d'interpréter les variations de déplacements chimiques observées dans le spectre de RMN de polyphénols naturels (flavones, xanthones) en présence de sel de lanthanide.
The 13C, H coupling constants in structural and conformational analysis. III.. Long‐range carbon–hydroxyl proton couplings as evidence of hydrogen bonding in some acylphloroglucinols
Authors: Äyräs Pertti , Widén Carl‐Johan
Published: May 2005

Proton coupled 13C NMR spectra have been recorded for some acylphloroglucinol derivatives. Significant couplings over two, three and four bonds were observed between the hydroxyl proton and aromatic carbons for those compounds where the hydroxyl group is hydrogen bonded strongly enough to the carbonyl carbon of the acyl side chain. Typical values were 2J = 4.8 Hz, and 3J = 5.6 Hz or 6.7 Hz corresponding to dihedral angles of c. 0° and c. 180°, respectively; the dihedral angle is defined as the angle between the O—H bond and the plane of the aromatic ring. A stereospecific 4J(COH) value of 1.2 Hz for a ‘W’ arrangement of coupled atoms was also found. An interesting example of ‘virtual’ J(CH) coupling was observed in the proton coupled spectrum of 1‐butyrylphloroglucinol 2‐monomethyl ether in acetone‐d6 caused by the accidentally equal chemical shifts of the two ring protons.
Stereochemical aspects of proton chemical shifts. VII. The γ effects of hydroxyl, methoxyl and methyl substituents
Authors: Tavernier Dirk , Anteunis Marc J. O.
Published: May 2005

The 1H NMR chemical shifts of some hydroxy, methoxy or methyl substituted trans‐decalins, trans‐1, 3‐dioxadecalins and cyclohexanes are reported. It is concluded that the replacement in a g+g+ HCCCH fragment of one hydrogen by hydroxy, methoxy or methyl results in a modest (0.1 ppm) upfield shift of the other hydrogen atom. Experimental limitations to the transferability of shift increments from one molecular environment to another are demonstrated. The syntheses of 1α,5β‐dimethoxy‐ and 1β,5α‐dimethoxy‐trans‐decalin are given.
Determination of pKa values using 15N and 13C nuclear magnetic resonance spectroscopy. The case of apramycin
Authors: Paschal Jonathan W. , Dorman Douglas E.
Published: May 2005

By comparison of pKa values derived from 15N and 13C nuclear magnetic resonance (NMR) spectroscopies, the assignment of the 15N resonances of apramycin is completed. 13C NMR spectra appear to provide accurate pKa determinations with this aminoglycoside. Hydroxylation adjacent to one of the basic nitrogens of apramycin appears to change the pKa values of all five amines of the molecule.
Etude par RMN 13C d'Hydrocarbures Benzéniques Tricycliques Condensés
Authors: Gobert F. , Gruber R. , Cagniant D. , Cagniant P.
Published: May 2005

Quelques benzocyclènes tricycliques ont été étudiés en RMN i3C. Il a été montré que les perturbations dues à l'interaction des deux cycles semiaromatiques restaient localisées aux carbones quaternaires.
Détermination par Résonance Magnétique Nucléaire de la Configuration d'alcools Bicycliques [4.2.0] et Tricycliques [6.4.0.02,7] ou [5.4.0.02,6]
Authors: Bouquant James , Chuche Josselin , Convert Odile , Furth Bernard
Published: May 2005

Les configurations d'une série de bicyclo[4.2.0]octanols sont déterminées par résonance magnétique nucléaire du proton en présence d'un réactif lanthanidique [Eu(dpm)3]. La détermination des paramètres intrinsèques des adduits formés entre les réactifs et ces substrats a permis de dégager un certain nombre de critères d'attribution des stéréochimies. De plus, cette étude met en évidence, contrairement à ce qui est généralement admis, que la constante de couplage vicinale trans entre les protons cyclobutaniques peut ětre supérieure à celle entre protons cis. Les attributions des configurations sont confirmées par une étude en 13C. En se basant sur les résultats précédents, il est possible d'établir sans ambiguïté les configurations de tricyclo[6.4.0.02,7]dodécanols et tricyclo[5.4.0.02,6]undécanol.
Effet de Solvant en Résonance Magnétique Nucléaire du Carbone‐13. V. Autoassociation des Cétones Aliphatiques et Alicycliques Saturées
Authors: Tiffon Bernard , Dubois Jacques‐Emile
Published: May 2005

L'influence de l'autoassociation en phase liquide de 15 cétones sur la constante d'écran en RMN du carbone du carbonyle est déterminée. On montre que le terme de constante d'écran correspondant ne dépend que du moment dipolaire et du volume molaire de la cétone, que celle‐ci soit aliphatique ou alicyclique. La distance moyenne séparant les deux carbonyles dans le modèle d'association bimoléculaire où les deux dipǒles sont antiparallèles est évaluée. Cette distance croǐt avec l'encombrement des substituants de 3,1 Å pour l'acétone à 4,75 Å pour la cétone encombrée C(Et)3COC(Me2tBu) pour laquelle l'effet de l'autoasssociation est encore important. Les cyclanones s'inscrivent dans ce modèle mais présentent un effet d'autoassociation plus marqué que les cétones aliphatiques ayant le měme nombre de carbones.
Applications of NMR spectroscopy of chiral association complexes. 6. rotation about the C(sp2)—C(aryl) bond in 2,6‐disubstituted pivalophenones
Authors: Holík Miroslav , Mannschreck Albrecht
Published: May 2005

For the investigation of the barrier to rotation about the C(sp2)—C(aryl) bond in non‐planar pivalophenones five derivatives were prepared and their 1H and 13C NMR spectra assigned. Methyl and bromine groups in the 3‐position have opposite substituent effects on the chemical shifts of the 1H and 13C signals of Me2 and Me4. The ΔG values were determined from the coalescence temperatures of the signal splittings generated by the addition of optically active shift reagents. The accuracy of this method was estimated by using different signals of 3‐bromo‐2,4,6‐trimethylpivalophenone and by computer simulation of the line shape. A buttressing effect of substituents in the aromatic ring was observed. A change of the twist angle by the substitution of methyl by bromine in the tert‐butyl group was suggested in order to explain the changes in ΔG and the chemical shifts.
Carbon‐13 magnetic resonance studies of cyclic compounds. 2. Carbon‐13 chemical shift parameters for equatorial and axial substituents in cyclohexane: The substituents methyl, ethyl, isopropyl, methoxy and phthalimido
Authors: Booth H. , Everett J. R. , Fleming R. A.
Published: May 2005

Carbon‐13 chemical shift parameters for equatorial and axial substituents in cyclohexane are reported for methyl, ethyl, isopropyl, methoxy and phthalimido substituents. The usefulness of the alkyl parameters is demonstrated by the agreement between calculated and observed 13C shifts for trans‐1,4‐dialkylcyclohexanes (alkyl = Me, Et, i‐Pr) and for both conformations of cis‐1,4‐dialkylcyclohexanes (alkyl = Me, Et, i‐Pr).
13C NMR of polycyclic aromatic compounds. A review
Authors: Hansen Poul Erik
Published: May 2005

The analysis of the 13C NMR spectra of polycyclic aromatics is discussed briefly. Basic trends of chemical shifts are mentioned, but the emphasis is placed on substituent‐induced chemical shifts (SCS). Semi‐empirical approaches and regressional analysis are treated. The factors controlling SCS are discussed and steric, mesomeric and π‐inductive effects are analysed.

CH, CF, CC, CP and C, Metal coupling constants are investigated and the influence of steric effects, bond order, mesomerism and angle distortions in relation to some of these coupling constants is discussed. Relaxation times are described in a series of compounds. The effects of dissolved oxygen or radicals are shown and the use of T1 as a monitor of molecular tumbling is depicted. The impact of 13C NMR on the understanding of charged aromatic species, both positive and negative ions, is mentioned and new information about reaction intermediates in electrophilic aromatic substitution is outlined. The possibility of using 13C NMR to investigate charge transfer complexes is also discussed. Among other subjects treated are automerization, deuterium exchange and biosynthetic incorporation of labelled materials and, finally, quantitative analysis is briefly touched upon.
Sur la Similitude des Déformations du Noyau Cyclohexanonique Induites par les Groupes Tertiobutyle et gem‐Diméthyle
Authors: Grenier‐Loustalot M. F. , Iratçabal P. , Lichanot A. , Metras F.
Published: May 2005

L'étude par RMN á 250 MHz de six chlorodiméthyl–4,4 cyclohexanones et la connaissance de deux structures cristallines permettent les conclusions suivantes: dans les séries des tertiobuty–4 et diméthyl–4,4 cyclohexanones l'influence du carbonyle et du chlore sur les constantes de couplage 2J et 3J sont similaires. Par ailleurs, les groupes gem diméthyle et tertiobutyle induisent sur le noyau cyclohexanonique des constantes de couplage 4J(H–3′–C–3–C–4–C–4–C–5–H–5′) fortes et semblables; ces observations s'interprétent bien en termes de deformation locale de structure et d'additivité de ces déformations. La détermination d'angles diédres parla méthode de Lambert et par diffraction des rayons X montre, d'une part, une bonne transférabilité des structures de l'état solide á l'état dissous, confirme, d'autre part, la trés grands similitude structurale des dérivés tertobutylés et gem diméthylés de la cyclohexanone.
Unusual carbon shielding effects of cyclopropanes and double bonds in strained bicyclo[3.1.0]hexanes and cyclopentenes
Authors: Christl Manfred , Herbert Rainer
Published: May 2005

Carbon‐13 shieldings and one‐bond 13CH coupling constants of bicyclo[2.1.1]hexane, bicyclo[2.1.1]hex‐2‐ene, tricyclo[3.1.1.02,4]heptane and benzvalene are presented and compared to the data of related compounds. If a bicyclo[3.1.0]hexane system is part of a rigid skeleton, the cyclopropane ring exerts specific γ substituent effects of two kinds. In the case of the bicyclohexane boat form an upfield shift of the C‐3 signal is observed and in the case of the chair form a downfield shift of 15–20 ppm. Compared to the corresponding cyclopentanes the double bond in strained cyclopentenes causes downfield shifts of the C‐4 absorption. This effect increases with increasing strain, reaching a 45.9 ppm maximum in benzvalene. Hence it is the only known bicyclo[1.1.0]butane having a reversed order of carbon shieldings. The downfield shifts are explained by means of simple orbital interaction schemes.
INDO‐FPT calculations of the dihedral angle dependence of 1J(CH) in groups adjacent to a cationic carbon atom
Authors: Pachler K. G. R. , Pachter R.
Published: May 2005

INDO‐FPT calculations of 1J(CH) in the hypothetical ethyl cation are presented in support of a recently derived empirical relationship which describes the effect of a cationic carbon on 1J(CH) in an adjacent CHn group.
13C‐NMR‐Untersuchungen zur Strukturaufklärung von Polysacchariden und deren Methylderivaten
Authors: Friebolin H. , Keilich G. , Frank N. , Dabrowski U. , Siefert E.
Published: May 2005

Die 13C‐NMR‐Spektren einer Reihe von Polysacchariden und ihrer Methylderivate wurden aufgenommen, zugeordnet und für die methylierten Polysaccharide außerdem die Kopplungskonstanten 1J(CH) bestimmt. An Beispielen wird gezeigt, daß die Zahl der 13C‐Signale und deren Lage im Spektrum Aussagen über den Aufbau der Polysaccharide, sowie über die Verknüpfungsstellen der glykosidischen Bindung gestatten. Während aus den Signallagen die anomere Konfiguration nicht eindeutig zu ermitteln ist, gelingt dies bei den methylierten Polysacchariden mit Hilfe der Kopplungskonstanten 1J(C‐1, H); diese weisen Unterschiede von durchschnittlich 12 Hz (aber mindestens 5 Hz) zwischen den α‐ und β‐Anomeren auf, wobei die gröβeren Werte den α‐Anomeren entsprechen.
Application de la Résonance Magnétique de l'Azote 15 à l'Etude de la Délocalisation Electronique dans les Anilines, Aminopyridines et Enamines
Authors: Dorie Jean , Mechin Bernard , Martin Gérard
Published: May 2005

La spectrososcopie 15N en abondance naturelle a été appliquée à l'étude de la délocalisation électronique dans des anilines ortho, méta et para substituées. Les relations qui permettent d'estimer le degré de délocalisation électronique de la paire libre de l'atome d'azote (en unités de ΔG≠T) à partir de δ 15N, ont été étendues aux amino‐pyridines, ‐pyrimidines et à quelques nucléosides. La cohérence des résultats obtenus dans la série des anilines (et énamines) a été vérifiée par comparaison avec les données d'une étude antérieure réalisée sur les amides et composés analogues. Les données de la spectros copie 15N permettent ainsi d'établir des échelles de délocalisation électronique dans de nombreuses séries de composés azotés.
Ring inversion in a substituted 3,4‐dihydro‐2H‐thiopyran
Authors: Brunskill John S. A. , De Asish , Ewing David F.
Published: May 2005

Activation parameters have been determined for ring inversion in a 3,4‐dihydro‐2H‐thiopyran and this system has been compared with analogous 6‐membered ring systems.
Etude en RMN: Couplages a Longue distance dans les Perfluoro‐alkyl‐1 Dihydro‐3,4 Isoquinoléines et Perfluoro‐alkyl‐1 Isoquinoléines
Authors: Pastor R. E. , Cambon A. R. , Musso J.
Published: May 2005

Dans l'étude en RMN du proton et du fluor des perfluoro‐alkyl‐1 dihydro‐3,4 isoquinoléines et perfluoro‐alkyl‐1 isoquinoléines, nous avons pu observer de nombreux couplages à longue distance. Outre le couplage homoallylique avec les protons méthyléniques en 3 dans les perfluoro‐alkyl‐1 dihydro‐3,4 isoquinoléines et le couplage interbenzylique en 7J avec les groupements méthyles en 4 dans perfluoro‐alkyl‐1 méthyl‐4 isoquinoléines, les fluors α des chaines perfluoro‐alkyles sont couplés avec les protons H‐8 dans tous les composés étudiés. Ce dernier type de couplage en5J entre un proton aromatique et un atome de fluor est mis en évidence pour la première fois. Les divers types de couplages à longue distance ont pǔ ětre expliqués par des considérations d'ordre géométrique, stérique et électronique.
Geometrical isomerism and 13C spectra of the β‐substituted Enones R1C(1)OC(2)HC(3)HR2
Authors: Kozerski Lech , Kamieńska‐Trela Krystyna , Kania Lidia
Published: May 2005

The 13C chemical shifts of the unsaturated carbons were measured in 31 cis and trans pairs of β‐substituted enones R1C(1)OC(2)HC(3)HR2. In these polarized ethylenes the chemical shifts of the olefinic carbons are simply related by the equation δc=δt+A. The steric and electronic effects introduced by the R1 and R2 substituents influence the chemical shifts of C‐2 and C‐3 in both isomers. It is shown that the sign and magnitude of the intercept A mainly reflect the π‐charge electronic density changes which arise in the cis isomer and are transmitted via the π‐framework. The effect of the steric interaction on the chemical shift of C‐3 in the cis isomers is postulated to be related to the symmetry of the substituents. Therefore, the differential shielding of C‐3 is indicative of the conformational structure of the cis molecule.
Carbon‐13 magnetic resonance: γ‐anti substituent effects
Authors: Forrest T. P. , Webb J. G. K.
Published: May 2005

γ‐anti Substituent effects of the first row elements (CH3, NH2, OH, F) and the higher‐row halogens on 13C chemical shifts are shown to have separate linear relationships with element electronegativity. The halogens generally show an increasing upfield shift with increasing electronegativity, but the response of the effect of the first‐row elements to changing electronegativity is dependent upon the substitution pattern of the atoms involved. In molecules with the substituent at a bridgehead, increasing electronegativity causes increasing downfield shift of the γ‐anti carbon, whereas in other systems which have the substituent at a secondary carbon, increasing electronegativity causes an increasing upfield shift. Examples are cited to show that the γ‐anti effect of a hydroxyl group is more shielding (by about 2 ppm) when a 1,3‐diaxial interaction between an α and a γ hydrogen is present, than when this interaction is removed by replacement of either of the hydrogens. This correlation is taken as evidence of this hydrogen‐hydrogen interaction as one pathway for the transmission of the γ‐anti substituent effects of first‐row elements.
Contribution of the trityl group to magnetic asymmetry in N‐trityl amino acid benzyl esters
Authors: Matsoukas J. , Theodoropoulos D.
Published: May 2005

The magnetic nonequivalence of the O‐methylene protons of certain N‐trityl amino acid benzyl esters is reported. It is shown that magnetic asymmetry arises from hindered internal rotation of the α‐benzyl group. The degree of proximity of the bulky N‐trityl to the α‐benzyl group, and consequently the degree of free rotation of the latter, is dependent on the nature of the amino acid side‐chain R.
Chemical shifts for tritons in chlorobenzene, bromobenzene, fluorobenzene and toluene as determined by tritium NMR spectroscopy
Authors: Long Mervyn A. , Lukey Christopher A.
Published: May 2005

Chemical shifts for tritons in chlorobenzene have been measured in the pure compound and in a dilute solution in cyclohexane using a 64 MHz NMR spectrometer. The order of shifts is o>m>p. Triton shifts in pure bromobenzene, fluorobenzene and toluene have also been measured and the influence of CCl4 solvent on the aromatic triton shifts in toluene explored. Complete resolution of the three aromatic triton positions is achieved in pure toluene, but the ortho and para shifts are not resolved in 25% solution in CCl4.
Tritium labelling of hexamethyldisiloxane for 3H NMR referencing
Authors: Long Mervyn A. , Garnett John L. , Lukey Christopher A.
Published: May 2005

Tritium labelled hexamethyldisiloxane is a suitable material for the internal referencing of 3H NMR spectra. Such a referencing procedure is necessary where the instrument is not capable of scanning 1H resonance under identical experimental conditions. Hexamethyldisiloxane may be tritiated to high activity (typically 1 Ci ml−1) by Raney nickel catalysed exchange with elemental tritium in a simple one‐step procedure. A variety of heterogeneous catalysts are shown to be inactive in the common labelling method involving exchange with tritiated water.
Carbon‐13 NMR analysis of cyclobutane dimers from benzocycloalkenes
Authors: Browne C. E. , Ruehle P. H. , Dobbs T. K. , Eisenbraun E. J.
Published: May 2005

13C NMR Spectra for a series of 11 substituted cyclobutanes derived from photodimerization of benzocycloalkenes were recorded. Comparison of the carbon chemical shifts for the head‐to‐head and head‐to‐tail cis‐syn‐cis and cis‐anti‐cis isomers reveals shielding trends which should facilitate structural and stereochemical assignments for related compounds. The head‐to‐head isomers show a larger separation of cyclobutane carbon resonances than the head‐to‐tail isomers. The cis‐syn‐cis isomers relative to the cis‐anti‐cis isomers exhibit distinctive upfield shifts of all carbon resonances, except those of aromatic carbons ortho to alkyl‐substituted aromatic carbons.
Etude en Résonance Magnétique Nucléaire du Carbone‐13 de N‐Aryl Pyrazolines‐2 Diversement Substituées. Effets de Substituant et Etude Conformationnelle
Authors: Faure Robert , Llinares Jeanine , Vincent Emile‐Jean , Elguero José
Published: May 2005

Les déplacements chimiques du carbone‐13 de la phényl‐1 pyrazoline‐2 et de vingt‐cinq N‐nitrophényl pyrazolines‐2, diversement substituées sur l'hétérocycle, ont été complétement attribués. Ces valeurs sont discutées en fonction des contraintes électroniques et stériques des différents substituants. Les effects stériques entrainent des modifications de la conformation aussi bien du groupement nitrophenyle, que du cycle pyrazoline‐2, ce qui explique les variations de certains déplacements chimiques.
13C‐NMR‐Untersuchungen an Steroiden. IV—Substituenteneffekte an 16‐mono‐ und 16,17‐disubstituierten 3‐Methoxyöstra‐1,3,5(10)‐trienen
Authors: Engelhardt Günter , Zeigan Dieter , Schönecker Bruno
Published: May 2005

Die 13C‐NMR‐Spektren einiger stereoisomerer 16‐mono‐ und 16,17‐disubstituierter 3‐Methoxyöstratriene (16‐Substituent: OH, Br, N3, NHAc, SCN, SeCN, SH, NCS; 17‐Substituent: OH) wurden aufgenommen und vollständig zugeordnet. Für die 16‐monosubstituierten Verbindungen zeigt sich, daß die durch den 16‐Substituenten induzierten Verschiebungseffekte wietgehend unabhängig von dessen sterischer Anordnung (16α oder 16β) snd und somit zur Konfigurationsbestimmung nicht verwendet werden Können. Die Untersuchung der Substituenteneffekte in den 16,17‐disubstituierten Verbindungen ergibt, daß die vicinale Disubstitution z̀ beträchtlichen Abweichungen von der Additivität besonders für die substituierten C‐Atome führt, die bis nahezu 14 ppm betragen können.
Concerning the chemical shifts of the ring protons of toluene as determined by 1H NMR spectroscopy of deuterated material
Authors: Schaefer T. , Hutton H. M.
Published: May 2005

Chemical shifts of the ring protons are determined by 1H NMR of 99% deuterated toluene. At low temperatures the deuterons relax rapidly, yielding sharp 1H peaks for the ortho, meta and para protons. These are compared with shifts obtained by other methods.
Solvent and temperature studies of some indenyl‐ and fluorenyllithiums using13C NMR spectroscopy
Authors: Edlund Ulf
Published: May 2005

13C NMR spectra of indenyl‐ and fluorenyllithium and some of their methyl substituted derivatives have been obtained. The shielding differentials induced by varying the temperature or coordinating ability of the solvent are discussed in terms of an equilibrium between discrete ion pairs or differences in external solvation. An increase of the coordinating ability of the solvent induces shift differentials of similar signs as those given by lowering the temperature. Methyl substituents close to the cation location are found to have only a minor effect on the observed ion pair ratio but seem to influence the preferred cation position in the tight ion pair structure.
Angular dependence of the vicinal interproton spin–spin coupling in silacyclohexanes. The conformational energy term of the methyl group in 1‐methyl‐1‐silacyclohexane
Authors: Carleer Robert , Anteunis Marc J. O.
Published: May 2005

An approximate Karplus‐Conroy relationship between the vicinal coupling constantsJ(HSiCH) in a silaethane fragment and the corresponding torsional angles τ in silacyclohexanes is proposed. The relationship3J(HSiCH)VSτ is asymmetric. The1H NMR parameters and conformational features ofcis‐ andtrans‐3,5‐dimethyl‐1‐silacyclonexane and 3‐silabicyclo[3.2.1]octane are discussed, and the conformational energy term for the methyl group in 1‐methyl‐1‐silacyclohexane is found to be approximately 1.45 kJ mole−1in favour of the axial position for the methyl group, in good agreement with previously calculated values.
1H and 31P nuclear magnetic resonance spectra of compounds containing the PIIINPV skeleton
Authors: Bulloch Gordon , Keat Rodney , Rycroft David S. , Thompson David G.
Published: May 2005

The 1H and 31P NMR spectra of a series of compounds containing the PIII‐N‐PV skeleton including Cl2PNMeP(Z)Cl2 (ZO or S), Cl2P·NMe·P(O)CINMe2, P4(NMe)6Zn (ZS, n = 1−3; ZSe, n = 1), XP(NBut)2P(Z)X (XCl, ZO or S; XOMe, ZS or Se; XNMe2, ZS or Se; XNEt2, ZSe), (XO or S), and Ph2PNRP(S)Ph2 (RMe, Et) have been obtained. 1H‐{31P} double resonance, and in selected cases, 31P‐{1H, 77Se} and 31P‐{1H, 31P} triple resonance experiments, indicate that 2J(PIII NPV) is positive in acyclic compounds, negative in most cyclic or cage compounds, and furthermore, is related to the conformation adopted by the PIII‐N bond.
Carbon‐13 NMR spectra of some tetra‐ and pentacyclic triterpene methyl ethers
Authors: Blunt J. W. , Munro M. H. G.
Published: May 2005

The carbon‐13 NMR spectra have been recorded for representatives of three previously unexamined classes of pentacyclic triterpenes—lupanes, fernanes and arboranes. In addition to the spectra of lupeol methyl ether, cylindrin and arundoin, the spectra of a number of other triterpene methyl ethers are also recorded. The effect of methyl ether formation on the shilding values for carbons in the 3β‐hydroxy‐4,4‐dimethyl‐ ring A system is defined.
The determination of the COOH substiuent effect for branched carboxylic acids from carbon‐13 chemical shifts
Authors: Marr David H.
Published: May 2005

The carboxyl substituent effects for branched carboxylic acids have been determined by carbon‐13 Fourier ransform nuclear magnetic resonance of eighteen measured and reported branched acids. For α‐branched systems the substituent effects are α = 15.3 ppm, β = 2.6 ppm, γ = −1.9 ppm, δ = 0.9 ppm and ϵ = 0.5 ppm. For other branched acids, the determined carboxyl substituent effects are α = 19.2 ppm, β = 2.1 ppm, γ = −1.4 ppm, δ = 0.6 ppm, and ϵ = 0.6 ppm.
15N NMR spectroscopy. 19—spectroscopic characterization of cyclodipeptides (2,5‐dioxopiperazines)
Authors: Kricheldorf Hans R.
Published: May 2005

Various cyclodipeptides containing glycine, alanine, leucine, valine, phenylalanine, phenylglycine and sarcosine units were synthesized by cyclization of dipeptide pentachlorophenyl esters. The 13C and natural abundance 15N NMR spectra of these heterocycles were measured in trifluoroacetic acid and compared with the spectra of the corresponding amino acids and polypeptides. The 13C NMR carbonyl signals of all cyclodipeptides show a 1.5–4.0 ppm upfield shift relative to the corresponding polypeptides. The 15N NMR signals show no such consistent relationship. The substituent effects and the neighbouring residue effects observed in the 15N NMR spectra of the cyclodipeptides are different from those of polypeptides, while the one bond NH coupling constant of cis and trans amide groups was almost identical. The nitrogen and the carbonyl signal of the Gly units in cyclo‐Gly‐Phe show an extraordinary downfield shift, reflecting the interaction of the phenyl group with the 2,5‐dioxopiperazine ring.
Substituent effects on carbon‐13 chemical shifts of para‐substituted benzylbenzenes
Authors: Nakai Yoshimi , Takabayashi Tetsuo , Yamada Fukiko
Published: May 2005

Carbon‐13 chemical shifts of fourteen para‐substituted benzylbenzenes have been determined. The relative substituent chemical shifts (SCS) of the methylene carbons and the aromatic ring carbons (C‐4, C‐1′ and C‐4′) correlated well with the Hammett substituent effects using the dual substituent parameter method. The transmission of substituent effects through the benzylbenzene system is briefly discussed.
Application of rank correlation to lanthanide induced shift data
Authors: Li Wai‐Kee , Lee Sik‐Yum
Published: May 2005

Spearman's rank correlation method is suggested as an alternative procedure for the treatment of lanthanide induced shift data. When this method is applied to Sullivan's data [J. Am. Chem. Soc. 98, 7162 (1976)], the results are similar to those obtained by the jack‐knife and Kendall techniques, which were introduced in a previous article. All three methods are able to distinguish between closely related structures. Among these three non‐parametric methods, the Spearman procedure is probably the simplest.
Carbon‐13 nuclear magnetic resonance spectroscopy of cephalotaxus alkaloids
Authors: Weisleder David , Powell Richard G. , Smith Cecil R.
Published: May 2005

Carbon‐13 chemical shift assignments have been obtained for the naturally occurring Cephalotaxus alkaloids, cephalotaxine, acetylcephalotaxine, harringtonine, isoharringtonine, drupacine and cephalotaxinone.
Applications of 15N NMR spectroscopy to the study of unsymmetrically N‐substituted amides and model peptide compounds
Authors: Dorie J. , Gouesnard J. P. , Mechin B. , Naulet N. , Martin G. J.
Published: May 2005

13C and 15N spectra of unsymmetrically N‐substituted formamides and alkyl‐, substituted alkyl‐, and arylcarboxamides, which can be considered as model peptide compounds, were determined and discussed in terms of nitrogen lone pair delocalization. Differential solvent shifts and through‐space steric effects are considered as a tentative explanation of the difference in screening between geometrical diastereoisomers. Z‐E assignment and the thermodynamic stability of diastereoisomers can also be predicted in some circumstances from a consideration of the 15N chemical shifts. Data concerning small peptides are discussed in the light of the results obtained using the model compounds.
13C chemical shifts of phenol derivatives. A correlation with electronic structure
Authors: Ilczyszyn Marek , Latajka Zdzisław , Ratajczak Henryk
Published: May 2005

The 13C chemical shifts of twenty chloro‐ and nitro‐substituted phenols have been measured in d‐chloroform. The influence of substituents on the screening at C‐1, on the total charge at this position and on the dipole moments is reported and analysed. The results of this study suggest that variations of the chemical shifts at C‐1 for meta‐methyl‐, meta‐chloro‐, meta‐nitro‐, ortho‐ and para‐methyl‐, ortho‐ and para‐chlorosubstituents mainly reflect charge density changes. The influence of ortho‐nitro groups on the screening of C‐1 is more complex.
Carbon‐13, 1H spin‐spin coupling. V—π‐benzenechromium tricarbonyl and the π‐tropyliumchromium tricarbonyl cation
Authors: Aydin Rafet , Günther Harald , Runsink Jan , Schmickler Hans , Seel Horst
Published: May 2005

The 13C, 1H spin‐spin coupling constants have been determined for π‐benzenechromium tricarbonyl (3) and the π‐tropyliumchromium tricarbonyl cation using the 13C{2H}double resonance technique described in a previous paper. In addition, conventional analysis of the 1H‐coupled 13C NMR spectrum of 3 was carried out and the 1H NMR spectrum of 3 partially oriented in the nematic phase was analysed. Both treatments also allowed the determination of the 1H, 1H coupling constants for this compound. The nJ(CH) results are discussed on the basis of structural data and the theoretical results available. The complexation effects for 1J(CH) are found to correlate with the CH overlap population and hybridization changes, and those for 3J(CH) with the CC bond lengths and π‐bond orders. The dependence of 2J(CH) on CC bond length as well as on the CCH bond angle is indicated. The liquid crystal results are compared with those of related studies.
Nuclear spin magnetization transfer by doubly selective irradiation
Authors: Craig Robert A. , Harris Robin K. , Morrow Robert J.
Published: May 2005

A procedure for doubly selective irradiation of an AX NMR spin system so as to achieve complete magnetization transfer from X to A is described. In combination with suitably gated decoupling this sequence will give substantial savings of time in determinations of T1 for low‐sensitivity spin‐½ nuclei, particularly those with negative magnetogyric ratios.
The temperature dependence of 13C NMR shifts in polar compounds and its role for the determination of conformational equilibria
Authors: Schneider Hans‐Jörg , Freitag Wolfgang , Hoppen Volker
Published: May 2005

Intrinsic temperature dependencies of 13C NMR shifts in alkanes bearing one polar C‐αX bond are determined with neopentyl and 4‐tert‐butylcyclohexyl derivatives as conformationally homogeneous model compounds. The increased shiedling for C‐α at higher temperatures can be related to a C‐α—X bond length increase and, for less polarizable CX bonds, essentially to a decrease of solvent polarity on raising the temperature. The use of temperature dependent 13C shifts in conformationally mixed compounds for the determination of the equilibrium constants, K, is evaluated with n‐propyl halides; the computer fit of the unknown conformer shifts and the conformational enthalphy difference, δH° to the time averaged shifts yields δH° values which, although converging rather broadly, are in general agreement with literature data. In compounds with higher conformational barriers, such as methoxy‐ and bromocyclohexane, low temperature signal integration yields accurate δG° values; inclusion of shifts above coalescence, however, yields unreliable δH° and δS° parameters. This can only partially be remedied by application of temperature shift corrections obtained from parent t‐butylcyclohexyl compounds.
On the convergence of iterative computation in the LAOCOON 3 program
Authors: Attimonelli M. , Sciacovelli O.
Published: May 2005

The reasons which sometimes cause failure of convergence in the iteration of NMR spectra by LAOCOON 3 are discussed. The problem can be avoided by retaining the sequence of the eigenfunctions throughout the iterative process. In addition, assignment of the lines to start the iterative analysis can be facilitated by considering the dependence of the transitions on the NMR parameters in the simulation stage. LAOCOON 3, modified and extended to handle eight spin systems, has been successfully tested in the iterative analysis of the 1H NMR spectrum of naphthalene.
1H NMR assignments for t‐2‐deuterio‐r‐1‐methyl‐1‐phenylcyclopropane and c‐2‐deuterio‐r‐1‐methyl‐1‐phenylcylclopropane. A literature correction
Authors: McKinney Michael A. , Nagarajan Sridhar C.
Published: May 2005

The synthesis and 1H NMR spectra of the cis and trans monodeuterated isomers of 2‐deuterio‐1‐methyl‐1‐phenylcyclopropane have been previously reported. We have prepared one of the isomers, c‐2‐deuterio‐r‐1‐methyl‐1‐phenylcyclopropane, by a different, stereospecific, route. We now wish to correct the original 1H NMR assignments which were in error.
Evidence for an important 13C NMR shielding effect for carbon atoms bearing a heavy chalcogen substituent
Authors: Laitem Leopold , Christiaens Leon , Renson Marcel
Published: May 2005

An important 13C NMR shielding effect on carbons bearing a heavy chalcogen is demonstrated. This effect is parallel to that induced by iodine, but to a lesser extent. For acyclic compounds and for partially saturated heterocycles, there is an excellent linear correlation between the 13C chemical shifts of carbons bearing a chalcogen and carbons bearing a halogen atom in the corresponding compound. The linearity of the relationship is less satisfactory with heteroaromatic compounds.
1H NMR utilization of through‐space effects in configurational assignments. I—application to nitriles; determination of the separate effects of the electric field and anisotropy of the CN group
Authors: Rouillard Michel , Geribaldi Serge , Khazarian Jean , Azzaro Marcel
Published: May 2005

The changes in chemical shift induced by isomerization for all the ring protons of the Z‐ and E‐5,5‐dimethyl‐2‐cyclohexenylidene acetonitriles depend only on the through‐space effects of the cyano group. The configurational assignments were made taking into consideration the anisotropic and electric field effects, either separately or together. In the first case, the total effects are ΔXCNT=−14.7×10−6cm3 mol−1 and bμCNT=14.7×10−30 cm3, respectively. The second approach allows the estimation of the values ΔXCN=−4.9 × 10−6 cm3 mol−1 and bμCN=9.8 × 10−3 cm3, reflecting the combined contributions of magnetic anisotropy and electric field to the total effect.
The rα‐structure and the 1H and 199Hg shielding anisotropies of dimethylmercury as determined in nematic and smectic liquid crystal solvents
Authors: Jokisaari J. , Diehl P.
Published: May 2005

The complete rα‐structure of dimethylmercury in the nematic ZLI 1167 liquid crystal was determined. This study confirms the earlier results, indicating that the structure is practically independent of the liquid crystal solvent, although some minor deviations exist. The HgC distance was found to be 207.97±0.05 pm, when the vibration corrections in the dipole‐dipole coupling constants were taken into account. This is rather similar to the distances obtained with other spectroscopic methods. The anisotropies of the 1H and 199Hg chemical shifts were obtained by using a smectic liquid crystal and recording the corresponding spectra, the optical axis being parallel with or perpendicular to the external field direction. The experimental ratio‐2.007±0.017 of the D∥ (HgH) and D⟂ (HgH) coupling constants proves that the indirect contributions in these coupling constants are negligible. Shielding anisotropies of 3.70±0.3 ppm and 7325±55 ppm for 1H and 199Hg, respectively, were obtained.
Carbon‐13 nuclear magnetic resonance spectroscopy. Substituent‐induced chemical shift effects on cyclopropyl carbons of 4‐substituted cyclopropylbenzenes
Authors: Kusuyama Yoshiaki , Dyllick‐Brenzinger Christina , Roberts John D.
Published: May 2005

Carbon‐13 chemical shifts of the cyclopropyl carbons of eleven 4‐substituted cyclopropylbenzenes have been measured under conditions effectively corresponding to infinite dilution in DCCI3. The substituent‐induced chemical shifts (SCS) of both the α and β carbons of the cyclopropane ring were found to be downfield with electron‐attracting groups and upfield for electron‐donating groups. The trends for the β carbons correspond to those observed for the β carbons of 4‐substituted phenylethenes, while the trends of the α carbons are similar to those found for the α carbons of 4‐substituted isopropyl benzenes. The results for the β carbons can be rationalized by postulating a substantial contribution from a hyperconjugative resonance effect involving the σ system of the benzene ring (and its 4‐substituent) and the C‐α—Cβ bonds of the cyclopropane ring. The effects on the α carbons are in accord with a very reasonable smaller inductive polarization of the C‐αC‐β bonds than encountered for the carbons of corresponding ethenyl‐ or ethynylbenzenes.
Configurational assignment and 1H NMR spectral parameters of isomeric 1,2‐diacetoxy‐4‐alkyl‐3‐methylcyclopentanes
Authors: Hanselaer R. , De Clercq P.
Published: May 2005

The 1H NMR spectral parameters of all eight 1,2‐diacetoxy‐3,4‐dimethylcyclopentanes and 1,2‐diacetoxy‐4‐t‐butyl‐3‐methylcyclopentanes are discussed.
The structure and intramolecular motion of benzaldehyde as studied on the basis of proton spectra with 13C satellites of the oriented molecule
Authors: Diehl P. , Jokisaari J. , Amrein J.
Published: May 2005

The proton spectrum with 13C satellites of benzaldehyde oriented in a liquid crystal solvent has been analysed and the structure of the proton and carbon skeleton has been determined. The large number of observed direct couplings also allows the study of the intramolecular rotation. The depth of the hindering potential is extremely model dependent, however, so that no unique result has been obtained.
35Cl NQR spectra and 13C NMR spectra of polycyclic chlorinated hydrocarbons with 10 and 12 carbon atoms
Authors: Fitzky Hans Georg , Gäb Siegmar
Published: May 2005

The structure of cyclic chlorinated hydrocarbons can be elucidated by the use of combined 13C nuclear magnetic resonance and 35Cl nuclear quadrupole resonance. The advantages obtained and the techniques employed with respect to some new and already investigated compounds, and typical shift values aiding studies of similar derivatives, are reported.
1H NMR. Interaction of lanthanide salts with phenols in basic solutions
Authors: Davoust Daniel , Molho Darius , Platzer Nicole
Published: May 2005

Lanthanide salt induced shifts in the NMR spectra of phenols are found to increase in basic media. The empirical relationships governing the interaction of phenolic hydroxyl groups, reported earlier, still apply.
Downfield 1H NMR shifts induced by electron‐rich substituents
Authors: Hand E. Smakula , Paudler W. W.
Published: May 2005

The 1H NMR signal due to the peri proton H‐5 in imidazo[1,2‐a]pyridines exhibits large downfield shifts when the 3‐position bears a substituent (−XY) containing an electron‐rich atom (Y) two bonds removed from C‐3. Such shifts are observed not only when the ring electron density can be decreased by resonance interaction [from −1.29 to −1.87 ppm for 3‐COR, 3‐(2′‐quinoxalyl) and 3‐No in CDCl3], but also when electron withdrawal must be minimal: −1.10 ppm when X is an sp3 center [3‐CH(OH)CCl3 in CDCl3], −1.0 ppm when the 3‐substituent is negatively charged (3‐CO2 −Na+ in D2O), and −1.32 to −1.46 ppm when the ring system is protonated (3‐COR and 3‐NO2 in TFAA). The effect is largest in those compounds for which orientation of lone‐pair electrons on atom Y toward H‐5 can be invoked. The desielding is attributed primarily to a through‐space electric field effect.
The 1H NMR spectra of exo‐ and endo‐3‐thiatricylo[4.2.1.02,5]non‐7‐ene 3,3‐dioxide. The shielding effect of the sulfone group
Authors: Martin H.‐D. , Iden R. , Scheutzow D. , Jackman L. M.
Published: May 2005

The proton spectra of exo‐ and endo‐3‐thiatricyclo[4.2.1.02,5]non‐7‐ene 3,3‐dioxide have been analysed and completely assigned. Considerations of coupling constants indicate that the thietane ring is nonplanar and that the norbornene residue is significantly distorted from the geometry of norbornene itself. The sulfone group induces significant changes in the shielding of the proximate olefinic proton in the endo isomer and the bridge protons in the exo isomer. These shifts appear to be the result of the electrostatic effects and effects associated with the diagmagnetic anisotropy of the sulfone group.
13C and15N NMR study of acyclic vicinal diastereoisomers. Conformational effects
Authors: Levy George C. , Pehk T. , Lippmaa E.
Published: May 2005

Conformations of aliphatic diastereoisomers with vicinal asymmetric centers (2,3‐disubstituted butanes and 5,6‐disubstitutedn‐decanes) are discussed in terms of their13C and, in some cases,15N chemical shifts and spin‐lattice relaxation times. Solvent and protonation effects are explained by conformational changes in the isomers.
Analysis of the 19F and 1H NMR spectra of a number of polyfluoroindenes
Authors: Matthews R. S. , Preston W. E.
Published: May 2005

19F and 1H NMR spectra of the products of nucleophilic attack on octafluoroindene are analysed and structures assigned. The major product in the reaction of butyllithium with octafluoroindene is 3‐methylheptafluoroindene, with sodium borohydride it is 2‐hydroheptafluoroindene and with sodium methoxide it is 3‐methoxyheptafluoroindene. Vacuum pyrolysis of undecafluorotricyclo[5.2.2.02,6]undeca‐ 2,5,8‐triene, with elimination of C2F4, gives 6‐hydroheptafluoroindene as the major product. The NMR assignments are based on the unambiguous synthesis via vacuum pyrolysis of 5,6‐dihydrohexafluoroindene, 3‐hydro‐ and 3‐methyl‐heptafluoroindene and the large long‐range coupling of 15 Hz assigned to the F‐2, F‐6 interaction.