bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen NMR spectroscopy: Application to some substituted pyrroles
Authors: King Michael M. , Yeh Herman J. C. , Dudek Gerald O.
Published: May 2005

A series of 15N labeled 2‐acylpyrroles was prepared and the nitrogen and proton n.m.r. spectra obtained. 15N chemical shifts for these compounds are reported for the first time. No correlation between the nitrogen chemical shift and any Hammett substituent constant could be found. No variation in J(15NH) was observed for any compound with changes in solvent, temperature or concentration, ruling out any observable tautomeric equilibria for these systems. An increase in J(15NH) with the addition of electron withdrawing groups indicates increasing polarization of the NH bond and acidity of these molecules. Two and three bond 15N couplings are also reported.
A 13C NMR investigation of some tetrakisisocyanocopper(I) tetrafluoroborate complexes: Chemical shift of, and coupling to, the isocyano carbon
Authors: Knol D. , Koole N. J. , de Bie M. J. A.
Published: May 2005

The 13C n.m.r. spectra twelve isocyanides, RNC, and their Cu(I) complexes, Cu(RNC)4BF4, were recorded in the solvents CDCl3 and DMSO. The resonances of the isocyano carbon, C0, could be observed for both free and coordinated isocyanides. In the spectra of the complexes this C0 resonance was present as a broad line. For some complexes the 14N13C0 coupling could only be detected after heating the sample or by adding small amounts (<7 mo1%) of Cu(CH3CN)4BF4. For the remaining complexes neither J(14N13C0) nor J(14N13C1), could be detected. No carbon‐copper coupling could be detected. The line shape of C0 is discussed in terms of exchange of an isocyanide ligand and in terms of quadrupolar nitrogen and copper relaxation. In most complexes exchange seems to be dominant, whereas in other complexes quadrupolar nitrogen relaxation is also of importance. On coordination of the isocyanide, the C0 resonance shifts upfield (15 to 20 ppm) and J(14N13C0) shows a threefold increase. The upfield shift is associated with a larger excitation energy while the increase of J(14N13C0) is ascribed to a larger effective nuclear charge on C0. The chemical shifts of the α‐carbon, the β‐carbon and the solvent effect on all n.m.r. parameters in both free and coordinated isocyanides are also discussed.
Experimental data for gauche couplings in carbohydrates
Authors: De Bruyn André , Anteunis Marc
Published: May 2005

Typical sets of values for vicinal gauche coupling constants are given, allowing configurational predications in pyranose chairs.
Determination of ΔH≠ and ΔS≠ by simultaneous 1H and 13C dynamic n.m.r. studies: Importance of the accuracy of temperature measurement
Authors: Piccinni‐Leopardi C. , Fabre O. , Reisse J.
Published: May 2005

From ΔGTc≠ values obtained by 1H and 13C dynamic nuclear magnetic resonance studies of the same dynamic process, it is possible to estimate ΔH≠ and ΔS≠. Nevertheless, the accuracy of the temperature measurement is a factor which limits the applicability of this method. A very simple procedure for calibrating the usual temperature sensors is described, which can be applied to all types of n.m.r. probes. By the use of this procedure it is possible to measure coalescence temperatures in 1H and 13C n.m.r. with such an accuracy that ΔS≠ can be effectively determined from the difference between ΔGTc≠ values.
15N n.m.r.: Substituent effects on nitrogen chemical shifts in anilinium ions
Authors: Axenrod T. , Wieder M. J.
Published: May 2005

15N chemical shifts were measured in a series of anilinium fluorosulfonate salts and compared with chemical shift data from a comparable series of 15N‐enriched aniline derivatives. A smaller overall range of nitrogen chemical shifts was observed for the protonated aniline series compared with that for the unprotonated anilines and is attributed to the elimination of nitrogen lone pair delocalization in the former series. Further‐more, it was found that the range of nitrogen chemical shifts in the protonated anilines is determined primarily by substituent electronic effects from the ortho ring position with almost negligible contributions from the para position.
La résonance magnétique du 77Se dans des composés organiques
Authors: Christiaens L. , Piette J‐L. , Laitem L. , Baiwir M. , Denoel J. , Llabres G.
Published: May 2005

La résonance magnétique du 77Se a été observée dans vingt‐six composés organiques dont certains contiennent un atome de sélénium endocyclique. Nous avons pu ainsi compléter l'échelle de déplacements chimiques établie par McFarlane. II apparaît difficile de définir une gamme de déplacement chimique du 77Se caractéristique de son état de valence ou de sa position endo‐ ou exocyclique. Certains résultats sont discutés qualitativement. Dans le cas du sélénolo [2,3‐b]thiophène, des arguments en faveur d'un couplage 4J(Se, H) à travers l'atome de soufre ont été découverts.
13C n.m.r. spectra of 2‐substituted pyrimidines
Authors: Turner Christopher J. , Cheeseman Gordon W. H.
Published: May 2005

13C n.m.r. chemical shifts and carbon‐proton coupling constants of 2‐substituted pyrimidines are reported. The carbon chemical shifts are correlated with π‐electron densities. Substituents which cause deshielding at the directly bound carbon (e.g. NH2, OCH3 and F) exert a more powerful effect in the benzene series than in the pyridine or pyrimidine series. The carbon‐proton coupling constants do not correlate with the electronegativity of the substituents. Carbon‐proton coupling constants and proton‐proton coupling constants over the same number of bonds do not obey the Karabatsos relationship. The changes in the carbon‐proton coupling constants in 2(1H)‐pyrimidinone and 2(1H)‐pyrimidinethione which accompany anion and cation formation are reported.
Spectres RMN de 27Al d'hydrures d'aluminium
Authors: Huet J. , Durand J. , Infarnet Y.
Published: May 2005

Les spectres RMN de 27Al de LiAlH4, AlH3 et LiAlH (YR)3 (Y = O ou S et R = Me ou t‐Bu) ont été enregistrés. Plusieurs remarques ont pu être faites sur les paramètres obtenus (δAl, J(AlH), largeur à mi‐hauteur).
Pattern recognition of geminal proton nonequivalence and second‐order coupling in 13C single‐frequency off‐resonance decoupled spectra. Assignment criteria and structure elucidation
Authors: Hagaman Edward W.
Published: May 2005

13C n.m.r. single‐frequency off‐resonance decoupled (sford) CH multiplet resonance which deviate from normally assumed, isolated AnX spin descriptions have been characterized. Methylene carbons whose appended protons are nonequivalent generate doublets of doublets in sford spectra provided the proton chemical shift difference exceeds c. 3 × (Jgem). The isolated moiety–CHH′–closely approximates an AMX spin system. The strong chemical shift nonequivalence of geminal aminomethylene protons induced by the nitrogen lone pair in some N‐substituted piperidine derivatives is accompanied by preferential modification of the one‐bond CH coupling constants of the α‐amino protons. In N‐methyl‐4‐t‐butylpiperidine the natural coupling constants were shown to differ by 6–12 Hz. The 13C sford resonances of protonated carbons display varying degrees of second‐order coupling depending on the coupling strength of a carbon's appended protons with a strongly coupled spin set, the number of nuclei in the spin set, and the magnitude of the carbon's residual one‐bond splitting. Qualitative criteria that allow the classification of degrees of second‐order coupling have been established and utilized in signal assignment and structure analysis.
Investigation of substituent effects of chalcones by 13C n.m.r. spectroscopy
Authors: Soĺǎniová E. , Toma Š. , Gronowitz S.
Published: May 2005

13C chemical shifts for 23 para‐ and meta‐substituted chalcones of the types 1 and 2 have been determined. The aromatic shieldings are compared with previous results for other aromatic derivatives. Correlations of the 13C chemical shifts of vinyl carbons and carbonyl carbons as well as ring carbons with Hammett σ parameters, π electron densities and the reactivity parameters of Swain and Lupton provide a consistent picture of electronic effects transmitted through the carbon framework of the compounds studied.
Temperature effects on 13C n.m.r. chemical shifts of normal alkanes and some line r and branched 1‐alkenes
Authors: de Haan J. W. , van de Ven L. J. M. , Wilson A. R. N. , van der Hout‐Lodder A. E. , Altona C. , Faber D. H.
Published: May 2005

13C n.m.r. chemical shifts of a number of 1,1‐disubstituted ethylenes are presented. Moreover, effects of changing temperatures on the 13C n.m.r. chemical shifts of some of these compounds as well as of three normal alkanes are given. These variations in chemical shifts are attributed to varying amounts of sterically induced shifts in the different conformational equilibria. In addition to the well‐known 1,4 interaction between two alkyl groups shielding effects on the carbon atoms of the connecting bonds are also proposed. No definite explanation of this effect is presented at this time. It is further shown that no simple correlations exist between 13C n.m.r. chemical shifts and calculated total charge densities at this level. Instead, the experimental results in 1‐alkenes are rationalized by assuming a linear dependence of the 13C n.m.r. chemical shifts of C‐1 and C‐2 via rehybridizations on changes in bond angles for small skeletal deformations caused by steric interactions. These changes in geometries, as well as conformational energies in three 1‐alkenes, were calculated by means of VFF calculations. Finally. upfield shifts for both C‐2 and C‐4 are proposed for those conformations of 1‐alkenes in which the C‐3C‐4 group interacts with the pz‐orbital of C‐2.
13C n.m.r. spectra of some thiobenzamides. Correlation between 13C and 1H n.m.r. spectra and signal assignments of syn and anti CH2 groups
Authors: Piccinni‐Leopardi C. , Fabre O. , Zimmermann D. , Reisse J. , Cornea F. , Fulea C.
Published: May 2005

13C n.m.r. spectra of a series of N,N‐disubstituted thioamides have been recorded and signal assignments were performed. Separate signals are observed for methylene groups fixed on the nitrogen atom. Since the carbon atom syn to the thiocarbonyl sulfur resonates at higher field than the anti carbon, the syn‐anti assignment in 1H n.m.r. is easily obtained by selective double irradiation. This method, which is rapid and reliable, affords a rather general solution to the interesting problem of resonance assignments in tertiary amides and thioamides (and in analogous molecules such as oximes and nitrosamines).
Pteridine studies: III—13C n.m.r. data of pteridine, some of its derivatives and their covalent σ‐adducts with ammonia and water
Authors: Geerts J. P. , Nagel A. , van der Plas H. C.
Published: May 2005

13C n.m.r. spectral data of pteridine and nineteen of its derivatives (containing one or more chloro, methylthio, methyl, t‐butyl or phenyl substituents) are reported. The 13C n.m.r. spectrum of the title compound has been assigned conclusively. 13C n.m.r. substituent effects are shown to be very useful in discerning between 6‐ and 7‐substituted pteridines. Additionally, the 13C n.m.r. spectra of several covalent amination products, i.e. the 3,4‐dihydro‐4‐ amino‐ and the 5,6,7,8‐tetrahydro‐6,7‐diaminopteridine derivatives, formed by dissolving the appropriate pteridine in liquid ammonia, have been recorded. The 13C n.m.r. spectra of the corresponding covalent hydrates are also reported.
High resolution proton coupled 13C spectrum and structure of butadieneiron tricarbonyl
Authors: Bachmann K. , von Philipsborn W.
Published: May 2005

A complete analysis of the proton coupled 13C spectrum of butadieneiron tricarbonyl is presented. The structure of the diene ligand is discussed on the basis of vicinal C,H and H,H coupling constants as well as 2J(HH), 1J(CH) and 1J(CC) data. These data are interpreted in terms of a non‐planar C,H skeleton in which C,C bond lengths are nearly equal and the terminal carbon atoms exhibit some rehybridization towards sp3. The results obtained from the complex in solution agree with a structural model from X‐ray data of substituted butadieneiron tricarbonyl complexes.
1H n.m.r. spectra and ensuing conformational evidence on carbon–carbon double bonded systems. (Electrically neutral organic Lewis acids—33)
Authors: Haslinger E. , Wolschann P.
Published: May 2005

The n.m.r. spectra of various derivatives of the cyclic acylal of malonic acid and of dimethylbarbituric acid are described. From the long range coupling constant, conformational evidence on the dihedral angle θ between the aromatic ring and the diketodioxane ring or the N,N‐dimethylbarbituric acid ring can be derived. The investigated substances show a dependence of θ on the aromatic substitution.
Constituents of Satureia calamintha. Application of Eu(fod)3 to the assignments of the methyl resonances of triterpenes related to 12‐ursene
Authors: Romeo G. , Giannetto P. , Aversa M. C.
Published: May 2005

The n.m.r. spectra of triterpenoids related to 12‐ursene have been examined using the shift reagent Eu(fod)3. The assignment of all the methyl resonances has been achieved for ursolic acid derivatives and the corresponding compounds of the 3‐epi series, which have not been investigated previously. The additive shielding effects of various substituents on the methyl resonance frequencies have been deduced from the results.
Zur theoretischen Interpretation von NMR‐chemischen Verschiebungen tetrakoordinierter zentralatome. IV—CNDO/2‐Berechnungen von 29Si‐NMR‐chemischen Verschiebungen. Der Einfluß der ΔE‐Näherung
Authors: Wolff R. , Radeglia R.
Published: May 2005

Auf der Basis des CNDO/2‐Verfahrens werden paramagnetische Abschirmungskonstanten für das Zentralatom tetrasubstituierter Siliciumverbindungen Me4–nSiXn (X = F, OMe, NMe2, C1) mit und ohne ΔE‐Näherung berechnet und mit den experimentellen 29Si‐NMR‐chemischen Verschiebungen verglichen. Die aus dem Vergleich der berechneten Werte erhaltenen ‘mittleren Anregungsenergien’ ΔE sind von der Ladung am Zentralatom abhängig und können für quantitative Betrachtungen nicht als konstant angesehen werden.
Conformational analysis of N,N‐diisopropylamides by combined use of n.m.r. lanthanide‐induced shifts and conformational energy calculations
Authors: Graham Laurine L. , Vanderkooi Garret , Getz Joseph A.
Published: May 2005

A new method of conformational analysis has been developed, in which energy minimization calculations are combined with lanthanide‐induced shift data. First, exhaustive energy calculations are carried out on the free molecules in order to determine the conformations of lowest energy. Then, the coordinates of all low energy conformations or pairs of conformations are used in the pseudocontact shift equation for lanthanide‐induced shifts in order to find which of the theoretically obtained conformation(s) gives the best agreement with experiment. The molecules complexed to the lanthanide shift reagent were N,N‐diisopropylformamide (DIPF) and N,N‐diisopropylacetamide (DIPA). Two different lanthanide shift reagents were used, Eu(fod)3

Fod is the anion of 1,1,1,2,2,3,3‐heptafluoro‐7,7‐dimethyl‐4,6‐octanedione‐d27.

and Pr(fod)3, in order to check the validity of the method. Proton magnetic resonance spectra were taken at 6 °C in carbon tetrachloride solution. The principal conformation found was different for each amide. DIPF was found to exist as a mixture of I (39 mol%) and II (61 mol%) with Eu(fod)3, and a mixture of I (37%) and II magnified image (63%) with Pr(fod)3. DIPA was found to exist as a mixture of I (79%) and IV (21%) with Eu(fod)3 and a mixture of I (87%) and IV (13%) with Pr(fod)3. For both molecules, the two conformations of lowest computed energy were also the pair which gave the best fit to the lanthanide shift reagent data. The location of the principal magnetic axis of the complex was found to lie between 0° and 14° from the lanthanide atom–oxygen atom bond axis. The technique of combining lanthanide shift reagent data with energy calculations shows great promise in conformational analysis.
13C n.m.r. spectra ofN,N‐dialkylamides
Authors: Fritz Hans , Hug Paul , Sauter Hanspeter , Winkler Tammo , Logemann Enno
Published: May 2005

Carbon‐13 n.m.r. spectra of formic, acetic, propionic and butyric acid amides withN,N‐di‐n‐alkyl substituents have been completely assigned with the aid of extensive double resonance experiments. The data obtained were used to study long range steric effects on chemical and solvent shifts.
13C spectra of some vicinal dimethylene derivatives of cyclic hydrocarbons
Authors: Pfeffer H. U. , Klessinger M.
Published: May 2005

Carbon chemical shifts of cyclic dimethylene compounds were determined and interpreted. It is suggested that steric compression leads to additional shielding of the exo‐methylene group, the chemical shifts of this group being a useful measure of the amount of steric hindrance.
Deuterium isotope effects in solutions of 2,4‐pentanedione
Authors: Leipert Thomas K.
Published: May 2005

Proton and deuterium n.m.r. measurements in acetylacetone and 3,3‐d2‐acetylacetone are reported. Deuterium‐isotope effects on chemical shifts and keto–enol equilibria as a function of concentration in the two solvents triethylamine and pyrrole are determined. A strong solvent concentration dependence for d‐isotope effects is observed in triethylamine; in pyrrole no dependence is obtained. The results are interpreted in terms of an equilibrium between the symmetrical (C2v) and asymmetrical (Cs) enolic forms in acetylacetone. The usefulness of 2H n.m.r. for the study of exchange processes is demonstrated.
1H n.m.r. spectra of 6‐acetoxy‐2,4‐cyclohexadienones
Authors: Bubb W. A. , Fallick C. J. , Sternhell S.
Published: May 2005

1H n.m.r. spectra of 36 derivatives of 6‐acetoxy‐2,4‐cyclohexadienones were analysed. All available evidence indicates that all members of the series have similar conformations which do not depart significantly from planarity. Substituent‐induced chemical shifts and interproton coupling constants correlate well with those in the analogously substituted ethylene and benzene derivatives. In particular, it appears that a substituent on the central carbon atom exerts a similar influence on 4J(HH) across a ‘W’ path when the three intervening carbon atoms are a part of a benzene ring, an allylic system (i.e. sp3–sp2–sp2), a localized sp2–sp2–sp2 system or a saturated (i.e. sp3–sp3–sp3) system.
Calculation of some nitrogen nuclear screening constants
Authors: Ebraheem K. A. K. , Webb G. A.
Published: May 2005

Some nitrogen screening constants and their anisotropies are calculated within the CNDO/S level of approximation. Satisfactory agreement is found with available experimental data in most cases. In general the reported results are in closer agreement with experiment than are those found from ab initio calculations. The calculated data for the isoelectronic molecules N2O and CH2N2 would be in better agreement with experiment if the assignments of the two nitrogen nuclei were reversed in both cases. A reasonable correlation is obtained with some observed nitrogen chemical shifts. Contributions arising from electronic transitions are reported for N2, HCN, CH3CN, CH3NC, NO2+ and NO2−.
Study of molecular motions and 14N quadrupolar coupling in 1,3‐ and 1,4‐ diethylpyridinium bromides using 13C and 14N relaxation time measurements
Authors: Ghesquière Denis , Chachaty Claude
Published: May 2005

The internal and overall motions of 1,3‐ and 1,4‐diethylpyridinium bromides have been studied by 13C relaxation. The enthalpies of activation for the rotation of the ethyl groups in positions 1 and 3 are deduced from the temperature dependence of the T1 values of the methylene and methine carbons. The 14N quadrupolar relaxation time, Tq, together with 13C relaxation data provide an estimate of the 14N quadrupolar coupling constants.
Carbon‐13 n.m.r. and CNDO/S study of 1,2‐indandione and heterocyclic analogues
Authors: Galasso Vinicio , Pellizer Giorgio , Pappalardo Giuseppe C.
Published: May 2005

13C n.m.r. spectra are reported for 1,2‐indandione, coumarandione and thionaphthenequinone in CDCl3 solution and for isatin in dimethyl sulphoxide solution. The chemical shifts are assigned and discussed in connection with the influence of the heteroatom on the dicarbonyl group and the aromatic ring. The 13C shieldings have also been calculated by means of Pople's perturbation theory using CNDO/S wave functions.
13C n.m.r. studies of some phenanthrene and fluorene derivatives
Authors: Stothers J. B. , Tan C. T. , Wilson Nancy K.
Published: May 2005

The 1H and 13C spectra of fluorene, fluorenone, phenanthrene and their 4‐methyl and 4,5‐dimethyl derivatives have been examined. To complete the analyses for fluorenone and 4‐methylfluorenone, 1H spectra were recorded at 270 MHz. The results from the 1H spectra permitted unequivocal assignments for the protonated aryl carbons by selective proton decoupling. A consistent set of assignments for the quaternary carbons was obtained through consideration of the dominant relaxation processes operative at these centres. This series of compounds was examined to investigate the shielding effects produced by the close approach of methyl groups separated by five bonds for comparison with the contrasting trends found for methyl carbons separated by three and four bonds. The results indicate that the relative orientation of the methyl groups is an extremely critical factor governing their shieldings and those of neighboring centres.
Carbon‐13, proton spin–spin coupling constants in some 2‐substituted propanes
Authors: Wasylishen Roderick E. , Chum Kalvin , Bukata John
Published: May 2005

Carbon‐13, proton coupling constants have been measured in eighteen different 2‐substituted propanes. 1J(C‐2,H) shows variations similar to those observed previously for monosubstituted methanes. 2J(C‐2,H) is essentially independent of the substituent at C‐2, while 2J(C‐1,H) varies over a range of at least 5 Hz. The latter coupling constant becomes more positive as the electronegativity of the substituent increases while 3J(CH) decreases as the electronegativity of the substituent increases. The observed trends in nJ(CH) are compared with those calculated using semi‐empirical molecular orbital theory at the INDO level of approximation.
Nuclear magnetic resonance studies of 1,3‐butadienes. IX—The 1H spectra of isoprene and related compounds
Authors: Harris R. K. , Cunliffe A. V.
Published: May 2005

Full analyses of the five‐spin 1H n.m.r. spectra for the diene protons of isoprene, ethylbutadiene and β‐myrcene under conditions of decoupling the sidechain α‐protons are reported. The data are discussed in terms of spin–spin coupling mechanism and molecular conformation. The fully‐coupled spectra of the compounds were also examined and coupling information obtained.
Carbon‐13 n.m.r. studies of flavanone 5,3′,4′‐trihydroxy‐7β‐glucoside from Juelia subterranea (Balanophoraceae)
Authors: Desalbres X. , Duteil M. , Lallemand J. Y. , De Groot‐Pfleiderer W. , Veraloza C.
Published: May 2005

The complete structure and stereochemical elucidation of flavanone 5,3′,4′‐trihydroxy‐7β‐glucoside has been achieved by the aid of 13C n.m.r.
Zur Konformation von 3‐Chlormethylsubstituierten 2,3‐Dihydro‐1,4‐benzoxathiinen
Authors: Kleinpeter Erich , Mühlstädt Manfred , Kuhl Peter
Published: May 2005

Die Vorzugskonformation einer Reihe 3‐substituierter 1,4‐Benzoxathiane wird mit Hilfe der 1H‐NMR‐Spektroskopie bestimmt.
Iterative least‐squares analysis of dynamic n.m.r. spectra. Hindered rotation of the N‐nitroso group in N‐nitroso‐N‐cyanomethylmethylamine
Authors: Szymański S. , Stefaniak L. , Witanowski M. , Ejchart A.
Published: May 2005

Iterative analysis of dynamic n.m.r. (d.n.m.r.) spectra by the least‐squares method was applied to the entire proton spectrum of N‐nitroso‐N‐cyanomethylmethylamine and, separately, to the CH3 and CH2CN sub‐spectra. Resulting differences in the estimated rates of rotation of the NO group are discussed in terms of systematic errors which may be involved in determining spin exchange rates by d.n.m.r. methods. The most probable explanation is that quadrupolar broadening and then unresolved 14N1H spin–spin splitting may appear on increasing the temperature. Estimated entropies of activation indicate that the methyl sub‐spectrum gives more reliable results.
N.m.r. studies in the heterocyclic series: XVII—carbon‐13 spectra of indazole derivatives
Authors: Bouchet Philippe , Fruchier Alain , Joncheray Gérard , Elguero Jose
Published: May 2005

The 13C chemical shifts of 17 indazole derivatives are discussed as a function of substituent effects and the N‐1—H or N‐2—H structure of indazole. The presence in solution of the N‐1—H tautomer is confirmed.
II. Etude de l'Influence de la Nature et de l'Orientation d'un Substituant (Cl, CO) sur les Déplacements Chimiques en Série Tertiobutyl‐4 Cyclohexanonique par RMN Protonique à Haut Champ
Authors: Grenier‐Loustalot M. F. , Lectard A. , Metras F. , Forchioni A.
Published: May 2005

A partir des spectres de RMN protonique à 250 MHz d'une série homogène d'α chloro tertiobutyl‐4 cyclohexanones, nous montrons qu'il est possible d'évaluer les incréments ΔδCl eq et ΔδCl ax pour tous les protons du cycle; ils sont comparés à ceux trouvés par Anteunis pour le groupe OH. A partir des incréments publiés par Jackman pour le groupe tertiobutyle, nous tentons une détermination des incréments du groupe carbonyle.
Proton magnetic resonance spectra of some disubstituted naphthalenes
Authors: Lucchini Vittorio , Wells Peter R.
Published: May 2005

The chemical shifts and coupling constants for the ring protons of nine disubstituted naphthalenes (mainly halogenonitre compounds) in carbon tetrachloride solutions have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Substituent effects are essentially additive except when a strong π‐donor group is in direct conjugation with a strong π‐acceptor group.
Carbon‐13 n.m.r. studies of methylquinolines and methylisoquinolines
Authors: Su Ja‐An , Siew Ernest , Brown Ellis V. , Smith Stanford L.
Published: May 2005

Spectra are reported for all seven methylquinolines, nine dimethylquinolines, six methylisoquinolines and one dimethylisoquinoline. Substituent effects for the α, ortho, meta, para, vinylogous para and peri positions are reported for the monomethylcompounds. Additivity of these substituent effects is demonstrated for the dimethyl compounds which also exhibit a vicinal dimethyl steric effect.
Carbon‐13 NMR spectra of heterocycles. Sultones and sultams.
Authors: Kausch M. , Dürr H. , Doss S. H.
Published: May 2005

The 13C NMR spectra of 1,3‐propanesultam, 2,4‐butanesultam, 1,4‐butanesultam, 1,3‐propanesultone and 1,4‐butanesultone, as well as some of their unsaturated analogs 2,4‐dimethylbuta‐1,3‐diene‐1,4‐sultone and 2,4‐dimethylbuta‐1,3‐diene‐1,4‐sultam, have been recorded. The observed chemical shift data for the sultams and sultones can be explained mainly on the basis of inductive effects. The δ values of the dienesultone and the dienesultam are mainly affected by M‐effects. 1H NMR as well as mass spectra have.
Application of carbon‐13 n.m.r. Spectroscopy to the structural investigation of ezomycins
Authors: Sakata Kanzo , Uzawa Jun , Sakurai Akira
Published: May 2005

Ezomycins A1, A2, B1, B2, C1, C2, D1 and D2, antifungal antibiotics, are anhydrooctose uronic acid nucleosides. Their novel structures were confirmed by studying their natural abundance 13C n.m.r. spectra in detail from gated proton‐decoupled, long‐range selective proton‐decoupled and selective proton‐decoupled spectra. The J(CH) value of the anomeric carbon signal (C‐1″) supports the β‐configuration.
17O NMR: 2J(17O1H) coupling constants by line shape analysis
Authors: Delseth C. , Kintzinger J. P. , Nguyên T. T. Tâm , Niederberger W.
Published: May 2005

Two bond spin‐spin coupling constants 2J(17O1H) are determined for the oxygen in ether, aldehyde, acid, ester and amide groups by line shape analysis of the corresponding 17O NMR spectra.
A Karplus‐type relationship for the vicinal coupling 3J(CCCP) in phosphonates
Authors: Thiem Joachim , Meyer Bernd
Published: May 2005

The complete assignment of the 13C NMR spectrum of a conformationally rigid camphane phosphonate derivative leads to a Karplus‐type function for the vicinal 3J(CCCP) coupling constants in phosphonates. The general applicability of this relationship is demonstrated.
Determination of substituent chemical shifts in the proton resonance spectra of the porphyrins
Authors: Abraham Raymond J. , Eivazi Fahimeh , Nayyir‐Mazhir R. , Pearson Harry , Smith Kevin M.
Published: May 2005

Reproducible proton chemical shifts in the porphyrin series are obtained when the spectrum is measured in chloroform using the zinc (II) complex of the porphyrin in the presence of an excess of pyrrolidine. This method is specifically demonstrated for the case of 2,4‐dicyanodeuteroporphyrin‐IX dimethyl ester which, as the free base, shows dramatic effects due to aggregation phenomena. The shifts obtained using the zinc (II) complex plus pyrrolidine method, which allow compilation of substituent chemical shifts in the porphyrin series, are shown to be the same as the less easily accessible infinite dilution shifts of the porphyrin free bases.
13C‐NMR‐spektren von bicyclo[n.1.0]alkenen
Authors: Dürr Heinz , Albert Karl‐Heinz
Published: May 2005

Die 13C‐NMR‐Spektren einiger Bicyclo[3.1.0]hex‐3‐en‐2‐ole und Bicyclo[3.1.0]hex‐3‐en‐2‐one werden beschrieben. Die Bindungsparameter des Bicyclo[3.1.0]hex‐3‐en‐2‐ons werden aus der Kristallstruktur des endo‐6‐Methoxy‐1,3,6‐triphenylbicyclo[3.1.0]hex‐3‐en‐2‐ons abgeleitet. Mit der EHT‐Methode wird die Elektronendichte berechnet und mit den 13C‐Verschiebungen korreliert. Als Vergleichsspektrum wird das 13C‐NMR‐Spektrum eines Bicyclo[4.1.0]hepta‐1,5‐dionderivats analysiert. Die Einflüsse des an den Fünfring und an den Sechsring annellierten Cyclopropansystems werden miteinander verglichen. Während am Fünfring eine Konjugation zwischen der Carbonylgruppe und dem Cyclopropansystem auftritt, wird sie am Sechsring nicht beobachtet. Die Erklärung dafür wird auf die besonders starre Struktur des Fünfringsystems zurückgeführt.
Carbon‐13, 1H coupling constants for benzene and the tropylium ion
Authors: Günther Harald , Seel Horst , Günther Maria‐Eugenia
Published: May 2005

The 13C, 1H spin–spin coupling constants for benzene and tropylium fluoroborate have been measured from the 13C NMR spectra of [D5]benzene and the [D6]tropylium ion using a new experimental technique which employs highly deuterated compounds and 2D‐decoupling. For benzene the new data are in good agreement with earlier results. For the tropylium ion we find 1J = 166.79, 2J ≃ 0, 3J = 9.99 and 4J = (−)0.64 Hz. Secondary isotope effects for 13C chemical shifts, including one over four bonds, are reported.
Carbon‐13 NMR studies of thyroid hormones and model compounds. The conformational analysis of diphenyl ethers
Authors: Mazzocchi Paul H. , Ammon Herman L. , Colicelli Elena
Published: May 2005

The 13C spectra of a series of thyroid hormones and derivatives including thyroxine (T4) sodium salt, T4‐N‐acetyl methyl ester, triiodothyronine (T3), T3‐sodium salt, T3‐methyl ester hydrochloride, sodium triiodothyroacetate and ethyl triiodothyropropionate were assigned using chemical shift trends from model compounds, coupling constants and relaxation times. The 13C spectra of a series of diphenyl ethers were assigned and the chemical shift trends observed were analyzed on the basis of conformational changes engendered by mesomeric or steric effects.
Carbon‐13 NMR spectra of some pentacyclic triterpenoids with the olean‐12‐ene and 18α‐olean‐12‐ene skeleton
Authors: Ricca Giuliana Severini , Danieli Bruno , Palmisano Giovanni , Duddeck Helmut , Elgamal M. Hani A.
Published: May 2005

The 13C NMR spectra of some pentacyclic triterpenoids, 3β‐acetoxy‐11‐oxo‐olean‐12‐ene‐30‐oic acid methyl ester, 3β‐acetoxy‐11‐oxo‐olean‐12‐ene‐29‐oic acid methyl ester, the corresponding 11‐desoxo methyl esters, 3β‐acetoxy‐11‐oxo‐18α‐olean‐12‐en‐30‐oic acid methyl ester and 3β‐acetoxy‐11‐oxo‐18α‐olean‐12‐en‐29‐oic acid methyl ester are discussed. The shielding data are interpreted in term of the different orientation of the carbomethoxy group and of the change in configuration at the D/E ring junction and are diagnostically valuable for the differentiation of the mentioned compounds.
The interaction of metallophthalocyanines with electron‐acceptor metal chlorides
Authors: Białkowska Ewa , Graczyk Alfreda
Published: May 2005

It has been found that interactions of metallophthalocyanines with chlorides having electron‐acceptor properties results in the formation of charge transfer complexes of an ion‐pair nature. The electronic structure of these complexes and the mechanism of the interaction were studied by the EPR method. Spin‐Hamiltonian parameters were determined and the effect of the complex‐forming substance on the nature of the EPR spectrum was analysed. The experimental EPR results were correlated with the effective magnetic moments determined from measurements of magnetic susceptibility by the NMR method.
Chemical shifts for tritons in the ortho, meta and para positions of toluene as determined by tritium NMR spectroscopy
Authors: Calvert D. , Martin R. W. , Odell A. L.
Published: May 2005

Chemical shifts for tritons in ortho, meta and para positions in toluene have been determined using a 64 MHz tritium NMR spectrometer. The order of shift is meta>para>ortho, whereas the calculated shift order for protons is meta>ortho>para.
Carbon‐13 spectra of polycyclic systems Tricyclo[3.2.1.02,7]octanes as models for some tetracyclic sesquiterpenes and pentacyclic diterpenes. Ishwarane and trachylobane derivatives
Authors: Cory R. M. , Stothers J. B.
Published: May 2005

The 13C spectra of tricyclo[3.2.1.02,7]octane, its 1,5‐dimethyl derivative and ten tricyclo[3.2.1.02,7]octan‐6‐ones have been recorded as model compounds to aid the interpretation of the spectra of the naturally occurring polycyclic terpenes, ishwarane, ishwarone, ishwarol and methyl trachylobanate. The assignments for specific carbons in this series are based on the internal consistency of the observed shielding trends together with the effects of shift reagent on the shieldings of some of these derivatives.
13C13C spin coupling constants in phenanthrene derivatives
Authors: Berger Stefan , Zeller Klaus Peter
Published: May 2005

The synthesis of six 1‐X‐ (X = OH, OCH3, OCOCH3, CH3, CHO and CN) phenanthrene derivatives with a 13C label at C‐1 is described. An analysis of the 13C13C spin coupling constants shows the importance of π‐interaction for the coupling constant transmission. Small 13C13C spin coupling constants over 6 bonds are reported.
Carbon‐13 nuclear magnetic resonance spectroscopy of naturally‐occurring substances‐ LVII Triterpenes related to lupane and hopane
Authors: Wenkert Ernest , Baddeley G. Vernon , Burfitt Ivor R. , Moreno Louis N.
Published: May 2005

The 13C NMR spectra of lupeol and related triterpenes were recorded and all carbon shifts assigned. Their analysis aided in the shift assignment of the structurally related hopane‐like triterpenes.
Analyse Conformationnelle de Pseudoprotoberbérines Naturelles. II. Etude Structurale par RMN de 13C des Tétrahydropseudoprotoberbérines provenant de I'Isopyrum thalictroïdes
Authors: Moulis Claude , Stanislas Edouard , Rossi Jean‐Claude
Published: May 2005

Les quatre pseudoprotoberbérines extraites de l'Isopyrum thalictroïdes L. ont été réduites par NaBH4 en tétrahydropseudoprotoberbérines correspondantes. La confrontation de leurs données de RMN de 13C avec celles de protoberbérines de synthèse permet d'une part d'attribuer une configuration du type trans‐1 à ces quatre bases réduites et d'autre part de mettre en évidence pour cette configuration trans‐1 un critère sǔr de différenciation, basé sur le déplacement chimique du carbone C‐8, entre tétrahydroprotoberbérines (sub‐stituées en 9, 10) et tétrahydropseudoprotoberbérines (substituées en 10, 11).
1H, 13C, 31P NMR and conformational study of 7‐membered ring organophosphorus compounds. 1,3,2‐dioxaphosphepanes
Authors: Guimaraes A. C. , Robert J. B. , Taieb C. , Tabony J.
Published: May 2005

The 1H, 13C and 31P NMR data of several 2‐R‐2‐thiono‐1,3‐dioxa organophosphorus molecules with 7‐membered rings [R = Cl, OC6H5, C6H5, CH3, N(CH3)2] are reported. The conformation of the 7‐membered ring is discussed by reference to the 3J(POCH) coupling constants which are compared with those observed in 6‐membered 1,3,2‐dioxaphosphorinanes. It is shown that caution must be exercised in using the 3J(POCH) angular dependence as a stereochemical tool. The 31P spin lattice relaxation times of some of these 7‐membered rings have been measured and the values are discussed.
Carbon‐13 nuclear magnetic resonance spectroscopy of methyl‐substituted piperidines and their hydrochloride salts
Authors: Beguin Claude G. , Deschamps Marie‐Noëlle , Boubel Véronique , Delpuech Jean‐Jacques
Published: May 2005

Carbon‐13 chemical shifts and 1J(CH) coupling constants of piperidine, 4‐t‐butylpiperidine, five C‐methyl substituted piperidines and of the corresponding N‐methyl compounds have been measured. These NMR parameters have also been determined for the fourteen corresponding hydrochlorides. The N‐methyl‐C‐methyl piperidinium salts showed two stereoisomers on the positive nitrogen atom. The effect of protonation is discussed in relation to charge and steric effects and the methyl substituent effects are compared with those of methyl‐substituted cyclohexanes. Deviations from the general tendencies in the series are correlated with changes in ring conformations around the highly crowded substituted carbons.
15N nuclear magnetic resonance spectroscopy. Natural‐abundance 15N spectra of aliphatic oximes
Authors: Botto Robert E. , Westerman Philip W. , Roberts John D.
Published: May 2005

15N chemical shifts of the Z and E isomers of twenty‐two ketoximes and fourteen aldoximes have been determined at the natural‐abundance level of 15N, using Fourier transform methods. The influences of π delocalization, methyl substituents and solute concentration on the oxime nitrogen shielding have been determined. The 15N shifts for oximes of several cycloalkanones have been measured and the influence of ring size on the chemical shifts is discussed.
A carbon‐13 NMR study of some alkyl‐substituted indenes. An experimental study of the baker‐nathan order of hyperconjugation in the neutral ground state
Authors: Edlund Ulf
Published: May 2005

Carbon‐13 NMR spectra of several alkyl‐substituted indenes have been assigned and analysed. For structures having an alkyl substituent in the C‐2 position an increased shielding was observed for the remote conjugated positions C‐4 and C‐6, an alternating trend similar to that found for the 2‐cycloaminoindenes. The hyperconjugative behaviour was slightly more pronounced for the methyl group compared with an isopropyl or tert‐butyl substituent, a fact which supports a model where CH σ–π interactions are more efficient than those involving CC bonds.
NMR investigations on alanyl‐[15% 13C, 95% 15N]‐proline: 15N chemical shifts and 13C15N coupling constants
Authors: Blomberg F. , Rüterjans H. , Lintner K. , Toma F. , Fermandjian S.
Published: May 2005

The dipeptide alanylproline has been prepared with the proline residue both 13C (15%) and 15N (95%) enriched. 15N NMR spectra of alanylproline reveal signals for both possible conformations—cis and trans—of the dipeptide backbone in solution. Different pK values for both conformers are obtained from the pH dependence of the 15N chemical shifts using a least square programme based on the Henderson–Hasselbach equation. These different values are discussed in terms of interaction between the α‐amino group and the carboxylate group and between the carboxylate oxygen and the carbonyl oxygen of the dipeptide via hydrogen bonding. Further evidence for these interactions is obtained from the pH dependence of the ratio of the 15N NMR signal intensities of the two conformers. One, two or three bonded 13C15N coupling constants measured in the 13C NMR high resolution spectra have different values in the cis and trans isomers of alanylproline and thus indicate different geometry in the pyrrolidine ring.
Etude par RMN 13C de Dérivés Aromatiques Phénylés: Observation de Substituants Phényles en Rotation Restreinte
Authors: Caspar A. , Altenburger‐Combrisson S. , Gobert F.
Published: May 2005

La rotation restreinte de substituants phényles a été directement observée chez plusieurs dérivés aromatiques phénylés. Les barrières de rotation apparaissent en général supérieures à 14 kcal mol−1. Des critères utiles pour l'analyse structurale des dérivés aromatiques phénylés ont été dégagés.
13C NMR: Substituent effects on one‐bond 15N13C coupling constants in anilines and anilinium ions
Authors: Axenrod T. , Wieder M. J. , Khin Tun , Webb G. A. , Yeh H. J. C. , Bulusu S.
Published: May 2005

1J(15N13C) values obtained from FT 13C NMR spectra were measured for a number of 15N‐enriched aniline derivatives and are found to exhibit varying degrees of dependence on the nature of the ring substituent. Theoretical calculations of 1J(15N13C) values for representative members of the systems examined were made using INDO parameters and a ‘sum‐over‐states’ perturbation approach. The calculated coupling constants are generally in fair agreement with experimental values when the integral products SN2(o)SC2(o) and (r−3)N(r−3)C have values of 34.437 au−6 and 2.770 au−6, respectively.
The complete analysis of the 1H NMR spectra of quinoline and two of its derivatives. sign determinations of inter‐ring coupling constants by means of the INDOR technique
Authors: Attimonelli M. , Sciacovelli O.
Published: May 2005

The complete 1H NMR spectral analyses of quinoline and two of its derivatives (4,7‐dichloroquinoline and 8‐nitroquinoline) have been performed. All the long‐range coupling constants were determined both in magnitude and sign. In determining the signs the INDOR technique was very useful and successful, allowing the resolution of transitions as close as a few hundredths of a Hz. The signs of the inter‐ring coupling constants alternate with the number of intervening bonds, according to McConnell's rule, except the all‐trans6J couplings. A linear relationship has been found between the 1H−1H and 19F−19F inter‐ring coupling constants for which the spin polarization is transmitted almost exclusively via the π‐electron system.
13C, 13C coupling constants in phenyl substituted ethylene, naphthalene, phenanthrene and cyclopentadienone. Dependence on dihedral angles. Determination of signs by the symmetrical double labelling (SDL) method. IV
Authors: Hansen P. E. , Poulsen O. K. , Berg A.
Published: May 2005

Carbon‐13, carbon‐13 coupling constants and carbon‐13 chemical shifts have been measured in a series of phenyl substituted ethylenes and aromatics all doubly labelled with 13C at the olefinic positions (α,β‐) or at neighbouring aromatic positions, tetraphenylcyclopentadienone labelled at the 3,4‐positions, and dichlorodiphenylmethane labelled at the α‐carbon. Signs of coupling constants were determined by the symmetrical double labelling (SDL) method. Coupling constants over as many as five bonds are reported. Two‐bond couplings between carbons in the aromatic skeleton belong to different classes according to the nature of the coupling path. The magnitudes of three‐bond coupling constants between such carbons correlate linearly with π‐bond orders and a separation of the δ‐ and π‐contributions is evident. The three‐bond couplings between the 2‐position in a phenyl substituent and the olefinic β‐position or a corresponding aromatic position depend on the out‐of‐plane twist of the phenyl ring and may lead to information about the twist angle. Contrary to findings with aromatic carbonyl compounds two‐ and three‐bond couplings to the α‐carbon in the present compounds are fairly constant. The reported data suggest that the signs of coupling constants over more than two bonds alternate in aromatic systems. Carbon‐13, carbon‐13 coupling constants in naphthalene have been calculated by the INDO‐SOS method.
13C, 13C coupling constants in anthracene, 9,10‐dihydroanthracene and phthalic acid derivatives. Determination of signs by the symmetrical double labelling (SDL) method V
Authors: Hansen P. E. , Berg A.
Published: May 2005

Carbon‐13, carbon‐13 one‐bound and long‐range coupling constants are determined for anthracene and 9,10‐dihydroanthracene labelled in the 9,10‐positions, and for thiophthalic anhydride and phthalimide, labelled in both carbonyl groups. Relative signs are determined by the SDL method. Signs in naphthalene, anthracene and pyrene derivatives are discussed. The general trends observed in many aromatic compounds, 3J|>|2J|>|4J| and 2J positive, 3J positive, 4J negative are mostly confirmed. However, evidence suggests that two‐bond couplings between carbon atoms in the same ring in aromatic hydrocarbons are negative.
Preferential protonation and methylation at the nitrogen atoms of N,N‐dimethylamino derivatives of pyridine
Authors: Barbieri Giorgio , Benassi Rois , Grandi Romano , Pagnoni Ugo Maria , Taddei Ferdinando
Published: May 2005

The relative reactivity toward protonation and methylation of the two nitrogen atoms in N,N‐dimethylaminopyridines has been examined by 1H NMR. The ring position of the dimethylamino group has no influence on protonation, which occurs in all the derivatives at the heterocyclic nitrogen. The N‐methylation reaction does not follow a homogeneous behaviour, occurring at the exocyclic nitrogen in the 2‐substituted dimethylamino derivative. The electronic characteristics of the molecules, determined by MO calculations at a semi‐empirical level, indicate that both protonation and methylation should occur at the heterocyclic nitrogen; the calculated relative stabilites, however, of the N‐protonated and N‐methylated forms are in full agreement with the experimental results, and it appears that the anomalous behaviour of 2‐dimethylaminopyridine in the N‐methylation reaction is caused by steric factors.
Carbon‐13 NMR spectra of some 4‐ and 5‐substituted pyrimidines
Authors: Cheeseman Gordon W. H. , Turner Christopher J. , Brown Desmond J.
Published: May 2005

Carbon‐13 NMR chemical shifts and carbon‐proton coupling constants for nine 4‐substituted and six 5‐substituted pyrimidines are reported. The carbon chemical shifts are correlated with π‐electron densities. Carbon‐proton coupling constants fail to correlate with substituent electronegativity.
Application of NMR spectroscopy of chiral association complexes. 8—Rotation about the C(sp2)–C(aryl) Bond in 2,6–disubstituted benzamides
Authors: Holik Miroslav , Mannschreck Albrecht
Published: May 2005

The barrier to rotation about the C(sp2)C(aryl) single bond in non‐planar benzoyl compounds was investigated using N,N‐dimethyl, N,N‐tetramethylene and N,N‐diisopropyl derivatives of 2,4,6‐trimethylbenzamide and 2,6‐dimethoxybenzamide and N,N‐dimethyl derivatives of the corresponding thiobenzamides. Their 1H and 13C NMR spectra were determined and assigned and the splittings in the 1H spectra due to the addition of the optically active shift reagent (+)‐Eu(hfbc)3, are discussed. The free enthalpy of activation was calculated from the coalescence temperature of the ortho‐methyl or ‐methoxyl signals and from a line‐shape analysis. An exact equation for the determination of the rate constant at coalescence and a valid approximation which includes the line‐width are presented. A distinct effect of the size of the N‐substituent on the barrier to rotation in 2,6‐dimethoxybenzamides was observed, while the π values for the 2,4,6‐trimethylbenzamides studied are practically identical.
Nitrogen‐15 nuclear magnetic resonance spectra of isocyanates, isothiocyanates and N‐sulfinylamines
Authors: Yavari Issa , Staral John S. , Roberts John D.
Published: May 2005

The 15N NMR spectra of ten isocyanates, four isothiocyanates, and four N‐sulfinylamines have been obtained at the natural‐abundance level by high‐resolution NMR spectroscopy. The results show that isocyanates and isothiocyanates have 15N chemical shifts over 200 ppm toward higher fields compared to those of N‐sulfinylamines. The sensitivity of the 15N shifts in these substances to substituent and electronic effects are discussed.