bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of silver(II) complexes with ketoxime, nitroso and isonitroso compounds: ESR spectroscopy of the radicals formed
Authors: Jezierski Adam 
Published: May 2005

AbstractReactions of silver(II) complexes with ketoxime, nitroso and isonitroso compounds in organic solvents were investigated by ESR. The oxidation yielded iminoxy radicals RR′CNO˙ and/or nitroxides R1R2NO˙. The silver(II) complexes with nitrogen ligands (mono‐, bi‐ and tri‐dentate) and AgO were used as oxidizing agents. The reaction products were analysed on the basis of the ESR spectra. The signs of the 14N hyperfine constants for the radicals were determined using the ESR spectra in an MBBA liquid nematic crystal as solvent. A linear correlation was found between the hyperfine 14N parameters and the Dimroth‐Reichardt ET(30) coefficients for the iminoxy radicals.
Definitive assignment of the 13C NMR signals of the indole C‐3 and C‐3a carbons of the ajmaline, picraline and sarpagine alkaloids
Authors: Morales‐Ríos M. S. , Joseph‐Nathan P. 
Published: May 2005

AbstractComparison of a 1H coupled natural abundance 13C NMR spectrum of 1‐oxo‐1,2,3,4‐tetrahydrocarbazole with a single‐frequency experiment in which the hydrogens three bonds away from C‐3 (indole numbering) were irradiated allowed the unambiguous distinction of the C‐3 and C‐3a signals. The results can be extrapolated for the assignment of the same signals in the ajmaline, picraline and sarpagine alkaloids, which also contain a carbonyl group as the substituent at the C‐2 position of the indole skeleton. The effect of this carbonyl group on the chemical shifts of the benzenoid carbons is also discussed.
13C NMR spectra of antiviral nucleosides' 3′‐azido‐3′‐deoxythymidine, 2′,3′‐dideoxyadenosine, 2′,3′‐dideoxycytidine and 2′,3′‐dideoxyinosine
Authors: Buchanan G. W. , Bourque K. 
Published: May 2005

Abstract13C NMR chemical shifts and one‐bond 13C1H couplings are reported for 3′azido‐3′‐deoxythymidine, 2′,3′‐dideoxyadeno‐ sine, 2′,3′‐dideoxycytidine and 2′, 3′‐dideoxyinosine. Unambiguous assignments were made on the basis of results from 2D INADEQUATE experiments to establish the carbon–carbon connectivities.
Nuclear magnetic resonance study of gentiobiose octaacetate in solution
Authors: Marchettini Nadia , Ulgiati Sergio , Rossi Claudio 
Published: May 2005

AbstractGentiobiose octaacetate, a disaccharide molecule, was investigated in order to define (i) the proton and carbon assignments and chemical shift values, (ii) the carbon relaxation behaviour in DMSO solution and (iii) the dynamic properties of the molecule. It was found that in solution it behaves like a rigid molecule characterized by an unique isotropic correlation time. Scalar coupling constant analysis allowed the identification of the H‐6 axial and H‐6 equatorial protons for both sugar ring moieties.
Two‐bond deuterium isotope effects on 13C chemical shifts. A measure of carboncarbon bond lengths
Authors: Sardella D. J. , El‐Din Alyaa Emad 
Published: May 2005

AbstractTwo‐bond deuterium‐induced isotope effects (2Δ) have been studied in several neutral π‐systems (6,6‐dimethylfulvene, cyclohexene and cyclohexa‐1,3‐diene). Isotope effects on the 13C shifts of adjacent carbons are invariably to higher field, and vary from −84 to −139 ppb. In combination with literature data for a number of aromatic systems, these results establish that, for fragments of the type DC(sp2)13C(sp2) in five‐ or six‐membered rings, 2Δ correlates linearly with carboncarbon bond length, the average deviation between calculated and experimental bond lengths being 0.01 Å. The correlation embraces bridgehead and non‐bridgehead carbons in both five‐ and six‐membered rings. As a test of the utility of this empirical relationship, 2Δ in ferrocene‐d was determined to be −91 ppb, corresponding to a carboncarbon bond length of 1.42 Å, in good agreement with the experimental value of 1.43 Å.
13C NMR spectral studies of some methoxycoumarin derivatives. A re‐assignment for citropten (limettin) and an examination of Peri‐proximity effects for the methyl‐methoxy and methoxy‐methyl couples
Authors: Osborne Alan G. 
Published: May 2005

AbstractThe 13C chemical shifts and 13C1H coupling constants of some methoxycoumarins are reported. Some earlier spectral assignments, including those for citropten (limettin), require revision. Methoxy substituent effects on longrange 13C1H couplings in coumarins are highlighted. Peri‐proximity effects for the methyl‐methoxy and methoxy‐methyl couples are derived, and the value of these effects in the assignment of peri‐substituted compounds is illustrated.
NMR study of the monomer—dimer equilibria of dimethylnitrosobenzenes in solution. Identification of mixed azodioxy dimeric species
Authors: Orrell Keith G. , Stephenson David , Rault Thierry 
Published: May 2005

AbstractThe monomer‐dimer equilibria of 2,6‐ and 3,5‐dimethylnitrosobenzenes in CDCI3 solution were investigated by 1H and/or 13C NMR spectroscopy. The mixed systems nitrosobenzene + 2,6‐dimethylnitrosobenzene and 2,6‐dimethylnitrosobenzene + 3,5‐dimethylnitrosobenzene were also studied, and mixed azodioxy dimers were identified. In all systems exchange occurs exclusively between dimer and monomer species, rates and activation energies being calculated from time‐dependent 1H 1D spectra and/or 1H 2D‐EXSY spectra measured at different temperatures.
Nuclear spin relaxation of oxygen‐17, silicon‐29 and carbon‐13 in octamethylcyclotetrasiloxane
Authors: Kowalewski Jozef , Berggren Elisabet 
Published: May 2005

Abstract17O, 13C and 29Si nuclear magnetic relaxation data are reported for neat liquid octamethylcyclotetrasiloxane in the temperature range 298–373 K. The electric field gradient at the site of the oxygen nucleus is estimated by ab initio calculations and the 17O relaxation data are interpreted in terms of isotropic rotational diffusion. The 13C dipole‐dipole relaxation rates are interpreted in terms of the Woessner model for internal methyl rotation superimposed on the isotropic overall tumbling. The 29Si spin‐lattice relaxation is composed of dipole‐dipole and spin‐rotation contributions, which are interpreted in a semi‐quantitative fashion.
Analysis of the 1H NMR spectra of the carboxylic ionophore narasin A in its Apo and cation‐bound forms
Authors: Caughey Byron W. , Gibbons William A. , Painter George R. 
Published: May 2005

AbstractAs a first step in the conformational analysis of the cation‐binding reactions of the carboxylic ionophore narasin A, 1H NMR spectra of narasin A in its apo and H+ ‐, K+ ‐ and Na+ ‐bound forms in CD3OD were assigned. In addition, new assignments for the spectrum of H+ ‐narasin A in CDCl3 were obtained. Two dimensional 1H−1H chemical shift correlation, one‐dimensional nuclear Overhauser effect and decoupling difference techniques were used to determine the chemical shifts and 1H1H coupling constants.
13C NMR study of the substituent effects on the internal steric hindrances in amidines
Authors: Wawer Iwona 
Published: May 2005

Abstract13C NMR spectra of ten formamidines, five acetamidines and five butyramidines were recorded at low temperatures. The barrier to rotation around the CN1 bond for N2‐alkylformamidines is approximately 50 kJ mol−1 and for N2‐benzylformamidines approximately 52 kJ mol−1, and is thus ca. 10 kJ mol−1 lower than for N2‐phenylformamidines. The height of the barrier is related to Taft's substituent constants at N2, δG* = 49.25 + 8.08σ* −3.21Es. In the acetamidines the steric hindrance between the alkyl substituent at N2 with CFCH3 contributed to the decrease in δ* (lower than 40 kJ mol−1). The i‐C3H7 substituent at CF in butyramidines forces isomerization and these amidines become Z isomers. MNDO calculations indicate no significant changes of bond length on E/Z isomerization, and the low rotational barrier in butyramidines is probably caused by the steric interaction of the aromatic ring at N2 with the N1 (CH3)2 group.
Carbon‐13 NMR of the N‐substituents in 2,4,6‐trisubstituted pyridinium salts
Authors: Salman Salman R. , Khayat M. A. R. 
Published: May 2005

AbstractThe carbon‐13 chemical shifts of seven N‐substituted trimethylpyridinium and triphenylpyridinium salts and seven amines are reported.
Utilization of the selective pulse INEPT NMR experiment (INAPT) for the facile distinction of quaternary carbons attached to a trisubstituted alkene
Authors: Bernstein Michael A. 
Published: May 2005

AbstractThe INEPT experiment which uses selective 1H pulses (INAPT) was used to assign quaternary carbon NMR signals in trisubstituted alkenes. Given that 3J(CH) across the double bond is usually larger for the trans than the cis disposed nuclei, experimental conditions may be chosen such that more polarization transfer is effected in the case of the trans nuclei. We applied this approach to two important pharmaceutica Is, cyclobenzaprine and ami‐triptyline, and some structurally related compounds. In each case the INAPT experiment quickly afforded a stereochemical assignment. Assignments were corroborated with the data from two‐dimensional selective hetero‐nuclear J‐resolved and heteronuclear nuclear Overhauser effect experiments.
Complete assignment of the 13C and 1H NMR spectra of thyrsiferyl acetate
Authors: Blunt John W. , McCombs John D. , Munro Murray H. G. , Thomas Frank N. 
Published: May 2005

AbstractThe assignment of all reasonances in the 13C and 1H NMR spectra of thyrsiferyl acetate has been made through the application of 2D NMR experiments, together with the use of difference NOE spectroscopy.
Complete assignment of the 1H and 13C NMR spectra of 1,3‐diaza‐2,4‐diboranaphthalene derivatives by two‐dimensional NMR spectroscopy
Authors: Allaoud Smail , Bitar Hassan , Frange Bernard , Faure Robert 
Published: May 2005

AbstractThe total assignment of the 13C and the 1H NMR spectra of four derivatives of 1,3‐diaza‐2,4‐diboranaphthalene has been performed. The interpretation of the spectra was achieved from the concerted application of direct and long‐range heteronuclear chemical shift correlation and homonuclear COSY two‐dimensional NMR spectros‐copy. In addition, the 11B NMR chemical shifts of one of the compounds are reported and tentatively assigned.
Natural abundance carbon‐13 and deuterium NMR studies on the liquid and solid phases of tert‐butyl iodide
Authors: Aksnes D. W. , Ramstad Kari 
Published: May 2005

AbstractCarbon‐13, deuterium and proton NMR line shapes of polycrystalline tert‐butyl iodide (1) have been studied between 200 K and the melting point (239 K). Carbon‐13 and deuterium spin‐lattice relaxation times (T1) were measured between 313 and 200 K in the liquid and solid phases of 1.The NMR line shape data indicate the occurrence of two disordered phases of 1 between the melting point and 222 K. An analysis of the 13C and 2H T1 relaxation times is reported. The 13C and 2H T1 relaxation is governed by overall molecular tumbling in the liquid and disordered phases of 1, whereas the 13C T1 relaxation in the ordered solid is governed by uniaxial molecular reorientation of the tert‐butyl group. Rotational correlation times, activation energies and pre‐exponential factors were obtained from the T1 data by using the Arrhenius equation. Significantly different activation parameters were obtained for the two disordered solids. The effective correlation time at the melting point of 1 (ca. 5 ps) is 2–3 times longer than for other globular tert‐butyl compounds.
Structure of norbornene‐fused 3,1‐oxazine double cycloadducts
Authors: Sohár Pál , Bernáth Gábor , Stájer Géza , Szabo Angela E. 
Published: May 2005

AbstractPentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene‐azetidinone‐fused 3,1‐oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments.
1H and 13C NMR spectra of 4,4′‐substituted chalcones
Authors: Hayamizu Kikuko , Yanagisawa Masaru , Ishii Tetsuko , Yabe Atsuko , Yamamoto Osamu , Nakayama Masaharu , Hayashi Akio 
Published: May 2005

Abstract1H and 13C NMR spectra of chalcone (trans‐benzylideneacetophenone) and 54 4,4′‐substituted chalcones were studied. The 400 MHz 1H NMR and the 13C NMR spectra were observed, analysed and assigned and the substituent constants were calculated by the least‐squares method.
A 1H and 13C NMR study of N‐formylmorphinans and their 6,14‐bridged derivatives; Comparison with N‐Me and NH analogues
Authors: Linders J. T. M. , Prazeres M. A. , Lie T. S. , Maat L. 
Published: May 2005

AbstractThe 1H NMR and 13C NMR spectra of N‐formylated morphinans were compared with those of the N‐methyl and N‐demethyl analogues. The magnitude of the changes in chemical shift of C‐9, C‐16 and C‐10 depended crucially on the nature of the substituent at nitrogen. For the 6α, 14α‐ethenoisomorphinans and 6β,14β‐ethenomorphinans, the proton chemical shifts of the 6,14‐etheno bridge across ring C are differently affected by the nitrogen atom. In the 6α,14α‐ethenoisomorphinans, the vinylic proton shifts are found between δ5.3 and 5.9, whereas in the 6β,14β‐ethenomorphinans these proton signals are found downfield from δ6.0. A similar, but opposite, anisotropy effect of the nitrogen is observed for the 8β‐proton. These results are important for the elucidation of the structures of these types of compounds.
1H and 13C NMR study of the adsorption of alcohols on charcoals with various pore structures
Authors: Du You‐Ru , Yuan Han‐Zhen , Wu Dong‐Hui , Kong Yu‐Hua 
Published: May 2005

AbstractA 1H NMR study of methyl, ethyl, n‐propyl, isopropyl and allyl alcohols adsorbed on charcoals with various pore structures showed that the adsorption mechanism is by capillary condensation in pores with radii smaller than 30 Å, and by mono‐/multi‐layer adsorption on the solid surface of pores with larger radii. This mechanism is identical with that of adsorbed hydrocarbons. The 13C NMR parameters suggest that the adsorbed alcohols are preferentially oriented in the monolayer, with the methyl groups bonded to the solid surface. Longer chain alcohols are bent in capillaries with radii smaller than 10 Å. The broadening of the 13C resonances was partly eliminated in magic angle spinning experiments by using a spinning rate of 1.5–1.8 kHz.
Assignments of the 1H and 13C NMR resonances of C‐nucleoside analogues by means of two‐dimensional shift correlated NMR techniques
Authors: Dennin F. , Rousseaux O. , Blon‐Deau D. , Sliwa H. 
Published: May 2005

AbstractTwo‐dimensional 1H and 13C shift correlated NMR experiments were used for the unambiguous assignments for all proton and carbon chemical shifts of C‐nucleosides in [1,2,4]triazolo‐[1,5‐c]‐ and ‐[4,3‐c]‐pyrimidines.
Measurement of long‐range proton—carbon coupling constants in medium‐sized molecules
Authors: Hricovíni Miloš , Liptaj Tibor 
Published: May 2005

AbstractA modified version of the two‐dimensional semiselective INEPT experiment is presented which allows the determination of long‐range proton‐carbon couplings in medium‐sized molecules. The difference in the T1 relaxation times is utilized for the reduction of the number of protons from which coherence is transferred. This results in a simplification of the 1D and 2D spectra obtained. The capability of the proposed pulse sequence is demonstrated by the determination of the long‐range couplings in a model molecule.
Complete spectral assignments of tatsidine by two‐dimensional NMR techniques
Authors: Snyder John K. , Zhang Xiaolin , Joshi Balawant S. , Pelletier S. William 
Published: May 2005

AbstractHomonuclear 1H COSY, long‐range COSY and relay coherence transfer (RCT) correlation spectroscopy NMR experiments were used together with fixed‐evolution HETCOR and selective INEPT spectra for complete 13C and 1H spectral peak assignments for tatsidine. Stereochemical and conformational assignments were made from the two‐dimensional NOE spectrum. The results of these studies confirmed the location of the methylenedioxy group at C‐7/C‐8.
13C NMR spectra of some 4‐substituted N‐acetonyl ‐ N, N‐dimethyl‐N‐phenacyl‐ammonium bromides
Authors: Grandjean Jean , Laszlo Pierre , Canto Eduardo Leite Do , Rittner Roberto 
Published: May 2005

AbstractThe 13C NMR signals for some 4‐substituted N‐acetonyl‐N,N‐dimethyl‐N‐phenacylammonium bromides were assigned. The HETERCOSY and COLOC sequences allow an unambiguous distinction between the very similar signals of the methylene carbons. The chemical shifts observed for the aromatic ring carbons are in close agreement with those calculated from substituent increments.
59Co NMR of cobalt(III) porphyrin complexes. III. Data base on substituent and solvent effects
Authors: Bang H. , Cassidei L. , Danford H. , Edwards J. O. , Hagen K. I. , Krueger C. , Lachowitz J. , Schwab C. M. , Sweigart D. A. , Zhang Z. 
Published: May 2005

AbstractA broad study of the 59Co NMR of cobalt(III) porphyrin complexes with axial amine ligands in a variety of solvents is reported. The data are presented in tabular form, as are the numerical correlations of chemical shift, δ, and line width, ω1/2, using the Kamlet‐Taft equation. The dependence of δ and ω1/2 on ligand substituents is discussed. Solvent data, including mixed solvent results, indicate that general factors such as acidity, basicity, polarity and hydrogen‐bonding capability are important, as are the specific nature of the functional groups on the ligands and the solvent.
13C NMR study of substituted 10,10‐diphenyl‐9‐phenanthrones. Structure determination and signal assignment using 2D NMR techniques
Authors: Mynott R. , Romão Maria J. , Herold B. J. 
Published: May 2005

AbstractThe 13C NMR spectrum of 10,10‐diphenyl‐9‐phenanthrone was assigned unambiguously using 2D 13C,1H shift correlated NMR spectra, optimized either for one‐bond or long‐range 13C1H couplings, and 2D RELAY NMR spectra. This information allowed the structures of a number of substituted 10,10‐diphenyl‐9‐phenanthrones to be deduced from their 13C NMR spectra. The results provide an insight into the mechanism of the reaction of 9‐fluorenone with chlorodiphenylmethyllithium.
Carbon‐13 NMR chemical shifts of 1‐alkyl‐3(5)‐cyano‐1H‐pyrazole‐4‐carboxylic acid esters
Authors: Babbitt George E. , Lynch Michael P. , Beck James R. 
Published: May 2005

AbstractA compilation of 13C NMR chemical shifts for 13 pairs of 3‐ and 5‐cyano‐substituted pyrazole regioisomers is reported. All of the ring carbon and cyano carbon 13C chemical shifts show a regular, predictable correlation with the particular isomer, whether 3‐cyano or 5‐cyano. These shifts occurred in very narrow ranges, precluding any confusion of assignment within the group of compounds studied. x‐ray crystallographic analysis was performed on one of the samples.
Isolation of spatulenol and (−)‐caryophyllene oxide from Vernonia mollissima don and 1H and 13C reassignment by two‐dimensional NMR spectroscopy
Authors: Krebs H. C. , Rakotoarimanga J. V. , Habermehl G. G. 
Published: May 2005

AbstractTwo sesquiterpenoids, spatulenol and (−)‐caryophyllene oxide, were isolated from the hexane extract of the Brazilian plant Vernonia mollissima Don. The 1H and 13C NMR spectra of these compounds have been reassigned completely by COSY experiments and 13C/1H shift correlation diagrams.
Use of selective excitation techniques for the rapid analysis of 13C NMR data for enriched carbohydrates
Authors: Bossenne V. , Firmin P. , Perly B. , Berthault P. 
Published: May 2005

AbstractOne‐dimensional selective scalar transfer experiments are presented for the analysis of 13C NMR data for multilabelled molecules. ‘Classical’ 13C COSY experiments rapidly show limitations when a complete determination of remote coupling constants is required. Conversely, combination of 1D COSY and RELAY affords all the required information very rapidly and accurately. Three 13C‐labelled monosaccharides exhibiting different degrees of spectral complexity are used to illustrate the merits of these techniques.
Aromatic ring dynamics in crystalline molecular solids by one‐ and two‐dimensional exchange spectroscopy
Authors: Twyman J. Mark , Dobson Christopher M. 
Published: May 2005

AbstractVariable‐temperature phase‐sensitive cross‐polarization/magic angle spinning magnetization transfer experiments in one and two dimensions, in conjunction with chemical shift line‐shape analyses, have been used in the quantitative characterization of slow aromatic ring dynamics in crystalline 4‐nitro‐1‐methoxybenzene and in crystalline penicillin G phenyl ester. The results obtained indicate the value of such approaches for investigating specific motional events in molecular solids.
α‐Nitroketones. Part 10.113C NMR spectra of alkylated 2‐nitrocyclohexanones
Authors: Zajac W. W. , Boyko W. J. , Gagnon J. L. 
Published: May 2005

AbstractThe 13C NMR spectra of 22 α‐nitrocyclohexanones were recorded and fully assigned. The one‐bond CH coupling constants for the nitromethine resonances of these compounds were also obtained and tabulated.
Carbon‐13 chemical shift assignment of (E)‐stilbenyloxyalkylthiouracils
Authors: Wybieralska Jadwiga , Wyrzykiewicz Elżbieta 
Published: May 2005

AbstractThe 13C NMR spectra of twelve isomeric 2‐and 4‐(E)‐stilbenyloxyalkylthiouracils have been calculated and fully assigned. The Ai and AiK empirical parameters of 4‐ketopyrimidyl‐2‐thioalkoxy, 2‐ketopyrimidyl‐4‐thioalkoxy, 2‐(E) ‐stilbenyloxyalkyl, 2‐(E)‐stilbenyloxyalkylthio, 4‐(E)‐stilbenyloxyalkyl and 4‐(E)‐stilbenyloxyalkylthio groups were calculated for the predictions of the chemical shifts of substituted uracils and benzenes.
17O NMR spectroscopic study of substituted benzoquinones and α,β‐unsaturated cyclic ketones
Authors: Boykin D. W. , Baumstark A. L. , Mehdizadeh A. , Venkatramanan M. K. 
Published: May 2005

AbstractThe17O NMR chemical shift data for a series of substituted benzoquinones and α,β‐unsaturated cyclic ketones in acetonitrile at 75°C are reported. In general, for the unsymmetrically substituted quinones two signals were observed, the assignments of which were made by17O enrichment and exchange experiments. For the benzoquinones, the effect of α‐methyl substitution (shielding) was greater on the signal for the 1‐carbonyl group than on that for the 4‐carbonyl group. α‐tert‐Butyl substitution resulted in deshielding of the proximate carbonyl group compared with that in the methyl analog. For the five‐ and six‐membered ring enones the shielding effect of β‐substituents was interpreted as electronic in origin. The large shielding effects observed for α‐substitution in the quinone and enone systems appeared to be the result of a combination of electronic and attractive van der Waals effects.
1H and 13C NMR conformational studies on quaternary nitrogen derivatives of the analgesic drug nefopam
Authors: Glaser Robert , Peleg Ariel , Geresh Shimona 
Published: May 2005

AbstractNitrogen quaternization in the analgesic nefopam [(±)‐3,4,5,6‐tetrahydro‐5‐methyl‐1‐phenyl‐1H‐2,5,‐ benzoxazocine hydrochloride] by either N‐trideuteriomethylation or N‐oxidation affords reaction product diastereomeric mixtures differing in N‐configuration. The axial to equatorial N‐CH3 product ratios were found to be ca. 3:2 (N‐trideuteriomethylation) and approximately equimolar (ca. 48:52, N‐oxidation). Both diastereomeric N‐oxides have boat‐(flattened chair) conformations of the octagonal ring in which the phenyl group is exo‐oriented. The quaternary ammonium salts showed considerable line broadening in the 1H NMR spectrum owing to rapid conformational equilibration. The same boat‐(flattened chair) conformation is clearly the preponderant contributor to the time‐averaged structure of nefopam methiodide in CD2Cl2 solution, similar to the case for the equatorial N‐methyl isomer of the parent hydrochloride salt. Conformational assignments were based on the vicinal coupling constants in the —OCH2CH2N—fragment and on the finding of an NOE intensity enhancement for the benzhydrylic‐H on irradiation of the equatorially oriented —OCH.