bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR shift reagents for organic salts: Shift mechanism, bound shifts and structural analysis
Authors: Wenzel Thomas J. , Cameron Kirk 
Published: May 2005

AbstractLanthanide tetrakis(β‐diketonate) anions are effective NMR shift reagents for organic salts. The shifts in the 1H NMR spectra were analyzed and explained without invoking a contact shift mechanism. The equilibria of the shift reagent‐substrate complex was examined. No evidence was found for a 1:2 shift reagent‐substrate complex. Bound shifts and association constants were determined for 1‐methyltetrahydrothiophenium iodide (1) and 1‐ethylquinolinium (3) iodide. The observed shifts for these salts were fitted to calculated shifts using the simplified dipolar shift equation. A single lanthanide location was identified with 3. A time average of at least two configurations of shift reagent‐substrate complex was required with 1.
Full assignments of the 1H and 13C NMR spectra of sodium fusidate in organic and aqueous media
Authors: Barber Jill , Lian Luyun , Morris Gareth A. , Tehrani M. Hassan 
Published: May 2005

AbstractThe 1H and 13C nuclear magnetic resonance spectra of sodium fusidate in methanol‐d4 and in D2O have been assigned using a range of one‐ and two‐dimensional NMR techniques.
EPR study of radicals derived from fumaronitrile and related carboxylic acids
Authors: Smith Peter , Donovan William H. , Parker Julie K. 
Published: May 2005

AbstractUsing aqueous TiCl3‐based continuous‐flow, radical‐generating methods, a comprehensive investigation was made of radicals derived from fumaronitrile and cis‐ and trans‐carboxylic acids of general structure CY(COOH)CH(COOH), where Y is H, CH3 or CH2COOH. All substrates were examined at 25°C but, where appropriate, the temperature was also varied over the range 10–40°C. The radicals observed from these compounds were of two main types, addition and electron transfer. This investigation emphasized the study of the addition radicals formed from fumaronitrile and maleic acid and of the electron‐transfer radicals formed from the carboxylic acids. Several of the addition radicals showed long‐range splittings. Among these, the radicals magnified image and magnified image were given particular attention, thus showing that they exist in axial and equatorial conformations—a situation not commonly encountered. All of the acids yielded one‐electron transfer radicals, some of which had interesting stereochemical properties, including intramolecular hydrogen bonding.
1H and 13C NMR analysis of three quinone‐methide triterpenoids
Authors: Gunatilaka A. A. Leslie , Fernando H. Chandrasiri , Kikuchi Tohru , Tezuka Yasuhiro 
Published: May 2005

AbstractDetailed analysis of the 1H and 13C NMR spectra of three natural quinone‐methide triterpenoids, pristimerin, tingenone and 20‐hydroxytingenone, was carried out by the application of two‐dimensional 1H1H and 1H13C shift correlation techniques. Some previous 1H and 13C assignments have been revised.
13C chemical shift assignments for isomers of some 1,2‐diaroyl‐3‐aryl‐cyclopropanes
Authors: Reddy D. Bhaskar , Reddy B. Venkataramana , Seshamma T. , Sankaraiah B. , Reddy M. V. Ramana 
Published: May 2005

AbstractThe 13C chemical shifts of some isomeric 1,2‐diaroyl‐3‐arylcyclopropanes have been determined. The δc, values of C‐1 and C‐2 of the cyclopropyl ring carbons and those of the C‐4 and C‐5 carbonyl carbons are used as a criterion for distinguishing between the stereoisomeric forms.
Structure of and electronic interactions in aromatic polyvalent iodine compounds: A 13C NMR study
Authors: Katritzky Alan R. , Gallos John K. , Durst H. Dupont 
Published: May 2005

AbstractAvailable data on the structures, electronic substituent effects and 13C NMR spectra of aromatic polyvalent iodine compounds, particularly iodoso and iodoxy derivatives, are summarized and discussed. A series of aromatic tri‐ and penta‐valent iodine compounds were synthesized, their 13C NMR spectra were measured and the substituent chemical shifts (SCS) for several polyvalent iodine functional groups were calculated. As the oxidation state of iodine increases (I → II → V), the strong shielding of the ipso‐carbon atom by iodine in aryl iodides due to the ‘heavy‐atom effect’ (30 ppm) decreases substantially, and this decrease is apparently general for stable hypervalent iodine compounds. Possible explanations are discussed and correlations between chemical shifts, structures and/or electronic effects are proposed.
Reaction of dibenzalacetone with hydroxylamine hydrochloride under phase‐transfer conditions. 1H and 13C 2D NMR structural elucidation of the products
Authors: Aguilera J. L. , Sosa G. , Reynolds W. F. , Diaz E. , Barrios H. 
Published: May 2005

AbstractThe constitution, configuration and conformation of three N‐hydroxydiphenylpiperidines were established by 1H and 13C 2D NMR spectroscopy. The products were obtained using phase‐transfer conditions.
13C NMR spectra of some halocarbons. Shift predictions in polychloro‐quinolines and ‐isoquinolines
Authors: Matthews R. S. , Jones M. , Banks J. 
Published: May 2005

AbstractThree methods, two empirical and one semi‐empirical, for predicting 13C chemical shifts in six poly‐chloroheterocyclics are considered. It was found that the semi‐empirical correlations with CNDO/2 calculated charges, although useful, could not be used in isolation from the other two methods. Of these, the MSCS (multiple substituent chemical shifts) method could be used to predict all eighteen carbon shifts in perchloroquinoline and perchloroisoquinoline, whilst the NIMS method (hypothetical nitrogen insertion method) was limited to the carbons in the heterocyclic ring. In brief, it was found that the MSCS method was the most accurate (less than ± 1 ppm) for predicting chemical shifts, intrinsically compensating for some of the errors arising from mutual atom‐atom interactions.New 13C data are reported for heptachloroquinoline, a mixture of two polychloroquinolines, hepta‐chloroisoquinoline and two, separable, new polychloroisoquinolines.
13C NMR spectra of amino‐alkylphosphonic acids
Authors: Głowacki Zdzislaw , Topolski Marek 
Published: May 2005

Abstract13C chemical shifts and 31P,13C coupling constants are reported for 20 amino‐alkylphosphonic acids and two phosphonic acids. The substituent‐induced chemical shifts of the phosphonate group were calculated and their non‐additivity in 1‐aminoalkylphosphonic acids was observed. Two stable conformers of 4‐aminobutylphosphonic acid were detected by 13C NMR.
Assigned cluster11B and1H NMR properties of [3‐(η6‐C6Me6)‐closo‐3,1,2‐RuC2B9H11]
Authors: Bown Mark , Plešek Jaromír , Baše Karel , Štíbr Bohumil , Fontaine Xavier L. R. , Greenwood Norman N. , Kennedy John D. 
Published: May 2005

AbstractThe cluster11B chemical shifts in members of the important class ofcloso‐3,1,2‐metalladicarbaboranes were previously unassigned, and their cluster1H chemical shifts previously unmeasured. The use of [11B11B]‐COSY and1H‐{11B} NMR spectroscopy to measure and assign the cluster11B and1H chemical shifts of (previously unreported) [3‐(η6‐C6Me6)‐closo‐3,1,2‐RuC2B9H11] as a model compound is reported. The11B shielding patterns of this species and the nonmetalla simple carbaborane analogue [1,2‐C2B10H12] are compared and briefly discussed.
Interpretation of the solvent effect on the screening constant of Xe‐129
Authors: Luhmer M. , Dejaegere A. , Reisse J. 
Published: May 2005

AbstractThe chemical shift (δ) of a xenon monoatomic molecule is very sensitive to the environment. The major contribution to this shift arises from the van der Waals interactions between the solvent and the xenon molecules. Usually, this solvent effect is interpreted via a reaction field model. This approach leads to a search for a correlation between δ and a function of the square of the refractive index of the solvent [f(n2)]. This paper illustrates the use of a theoretical model developed in our laboratory for the interpretation of the solvent effect on the xenon chemical shift. This model allowed the calculation of the xenon‐solvent dispersion energy (Edis) for different solvents, and the correlation of Edis with δ. The Edis‐δ correlation is clearly better than the f(n2)‐δ correlation.
The influence of crown ethers on cation migration processes. Part 7.1 The 2‐pivaloyl‐1,4‐benzoquinone radical anion
Authors: Flint Nicholas J. , Tabner Brian J. 
Published: May 2005

AbstractThe 2‐pivaloyl‐1,4‐benzoquinone radical anion has been prepared by alkali metal reduction in tetrahydrofuran in the presence of dibenzo‐18‐crown‐6, 15‐crown‐5, or 12‐crown‐4, and its ESR spectrum in each system has been recorded over a range of temperatures. Line‐width variation in the ESR spectrum is observed in some systems. This line‐width variation has been attributed to cation migration between sites adjacent to the non‐equivalent carbonyl groups rather than to restricted rotation of the pivaloyl group. In some systems, however, the rate of migration is too fast and in others too slow, compared with the time‐scale of the ESR experiment, for line‐width variation to be observed. The influence of each crown ether upon the rate of cation migration has been found to depend upon the size of the crown ether ‘cavity’ compared with the size of the alkali metal counter‐ion.
Stereochemical studies of the 4‐alkyl‐4‐arylpiperidine class of opioid ligand
Authors: Casy A. F. , Dewar G. H. , Al‐Deeb Omar A. A. 
Published: May 2005

AbstractThe 1H (270, 400 MHz) and 13C (67.5 MHz) NMR spectra of some 4‐methyl‐ (also 4‐n‐propyl‐ and ‐isobutyl)‐4‐(3‐hydroxy‐ and 3‐methoxy‐phenyl)piperidines and their 3‐methyl diastereoisomers are reported. Many of the compounds had opioid ligand activities. The data were analysed in terms of preferred conformation and configuration (3‐methyl derivatives). Only compounds with preference for axial 4‐aryl chair conformations displayed marked agonist properties and the one potent antagonist, cis‐1,3,4‐trimethyl‐4‐(3‐hydroxyphenyl)piperidine, favoured an equatorial 4‐aryl chair.
High resolution NMR study of some chromium compounds in solution
Authors: Dove Michael F. A. , Jones Eleanor M. Lloyd , Clark Ronald J. 
Published: May 2005

AbstractA study was made of some pseudo‐tetrahedral CrVI and octahedral Cr0 compounds by high‐resolution 53Cr NMR spectroscopy. Cr(PF3)6 and fac‐Cr(CO)3(PF3)3 provide the first examples of compounds showing a one‐bond coupling, 1J(53Cr, 31P), in a 53Cr NMR spectrum. This technique also provides proof of the formation of CrO2ClF in a mixture of the dichloride and difluoride.
1H, 13C 2D NMR experiments for the identification of an impurity in lauryl lactam from cyclododecane
Authors: Huvenne Jean‐Pierre , Atochem Bernard Lamy , Mouchel Bernard 
Published: May 2005

AbstractThe main impurity in lauryl lactam from cyclododecane has been identified as 1‐azabicyclo[8.3.0]tridecan‐13‐one by means of several two‐dimensional NMR techniques.
Two‐dimensional NMR study of ganwuweizic acid
Authors: Cui Yu‐Xin , Hua Su‐Ming , Cheng Jin‐Long , Yue Jian‐Min , Chen Yao‐Zu 
Published: May 2005

AbstractSeveral two‐dimensional NMR techniques were applied to assign completely the 1H and 13C chemical shifts and to study the configuration and conformation of a new triterpenoid, 3‐keto‐9,10,19‐cyclopropyllanost‐24‐en‐26‐oic acid (ganwuweizic acid). Some 13C NMR signals previously reported for the triterpenoid skeleton were corrected.
Suppression of artefacts in nuclear overhauser effect difference spectroscopy by reference deconvolution
Authors: Morris Gareth A. , Cowburn David 
Published: May 2005

AbstractReference deconvolution allows the effects of common instrumental imperfections in Fourier transform NMR, including field inhomogeneity, field/frequency ratio instability and pulse phase and amplitude irreproducibility, to be removed from spectra containing a well‐resolved reference signal. By applying reference deconvolution to the two component spectra, perturbed and unperturbed, of a nuclear Overhauser effect difference spectrum, the artefacts that instrumental imperfections normally cause in the difference spectrum may be suppressed. A small penalty in signal‐to‐noise ratio is paid for an improvement of several orders of magnitude in artefact suppression, allowing even very small Overhauser enhancements to be detected with confidence. Results are presented showing the reduction of difference artefacts for methyl singlets, normally the most severe test for NOE difference spectra, to below 1 part in 50 000.
Proton and carbon‐13 NMR studies of 1‐substituted pyridinium salts
Authors: Katritzky Alan R. , Dega‐Szafran Zofia 
Published: May 2005

Abstract1H and 13C NMR chemical shifts of a series of 1‐substituted pyridinium salts were measured in dimethyl sulfoxide. The effect of the quaternary pyridinium ring on the resonance of the methylene group of the substituent is reported. Increments of δ1H = 3.89 ± 0.16 ppm and δ13C = 47.5 ± 3.7 ppm and are estimated for replacing YCH2H with YCH2Py+. The effects of 1‐substituents on the pyridinium ring chemical shifts are discussed.
Natural abundance one‐bond 13C13C coupling constants and unambiguous assignments of 13C NMR spectra of thieno[c]quinolines and thieno[c]isoquinolines
Authors: Gronowitz Salo , Servin Rolf , Yang Youhua 
Published: May 2005

AbstractThe one‐bond 13C13C coupling constants [1J(CC)] in all structurally possible thieno[c]quinolines, thieno[c]isoquinolines, phenanthridine, quinoline and iso‐quinoline were measured at natural abundance by using the INADEQUATE pulse sequence technique. The unambiguous assignments of the 13C NMR spectra of thieno[c]quinolines and thieno[c]isoquinolines are reported.
1H and 13C NMR studies of some O‐carbamoyloximes
Authors: Wazeer Mohammed I. M. , Ali Sk. A. , Arab Mohammed 
Published: May 2005

AbstractThe 1H and 13C NMR spectra were assigned for a series of O‐carbamoyloximes of ortho‐ and para‐substituted benzaldehyde. These compounds exist exclusively in the E configuration. The aromatic protons and carbons show correlations with the appropriate substituent‐induced shifts and with Hammett parameters.
1H and 13C NMR studies on the oxydimethyleneaminomethyl fragment in six‐ and eight‐membered rings. The solution stereochemistry of N‐methyl diastereomers of phendimetrazine (an oxazine anorexic drug) versus nefopam (a benzoxazocine analgesic drug)
Authors: Glaser Robert 
Published: May 2005

AbstractThe 1H NMR spectrum (CD2Cl2) of the mesylate analogue of phendimetrazine bitartarate, a central nervous system stimulant and an anorexic drug, showed two isomers (ratio ≈︁ 17:1) differing in the stereochemistry of the N+HCH3 moiety. A similar diastereomeric ratio was also noted in 13C{1H} NMR spectra recorded in either CD2Cl2 or in acidic D2O (pD ≈︁ 1). For the major species in CD2Cl2 solution, four antiperiplanar vicinal 1H1H coupling constants indicated a chair‐conformation 2,3‐trans‐1,4‐oxazine ring with equatorially oriented 2‐phenyl, 3‐methyl and N‐methyl substituents. The minor species also has the same chair conformation with equatorially oriented 2‐phenyl and 3‐methyl substituents, since the coupling constant for the minor species vicinal OCH(Ph)CH(Me)N methine protons was also antiperiplanar in magnitude. Axial N‐methyl stereochemistry was assigned to the minor species, since chemical shifts of the ring carbons gauche to N‐methyl (and of the N‐methyl carbon atom itself) were shifted characteristically upfield relative to absorbances for the corresponding carbons in the major [equatorial N‐methyl] species. The R‐factor method was used to estimate an OC6C5N dihedral angle of 56.0(7)° for the major equatorial N‐methyl species in CD2Cl2 solution. CP‐MAS 13C NMR chemical shifts for solid‐state phendimetrazine bitartarate are the same as those for the solution‐state equatorial N‐methyl diastereomer. The oxydimethyleneaminomethyl fragment in the equatorial N‐methyl phendimetrazine chair conformation was used as a model for the corresponding fragment in the eight‐membered ring of nefopam. Comparison of OCH2CH2N+H(equatorial CH3)— and OCH2CH2N+H vicinal coupling constants in the two rings suggests dynamic weighted averaging for those in the octagonal ring of the nefopam equatorial NCH3 diastereomer.
NMR self‐diffusion measurements: A different approach to complexation phenomena
Authors: Geringer M. , Sterk H. 
Published: May 2005

Abstract1H and 133Cs NMR self‐diffusion measurements were performed by means of the pulsed gradient spin‐echo method (PGSE) to evaluate the complex formation constants of Cs and 18‐crown‐6 and those of Cs and some ethylene glycols in D2O. The calculated complex formation constants were checked as far as possible by using similar calculations based on relaxation data. Chemical shift measurements do not allow the evaluation of complex formation constants in these systems. A cross‐check was introduced to verify the calculations based on the diffusion data. Similar investigations were performed on Na, K, Cs complexes and N‐phenylaza‐15‐crown‐5 in methanol. In this case, analysis of the diffusion data and as the relaxation rate and chemical shift data led to complex formation constants for 1:1 complexes, which is in contrast to a previous report suggesting the formation of 2:1 complexes.
Revised 13C NMR signal assignments of 2‐(bromomethyl) naphthalene
Authors: Ernst Ludger 
Published: May 2005

AbstractThe assignments of the 13C NMR signals of 2‐(bromomethyl)naphthalene (1) were derived by comparison of its spectrum with those of the α,α‐D2 and 1‐D derivatives, by determination of relative spin‐lattice relaxation rates and by inspection of the 13C,1H spin coupling patterns. Literature assignments of 1 and of 2‐(bromomethyl)‐6‐methylnaphthalene are corrected. The procedure by which these assignments has been obtained is critically evaluated. Very good additivity of substituent effects on chemical shifts is observed in the 13C NMR spectra of 2,6‐ and 2,7‐bis(bromomethyl)naphthalene.
13C NMR data for isopimarane and 8‐epi‐isopimarane diterpenoids
Authors: Feliciano A. San , Medarde M. , Tomé F. , Hebrero B. , Caballero E. 
Published: May 2005

Abstract13C NMR spectra of several isopimarane and 8‐epi‐isopimarane diterpenoids without double bonds have been recorded. The most significant effects caused by the change in the stereochemistry of the B/C rings junction are discussed.
NMR coupling of 13C and 19F with 14N in nitro compounds
Authors: Coburn Michael D. , Storm Carlyle B. , Moore Donald W. , Archibald Thomas G. 
Published: May 2005

AbstractThe 13C and 14N NMR spectra of a variety of highly nitrated aliphatic, aromatic and heterocyclic compounds were obtained. The proton decoupled 13C peaks of the nitro‐substituted carbons in most of these compounds were split into the multiplets expected for coupling with spin 1 nuclei with negligible quadrupolar broadening. In addition, the 19F spectra of some fluoronitroaliphatic compounds showed that the 19F signals were also split into the expected multiplets from coupling with the 14N of the nitro groups.
Effect of the orientation of an α‐substituent on vicinal 13C–;1H spin–spin coupling constants
Authors: van Beuzekom Aart A. , de Leeuw Frank A. A. M. , Altona Cornelis 
Published: May 2005

AbstractThe magnitude of the NMR spin‐spin coupling constant, 3J(CH), between a vicinal 13C–1H pair depends, inter alia, on the value of the torsion angle ΦCH(13CCCH) and is influenced by the presence of an electronegative substituent located on the coupling 13C nucleus. The form and magnitude of the effect of the orientation ΨXC of such an α‐substituent were examined. The coupling constant between C‐1 and a hydrogen atom located on C‐3 in a series of α‐substituted propanes were studied by means of the semi‐empirical INDO method. In the calculations both Φ and Ψ(X13CCC) were systematically varied in steps of 30°. These calculations reveal that the variation of Ψ at a constant Φ has a pronounced effect on the calculated coupling constant Jcalc. The magnitude of this effect is shown to be strongly dependent on the electronegativity χ of the α‐substituent. Thus, it is shown that Jcalc depends on Φ and Ψ, in addition to χ. The resulting set of two‐dimensional Karplus‐type surfaces can be described by an equation that contains only nine adjustable parameters. Measurement of 3J(CH) in cis‐ and trans‐2,2,6,6‐tetradeuterio‐4‐tert‐butylcyclohexanol confirmed some of the theoretical predictions. In the cis compound (ΦCH = 180°, ΨOC = 60°) 3J(C‐1,H‐3eq) is 7.1 Hz, whereas in the trans compound (ΦCH = 180°, ΨOC = 180°) 3J(CH) equals 10.4 Hz, in qualitative agreement with the INDO calculations.
Applications of two‐dimensional NMR in spectral assignments of some friedelanes and secofriendelanes
Authors: Patra Amarendra , Chaudhuri Swapan K. , Acharyya Aditi K. 
Published: May 2005

AbstractCarbon‐13 spectral assignments of three friedelanes and nineteen secofriedelanes have been made from mutual correlations, 2D X‐H correlation analyses and comparison with the carbon shifts of friedelin, which were firmly established by an INADEQUATE experiment that required reassignment of some of its resonances. Specific methyl and methine proton resonance assignments for some friedelanes, established from X‐H correlation studies, are also reported.
Dependence of the pure quadrupole resonance frequency on temperature and molar specific heat for NaBrO3
Authors: Stahl Edward A. , Tipsword Ray F. 
Published: May 2005

AbstractThe molar specific heat of NaBrO3 in the temperature range 4.2–336 K was determined experimentally and compared with the theory developed by Stahl and generalized in this paper. The relationship between the molar specific heat and temperature was explicitly studied and compared with results obtained by other workers. The method developed also produces the Debye temperature, Θ the maximum angular frequency, omega;m, and the product Iωt2 of the BrO3 group, where I is the moment of inertia and ωl, is the lattice vibration. The relationships between the 79Br NQR frequency and temperature and between the NQR frequency and molar specific heat were obtained.
Conformational analysis of erythromycin A derivatives: A predictive method using NMR chemical shift and coupling constant data
Authors: Everett Jeremy R. , Hatton Ian K. , Tyler John W. 
Published: May 2005

Abstract1H and 13C NMR chemical shift data and 3J(H,H) values can be used to predict the conformational blend of new members of a series of erythromycin A derivatives in CDCI3 solution.
Computer simulation of proton spin relaxation in proteins: Application to Streptomyces subtilisin inhibitor
Authors: Shibata Susumu , Akasaka Kazuyuki 
Published: May 2005

AbstractA computer program has been developed which can calculate the time dependence of individual proton magnetizations in a protein, for a variety of relaxation measurements in solution, using non‐selective and selective excitation pulses. The basic design and capability of the program are described, together with its limitations. The program is used to simulate proton relaxation experiments by non‐selective and selective excitation, and to simulate spin diffusion in a typical globular protein Streptomyces subtilisin inhibitor (SSI). The mechanism of selective spin diffusion in SSI is discussed based on a comparison of the calculated results with results of cross‐saturation experiments.
Simple method for determining the parameters of a static NMR spectrum of nuclei with half‐integer spin in powder samples at a single frequency
Authors: Granger P. 
Published: May 2005

AbstractA simple method, which does not use any computer calculations, is described that allows the determination of the asymmetry parameter, the chemical shift and the quadrupole coupling constant directly from the experimental NMR spectra of quadrupolar nuclei with half‐integer spin in powder samples at a single frequency.