bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C NMR and lanthanide‐induced shifts in epoxides of Terpenes and related compounds
Authors: Schneider Hans‐Jörg , Agrawal Pawan K. 
Published: May 2005

AbstractBased on literature data, and new measurements with both simple and complicated skeletons, it is shown that epoxidation‐induced shifts (EIS) usually vary by only <4ppm if compared with the corresponding olefins, but by <9 ppm if compared with the saturated analogues. Shift differences between stereoisomers (E/Z or trans/cis) are consistent and, again, similar in epoxides and olefins. Larger variations are observed only for cyclic systems in which flexibility and conformational coupling can lead to significant conformational differences between the epoxide and olefin. Yb(fod)3‐induced LIS values are regular if normalized by setting the LIS for the α‐carbon atoms to 100%; these and the EIS values can be used to confirm or correct13C signal assignments.
Proton NMR data of some 1,3‐benzodithioles
Authors: Park K. L. , Stephenson D. S. , Gryff‐Keller A. M. , Szczeciński P. 
Published: May 2005

AbstractThe 1H NMR spectra of 1,3‐benzodithiole and eight derivatives have been analysed. Signals of the protons in positions 4 and 7 are shifted downfield compared with those for the protons in positions 5 and 6. The inter‐ring proton–proton couplings have been determined.
Conformation‐dependent 13C chemical shifts: A new means of conformational characterization as obtained by high‐resolution solid‐state 13C NMR
Authors: Saitô Hazime 
Published: May 2005

AbstractA survey of recent high‐resolution solid‐state 13C NMR studies is given to illustrate how and to what extent 13C chemical shifts of a variety of molecular systems are displaced upon conformational changes. Examples are taken from studies of alkanes, polysaccharides, polypeptides, and naturally occurring and synthetic ionophores, in which more than single conformations are available owing to either crystalline polymorphs or a variety of metal‐ligand interactions. The magnitude of the conformation‐dependent 13C chemical shifts are in many instances as large as 8 ppm and are well related to a set of torsion angles of nearby single bonds. The application of this concept to conformational characterization is also discussed.
Silicon‐29 nuclear magnetic resonance studies of aqueous silicate solutions. 8 spin–lattice relaxation times and mechanisms
Authors: Knight Christopher T. G. , Harris Robin K. 
Published: May 2005

AbstractThe 29Si spin–lattice relaxation times, T1(29Si), of the various silicate anions present in high‐purity alkaline silicate solutions are reported. Regular silicate cages display the longest T1(29Si) values and, in the case of the cubic octameric cage, an unexpectedly large nuclear Overhauser enhancement, indicating that, unlike the smaller silicate oligomers, the cubic octamer relaxes primarily via the (29Si, 1H) dipole‐dipole interaction. This phenomenon provides, inter alia, a simple diagnostic test for such cages.
Two‐dimensional NMR of sesquiterpenic compounds. I—application to complete assignment of 1H and 13C spectra of α‐longipinene
Authors: Faure R. , Vincent E. J. , Gaydou E. M. , Rakotonirainy O. 
Published: May 2005

AbstractTotal assignment of the 13C nuclear magnetic resonance spectrum of α‐longipinene was achieved from DEPT and double quantum coherence measurements, while concerted application of 1H1H homonuclear and 1H13C heteronuclear two‐dimensional chemical shift correlations provided all proton chemical shifts.
Conformational study of pyridiniumacetanilide salts by 1H NMR spectroscopy
Authors: Kovács Zsuzsanna H. , Sohår Pál 
Published: May 2005

AbstractThe temperature dependence of the 1H NMR spectra of some new pyridiniumacetanilide salts was investigated. In these compounds, hindered rotation around the amide NCO bond gives rise to two rotamers with unequal populations. The values of the free energy of activation (ΔG≠) were determined by the coalescence method. Correlation was observed between the values of ΔG≠, the equilibrium rotamer populations and the character of the substituent attached to the amide nitrogen. In some derivatives another conformational motion was detected, and interpreted in terms of slow rotation around the NCaryl bond.
Deuterium isotope effects on oxygen‐17 chemical shifts
Authors: Aime Silvio , Santucci Enrica , Fruttero Roberta 
Published: May 2005

AbstractLarge deuterium isotope effects on 17O resonances were observed for six common NMR solvents. Only in the case of acetone did the substitution of deuterium for hydrogen result in a downfield shift. The H/D isotope effect was also detected in a study of the reversible hydration of CH3CHO.
High‐field1H and13C NMR spectroscopy of some corticosteroids and related compounds
Authors: Duddeck Helmut , Rosenbaum Doris , Hani M. , Elgamal A. , Fayez Mohamed B. E. 
Published: May 2005

AbstractThe 400.13 MHz1H and 100.6 MHz13C NMR spectra of 12 corticosteroids and related compounds were investigated and the signals assigned by two‐dimensional techniques. The effects of substituents, carbonyl groups and epoxide formation on the chemical shifts of both nuclei are discussed in terms of intramolecular interaction and stereochemical dependence.
Application of partially relaxed 2D‐COSY spectra in spectral assignments of carbohydrates
Authors: Saunders John K. , Stevens John D. 
Published: May 2005

AbstractA simple procedure to simplify the 2D‐COSY spectra of molecules in which significant T1 variations occur is described. The procedure was applied to distinguish between the methine and methylene protons of the reducing sugar L‐idose.
Lanthanide porphyrin complexes: Investigation by means of NMR spectroscopy and mathematical simulation
Authors: Babushkina T. A. , Koreneva L. G. , Zolin V. F. 
Published: May 2005

AbstractThe structure of a lanthanide porphyrin complex was reinvestigated using a new treatment for the paramagnetic NMR shifts. It was found to differ from that obtained previously in that the ion was closer to the macrocyclic ligand. The new treatment is based on ab initio estimation of the coefficients describing the anisotropy of magnetic susceptibility, proportional to the pseudo‐contact shifts. These coefficients were estimated using an electrostatic model of the complex; the ‘extra’ ligand (β‐diketonate) was taken into account and shown to be essential. The NMR spectrum of a non‐axial complex under conditions of restricted rotation of the ‘extra’ ligand is described.
The observed and calculated oxygen‐17 quadrupolar coupling constant in nitrous oxide
Authors: Wasylishen Roderick E. , de P. Nicholas A. Martin 
Published: May 2005

AbstractNitrogen‐14 and oxygen‐17 NMR spin‐lattice relaxation measurements on nitrous oxide yield a 17O nuclear quadrupolar coupling constant of 12.4 ± 1.2 MHz. This result compares well with the value of 12.7 MHz obtained by scaling the value calculated using ab initio molecular orbital theory at the 6–31G* level.
Synthesis and EPR and ENDOR investigations of Coppinger's radical with perdeuteriated tert‐butyl groups
Authors: von Gersdorff J. , Kirste B. , Kurreck H. 
Published: May 2005

AbstractThe synthesis of Coppinger's radical (galvinoxyl) with perdeuteriated tert‐butyl groups is described. Its EPR spectrum exhibits markedly decreased line widths (0.015 mT) compared with the unlabelled radical (0.039 mT). The correspondingly higher resolution allows a complete analysis of the 13C hyperfine coupling constants. A comparison of the EPR and ENDOR spectra of unlabelled and of two selectively deuteriated Coppinger's radicals is given.
13C NMR spectra of polyalkoxymethanes, and their sulphur‐ and nitrogen‐containing analogues, of an aliphatic series. Inclusion of non‐bonded interactions by the use of CO bond increments
Authors: Dostovalova V. I. , Zlotsky S. S. , Rakhmankulov D. L. , Terent'ev A. B. 
Published: May 2005

Abstract13C NMR spectra of 40 substituted acetals, carbonates, ortho ethers, 1,3‐dioxocycloalkanes, 1,3‐oxothiolanes and 1,3‐oxazolidines were studied. The chemical shift of the C‐α carbon atom was found to depend both on the number (K) and type of the hetero substituents at C‐α. The effect of oxygen, nitrogen and sulphur atoms on the C‐α chemical shift was shown to be a non‐additive property relative to the unsubstituted isostructural hydrocarbons. The C‐α chemical shift in the linear and cyclic polyalkoxymethanes can be described by an equation incorporating CO bond increments and contributions from the RO substituents:

The CO increment depends quadratically on the number (K–1) of geminal neighbours of the oxygen atom under study. Good agreement between the experimental and calculated shifts can only be achieved by inclusion of nonbonded interactions between the geminal heteroatoms.
Investigation of molecular motions in a derivative of bisphenol‐A diglycidyl ether by variable‐temperature high‐resolution solid‐state carbon‐13 NMR
Authors: Everatt Brian , Harris Robin K. , Kenwright Alan M. , Packer Kenneth J. , Stark B. Peter 
Published: May 2005

AbstractVariable‐temperature solid‐state 13C NMR measurements show effects due to molecular motion in spectra of 2,2‐bis[p‐(2,3‐dihydroxypropoxy)phenyl]propane (BADGETOL), which is a derivative of bisphenol‐A diglycidyl ether. Features in the spectra indicate that the motions present may not be characterized by a simple exponentially decaying autocorrelation function (single correlation‐time process), and a study of the coalescence of doublets due to reorientation between non‐equivalent sites strongly suggests that the motions are more properly characterized by a spatially inhomogeneous distribution of single correlation‐time processes.
Assignments of the1H and13C NMR spectra of 1,4‐diazaphenanthrene (benzo[f]quinoxaline) derivatives
Authors: Defay N. , Nasielski‐Hinkens R. , Nasielski J. 
Published: May 2005

AbstractThe1H and13C NMR spectra of 1,4‐diazaphenanthrene (benzolfquinoxaline) (1) and some of its derivatives have been fully assigned and most of the coupling constants have been measured. The compounds examined bear a piperidino or methoxy group at the 2‐ or 3‐position, or a chlorine atom at the 2‐, 3‐ or 9‐position. The spectra of theN‐1‐oxides of 1 and of 1,4,5,8‐tetraazaphenanthrene are also given. The syntheses are described.
Proton and carbon‐13 NMR studies of 2‐aminothiazoles and 2‐iminothiazolines
Authors: Tseng C. K. 
Published: May 2005

AbstractProton and 13C NMR chemical shifts and coupling constants of 2‐aminothiazoles and 2‐iminothiazolines are reported. The one‐bond CH, vicinal H‐H, geminal CH and vicinal CH coupling constants of 2‐aminothiazoles and 2‐iminothiazolines are discussed in terms of tautomerism between amino forms and imino forms. The site of charge centered either on the ring nitrogen or the exocyclic nitrogen atom in the protonated 2‐aminothiazole is also discussed.
103Rh NMR studies of cyclometallated Rh(III) Schiff's base complexes
Authors: Arz C. , Pregosin P. S. , Anklin C. 
Published: May 2005

Abstract103Rh, 31P and 1H NMR data are reported for the cyclometallated Rh(III) complexes of the type RhH(Y)()L2, where Y can be either an anionic or neutral ligand, is a carbon—nitrogen bidentate ligand arising from cyclometallation at the imine carbon of the Schiff's bases derived from 2‐amino‐3‐methylpyridine and substituted benzaldehydes and L can be either PPh3, AsPh3 or SbPh3. There is only a modest dependent of δ (103Rh) on the nature of the benzaldehyde, a substantial change as a function of L and the most significant sensitivity, >800 ppm, as a function of Y. It is suggested that 103Rh NMR spectroscopy may be useful in the study of linkage isomers of SCN−.
An alternative to the 2D INADEQUATE experiment for detecting scalar coupling correlations between protonated and unprotonated carbons
Authors: Lee Kenneth S. , Morris Gareth A. 
Published: May 2005

AbstractThe two‐dimensional INEPT‐INADEQUATE experiment gives correlation peaks for unprotonated carbons which show only half of the total available signal, because the enhanced 13C signal generated by polarization transfer is shared equally between protonated and unprotonated coupling partners by the double quantum filtration step. If precautions are taken to attenuate unwanted signals from protonated carbons, then the double quantum filtration step may be dispensed with, leaving a hydrogen‐carbon‐carbon relay sequence. This gives unidirectional coherence transfer, ensuring that the maximum possible signal is concentrated in a single cross‐peak identifying the correlation between protonated and unprotonated carbons. By extending the basic HCC relay sequence to include an evolution period an enhanced 13C‐13C COSY 2D spectrum may be produced, with the further advantage over the 2D INADEQUATE experiment that the range of 13C‐13C coupling constants detectable is limited only by the available resolution.
Carbon‐13 NMR chemical shifts of representative nitriles and nitro compounds
Authors: Bailey William F. , Cioffi Eugene A. 
Published: May 2005

AbstractThe 13C NMR chemical shifts of nitriles and nitro compounds derived from nineteen aliphatic and seven aromatic systems have been recorded and assigned. The shifts are compared with those of the hydrocarbons to give the substituent effects of the CN and NO2 groups.
NMR structure of partially oriented tellurophene: Correction of molecular deformations and determination of bond interaction parameters
Authors: Diehl P. , Kellerhals M. , Lounila J. , Wasser R. , Hiltunen Y. , Jokisaari J. , Väänänen T. 
Published: May 2005

AbstractSolvent effects on the NMR geometry of tellurophene due to correlation between vibration and rotation have been determined and corrected in various liquid crystals, resulting in a unique solvent‐independent structure. Simultaneously, the bond interaction parameters, which describe the torques acting on the bonds of the molecule in the anisotropic liquid crystal potential (giving rise to deformations and to the molecular orientation), have been measured. A linear relationship has been detected between the CH bond interaction parameters for tellurophene and for methane in the same solvents.
Non‐ionic X‐ray contrast agents: Detection of ambient temperature isomers of congested hexasubstituted benzenes with multipositional hindered rotations
Authors: Bradamante Silvia , Vittadini Giorgio 
Published: May 2005

AbstractSerinol amides of triiodoisophthalic acid bearing an acylamino group are non‐ionic x‐ray contrast agents; in addition to the expected isomerism due to hindered rotations around the amide NCO bonds, the atropoisomerism associated with the hindered rotations around the aryl–CO and aryl–N bonds was investigated by 1H and 13C NMR.The assignment of signal multiplicity to the different rotamers in solution for a series of N, N′‐bis[2‐hydroxy‐1‐(hydroxymethyl)ethyl]‐2,4,6‐triiodoisophthaldiamides, 5‐substituted with (hydroxyacetyl)amino (5), S‐(–)‐ (2‐hydroxy‐1‐oxopropyl)amino (6), (hydroxyacetyl)methylamino (7), and S‐(‐)‐(2‐hydroxy‐1‐oxopropyl)‐methylamino (8) groups was approached by interpreting simpler systems such as S‐(–)‐3‐N‐[2‐hydroxy‐1‐ (hydroxymethyl)ethyl]‐5‐[(2‐hydroxy‐1‐oxopropyl)amino]‐2,4,6‐triiodoissophthalmic acid (2) and its corresponding amide 3, or more symmetric molecules such as N,N′‐bis[2‐hydroxy‐1‐(hydroxymethyl)ethyl]‐5‐amino‐2,4,6‐triiodoisopht haldiamide (4).It is shown that it is possible to discriminate between the contributions of the different types of hindered rotations in order to obtain the appropriate, although approximate, free energies of activation. Secondary aryl carboxamides 5‐8 constitute a rare case of aryl–CO hindered rotation detectable at room temperature. Analysis of the NMR data clearly indicates that in 5‐8 the population ratio of the syn and anti families is 1: 1 and also that of the E and Z conformers. In addition, the secondary anilides 5 and 6 show fast rotation around the aryl–N bond and exhibit a conformational preference for the endo isomer only. The tertiary anilides 7 and 8, instead, present the coexistence of the endo and exo forms whose ratio is dependent on the solvent.
Oxygen‐17 NMR spectral studies of selected aromatic sulfones
Authors: Kelly Jeffery W. , Evans Slayton A. 
Published: May 2005

AbstractOxygen‐17 NMR spectra of several organosulfur compounds containing the arylsulfonyl group (ArSO2–) are reported. Shielding effects are interpreted in terms of γ‐ortho CH interactions with the sulfonyl oxygens rather than conjugative interactions involving the aryl substituent and the attached SO2 group. The lanthanide shift reagent Eu(fod)3 is useful for discriminating ‘internal and external’ accidental chemical shift coincidence.
13C NMR spectroscopy of phorbol esters
Authors: Pieters Luc A. C. , Vlietinck Arnold J. 
Published: May 2005

AbstractThe 13C NMR spectral data of fourteen phorbol derivatives, which are commercially available or which were extracted from the seed oil of Croton tiglium L. (Euphorbiaceae), and of six common acyl substituents of naturally occurring phorbol esters were recorded and the signals assigned. The spectral data for this series of model compounds appeared to be important tools for the identification and the structure elucidation of naturally occurring and semi‐synthetic diterpene esters related to phorbol.
Dimethoxy aromatic compounds. IV.—determination of stereochemistry of 2,3,6,7‐tetraalkoxy‐9,10‐dihalomethyl‐9,10‐dihydroanthracenes by 13C NMR chemical shifts
Authors: Lamartina Liliana , Ceraulo Leopoldo , Natoli Maria C. 
Published: May 2005

AbstractThe analysis of the 13C NMR spectra of several 2,3,6,7‐tetraalkoxy‐9,10‐dihalomethyl‐9,10‐dihydroanthracenes showed a strong dependence of the chemical shift values on the orientation of the halomethyl groups. On this basis it was possible to determine both the configuration (cis or trans) and conformation of the isomers, even if only one isomer was available.
Stereochemical studies of 3‐aryl‐3‐methylpiperidines of potential opioid ligand activities by high‐resolution 1H and 13C NMR spectroscopy
Authors: Casy A. F. , Iorio M. A. , Madani A. E. 
Published: May 2005

AbstractThe 1H (270, 400 MHz) and 13C (22.5, 67.5 MHz) NMR spectra of a series of 2,3‐3,5‐ and 3,6‐dimethyl‐3‐(m‐hydroxy‐m‐methoxy‐phenyl)piperidines of proven or potential opioid ligand activity are reported. The data were analysed in terms of configuration and preferred conformation, and some key deductions were confirmed by NOED and 2D COSY experiments. In the 3,5‐dimethyl derivatives, isomers with preferred axial or equatorial 3‐aryl substituents were identified.
Carbon‐13 chemical shift assignment of alkoxycarbonylalkylthiouracils and 3‐oxothiazolo[3,2‐a(or ‐c)]pyrimidin‐5‐ones
Authors: Wyrzykiewicz ElżBieta , Wybieralska Jadwiga 
Published: May 2005

AbstractThe 13C NMR spectra of sixteen isomeric 2‐and 4‐alkoxycarbonylalkylthiouracils, eightnew 2,4‐dialkoxycarbonylalkylthiouracils and eight isomeric 3‐oxothiazolo[3,2‐a]‐and 3‐oxothiazolo[3,2‐c]‐pyrimidin‐5‐ones have been calculated and fullyassigned. The AiK empirical parameters of the 2‐thio, 4‐thio, 6‐methy1, 2‐alkoxycarbonylalkylthio, 4‐alkoxycarbonylalkylthio, P‐alkoxycar‐bonylalkyl, 4‐alkoxycarbonylalkyl, N‐3‐carbonylalkylthio‐2‐, N‐3‐carbonylalkylthio‐4, N‐3‐carbonylalkyl‐2‐thio and N‐3‐carbonylalkyl‐4‐thio groups were calculated for the predictions of the chemical shifts of substituted uracils.
NMR study of the lithium salts of aniline derivatives
Authors: Ide Shoichi , Iwasawa Kazuhisa , Yoshino Akihiro , Yoshida Tadayoshi , Takahashi Kensuke 
Published: May 2005

Abstract1H, 7Li, 13C, and 15N NMR spectra were observed for lithium salts of aniline derivatives in THF solutions. The delocalization of excees charge into the phenyl ring of the salts was confirmed from the 1H and 13C chemical shift data in comparison with those of the neutral molecules. Their 15N atoms were approximately 40 ppm less shielded comparison with those of the neutral molecules, and these are discussed in terms of hybridization change and electron densities at the nitrogen atoms. The one‐bond 15N‐1H coupling constants of the salts are approximately 55 Hz and are smaller than those of the neutral molecules.
Restricted rotations about exocyclic partial double bonds. The electronic state of heteroaromatic six‐membered rings
Authors: Kleinpeter E. , Spitzner R. , Schroth W. 
Published: May 2005

AbstractTemperature‐dependent13C and1H NMR spectra of three series of six‐membered heteroaromatic systems with NR2substituents attached to pyrylium/thiopyrylium salts and pyrones/thiopyrones have been recorded. The rotational barriers thus determined about the exocyclic partial double bonds are discussed in terms of dominating mesomeric structures, in order to describe the electronic state and the spatial conditions in the molecular framework. Cyanine and merocyanine substructures have been identified by NMR and express the electronic state predominantly present in the compounds.
Compounds with bridgehead nitrogen 52—NMR spectra and stereochemistry of the 2‐alkylperhydroimidazolo[3,4‐a]pyridines
Authors: Banting Lee , Crabb Trevor A. 
Published: May 2005

AbstractIn contrast to perhydro‐oxazolo[3,4‐a]pyridine and perhydrothiazolo[3,4‐a]pyridine, which adopt equilibria in CDCl3 solution at room temperature containing ca 70% trans‐fused conformers in equilibria with O‐ or S‐inside cis‐fused conformers, 2‐alkylperhydroimidazolo[3,4‐a]pyridines are found to adopt equilibria containing >98% trans‐fused conformers. Comparison of NMR parameters of 2‐methylperhydroimidazolo[3,4‐a]pyridine with those of the two isomers of 1,2‐dimethylperhydroimidazolo[3,4‐a]pyridine indicates an equilibrium for the former compound between the two trans‐fused conformers, with ca 83% of that conformation containing a trans arrangement of nitrogen lone pairs of electrons. These observations are explained in terms of the generalized anomeric effect.
Medium effects on nitrogen nuclear shielding in methyl nitrate and methyl isothiocyanate assessed by the solvaton model
Authors: Witanowski M. , Sitkowski J. , Biernat S. , Sudha L. V. , Webb G. A. 
Published: May 2005

Abstract14N nuclear shielding data are reported for methyl nitrate and methyl isothiocyanate in a variety of solvents covering a wide range of polarizabilities and hydrogen bonding properties. The non‐specific solute‐solvent effects on the nitrogen shielding are accounted for by means of INDO/S‐SOS shielding calculations incorporating the solvaton model. Specific hydrogen bonding effects on the nitrogen shielding are estimated from a four‐parameter equation which reflects both solvent properties and the corresponding solute responses.
Analyses of the 500 MHz 1H spectra of the 3‐Methyl ethers of estrone, estradiol and their 14α‐methyl analogues
Authors: Bischofberger Karl , Bull James R. , Chalmers Anthony A. 
Published: May 2005

AbstractThe 500 MHz 1H spectra of the 3‐methyl ethers of estrone, estradiol and their 14α‐methyl analogues were assigned by proton decoupling and analysed by second‐order calculations for chemical shifts and coupling constants. Introduction of a 14α‐Me group effects consistent deshielding of 1,3 diaxially disposed protons. Coupling constant values show characteristic changes for ring D protons, and suggest that some minor perturbation in the H‐9α, ‐11α, ‐11β region is caused by the additional methyl group.
Quantitative proton magnetic resonance of plasma from uraemic patients during dialysis
Authors: Grasdalen Hans , Belton Peter S. , Pryor Jack S. , Rich Gillian T. 
Published: May 2005

AbstractProton nuclear magnetic resonance (1H NMR) has been used to measure rapidly concentrations of metabolites in plasma from patients with chronic renal failure (CRF) and normal subjects. Detailed quantitative analyses of spectra are presented for four CRF patients during haemodialysis, two patients in early stages of renal failure and two normal subjects. For patients on acetate dialysis, the method clearly shows how well exogenous acetate is metabolized during and after dialysis. Our results indicate a discrepancy between creatinine concentrations measured by 1H NMR and by the kinetic Jaffé reaction method, and also point to high betaine concentrations in plasma from some patients on maintenance haemodialysis and taking folate supplement.