bluuebunny/crossref_metadata_2025_split huggingface dataset:
ENDOR and EPR studies on polycyclic aromatic radical cations
Authors: Sang Hong , Wang Hanqing , Such K. P. , Jent F. 
Published: May 2005

AbstractSeveral polycyclic aromatic radical cations produced in Friedel–Crafts alkylation reactions were studied by EPR and ENDOR methods, and the following were identified: 1,2,5,6‐tetramethylanthracene, 2,3,6,7,9,10‐hexamethylanthracene, 3,6,11,14‐tetramethyldibenzo [a,c]triphenylene and 2,6,9,10‐tetramethylanthracene radical cations.
31P Hyperfine interaction in a new type of phosphorus‐containing iminoxy free radicals. An ESR study
Authors: Siatecki Zdzislaw , Chmielewski Piotr J. , Jezierski Adam 
Published: May 2005

AbstractIminoxy radicals of a new type, having the general formula RC(NO˙)P(O)(OEt)2, were synthesized and characterized by means of ESR spectroscopy. The presence of two isomers due to the different position of the CNO˙ fragment with respect to the R substituent and the P atom, and the relative stability of the isomers, was established. The influence of the R substituent on the relative population of the isomers was found. The nitrogen hyperfine constants for the isomers differ by about 10%, while the phosphorus hyperfine constant for the less populated isomer is about six time greater, reaching a value of 60 G. A linear correlation was found between the values of this hyperfine constant and Dimroth–Reichardt ET(30)solvent parameters. The solvent dependence of the 31P hyperfine constant was shown to be stronger than the dependence found for the 14N hyperfine constant of nitroxides and iminoxyls.
13C NMR chemical shift assignments for substituted 2‐azabicyclo[3.3.1] nonan‐7‐ones
Authors: Casamitjana Núria , Bonjoch Josep , Gràcia Jordi , Bosch Joan 
Published: May 2005

AbstractThe 13C NMR spectra of 26 substituted 2‐azabicyclo[3.3.1]nonan‐7‐ones are reported, providing a diagnostic method for the stereochemical elucidation of the relative configuration of these products.
1H and 13C NMR spectra of the reverse transcriptase inhibitor (+)‐(S)‐4,5,6,7‐tetrahydroimidazo‐9‐chloro‐5‐methyl‐6‐(3‐methylbut‐2‐enyl)imidiazo[4,5,1‐jk] [1,4]benzodiazepin‐2(1H)‐thione (TIBO)
Authors: Leo Gregory C. , Gauthier A. Diane , Caldwell Gary W. , Kukla Michael J. 
Published: May 2005

AbstractProton and carbon NMR chemical shift assignments for (+)‐(S)‐4,5,6,7‐tetrahydroimidazo‐9‐chloro‐5‐methyl‐6‐(3‐methylbut‐2‐enyl)imidazo[4,5,1‐jk][1,4] benzodiazepin‐2(1H)‐thione (TIBO) were made based on 1D and 2D NMR measurements at 9.4 T.
NMR multinuclear study (13C, 14N, 17O) of indane‐1,3‐diones
Authors: Petrova M. V. , Liepiņš E. , Pauliņš J. , Gudriniece E. 
Published: May 2005

Abstract13C, 17O and 14N NMR chemical shift data for a series of 1,3‐indandiones are reported. Linear correlations were established between some chemical shifts and the electron densities for the compounds in question. Chemical reactivity predictions were based on the results obtained.
1H, 13C and 17O NMR study of chlorovanillins and some related compounds
Authors: Kolehmainen Erkki , Laihia Katri , Knuutinen Juha , Hyötyläinen Juha 
Published: May 2005

Abstract1H, 13C and 17O NMR chemical shifts and nJ(H,H), 1J(C,H) and 3J(C‐6, H‐formyl) spin—spin coupling constants of chlorinated vanillins (3‐methoxy‐4‐hydroxybenzaldehydes) were determined. The variation in the long‐range 4J(H,H) value between the formyl proton and an ortho‐proton suggests that the ortho‐substituent strongly forces the formyl group out of the aromatic plane. This can also be observed by considering the 3J(C‐6,H‐formyl) values and the 13C and 17O NMR chemical shifts. The 17O NMR chemical shifts show a linear correlation with the torsion angle of the formyl group calculated by molecular mechanics. The 13C and 17O NMR chemical shifts of the methoxyl group also possess strong predictive power in estimating the torsional characteristics of this group.
Substituent effects on 1H chemical shifts. I—complete 1H chemical shift assignments of methyl‐substituted cyclic systems
Authors: Fisher Julie , Gradwell Michael J. 
Published: May 2005

Abstract1H chemical shift assignments are presented for 2‐methyladamantane, 2‐methylnorbornane (endo and exo) and 2‐methylnorbornene (endo and exo). Resonance assignment was achieved using a variety of 1D and 2D homo‐ and heteronuclear (1H–13C) experiments. The methyl group‐induced substituent chemical shift (SCS) is derived and the SCS of protons vicinal to this group is discussed.
1H NMR study of the intramolecular rearrangements of the complexes of 2‐hydroxypropane‐1,3‐diaminetetraacetic acid with metal ions
Authors: Song Ruifang , Li Fei , Li Liang 
Published: May 2005

AbstractThe kinetics of the intramolecular processes of barium(II), zinc(II), cadmium(II) and lanthanum(III) complexes with 2‐hydroxypropane‐1,3‐diaminetetraacetic acid (HPDTA) were investigated by 1H NMR spectrometry. A novel result, the slow Δ, Λ conversion process at room temperature for Zn and LaHPDTA chelates, was observed. The best fittings of the experimental spectra were obtained by computer analysis. These indicate that the activation energy of the Δ, Λ conversion process increases with increasing electrostatic potential for these chelates.
Solid‐state 13C and 1H NMR study of anomalous acid salts of dibasic carboxylic acids
Authors: Merwin Lawrence H. , Ross Sidney D. 
Published: May 2005

AbstractHigh‐resolution solid‐state 13C and 1H NMR techniques were used to study the structure of a number of anomalous acid salts of adipic, azelaic, dodecanedioic, maleic and fumaric acids. To assist in the understanding of these results, solid‐state NMR data were also obtained for the corresponding acids and a number of their ‘normal’ salts. The resulting information provides insights into the solid structure of these complexes, including approximations of the length of the hydrogen bonds present in these systems. Strong evidence is given for the presence of a symmetrical hydrogen bond for tetramethylammonium didodecanedioate. Carbon‐13 NMR measurements carried out over a range of temperatures have revealed differences in the behavior of several of these compounds which may provide clues regarding the nature of the hydrogen bond in these systems.
Conformational studies of benzophosphabicyclooctenes
Authors: Tóth Gábor , Kovács Attila , Keglevich György , Duddeck Helmut 
Published: May 2005

AbstractThe Friedel–Crafts reaction of P‐substituted 6,6‐dichloro‐3‐phosphabicyclo [3.1.0] hexane 3‐oxides with benzene derivarives yields selectively new tricyclic benzophosphabicyclooctenes. The relative configuration and conformation of these products were elucidated by various 1H and 13C NMR methods.
Sequential proton saturation for the heteronuclear 1D NOE experiment
Authors: Mueller C. , Bircher H. R. , Bigler P. 
Published: May 2005

AbstractAn improved 1D pulse sequence for detecting heteronuclear NOEs on a qualitative level is described and demonstrated. It makes use of shaped selective pulses and takes advantage of sequential perturbation of several proton resonances during one experiment and correspondingly more efficient data accumulation schemes. The method is particularly suitable for assigning quaternary carbons and for establishing connectivities between assigned molecular fragments bound to these quaternary centres.
Effect of pH on carbon‐13 NMR spectra of N‐dodecyl‐N, N‐dimethylamine oxide solution
Authors: Brycki Bogumil , Szafran Miroslaw 
Published: May 2005

AbstractCarbon‐13 NMR chemical shifts of the non‐ionic‐cationic surfactant N‐dodecyl‐N, N‐dimethylamine oxide (C12DAO) were measured and identified by an INADEQUATE experiment. On micellization, downfield chemical shifts were found for all carbon atoms except NCH2. The shifts are most pronounced for the carbon atoms in the central part of the chain. Protonation of the micelles resulted in upfield shifts of all the carbon atoms; the magnitudes decreased with increasing distance from the nitrogen atom. A plot of several chemical shifts against pH gave titration curves and pKa values. The pKa values vary with the carbon atom used in the calculation (from pKa = 5.05 to 5.66). An AMI calculation of charge densities suggests that these variations in pKa are caused by the electric field of the OH group. The effect of N‐oxidation on the chemical shifts of the carbon atoms in five solvents was estimated.
Tautomerism of 2‐benzothiazolylmalonates and 2‐oxobenzodihydrothiazol‐3‐yl‐malonates
Authors: Solčániová Eva , Liptaj Tibor , Sutoris Viktor 
Published: May 2005

AbstractThe tautomerism of alkyl 2‐benzothiazolyl‐malonates and 2‐oxobenzodihydrothiazol‐3‐yl‐malonates was studied by 1H, 13C and 15N NMR spectroscopy. 2‐Benzothiazolylmalonates isomerize in solution to the NH tautomers with an intramolecular hydrogen bond between the NH …︁ OC groups, whereas 2‐oxobenzodihydrothiazol‐3‐yl‐malonates are in the CH forms. The complete assignments of the 13C NMR resonances are reported.
Comparison of different 2D NMR techniques for 13C, 31P correlation
Authors: Bast Peter , Berger Stefan , Günther Harald 
Published: May 2005

AbstractThree different experimental techniques are compared to find the most efficient protocol for 2D 13C, 31P correlation spectroscopy. It is shown that the best signal‐to‐noise ratio is given by the polarization transfer experiment for 31P detection and by the HMQC experiment for 13C detection. Applications of these techniques for 13C,31P correlation of β‐nicotinamide adenine dinucleotide (NAD+) and a mixture of three different mononucleotides are described.
A variable‐temperature 13C cross‐polarization magic angle spinning NMR study of some unusual dynamic and phase properties of (±)‐3,4‐di‐O‐acetyl‐1,2,5,6‐tetra‐O‐benzyl‐myo‐inositol, ‘jumping crystals’
Authors: Fattah Jamila , Twyman J. Mark , Dobson Christopher M. 
Published: May 2005

AbstractVariable‐temperature 13C CP/MAS NMR experiments were carried out on crystalline (±)‐3,4‐di‐O‐acetyl‐1,2,5,6‐tetra‐O‐benzyl‐myo‐inositol. Three distinct phases can be distinguished from their NMR characteristics, each stable over a well defined temperature range, in accord with previous calorimetric studies. The differences between the spectra of the distinct phases suggest that structural variations between them are small. At least two of the aromatic ring moieties of the molecule were shown to be experiencing motional averaging in each of the three phases. Transitions between the phases, monitored by following changes in the NMR spectra, exhibited significant hysteresis but showed no evidence for pre‐organizational behaviour in the form of intermediate species. These results are discussed in the context of the unusual ‘jumping’ motion of the crystals associated with passage through the phase II–III and III–II transitions.
35Cl nuclear quadrupole resonance in 2,4‐ and 2,6‐dichlorobenzyl alcohols
Authors: Roy S. K. , Amitha B. , Uchil J. 
Published: May 2005

Abstract35Cl nuclear quadrupole resonance (NQR) was studied in 2,4‐dichlorobenzyl alcohol (2,4‐DCBA) and 2,6‐dichlorobenzyl alcohol (2,6‐DCBA). The NQR spectrum of 2,4‐DCBA show four lines and that of 2,6‐DCBA two lines. The temperature dependence of the NQR frequencies from 77 K up to the respective melting points was studied. An order–disorder transition was observed in 2,6‐DCBA around 215 K. Torsional frequencies and their temperature coefficients were calculated using the temperature dependence of the NQR frequencies, and were compared with the laser Raman spectra obtained at room temperature.
1H and 13C NMR analysis of brassinosteroids
Authors: Porzel Andrea , Marquardt Volker , Adam Günter , Massiot Georges , Zeigan Dieter 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of the two phytohormones, brassinolide and 24‐epi‐brassinolide, and the two synthetic analogues 22,23,24‐trisepi‐brassinolide and (22S,23S)‐28‐homo‐brassinolide, were assigned using 1D and 2D NMR techniques. Independent assignment strategies are presented for the 1H and 13C chemical shifts of the steroidal side‐chain.
ESR spectroscopic investigation of some 4‐substituted 1,3,2‐dithiazolyl and 2,3,1‐dithiazolyl radicals
Authors: Chung Yuen‐Li , Fairhurst Shirley A. , Gillies Duncan G. , Preston Keith F. , Sutcliffe Leslie H. 
Published: May 2005

AbstractFurther information has been obtained on the electronic structure of 1,3,2‐dithiazol‐2‐yl radicals. The structure has been well characterized previously except for positions 4 and 5 in the
equation image
ring. We have obtained solution and powder ESR spectra of radicals substituted with 13C in both positions and of radicals substituted with nitrogen or phosphorus in the 4‐position. It is probably the first time that a compound has been prepared containing the
equation image
ring. Two especially interesting facts emerged from the ESR spectra of these 1,3,2‐dithiazolyl radicals: the 13C‐substituted radical has a considerable amount of p spin density in the plane of the ring and the phosphorussubstituted radical has a very low unpaired spin density at the phosphorus atom. It is known that 1,3,2,4‐dithiadiazolyl radicals isomerize readily by photolysis to the symmetrical 2,3,1,4‐dithiadiazolyl radicals; we attempted the same reaction with But
equation image
and a new radical was produced that we have been unable to identify.
High‐field NMR study of the tautomers resulting from the condensation of 2‐methylindole and phenalenone in the presence of p‐toluenesulphonic acid
Authors: Tort F. , Waegell B. , Zahra J. P. , Bernasconi C. , Germanaud L. , Bessibes C. , Bounoure J. 
Published: May 2005

AbstractAs phenalene is an alternant hydrocarbon it is oxidized very easily to phenalenone, which condenses with various nitrogen nucleophiles in the presence of p‐toluenesulphonic acid. 2‐Methylindolylphenalene is obtained with 2‐ methylindole, together with other products. This product is a mixture of five tautomers in equilibrium, and these were analysed by homo‐ and heteronuclear two‐dimensional high‐field NMR (500 MHz) spectroscopy.
195Pt and 1H NMR study of the products of hydrolysis of Pt(L)X2, where L is an ethylenediamine derivative, and the crystal structure of [Pt(N,N‐dimethylethylenediamine) (μ‐OH)]2 (NO3)2
Authors: Rochon Fernande D. , Melanson Robert , Morneau André 
Published: May 2005

AbstractThe hydrolysis reactions of complexes of the type Pt(L)X2 where L is ethylenediamine (en), N,N‐ dimethylenediamine (N,N‐Me2en), N,N‐dimethylenediamine (N,N′‐Me2en) and N,N,N′, N′‐tetramethylethylenediamine (Me4en) were studied. The halo ligands were removed by precipitation with AgNO3 and the pH of the resulting filtrate, which was about 2, was adjusted to 5.8 (pD = 6.2). The study of the products formed was carried out by multinuclear NMR spectroscopy. The 195Pt NMR spectra showed the presence of several hydrolysed products, especially with en. The hydroxo‐bridged dimer can be synthesized in a pure state with all the ligands except en. The results on the latter ligand contradict the published results on the synthesis of the en hydroxo‐bridged dimer whose biological properties were studied. When Pt(L)I2 is used as starting material a small quantity of chloro species was always observed, indicating that the reactant contained a small quantity of Pt(L)ICI. The crystal structure of the [Pt(N,N‐Me2en)(μ‐OH)]2(NO3)2 dimer was determined. The compound belongs to the P21/c space group, with a = 8.262(5), b = 10.960(8), c = 11.405(8), β = 121.07(5)°, Z = 2 and ρcalc = 2.720 mg m−3. The results showed that this is the trans isomer with an inversion centre between the two Pt atoms. There is a considerable strain inside the four‐membered ring, as shown by the reduced internal angles OPtO′ = 79.1(6)0 and PtOPt′ = 101.0(6)°.
Dynamics of lysine hydrochloride dihydrate measured by carbon‐13 NMR spectroscopy
Authors: Swanson Scott D. , Bryant Robert G. 
Published: May 2005

AbstractThe 13C NMR spectra for L‐lysine hydrochloride dihydrate are reported for static samples and samples spinning at the magic angle, which provide resolution of each carbon resonance. The spectra and the T1s, T1p and T1 relaxation times for the carbon atoms demonstrate that there is little motion of the side‐chain in this crystal environment. The carbon spin–lattice relaxation is approximately accounted for by rotational motions of the ammonium ions in the range 50–100 ns and motions of the water molecules in the region of 50 ps or 70 ns. The backbone motions are relatively unimportant for relaxation of the carbon spins.
Application of HMQC to the measurement of J(H, H) homonuclear coupling constants
Authors: Yang Daiwen , Xu Xiaolong , Ye Chaohui 
Published: May 2005

AbstractHomonuclear scalar coupling constants can be measured in HMQC experiments by increasing the resolution in the F2 dimension; in addition, the CH chemical shift correlation can be obtained. This approach is illustrated using the experimental spectra of chenodeoxycholic acid (CDCA). The 1H NMR spectrum for CDCA was completely assigned; the J(H, H) and 1J(C,H) values and the CH correlation were obtained from the 2D HMQC spectrum.
Carbon‐13 relaxation study of motional properties of lacto‐N‐neotetraose in solution
Authors: Bagley Stephen , Kovacs Helena , Kowalewski Jozef , Widmalm Göran 
Published: May 2005

AbstractCarbon‐13 spin–lattice relaxation times and NOE factors are reported for a tetrasaccharide, lacto‐N‐neotetraose, in solution as a function of temperature and magnetic field. The data that are outside the extreme narrowing regime are analysed using the ‘model‐free’ approach of Lipari and Szabo. The global reorientation is assumed to be isotropic. The experimental data for the inner rings can be fitted very well using a simplified version of the equations, neglecting the local motion term in the spectral densities. The complete expression for the spectral densities is required for the outer rings, and three different fitting procedures are compared.
13C NMR study of the substituent effects in ortho‐substituted nitrobenzenes
Authors: Rasala Danuta , Gawinecki Ryszard 
Published: May 2005

Abstract13C NMR chemical shifts of 22 ortho‐substituted nitrobenzenes are reported. Except for those on C‐3 and C‐5, the effects of the interacting nitro group and the substituent are non‐additive. The chemical shifts of the ipso, ortho and para carbons in the spectra and those of monosubstituted benzenes are linearly dependent. Multiparameter correlation analysis shows a predominant field/inductive effect on the ipso compared with both the ortho and para carbon chemical shifts. It shows that the Reynolds non‐electronic factors evaluate the substituent chemical shifts of the ipso and ortho positions much better than the Charton steric parameters. Moreover, both in ortho‐ and para‐substituted nitrobenzenes the substituent exerts almost the same shift on the ipso carbon atom. This suggests that the studied compounds, except those carrying very bulky groups, show a high tendency to be planar.
Characterization of symmetrical and unsymmetrical thiol–disulfide interchange reactions by one‐and two‐dimensional magnetization transfer NMR spectroscopy
Authors: Keire David A. , Guo Wei , Rabenstein Dallas L. 
Published: May 2005

AbstractOne‐ and two‐dimensional magnetization transfer NMR methods were used to characterize symmetrical and unsymmetrical thiol–disulfide interchange reactions in the glutathione‐cysteamine system. The chemical system consists of four symmetrical and two unsymmetrical thiol–disulfide interchange reactions. In terms of the magnetization transfer experiment, these reactions can be treated as two three‐site exchange networks, one for exchange of the cysteamine moiety among cysteamine, cystamine and the cysteamine part of the glutathione–cysteamine mixed disulfide and another for exchange of the glutathione moiety among glutathione, glutathione disulfide and the glutathione part of the mixed disulfide. Two‐dimensional 13C{1H} EXSY NMR spectroscopy was used to identify specific exchange reactions which take place on the time scale of the magnetization transfer experiment at a given pD. The kinetics of the interchange reactions were quantitatively characterized using an overdetermined version of the one‐dimensional 13C{1H} EXSY experiment and a 13C{1H} selective inversion‐transfer experiment with a linear‐least‐squares analysis of the time course data. Second‐order rate constants were calculated for all six of the thiol–disulfide interchange reactions from the pseudo‐first‐order rate constants obtained from the selective inversion‐transfer experiments.
1H, 13C and 17O NMR spectroscopic study of four bicyclo [3.1.1]heptenes (derivatives of α‐pinene) and four bicyclo[3.1.1]heptanes (derivatives of β‐pinene)
Authors: Laihia Katri , Kolehmainen Erkki , Malkavaara Petteri , Korvola Jorma , Mänttäri Pia , Kauppinen Reijo 
Published: May 2005

AbstractFour derivatives of 2, 6, 6‐trimethylbicyclo[3.1.1]hept‐2‐ene (α‐pinene) and four derivatives of 2‐methylene‐6, 6‐dimethylbicyclo[3.1.1]heptane (β‐pinene) were synthesized and their 1H, 13C and 17O NMR spectra were measured, analysed and assigned. The 1H NMR spectral parameters were obtained by computer‐aided analyses of the very complex multi‐spin, second‐order spectra. Some of the 13C NMR chemical shift assignments of these compounds reported in the literature should be changed, based on these accurate 1H NMR spectral analyses and carbon‐proton chemical shift correlated spectra (COSY). The new assignments are supported by the 1J(C, H) values, which show a strong dependence on the bond angle and the steric strain of the ring system concerned.
13C NMR studies of α,ω‐bis(p‐anisyl)alkanes and α,ω‐bis(3‐iodo‐4‐methoxyphenyl)alkanes
Authors: Asleson Gary L. , Catlin Kelly K. , Heldrich Frederick J. 
Published: May 2005

Abstract13C NMR studies were performed for a series of homologous iodinated and uniodinated α,ω‐bis(aryl)alkanes. Spectral assignments were made by utilization of DQCOSY, HETCOR‐LR and 1D coupled and decoupled 13C experiments.
Sesquiterpenes. 13C and 1H NMR chemical shifts of new thujopsane and nootkatane derivatives
Authors: Wolff Peter 
Published: May 2005

AbstractThe 13C and 1H NMR spectra of thujopsanone oxime, 7‐halo‐7‐nitrosothujopsanes, nootkat‐1‐one oxime and 1‐chloro‐1‐nitrosonootkatane are reported.
Structural studies in the bicyclo [3.1.1]heptane series by 1H and 13C NMR
Authors: Badjah‐Hadj‐Ahmed A. Y. , Meklati B. Y. , Waton H. , Pham Q. T. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 22 pinane derivatives have been recorded and completely assigned. The spectral data for this set of compounds provide information about the conformation of these molecules and allow the deduction of the various structural effects observed in the bicyclo[3.1.1]heptane series.
Oxygen‐17 NMR study of electronic and steric effects in furan‐2,3‐dione derivatives
Authors: Hnach M. , Zineddine H. , Faure R. , Aycard J. P. 
Published: May 2005

Abstract17O NMR was used to probe the steric and electronic substituent effects in furan‐2,3‐dione derivatives. The carbonyl 17O chemical shifts correlate with Hammett constants and IR carbonyl stretching band frequencies for 5‐(para‐substituted‐phenyl)furan‐2,3‐diones.
13C NMR spectra of linear trimers of buta‐1,3‐diene obtained from the Ziegler–Natta process
Authors: Lubnin A. V. , Podkorytov I. S. , Bresler L. S. 
Published: May 2005

AbstractTitanium‐based Ziegler–Natta catalysts for the polymerization of buta‐1,3‐diene give linear trimers of butadiene among other by‐products. A combination of 1H and 13C NMR, DEPT and 2D‐INADEQUATE gives exhaustive assignments of their 13C NMR spectra and affords their structures. All these trimers are dodeca‐2,4,6,10‐tetraenes which have an isolated cis double bond. The internal double bond of the conjugated triad has a trans configuration in each isomer, and the trimers differ only in the outer double bonds. The 13C NMR spectra of the timers reveal that the signal position of the carbon involved in the conjugated double bond series is mainly controlled by the configuration of the adjacent double bond and, to a lesser extent, by the geometry of its own double bond. The oligomers studied serve as models for polyacetylene. Some reassignments in the spectra of oligomers of terminal acetylenes are proposed.