bluuebunny/crossref_metadata_2025_split huggingface dataset:
On triazoles. IV—NMR study of 5‐amino‐1,2,4‐triazole isomers
Authors: Dvortsák P. , Reiter J. , Somorai T. , Sohár P. 
Published: May 2005

AbstractA 1H NMR and 13C NMR study of all possible isomers of monoalkylated 3‐methylthio‐5‐amino‐1,2,4‐triazoles was carried out. The 13C NMR spectra, including the corresponding proton coupled measurements, proved unambiguously the structures of all derivatives studied.
17O NMR spectra of tertiary alcohols, ethers, sulfoxides and sulfones in the cyclohexyl and 5‐substituted 1,3‐dioxanyl series and related compounds
Authors: Manoharan Muthiah , Eliel Ernest L. 
Published: May 2005

Abstract17O NMR spectra of fifteen cyclohexane‐derived tertiary alcohols and related ethers and acetals, six 1,3‐dioxane‐derived orthoesters, four cyclohexane‐ and 1,3‐dioxane‐derived sulfones and the four corresponding sulfoxides, three acyclic sulfones, six alcohols derived from norbornane and 1,3‐dithiane and two esters have been recorded. Attention is drawn to δ‐compression effects and saturation effects in several of these compounds.
Definitive identification of the C‐5 and C‐7 NMR signals of adamantan‐2‐ol
Authors: Srivastava S. , Cheung C. K. , Le Noble W. J. 
Published: May 2005

AbstractThe E‐ and Z‐5‐deuterioadamantan‐2‐ols have been synthesized by an unambiguous route. The 13C NMR spectra show the familiar 1:1:1 splitting of one of the C‐5 or C‐7 signals, thus allowing a definite assignment of the δ‐atoms to be made. This assignment is in accord with the conclusion of Duddeck and Islam. Revised assignments are offered for the reported configurations of the 5‐bromo‐ and ‐chloro‐adamantan‐2‐ols, and several unusual remote deuterium isotope shifts are reported.
Very high frequency proton NMR studies of the conformations of opiate agonists and antagonists
Authors: Glasel Jay A. , Reiher Herbert W. 
Published: May 2005

AbstractThe solution conformational properties of the opiate agonist‐antagonist pairs morphine‐nalorphine and oxymorphone‐naloxone have been investigated by NMR spectroscopy of their salts and free bases in aqueous and non‐aqueous solutions, respectively. Nitrogen inversion in the piperidine ring takes place in these compounds. However, the equilibrium ratios differ between pairs. The conformations of the piperidine rings are chairs with differing degrees of distortion from ideality. On the NMR time scale the dynamically averaged orientations of the N‐allyl substituents in the antagonists differ from one another with respect to a fixed molecular coordinate system. The C‐14 hydroxy group in oxymorphone‐naloxone appears to be solvated, and this has important conformational effects. In these latter compounds a stereoelectronic effect takes place involving the C‐6 carbonyl position (D ring), which results in differential labilization of the C‐7 protons.
Inconsistent Solvent Shifts Caused by benzene in the NMR spectra of N‐alkyl(thio)phosphonothioamides
Authors: Tashma Zeev 
Published: May 2005

AbstractReplacement of chloroform by benzene as an NMR solvent for a series of (thio)phosphonothioamides results in an exceptionally wide range of shifts for the NCH proton signals, from an upfield shift of approximately 1 ppm to a downfield shift of about 0.1 ppm, depending on the phosphonate esterifying groups, the type of the N‐alkyl moiety and whether it is a PO or a PS compound. The last factor is believed to operate indirectly by affecting the aggregation state of the compounds in benzene.
17O, 15N and 13C NMR chemical shifts of N,N‐dimethylmethanesulphinamide in various solvents
Authors: Häkkinen A.‐M. , Ruostesuo P. , Kurkisuo S. 
Published: May 2005

AbstractThe 17O, 15N and 13C NMR chemical shifts have been determined for N,N‐dimethylmethanesulphinamide (1), both as the neat liquid and in dimethyl sulphoxide, acetone, chloroform and various alcohols. The 17O and 15N nuclei of 1 resonate at a lower frequency than those of the corresponding sulphonamide, and depend on the solvent and concentration of the components in binary solution mixtures. Hydrogen bond‐forming solvents shift the signals to lower frequency than those of the neat amide. On changing the solvent, the change in the 17O NMR chemical shift of the sulphinamide is smaller than that of carboxamides, but the difference in the 15N NMR chemical shifts between these two systems with a solvent change is much lower and opposite in direction, reflecting the differences in the resonance structures of carboxamides and sulphinamides.
Equilibrium constants for association of caffeine and theophylline with aromatic salts in aqueous solutions studied by 1H NMR chemical shift measurements
Authors: Aradi Ferenc , Földesi András 
Published: May 2005

AbstractThe interaction of caffeine and theophylline with sodium benzoate and sodium salicylate has been studied in deuterium oxide at 35 °C by measuring the aromatic salt‐induced changes in the chemical shifts of the N‐methyl protons. Taking into account the self‐association of the N‐methylxanthines, on the basis of a 1:1 complexation model the association constants for caffeine‐sodium benzoate, theophylline‐sodium benzoate, caffeine‐sodium salicylate and theophylline‐sodium salicylate were found to be 2.1 ± 0.1, 1.5 ± 0.2, 7.8 ± 0.2 and 5.0 ± 0.21 mol−1, respectively.
Carbon‐13, nitrogen‐15, oxygen‐17 and sulphur‐33 NMR chemical shifts of some sulphur amides and related compounds
Authors: Häkkinen A.‐M , Ruostesuo P. 
Published: May 2005

Abstract15N, 17O and 33S NMR chemical shifts were determined for some aliphatic and aromatic sulphonamides, sulphinamides, sulphenamides and related sulphones and sulphoxides. The 17O and 33S NMR chemical shifts change only slightly for the sulphonyl compounds. In the sulphinyl compounds, on the other hand, the presence of nitrogen causes a noticeable shift to higher frequencies in the 17O resonance. The differences between the 17O chemical shifts of sulphinyl and sulphonyl compounds are more noticeable than those between sulphinamides and sulphoxides. The 15N NMR chemical shifts of sulphon‐, sulphin‐ and sulphen‐amides reflect well the effect of the environments of both nitrogen and the adjacent sulphur atom. The correlations between 15N, 17O and 33S NMR chemical shifts and the structures of sulphur amides and related sulphones and sulphoxides are discussed. The chemical shifts of the 13C nuclei are also presented.
NMR Spectra and Stereochemistry of some 7‐Substituted 6,14‐Bridged Thebaine Derivatives
Authors: Uff Barrie C. , Mallard Angela S. , Davis John A. , Henson Ray 
Published: May 2005

AbstractThe NMR spectra of eighteen 7α‐ and 7β‐substituted 6,14‐bridged thebaine derivatives are reported and the steric and other effects of the 7‐substituent on the C‐5‐H atoms examined. Although the H‐5 proton shift enabled compounds epimeric at C‐7 to be distinguished in the examples studied (values falling between δ 4.75‐4.40 ppm in the 7α series and δ 5.21‐4.97 ppm in the 7β series), the C‐5 shift values proved less useful owing to overlapping ranges.
Origin of the shielding effect in the 29Si NMR spectra of silatranes
Authors: Sidorkin V. F. , Pestunovich V. A. , Voronkov M. G. 
Published: May 2005

AbstractThe diamagnetic and paramagnetic terms of the 29Si nuclear shielding constant of silatranes, XSi(OCH2CH2)3N, and the related four‐coordinated silicon compounds, triethoxysilanes, XSi(OC2H5)3, have been estimated to explain the experimental peculiarities of their 29Si NMR spectra. High‐field shifts of the 29Si NMR signals of silatranes relative to triethoxysilanes are of diamagnetic origin, arising mainly from the existence of the Si←N bond and pentacoordination of the silicon atom in silatranes. At the same time, the decrease in the positive charge on the silicon atom upon Si←N interaction increases the absolute value of the negative paramagnetic term. When the Si←N bond in silatrane molecules becomes stronger through introduction of a more electronegative substituent X, the absolute value of the difference in the paramagnetic terms between silatranes and the related triethoxysilanes increases to a greater extent than that in the diamagnetic terms. This reduces the difference in 29Si chemical shifts of the corresponding four‐ and five‐coordinated silicon compounds with increasing electronegativity of the substituent X.
Carbon‐13/carbon‐12 isotope effects on 119Sn nuclear shielding
Authors: Kerschl Susanna , Sebald Angelika , Wrackmeyer Bernd 
Published: May 2005

AbstractSecondary 13C/12C isotope effects (Δδi) over one bond on the 119Sn nuclear shielding have been determined for 42 organotin compounds. Changes in the magnitude and sign of Δδi are related to the nature of the carbon atom and the nature of the other substituents at the tin atom. In addition to the rotational and vibrational effects connected with the Sn13C bond itself, Δδi is affected by the bonding of tin to the other substituents. In the case of polar bonds this leads to deshielding of the tin atom in the heavy isotopomer, which compensates the shielding effect normally associated with heavy isotopic substitution. Therefore, the magnitude of Δδi values and of the SnC bond distances are not related in a simple manner. A relationship exists between J(119Sn13C) and Δδi in alkynyltin compounds. The Δδi (13C/12C) values for 29Si and 207Pb shielding in some representative organo‐silanes and ‐plumbanes are reported for comparison.
Dynamic NMR: Field dependence of the coalescence temperature and temperature dependence of T2 Relaxation times in N,N‐dimethyltrichloroacetamide
Authors: Dimitrov V. S. , Ladd J. A. 
Published: May 2005

AbstractThe field dependence of the 1H and 13C coalescence temperatures in N,N‐dimethyltrichloroacetamide has been used to determine the most reliable activation parameters for internal rotation of the amide moiety. The results were found to be in excellent agreement with those obtained earlier by the double‐fitting procedure and demonstrate its validity. Direct measurements of the T2 relaxation times of the methyl protons show that T2 depends exponentially on temperature.
Residual (13C,14N) dipolar coupling in13C NMR of solid nitrogen‐containing aromatic compounds
Authors: Harris R. K. , Jonsen P. , Packer K. J. 
Published: May 2005

AbstractCarbon‐13 NMR spectra of some solid substituted anilines and aromatic diazonium salts, taken under conditions of cross‐polarization with high‐power proton decoupling, are presented. In the case of the aromatic diazo compounds the carbon directly attached to the diazo group gives rise at 22.6 MHz to a line shape which has approximately the appearance of a 2:1:1 triplet but which is shown to be in reality a 2:1 doublet of 2:1 doublets. This arises from the presence of both a long‐range and a short‐range residual (13C,14N) dipolar coupling. Isotopic labelling of the nitrogen in the diazo group allowed the determination of the nuclear quadrupole coupling constants of the two14N nuclei and, consequently, theoretical simulation of the apparent triplet line shape. The orientations of the electric field gradient tensors for the14N nuclei in these compounds are discussed in terms of their electronic structure.
73Ge and 13C NMR spectra of some methylgermacyclohexanes
Authors: Takeuchi Yoshito , Shimoda Masakatsu , Tomoda Shuji 
Published: May 2005

AbstractThe 73Ge and 13C NMR chemical shifts of a variety of methyl‐substituted germacyclohexanes have been determined. The chemical shifts are very sensitive to steric effects, and can provide a useful means of conformational analysis of organogermanium compounds.
Carbon‐13 NMR studies of olefins having nitrile and methoxycarbonyl substituents. Additivity relationships
Authors: Barfield M. , Gotoh T. , Hall H. K. 
Published: May 2005

AbstractCarbon‐13 NMR chemical shifts are reported for a series of seventeen olefins with tetra‐, tri‐, di‐ and mono‐substitution by nitrile and methoxycarbonyl groups. Analyses of the data for the nitrile, methoxy and carbonyl chemical shifts by multiple linear regression provide a good correlation with the pattern of geminal, cisoid and transoid substitution. The olefinic shielding data are more complicated, and the analysis requires the introduction of pairwise additivity parameters. It scems likely that the greater complexity arises from steric effects associated with cisoid and geminal methoxycarbonyl substituents, which produce deviations from planarity. The empirical relationships, which are reported here, are useful in removing several ambiguities in the spectral assignments. In this series of compounds it is also observed that substituents which are cis to the nitrile, shift the nitrile resonance 1–2 ppm to high field of those for the trans substituents.
A theoretical and empirical approach to solvent effects on nitrogen nuclear shielding
Authors: Witanowski M. , Sitkowski J. , Biernat S. , Kamienski B. , Hamdi B. T. , Webb G. A. 
Published: May 2005

AbstractSolvent effects on nitrogen shieldings are shown to vary from almost zero to about 26 ppm. These shielding variations can be analysed in terms of a variety of hydrogen bonding interactions and non‐specific solute–solvent interactions. Steric effects are also taken into account. The non‐specific interactions are found to be well accounted for by INDO/S‐SOS shielding calculations incorporating the solvaton model. Nitrogen NMR is shown to be very suitable for distinguishing between a variety of solute–solvent interactions.
Analysis of nitration products of 1‐methylpyrene by 1H nuclear magnetic resonance
Authors: Chow F. L. , Garner R. C. , Martin C. N. , Mann B. E. 
Published: May 2005

AbstractNitration of 1‐methylpyrene yields a mixture of isomers which have been difficult to resolve by chromatography. By using the addition of substituent effects, the products have been identified by 1H NMR as 3‐, 6‐and 8‐nitro derivatives of 1‐methylpyrene in the proportions 0.65:1:1.
Substituent chemical shifts in NMR. 2—Bromine SCS in rigid molecules
Authors: Abraham Raymond J. , Fisher Julie 
Published: May 2005

AbstractThe complete analysis and assignment of the 1H NMR spectra of 2‐exo‐bromonorbornane (1) and 2‐bromoadamantane is reported, using high‐field NMR and COSY and proton—carbon correlation experiments to assign the spectra. These data, together with those for the patent hydrocarbons, when combined with previous analyses of 1‐bromoadamantane, 1‐bromooctadeuterocyclohexane and the simple alkyl bromides, provide a data set of 38 proton SCS values for bromine in molecules of accurately known geometry. The effect of solvent on the SCS was investigated for 1 in five common solvents of very different polarity (C6D12 to DMSO). Only small (< 0.1 ppm) solvent shifts were observed, apart from the 2‐endo and 7s protons. A noteworthy feature of the SCS is the downfield shift of the CHX proton in all the series investigated, as X changes from C1 to Br to I. This is the reverse of the ‘normal’ trend and cannot be explained by present theories of SCS.
1H and 13C NMR spectra of new condensed tri‐ and tetra‐cyclic 1,2,4‐triazole ring systems
Authors: Goljer Igor , Světlík Jan , Tureček František 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 7,8‐dihydroimidazo[1,2‐e]‐1,2,4‐triazolo‐[1,5‐a]‐1,3,5‐triazine and 5‐methyl‐1,2,4‐triazolo[1′,5′ : 1,2]‐1,3,5‐triazino[5,6‐a]‐benzimidazole were investigated. Heteronuclear spin tickling proved to be a useful method for distinguishing heteroaromatic protons.
13C NMR spectra of 5β,14β‐hydroxysteroids
Authors: Habermehl Gerhard G. , Hammann Peter E. , Wray Victor 
Published: May 2005

AbstractThe 13C chemical shifts of 30 substituted 5β,14β‐hydroxysteroids are described and discussed. Substituent chemical shifts for 12α‐ and 12β‐hydroxy groups were evaluated, and interesting γ effects were observed. A correlation is shown to exist between the 1H shifts of H‐17 and the 13C shifts of C‐17 for various C‐12 substituents. A relationship for the distance of the substituent at C‐12 from H‐17 in the 14β,20‐lactones was demonstrated, where an increased distance between these atoms is associated with smaller shift differences.
Selective heteronuclear INADEQUATE as an assignment technique: Applications to 29Si‐13C couplings in pertrimethylsilylated products
Authors: Past J. , Puskar J. , Alla M. , Lippmaa E. , Schraml J. 
Published: May 2005

AbstractA selective heteronuclear version of the INADEQUATE experiment is described in detail. This technique allows the assignment of NMR lines of nuclei that are scalar coupled to other nuclei which can be assigned by a routine technique. The feasibility of this approach is demonstrated by the assignment of the 29Si NMR lines in two pertrimethylsilylated monosaccharides. In this particular case, the selective heteronuclear INADEQUATE experiment was used to determine two‐ and three‐bond 29Si‐13C couplings and to assign the 29Si lines.
13C and 17O NMR of some substituted oxiranes. Chemical shifts and quantitative correlations
Authors: Monti J. P. , Faure R. , Sauleau A. , Sauleau J. 
Published: May 2005

AbstractMeasurements of the 13C and 17O chemical shifts of mono‐ and di‐substituted oxiranes [CH3, C6H5, CHCH2 and C(CH3)CH2 substituents] allowed the determination of the direct additivity parameters, which depend solely on the nature of the substituent, and the cross terms due to pairwise contributions of the substituents. Pairwise interactions have been ascribed either to electron transfer between the epoxide ring and the substituent, or to steric interactions between the different substituents. A systematic study of oxiranes polysubstituted by methyl, phenyl, vinyl and isopropenyl groups allows a simple interpretation to be proposed for deviations between the theoretical results and the experimental values in most cases. A striking feature of the data is the possibility of distinguishing between different molecular configurations for isomeric compounds by 17O NMR.
1H NMR study and conformational aspects of 20′‐deoxy‐20′‐epivindesine
Authors: De Bruyn André , Verzele Maurice , Jans Arnold , Van Binst Georges , Noiret André , De Jonghe Jean‐Paul , Hannart Jean 
Published: May 2005

AbstractThe 1H NMR spectrum of 20′‐deoxy‐20′‐epivindesine has been unravelled at 500 MHz. COSY and 2D NOESY experiments were used. The conformational features are assigned.
Study of 13C–19F and 1H–19F couplings in some fluorinated aromatic compounds using two‐dimensional 13C–1H chemical shift correlation spectroscopy with proton homonuclear decoupling
Authors: Guo Wei , Wong Tuck C. 
Published: May 2005

AbstractThe magnitudes and relative signs of 13C–19F and 1H–19F coupling constants in 6‐F‐indole, 5‐ and 6‐F‐tryptamine, 5‐F‐indole‐3‐carboxaldehyde, 2‐ and 4‐F‐biphenyl, droperidol, flusperilene, 1‐F‐naphthalene and 3‐F‐fluroanthene (F = fluoro) have been determined using two‐dimensional 13C–1H chemical shift correlation spectroscopy with proton homonuclear decoupling. Except for one long‐range 1H–19F coupling constant, all the other observed 1H–19F couplings in these compounds were found to be of the same sign as the corresponding 13C–19F coupling constants. The variation of the magnitude of tlfe coupling constants due to substitution is relatively insignificant.
Medium effects on 33S NMR of inorganic sulphate
Authors: Belton Peter S. , Cox I. Jane , Harris Robin K. 
Published: May 2005

AbstractThe effects of counter‐ion binding, pH and viscosity on the line width, spin‐lattice relaxation rate and chemical shift of the 33S resonance for the inorganic sulphate ion are reported. The NMR parameters are shown to be sensitive even to weak interactions, such as sodium ion binding. It is concluded that 33S NMR may be a valuable technique in the study of the inorganic chemistry of the sulphate ion. Since the sulphate resonance is sensitive to the nature of the solution, its use as a chemical shift reference should be treated with caution.
Studies on the conformations in solution of 5β‐steroids having different side chains by 13C NMR spectroscopy
Authors: Seldes A. M. , Deluca M. E. , Gros E. G. 
Published: May 2005

Abstract13C NMR spectra for 23 3‐substituted‐5β‐steroidal derivatives have been obtained and individual resonances assigned. The different chemical shifts due to conformational and side chain changes are rationalized in terms of steric interactions. From these results a preferred is conformer is proposed for the cholanoic acid side chain derivatives in solution.
Carbon‐13 NMR investigation of some pharmacologically important heterocyclic N‐alkynylamines
Authors: Salman Salman R. , Muhi‐Eldeen Zuhair , Yasin Ali Hadi , Hatim Abdul Faris 
Published: May 2005

AbstractCarbon‐13 chemical shifts of 26 aminoalkynyl derivatives of 1,3,4‐thiadiazol‐2(3H)‐one and 1,3,4‐thiadiazolin‐2‐ylidene‐benzamide have been determined.
13C and 125Te chemical shifts in ortho‐substituted tellurophenetoles
Authors: Baiwir Marcel , Llabres Gabriel , Christiaens Léon , Luxen André , Piette Jean‐Louis 
Published: May 2005

AbstractIndirect evidence is provided for (a) the existence of an interaction between the Te d‐orbitals and the oxygen lone pair in COR and NO2 substituted compounds and (b) the Δδ(77Se) ≈︁ 0.6 Δδ(125Te) relationship.
Simple reference baseline subtraction–90° pulse sequence for acoustic ringing elimination in pulsed fourier transform NMR spectroscopy
Authors: Gerothanassis Ioannis P. 
Published: May 2005

AbstractA pulse sequence is proposed for the effective elimination of baseline distortions due to acoustic ringing in pulsed Fourier transform NMR spectroscopy. The method utilizes only 90° pulses with the same phase, and is based on the amplitude and phase characteristics of the distortions. The efficiency of the technique for recording resonances of low‐frequency nuclei having extremely fast relaxation rates, the achievable sensitivity and the off‐resonance effects are discussed.
Substituent chemical shifts in NMR. 3—Carbonitrile SCS in rigid molecules
Authors: Abraham Raymond J. , Fisher Julie 
Published: May 2005

AbstractThe complete analysis of the 1H NMR spectra of 2‐norbornene carbonitrile (exo and endo), 2‐norborname carbonitrile and (exo and endo)1‐adamantane carbonitrile is reported, using high‐field NMR and COSY and proton‐carbon correlation experiments to assign the spectra, these data, together with a previous analysis of 1‐octadeuteriocyclohexane carbonitrile, when combined with data for the parent hydrocarbons provide an extensive data set of substituent chemical shift (SCS) values Cor carbonitriles in molecules of accurately known geometry. The change in geometry on the introduction of a CN group was investigated using ab initio and MNDO methods, and found to be negligible for the carbon framework but significant around the C–N bond for the endo derivatives. A noteworthy feature is that the shielding of the 3x and 3n protons in the norbornane carbonitriles cannot be explained by the magnetic anisotropy of the CN bond.
Long‐range proton–proton spin–spin coupling constants in some aryl‐substituted methylenemalonaldehydes. Conformational dependence of meta‐ and ortho‐benzylic couplings in styrenoic systems
Authors: Kolehmainen E. , Laatikainen R. , Král V. 
Published: May 2005

AbstractThe 1H NMR spectra of some aryl‐ and heteroaryl‐substituted methylenemalonaldehydes were measured and analysed. The long‐range proton–proton spin–spin coupling constants were used to estimate the conformational behaviour of the aryl group relative to the vinyl and aldehyde groups. The compounds serve as model compounds for styrenoic systems, and models for the conformational dependences of the ortho‐ and meta‐benzylic couplings are given.