bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C and 1H two‐dimensional NMR characterization of the sodium perchlorate complex of a new tetraoxatetraaza lipophilic cage ligand
Authors: Anelli P. L. , Montanari F. , Molinari H. , Quici S. , Beringhelli T. 
Published: May 2005

Abstract13C and 1H NMR characterization of the sodium perchlorafe complex of a new tetraoxatetraaza lipophilic cage ligand (1) derived from 1,7‐dioxa‐4,10‐diazacyclododecane has been performed. 1H homonuclear correlated and 1H J‐resolved two‐dimensional experiments allowed the recognition of resonances due to different types of OCH2CH2N fragments, and of those of the hydrogens of the bridging chains. 13C resonances have been assigned on the basis of a 13C1H heteronuclear correlated two‐dimensional experiment, together with the 13C NMR spectra of the synthetic precursors of 1. 13C spin‐lattice relaxation times and NOE measurements established that the unique relaxation mechanism is dipole‐dipole; the calculated rotational correlation times indicated that molecular reorientation is isotropic. 13C spectra and relaxation times obtained in different solvents showed that specific solute‐solvent interactions are absent.
NMR study of protonated halothiophenes. III—1H NMR study of bromothiophenium ions
Authors: Yamashita Yukihide , Yoshino Akihiro , Takahashi Kensuke , Sone Tyo 
Published: May 2005

AbstractThe 1H NMR signals of the cations formed from bromothiophenes were observed in HSO3F solution at −70°C. Protonation occurs at one of the α‐carbons in all cases studied. Some bromothiophenium ions undergo rearrangement or fluorosulphonylation with an increase in temperature. Both protonated 2,5‐ and 2,3‐dibromothiophenes, for example, rearrange to the same 3,5‐dibromo‐2H‐thiophenium ion. 1H and 19F NMR spectral data of the related bromothiophenesulphonyl fluorides are also presented.
Correlated 1H13C NMR spectroscopy of peracetylated glycosphingolipids at 500 MHz
Authors: Dabrowski Janusz , Dabrowski Ursula , Hanfland Peter , Kordowicz Maria , Hull William E. 
Published: May 2005

AbstractThe assignments of the sugar and ceramide 13C and 1H signals of peracetylated ceramide penta‐ and deca‐saccharide from rabbit erythrocyte membranes, viz. Galα(1→3)Galβ(→4)GlcNAcβ(1→3)Galβ(1→4)Glcβ(1→1) Cer (Cer=ceramide) and Galα(1→3)Galβ(1→4)GlcNAcα(1→3[)Galβ(1→4)GlcNAcβ(1→6)]GalNAcβ(1→4)GlcNAcβ(1→3)Galβ(1→4)Glcβ(1→1)Cer, were obtained by the combined use of homo‐ and hetero‐nuclear shift‐correlated 2D and DEPT spectra. A few ambiguities resulting from exact coincidence of 1H resonances were resolved by relying on reference data for similar environments.
Nuclear magnetic resonance study of selected derivatives of 2,8,9‐trioxa‐5‐aza‐1‐silatricyclo[3.3.3.01,5]undecane (silatrane)
Authors: Bellama Jon M. , Nies J. Dirk , Ben‐Zvi Nava 
Published: May 2005

AbstractThe 1H, 13C and 29Si nuclear magnetic resonance spectra of the parent compound and twelve derivatives of 2,8,9‐trioxa‐5‐aza‐1‐silatricyclo[3.3.3.01,5]undecane (silatrane) are discussed. Effective Taft polarity constants for the silatrane substituents are proposed. An equation is developed to correlate the 29Si NMR chemical shifts of the silatranes with the corresponding organo‐triethoxysilanes.
13C NMR spin relaxation studies of molecular dynamics of substituted phenylbicyclo[2.2.2]octanes
Authors: Craik David J. , Adcock William , Levy George C. 
Published: May 2005

Abstract13C NMR spin‐lattice relaxation times (T1) have been measured for a series of meta‐ and para‐substituted phenylbicyclo[2.2.2]octanes in CDCl3 solution. The non‐equivalence of NT1 values (N = number of attached hydrogens) for the various protonated carbons in these molecules indicates that motion is highly anisotropic. Analysis of the T1 data using the Woessner formalism for axially symmetric ellipsoids yields a set of diffusion coefficients for overall and internal motion. In para‐substituted derivatives, motion about the symmetry axis is 3–12 times faster than motion about the perpendicular axes, depending on the substituent. Both the size (inertia) and the interacting properties of the substituent are important in determining the motional anisotropy, as indicated by the following observed order: H < NH2 < CH3 < NO2 < CH2OH < Br < NH3+ < CO2H. The change in anisotropy is a result of the anchoring effect of the substituent (via either its inertia or its hydrogen‐bonding ability), which restricts motion about axes perpendicular to the long axis of the molecule. In meta derivatives, a similar model of motional anisotropy is observed, although the absolute magnitudes of diffusion coefficients are smaller than for the para series. In both series, the bicyclooctane ring undergoes fast internal motion relative to the phenyl ring. This reflects the fact that the bicyclooctane ring is able to rotate essentially in its own volume, with minimum disturbance to neighbouring solvent molecules. On the other hand, the planar phenyl ring must displace solvent molecules as it rotates.
1H NMR spectra and the structure of the products of reaction between trans‐1‐N‐alkylaminotetralin‐2‐ols, trans‐3‐N‐alkylaminotetralin‐2‐ols and formaldehyde
Authors: Crabb Trevor A. , Robinson Paul 
Published: May 2005

Abstracttrans‐1‐N‐Alkylaminotetralin‐2‐ols condense with formaldehyde to form the expected trans‐(H‐3a, H‐9b)‐N‐alkyl‐1,2,3a,4,5,9b‐hexahydronaphtho[1,2‐d][1,3]oxazoles. On allowing solutions of these compounds in deuteriochloroform to stand for several hours a mixture of the original oxazole, together with a trans‐(H‐5a, H‐11b)‐N‐alkyl‐1,2,5a,6,7,11b‐hexahydronaphthol[1,2‐f][1,3,5]dioxazepine, was produced. This latter system was identified by the 1H NMR signals of the methylene protons situated between the heteroatoms. The reaction between the corresponding trans‐3‐N‐alkylaminotetralin‐2‐ols gave trans‐(H‐3a, H‐9a)‐N‐alkyl‐2,3,3a,4,9,9a‐hexahydronaphtho[2,3‐d][1,3]oxazoles, which were stable in deuteriochloroform solution.
Structural Studies of Hydroxylated D‐homo‐5α‐androstanes by 1H NMR decoupling difference techniques
Authors: Campbell Sheelagh A. , Crabb Trevor A. , Williams Roger O. 
Published: May 2005

Abstract1H NMR chemical shifts of thirteen D‐homo‐5α‐androstan‐17a‐ones have been determined by decoupling difference techniques. Shift changes, primarily of the H‐8, H‐9 and H‐14 protons, produced by the introduction of hydroxy groups in the steroid have been shown to be of diagnostic importance.
1H NMR spectrum and conformation of the proline ring in propionylalanylprolineethylamide
Authors: Abraham R. J. , Hudson B. D. , Thomas W. A. 
Published: May 2005

AbstractThe 400 MHz 1H NMR spectrum of propionylalanylprolineethylamide (PAPE) has been obtained in CDCI3 solution. Analysis of the spectrum for the protons of the pyrrolidine ring shows a 4:1 preference for the S, or C‐γ‐endo, form of the ring. This preference is more pronounced than is commonly observed for trans‐proline derivatives.
A set of alkyl substituent constants for correlating chemical shifts of a variety of nuclei
Authors: Poh Bo‐Long 
Published: May 2005

AbstractA set of substituent constants for alkyl groups has been calculated and shown to be useful in the correlations of chemical shifts of atoms that have a directly bonded alkyl group(s). The correlation equation used is δ(X) = mσn + b, where δ(X) is the chemical shift of atom.X, δ. is the alkyl substituent constant and m and b are constants for a given series of compounds. Forty‐two series of compounds, consisting of thirteen different X nuclei (13C, 14N, 15N, 17O, 19F, 29Si, 31P, 35CI, 75As, 77Se, 113Cd, 125Te, 199Hg) have been correlated.
Substituent effects on carbon‐13 chemical shifts and the stereochemistry of ent‐beyeranic and ent‐beyer‐15‐enic compounds substituted on the bicyclo[3.2.1]octane moiety
Authors: García‐Granados A. , Martínez A. , Onorato M. E. , Santoro J. 
Published: May 2005

AbstractA detailed analysis of the 13C NMR spectra of 39 isomeric ent‐beyer‐15‐enes and ent‐beyeranes functionalized at C‐7, C‐14, C‐15 and C‐16 has been performed. This diterpenic skeleton is a good example of a semirigid bicyclo[3.2.1]octane system. The sensitivity of 13C shielding to the stereochemical environment, particularly in polyfunctional compounds, has been confirmed. In some cases the ent‐beyer‐15‐enes and ent‐beyeranes show similar behaviour to that of similarly functionalized bicyclo[3.2.1]octane derivatives, but in other cases the shielding effects are very different. The compounds studied are a good model for the evaluation of shielding effects in exo/endo isomers of strained and rigid carbocyclic compounds.
Use of high‐field 119Sn NMR and the pairwise additivity model for chemical shifts in the identification of complexes in the SnBr4–KSCN–MeOH system
Authors: Blunden Stephen J. , Cusack Paul A. , Gillies Duncan G. 
Published: May 2005

AbstractThe interaction of SnBr4 and KSCN in methanol solution has been studied by 119Sn NMR at 149 MHz and −30°C. Evidence was obtained for the existence of both the cis and trans isomeric forms of SnBr4·2MeOH. A pairwise additivity model for chemical shifts was used to explain the observed peaks and many of the possible species, SnBrn(NCS)4‐n·2MeOH. [SnBrn(NCS)5‐n·MeOH]‐ and [SnBrn(NCS)6‐n2−], (n=0–4), and their somecies, forms were identified and shown to exist simultaneously in solution in complex equilibria. In some cases 119Sn–14N coupling was observed. The implications for possible synthesis of these types of compounds and the necessity for measurement at high field are discussed.
1H, 13C and 15N NMR studies of 13C and 15N labeled 2‐methylthiooxazoline derivatives of pentoses and hexoses. Stereoelectronic effects on chemical shifts and mass fragmentation pathways
Authors: Davidson Robert M. , Byrd Gary D. , White Edward , Samm V , Margolis A. , Coxon Bruce 
Published: May 2005

AbstractA facile synthesis of 2‐methylthio‐(glyco)oxazoline derivatives has been developed which involves methylation of 2‐thiono‐(glyco)oxazolidines prepared by condensation of aldoses with thiocyanate ion. The synthesis has been applied to the preparation of six 2‐methylthiooxazoline derivatives in the pentose series and six derivatives in the hexose series. For several sugars, both pyranoid and furanoid forms were isolated, and the use of either 13C‐ or 15N‐labeled thiocyanates yielded either 2‐13C‐labeled or 3‐15N‐labeled derivatives. The structures of the products have been studied by 1H, 13C and 15N NMR spectroscopy and by electron‐impact and field desorption mass spectrometry. Multinuclear chemical shift correlations and analyses of fragmentation pathways have facilitated the assignment of ring size in the 2‐methylthio‐(glyco)oxazoline derivatives.
Determination of carbon multiplicities by a double echo sequence and gated decoupling
Authors: Canet D. , Millot C. , Brondeau J. 
Published: May 2005

AbstractA simple pulse sequence, based on a double 13C echo and off gated proton decoupling, is shown to yield four subspectra (C, CH, CH2 and CH3) from linear combinations of four different experiments. This procedure has two advantages: (1) experimental simplicity, keeping instrumental adjustments to a minimum and (2) acquisition of the four experiments under identical lengths of the evolution period, thus eliminating any spurious effects due to transverse relaxation.
ESR line width studies of some binary and ternary copper(II) compounds in solution
Authors: Pisipati V. G. K. M. , Rao N. V. S. , Padmaja S. , Anjaneyulu Y. , Rao R. Prabhakara 
Published: May 2005

AbstractThe line widths of the hyperfine components of the ESR spectra of a number of binary and ternary copper(II) compounds formed with ligands such as acetylacetone, 8‐hydroxyquinoline, salicylic acid and diethyldithiocarbamate, in dimethylformamide solution at room temperature, were analysed using the theory developed by Wilson and Kivelson. The results are compared with the experimental hyperfine line widths, and the limitations of the theory are discussed. The agreement between the experimental hyperfine line widths and the theoretical values is very poor.
13C and 15N nuclear magnetic resonance studies of selected tetrazoles: Relationships with the chemistry of tetrazoles
Authors: Nelson John H. , Takach Nicholas E. , Henry Ronald A. , Moore Donald W. , Tolles William M. , Gray George A. 
Published: May 2005

AbstractNatural abundance 13C and 15N nuclear magnetic resonance studies have been carried out on a series of sodium tetrazolate salts, 1,5‐ and 2,5‐disubstituted tetrazoles, bitetrazoles, and cobalt(III) tetrazolate complexes of the type (PBu3n)Co(DH)2(5‐R‐tetrazolate), where DH is the monoanion of dimethylglyoxime. The 15N chemical shifts have been analysed with respect to structure, substituent effects, electron density as determined by molecular orbital calculations, Brønsted acidity, Lewis basicity and nucleophilicity of the nitrogen atoms in the ambidentate tetrazoles.
Carbon‐13 and proton NMR data for two series of mesogenic compounds
Authors: Poon Chi‐Duen , Afzal Jalees , Gangoda Mahinda , Fung B. M. 
Published: May 2005

Abstract13C and 1H NMR spectra of two series of mesogenic compounds dissolved in CDCl3 were studied. The compounds are 4‐n‐alkyl‐4′‐cyanobiphenyls and 4‐n‐alkyloxy‐4′‐cyanobiphenyls, with the alkyl group ranging from pentyl to octyl. 13C and 1H chemical shifts and 13C–1H scalar coupling constants are tabulated.
CC coupling constants of unsaturated hydrocarbons
Authors: Hübers Reinhard , Klessinger Martin , Wilhelm Konrad 
Published: May 2005

AbstractThe 13C NMR spectra of 24 unsaturated hydrocarbons (mono‐ and dienes) were investigated by means of the INADEQUATE pulse technique. All coupling constants larger than 1.5 Hz could be determined with an accuracy of ± 0.2 Hz.
Benzo[b]phenanthro[4,3‐d]thiophene: Spectral assignment by two‐dimensional NMR methods and tertiary structure determination
Authors: Musmar M. J. , Zektzer Andrew S. , Martin Gary E. , Gampe Jr. Robert T. , Lee Milton L. , Tedjamulia Marvin L. , Castle Raymond N. , Hurd Ralph E. 
Published: May 2005

AbstractTwo‐dimensional heteronuclear chemical shift correlation, heteronuclear relayed coherence transfer and autocorrelated 13C—13C double quantum coherence have been used to assign the proton and 13C NMR spectra of benzo[b]phenanthro[4,3‐d]thiophene. The highly complementary nature of the heteronuclear relay and carbon–carbon double quantum spectra conveniently provides the means of avoiding breaks in the carbon–carbon connectivity network assembled by the latter, which may arise when strongly AB rather than AX carbon–carbon pairings are encountered. Nuclear Overhauser difference spectra have shown the title compound to possess a tertiary helical structure similar to that of phenanthro[3,4‐b]thiophene; the average separation between the H‐1 and H‐13 atoms of the title compound was found to be 2.06 ± 0.04 Å.
Carbon‐13 spin–lattice relaxation of tropane alkaloids. II—models for isotropic, axially symmetric and fully anisotropic overall rotational diffusion with diffusional or three‐state jump internal motion, and their application to the N‐methyl groups of tropine and pseudotropine
Authors: Uusvuori Raimo , Lounasmaa Mauri 
Published: May 2005

AbstractModels for isotropic, axially symmetric and fully anisotropic overall rotational diffusion with single diffusional or three‐state internal motion are reviewed or derived and applied to 13C spin‐lattice relaxation data for the N‐methyl groups of tropine and pseudotropine. The results are compared. Complete equations containing the dependence on the equilibrium positions are given for the three‐state jump models. Despite the considerable approximations which these models imply, they are able to predict the expected features of the internal N‐methyl group motion in tropine and pseudotropine: hindered three‐state jumping, which is of the same rate for tropine and pseudotropine and which is moderately independent of concentration and the model for overall motion. Although the nitrogen inversion in these compounds is slow compared with methyl rotation, and does not affect the relaxation, the equations are also derived for double internal motion where the internal rotation axis jumps between two non‐equivalent sites having an arbitrary but fixed orientation within the molecule, and where the innermost internal motion is diffusional or jumpwise as in single internal motion. Some considerations regarding the units of the rotational diffusion constants, errors in T1 measurements, and the reduction of the equations for fully anisotropic overall motion to equations for axially symmetric and, further, for isotropic overall motion are presented.
An increment system for deuterium isotope effects on 13C chemical shifts of methylated benzenes
Authors: Berger Stefan , Diehl Bernd W. K. 
Published: May 2005

AbstractThe complete series of all possible benzenes bearing one deuterium atom and one to five methyl groups was synthesized. The deuterium isotope effects on the carbon chemical shifts of the aromatic and aliphatic carbon atoms were measured and shown to obey an empirical increment system. The isotope effects over one bond correlate with the C,H spin coupling constants.
33S and 14N nuclear magnetic resonance spectra of some sulphur–nitrogen compounds
Authors: Belton Peter S. , Woollins J. Derek 
Published: May 2005

Abstract33S and 14N NMR spectra of nine sulphur‐nitrogen compounds are reported. It is demonstrated that 14N NMR gives high signal‐to‐noise spectra with good discrimination of chemical shifts. It is concluded that both 14N and 33S NMR can make a useful contribution to the study of sulphur‐nitrogen chemistry and that 14N may have advantages over 15N NMR in terms of speed of spectral acquisition and cost.
New pulse sequence for long‐range two‐dimesional heteronuclear NMR chemical shift correlation
Authors: Zektzer Andrew S. , Quast Michael J. , Linz Gary S. , Martin Gary E. , McKenney J. Dew , Johnston Milton D. , Castle Raymond N. 
Published: May 2005

AbstractTechniques available for long‐range heteronuclear chemical shift correlation are briefly reviewed. A new pulse sequence for long‐range heteronuclear chemical shift correlation is described. Comparison of the results obtained using the new pulse sequence with those from conventional long‐range optimized heteronuclear chemical shift correlation is presented. Total Assignments of the 1H and 13C NMR spectra of 1‐benzothieno[2,3‐çlquinoline], the model compound used for the study, are reported.
Carbon‐13 NMR study of aniline derivatives
Authors: Bulbarela Arturo , Tlahuext Hugo , Morales Hilda Rosa , Cuéllar Laura , Uribn Guillermo , Contreras Rosalinda 
Published: May 2005

Abstract13C NMR chemcical shifts of 23 aniline and 1,8‐diaminonaphthalene derivatives are reported; the parent compounds are also included for purposes of comparison.
An NMR study of A‐ring conformation in some 4‐en‐3‐one steroids
Authors: Marat Kirk , Templeton J. F. , Kumar V. P. Sashi 
Published: May 2005

AbstractNMR spectral data are given for the A‐ring in ten 4‐en‐3‐one steroids, and the strategy of the spectral analysis is described. The data are interpreted in terms of an equilibrium between normal and inverted half‐chair conformations, with the normal conformation predominant in all cases except when 2β‐acetoxy substitution forces inversion. Substitution at the 17α position has no measurable effect upon the A‐ring conformation while 6α and 19‐nor substitution have only a small effect. Unsaturation at the C‐5 position results in a flattened A‐ring. The results obtained from NMR are compared with those obtained by x‐ray crystallography. The A‐ring conformation shows far less variation in solution than it does in the solid.
Molecular processes in 2‐nitroenamines studied as neutral molecules and under cationic and anionic activation conditions; 1H, 13C and 15N NMR
Authors: Kozerski L. , Krówczyński A. 
Published: May 2005

AbstractThe interpretation of the 1H, 13C and 15N NMR chemical shifts and spectral processes in 2‐nitroenamines, studied as neutral molecules and under cationic and anionic activation conditions, is presented in terms of molecular stereochemistry and electron distribution along the main skeleton. A comparison of the latter effects in the cationic and anionic molecules with respect to the neutral molecule allows hypotheses regarding the activity of various reactive centres, i.e. the C‐2 and NO atoms. In the case of cationic activation a variety of products can be synthesized; the regioselectivity of the reaction in acids is rationalized on the basis of the spectral characterization of the reactive species, the structure of which depends on the nature of the substituent on the enamine nitrogen atom.
Revised assignments of the 13C NMR spectrum of hibalactone using 2D heteronuclear 1H/13C correlations
Authors: San Feliciano A. , Medarde M. , López J. L. , Barrero A. F. , del Corral J. M. Miguel 
Published: May 2005

AbstractOne‐bond and long‐range two‐dimensional 1H/13C NMR experiments allow the unequivocal and simultaneous assignment of 13C and 1H spectra. On this basis, previous assignments of 13C signals of hibalactone have been revised.
ESR investigation of the dimerization of some dithiazolidinyl radicals
Authors: Fairhurst Shirley A. , Stewart Neil J. , Sutcliffe Leslie H. 
Published: May 2005

AbstractFour types of dithiazolidin‐2‐yl radical were selected for dimerization measurements in solution. The radicals had different types of substituents and/or different amounts of strain; ESR measurements for a new dithiazolidinyl radical prepared from trans‐cyclooctene are presented. Toluene, diethyl ether and chloroform were used as solvents. Radical concentration measurements incorporated corrections for the variation of the Q of the spectrometer cavity with solvent and temperature. It was found that ΔH⊖ for the dimerization process is dependent only on the radical structure.
cis‐cyclohexyl‐15‐crown‐5 ether: Dynamic stereochemistry in solution as studied by carbon‐13 NMR techniques
Authors: Buchanan G. W. , Bourque K. , Diedrich G. K. , Khan M. Z. 
Published: May 2005

Abstract13C NMR spectra of cis‐cyclohexyl‐15‐crown‐5 ether in the temperature range 298–173 K have been recorded. A single degenerate conformational process, attributed to cyclohexyl ring inversion, has been detected with a barrier of ca 10.3 kcal mol‐1. Sodium ion complexation increases this barrier by ca 0.5 kcal mol−1, whereas potassium ion complexation has no measurable effect. Spin‐lattice relaxation time results also indicate more effective complexation of sodium ion than potassium ion by the macrocyclic crown ether system.
Group assignment and carbon and proton shift measurement by heteronuclear zero‐quantum carbon‐shift correlated 2D NMR in a single experiment
Authors: Egli Huldrych , Graf Walter 
Published: May 2005

AbstractA two‐dimensional heteronuclear multiple‐quantum NMR experiment, based on the DEPT pulse sequence, for the simultaneous determination of the nature of proton‐bearing chemical groups together with the measurement and correlation of carbon and proton chemical shifts is presented. Time and computer memory requirements for the proposed experiment are comparable to the acquisition of a two‐dimensional C,H shift correlation spectrum. The data evaluation of the proposed zero‐quantum carbon‐shift correlated spectrum provides a list of chemical groups corroborated with their carbon and proton chemical shifts.
29Si and 13C NMR spectra of all possible pertrimethylsilylated β‐D‐xylopyranosyl‐substituted methyl 4‐O‐β‐D‐xylopyranosyl‐β‐D‐xylopyranosides assigned by 2D heteronuclear 1H‐29Si and 1H‐13C chemical shift correlations
Authors: Schraml J. , Petráková E. , Hirsch J. 
Published: May 2005

Abstract29 and 13C NMR spectra of all possible pertrimethylsilylated β‐D‐xylopyranosyl‐substituted methyl 4‐O‐β‐D‐xylopyranosyl‐β‐D‐ XYLOPYRANOSIDES ARE ASSIGNED BY HETERONUCLEAR 1H‐X 2D NMR chemical shift correlation experiments, where X = C or Si. It is shown that the 29Si NMR spectra can be used for identification of the glycosidation site and ring assignments. The silicon chemical shifts do not follow any simple rule that would allow empirical assignment.