bluuebunny/crossref_metadata_2025 huggingface dataset:
Mercuration effects on nucleoside chemical shifts: 15N and 13C NMR studies of methylmercury(II) ion addition to cytidine‐3′‐monophosphate and guanosine‐5′‐monophosphate
Authors: Buchanan G. W. , Bell M.‐J.
Published: May 2005

Methylmercuration of cytidine‐3′‐monophosphate is shown to occur at the N‐3 site, resulting in a substantial upfield shift in the 15N resonance of this nitrogen. For guanosine‐5′‐monophosphate the 15N NMR data show N‐1 to be the site of complexation of CH3Hg+ at pH 8. The large downfield shift observed for N‐1 as a result of this binding is explained in terms of a concomitant deprotonation phenomenon. Changes in 13C NMR chemical shifts on methylmercuration are less pronounced, but consistent with these binding sites.
Solvation of alkylaromatic hydrocarbons towards a paramagnetic relaxation reagent, tris(acetylacetonato)chromium(III)
Authors: Holak Tadeusz A. , Aksnes Dagfinn W. , Grahn Hans , Edlund Ulf
Published: May 2005

A 13C electron–nuclear spin–lattice relaxation study showed that the interaction between alkyl‐substituted aromatics and a paramagnetic relaxation reagent, tris(acetylacetonato)chromium(III), is purely electrostatic, i.e. of a dipole–dipole or dipole–induced dipole type. Except for aromatics having bulky alkyl groups, the preferred chelate position is close to the positive end of the dipole, i.e. close to the α‐position. However, the major electron–nuclear mechanism is non‐specific, and the relaxation rate is mainly controlled by the mutual translational/rotational diffusion of the two species. Paramagnetic shifts induced on addition of Cr(acac)3 support the suggested interaction mechanism.
An application of nJ(CH2,H) and 5J(OH,H) long‐range couplings in the conformational analysis of 2‐hydroxybenzyl methyl ether in various solvents. Computational strategies for spectral analysis and determination of association thermodynamic parameters
Authors: Laatikainen Reino
Published: May 2005

1H NMF spectra of 2‐hydroxy‐ and 2‐methoxy‐benzyl methy1 ethers were measured in various solvents and solvent mixtures. Precise nJ(CH2,H), where n = 4, 5 or 6, and 5J(OH,H) long‐range couplings were applied to the characterization of the conformational behaviour of the systems. Qualitatively, the compounds appear to exist in two Principal conformations: in a closed syn with an internal hydrogen‐bonded form, and/or in an open anti conformation with the CH2OR group tilting fairly freely in the benzene plane. The open form is favoured in acetone and dioxane. The computational strategies used in the spectral analysis of the long‐range couplings and in the analysis of the solvent‐solute association equilibria are described.
Thermal cycloaddition reaction of xanthene‐9‐thione with allenes: An ESR study
Authors: Kamphuis J. , Bos H. J. T. , Huizer A. H.
Published: May 2005

During the parallel (2 + 2)‐ and (4 + 2)‐cycloaddition reactions of aromatic thiones such as xanthene‐9‐thione with substituted allenes XCHCCH2 (X = OR, SR, NMe2, Ph), a strong ESR signal is observed. This signal is associated with the (4 + 2)‐cycloaddition reaction, affording thiopyran derivatives 3,11b‐dihydro‐2‐(X‐methylene)‐2H‐thiopyrano[4,3,2‐kl]xanthene F or 3,11b‐dihydro‐3X‐2‐methylene‐2H‐thiopyrano[4,3,2‐kl]xanthene E. Computer analyses of this signal made possible its identification as emanating from a 9‐xanthenyl radical substituted at the 1‐ and 9‐positions. The type of xanthenyl radical that is formed in the thermal reaction E rad or F rad depends on the nature of the substituent X at the allenic system H2CCCHX. This investigation shows that where X = Ph and NMe2, xanthenyl radicals of structure E rad are produced, and where X = O‐t‐Bu and S‐t‐Bu xanthenyl radicals of structure F rad are produced. It is striking that this production is so selective.

On irradiation (λ>254nm), the production of xanthenyl radicals is enhanced. The conformation of xanthenyl radicals E rad and the role of E rad and F rad in the formation of addition products E and F are discussed.
A new approach utilizing high‐resolution proton NMR in structural analysis of intercalation complexes of natural DNA
Authors: Chandrasekaran S. , Kusuma S. , Boykin David W. , Wilson W. David
Published: May 2005

Protons on the antimalarial intercalator quinacrine and a substituted phenanthrene intercalator were monitored on titration with sonicated DNA. The titrations were carried out below the DNA Tm but at a temperature, ionic strength, and intercalator concentration sufficient to give fast exchange conditions and a minimum of dimerization of the planar aromatic intercalators. Line widths were kept within reasonable limits by using sonicated DNA, high temperature, fast exchange conditions and an excess of intercalator over DNA binding sites.

Proton assignments were made using analysis of chemical shifts, coupling patterns, NOE and 2D methods. 2D COSY experiments on DNA‐intercalator complexes were performed to assist in assigning protons for the bound intercalator. Line broadening with quinacrine is more severe than with the phenanthrene, and the acridine essentially represents the limit of the NMR titration method. The phenanthrene intercalator, on the other hand, illustrates the power of the method, particularly when analyzing a series of compounds. Using chemical shift changes of the phenanthrene on titration with DNA and space filling molecular modeling studies, we have been able to propose a general structure for the phenanthrene intercalation complex.
13C chemical shifts and 13C13C coupling constants of some alkyl(aryl)sulphonates
Authors: Millot C. , Brondeau J. , Canet D.
Published: May 2005

The 13C resonances of sodium n‐octylsulphonate, octylbenzene‐sulphonate and 4‐dodecylbenzenesulphonate in aqueous solutions have been assigned, either physically by selective detection of their 13C satellites, or by comparison. Some one‐bond carbon‐carbon couplings have been accurately determined.
Long‐range deuterium isotope effects on 1H chemical shifts in some simple organometallic compounds
Authors: Wei Yong‐Cheng , Wells Peter R. , Lambert Lynette K.
Published: May 2005

Proton NMR spectra are reported for chlorotrimethylstannane, tetramethylstannane, tetramethylplumbane and dimethylmercury containing various combinations of CH3 and CD3 groups. Additive long‐range isotope effects on chemical shifts, 4ΔH(D), are observed to result in increased shielding of essentially the same magnitude in each case. There appears to be no significant isotope effect on the 2J coupling constant.
1H and 13C chemical shift assignments of homoisoflavanones
Authors: Adinolfi Matteo , Lanzetta Rosa , Laonigro Guglielmo , Parrilli Michelangelo , Breitmaier Eberhard
Published: May 2005

13C chemical shifts of various homoisoflavanones were assigned, mainly on the basis of long‐range heteronuclear 2D NMR shift correlation experiments and of long‐range proton‐carbon coupling constants. In addition, 1H chemical shift data are reported. Some general relationships between substitution patterns and nuclear shielding, useful for the identification of naturally occurring homoisoflavanones, are discussed.
Detection and localization of solvent effects on the structure of molecules with C3 or C2v symmetries derived from NMR spectra in anisotropic solvents
Authors: Diehl P.
Published: May 2005

Methods are suggested that allow the detection and localization of solvent effects on direct coupling constants, i.e. molecular structure. Results are presented for the methyl cyanide and ethylene molecules.
35Cl NQR investigations on crystalline α,α′‐dichloro‐o‐xylene
Authors: Venkatacharyulu P. , Prasad N. V. L. N. , Rao C. H. Bhaskar , Premaswarup D.
Published: May 2005

The Zeeman spectrum of the 35Cl NQR line in a cylindrical single crystal of α,α′‐dichloro‐o‐xylene was recorded at room temperature and analysed to obtain information regarding the nature of the crystalline unit cell. The crystal system is determined from the analysis. The two observed loci are due to the two chlorines in a single molecule, and all the benzene rings are parallel to one another whereas the two CCl bonds are inclined to one another at an angle of 102°. The absence of a cleavage plane may be due to the out‐of‐plane CCl and CH bonds in the chloromethyl groups. The ionic, single bond and double bond characters are in the ratio 28.54:70.64:0.82.
Analysis of unusual 13C77Se couplings in the 13C NMR spectra of selenoimidates
Authors: Contreras R. H. , de Azúa M. C. Ruíz , Giribet C. G.
Published: May 2005

The difference between cis and trans 13C77Se couplings reported recently for selenoimidates is analyzed using the IPPP‐INDO method, which allows a study of the stereochemical behaviour of differently transmitted components of electron‐mediated spin‐spin coupling constants. It is concluded that a large through‐space transmission of the Fermi contact term takes place for the cis 13C77Se coupling via an Se‐electron‐pair…HC bond coupling pathway. The influence of the steric compression of the Se‐electron pairs on the one‐bond 13C77Se couplings is also discussed.
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

13C 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

The 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

The 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

The 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

13C 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

trans‐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

1H 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

The 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

A 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

A 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

The 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

A 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

A 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

The 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

Natural 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

13C 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

The 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

Two‐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

Models 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

The 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

33S 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

Techniques 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

13C 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

NMR 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

The 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

One‐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

Four 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

13C 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

A 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

29 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.
13C NMR spectra of alcohols and corresponding nitrate esters
Authors: Narasimhan S. , Srinivasan S. K. , Venkatasu‐Bramanian N.
Published: May 2005

The 13C NMR spectra of alcohols and their corresponding nitrate esters were investigated. An empirical equation is suggested for the change in the chemical shift due to substitution by a nitro group. The spin‐lattice relaxation times are reported.
Correlation between 77Se and 125Te chemical shifts in related heterocycles
Authors: Baiwir Marcel , Llabrès Gabriel , Christiaens Léon , Evers Michel , Piette Jean‐Louis
Published: May 2005

A linear relationship was observed between the 77Se and 125Te chemical shifts in 14 model heterocycles (including 17 new data). The line slope, 1.3, is discussed in terms of Jameson and Gutowski's expression for the Ramsey paramagnetic term, σP. The shifts are also compared with the 17O chemical shifts in related compounds.
Carbon‐13 nuclear magnetic resonance study of the bromo derivatives of 5α‐cholestan‐3‐one and cholest‐4‐en‐3‐one
Authors: Römer Johannes , Scheller Dieter , Grossmann Gisbert
Published: May 2005

The 13C NMR spectra of nineteen bromo derivatives of 5α‐cholestan‐3‐one, cholest‐4‐en‐3‐one and cholest‐5‐en‐3‐one have been recorded. The substituent effects are analysed and examined with respect to additivity. The more interesting γsyn and γanti effects are considered in detail.
185Re and 187Re solid‐state NMR of metaperrhenates
Authors: Klobasa Dagmar G. , Burkert Paul K.
Published: May 2005

127I solid‐state NMR investigations of specific metaperiodates with alkyl‐ or aryl‐substituted cations of main Group V revealed second‐order quadrupole effects, except in the case of tetraethylammonium and tetramethylphosphonium metaperiodate. In these compounds the 127I quadrupole interactions are either very small or vanish. This allowed the approximate evaluation of the electric field gradients of the analogous isomorphous metaperrhenates. Despite the very large nuclear quadrupole moments of the rhenium isotopes, the estimated values of the 185Re and 187Re quadrupole coupling constants of tetraethylammonium and tetramethylphosphonium metaperrhenate have an order of magnitude accessible to solid‐state NMR measurements. The 185Re and 187Re NMR powder spectra of rhenium compounds in non‐cubic lattice structures were measured for the first time. The complete 185Re and 187Re solid‐state NMR spectra of polycrystalline tetramethylphosphonium metaperrhenate were observed, showing temperature‐dependent second‐order quadrupole splittings. In this compound the ReO anions show very small deviations from tetrahedral symmetry, which were estimated from a point charge model and the measured quadrupole splittings. In contrast, the tetrahedral symmetry of the ReO ions of tetraethylammonium metaperrhenate is nearly undistorted, because no quadrupole splittings of the 185Re and 187Re signals were detectable in the powder NMR spectrum.
Reverse anomeric effect of the carbamoyl group of 2,6‐disubstituted 6‐carbamoyl‐5,6‐dihydro‐2H‐pyrans
Authors: Chmielewski Marek , Jurczak Janusz , Priebe Waldemar , Horton Derek
Published: May 2005

The 1H NMR spectra of 2,6‐disubstituted 6‐carbamoyl‐5,6‐dihydro‐2H‐pyrans and their 6‐methoxycarbonyl analogs have been recorded. With the use of coupling constants between ring protons, the conformational preference of the carbamoyl group has been evaluated. The 1H6⇌6H1 conformational equilibria in the above compounds are discussed. It is found that the conformational tendency of the carbamoyl group to the equatorial disposition helps to determine the conformational equilibrium in the seven examples studied.
Carbon‐13 NMR spectra of some 4‐substituted phenacyl chlorides and iodides
Authors: Olivato Paulo Roberto , Guerrero Sandra Alvarez , Rittner Roberto
Published: May 2005

The 13 NMR singles for some 4‐substituted phenacylchlorides and iodides were assigned. The carbonyl carbons exhibit upfield shifts compared with those of the corresponding 4‐substituted acetophenones; in the chlorinated derivatives a downfield shift is observed for the α‐methylene carbons, while a reverse effect occurs in the iodinated compounds. The chemical shifts of the aromatic ring carbons are in close agreement with those calculated using substituent chemical shifts.
Structure of nitroguanidine: Nitroamine or nitroimine? New NMR evidence from 15N‐labeled sample and 15N spin coupling constants
Authors: Bulusu S. , Dudley R. L. , Autera J. R.
Published: May 2005

The structure of nitroguanidine was investigated by the application of 15N, 1H and 13C NMR spectroscopy of a fully 15N‐labeled sample in DMSO‐d6 and DMF solutions and by 15N CP/MAS NMR in the solid state. These spectra confirm the nitroimine structure which has been suggested by other investigations in recent years, and do not lend any support to the commonly used nitroamine structure or for a tautomeric equilibrium with the nitroamine. Useful 15N spin coupling constants to the 1H and 13C nuclei in the assigned structure are reported.
Re‐examination of the 13C NMR spectra of synthetic chlorins
Authors: Stolzenberg Alan M. , Stershic Matthew T.
Published: May 2005

The 13C NMR spectra of the synthetic chlorins H2(OEC), Ni(TMC) and H2(TPC) have been re‐examined. Evidence from single‐frequency proton decoupled, proton coupled, and 2D 13C‐13C INADEQUATE experiments show that the previous assignments of the meso‐substituted chlorins were incorrect. Corrected assignments establish that the α‐pyrroline carbons of chlorins occur at lower fields (150–175 ppm) than the α‐pyrrole carbons.
13C NMR study of polyphenyl‐, poly‐N‐azolyl‐and poly‐N‐benzazoyl‐methanes
Authors: Elguero J. , Claramunt R. M. , Garcerán R. , Julià S. , Avila L. , del Mazo J. M.
Published: May 2005

13C NMR chemical shifts of 69 substituted methanes (general formula R1R2R3R4C, where the substituents were H, C6H5, Cl, OH, OR, imidazol‐1‐yl, pyrazol‐1‐yl, 1,2,4‐triazol‐1‐yl, 1,2,4‐triazol‐4‐yl, benzimidazol‐1‐yl, indazol‐1‐yl, indazol‐2‐yl, benzotriazol‐1‐yl and benzotriazol‐2‐yl) are reported. The effects of the various N‐substituents on the 13C chemical shifts of the heterocyclic nuclei are reported. The chemical shifts of the methane carbon atom are discussed using an interactive model. Some 1H‐13C coupling constants have been measured.
Asymmetry parameters of the electric field gradient at the nuclei in compounds of the RC6H4COCl series
Authors: Feshin V. P. , Dolgushin G. V. , Voronkov M. G. , Sapozhnikov Yu. E. , Yasman Ya. B.
Published: May 2005

Asymmetry parameters of the electric field gradients at the 35Cl nuclei in compounds of the RC6H4COCl series (R = H, 4‐CH3, 2‐, 3‐ and 4‐COCl) have been measured at 77 K. They indicate a high asymmetry (> 20%) of the chlorine electron distribution in all the molecules studied. The substituent R in the aromatic ring has no significant effect on the asymmetry.
Relaxation processes in aromatic methly groups. II—Methyl hydrogen T1 values for some halo‐toluenes and ‐xylenes
Authors: Rae Ian D. , Sandbach Frances B.
Published: May 2005

Hydrogen T1 values are reported for deoxygenated solutions in CDCl3 of toluene, p‐xylene and nine derivatives in which the CH3 is flanked by one or two chlorine or bromine substituents. Only small differences were observed, the T1 values all being in the range 5.8–12.8 s, and there was no obvious correlation of T1 with structure.
1H and 13C NMR structural assignments of two isomeric isopropylidenepyridoxines
Authors: Nelson Janis T. , Nelson Peter H.
Published: May 2005

Acid‐catalyzed reaction between pyridoxine and acetone produced the isomeric six‐ and seven‐membered ketals, depending on the conditions used. The structures were assigned by means of the 1H and 13C NMR spectra of the free bases and hydrochlorides.
Long‐range 1H coupling interactions: Identification of different pathways by 2D NMR δ—δ correlated spectroscopy. Applications in structural analysis
Authors: Platzer N. , Goasdoue N. , Davoust D.
Published: May 2005

The simplest methods of 2D δ‐δ correlated spectroscopy (COSY and COSY LR) allow the easy observation of long‐range coupling interactions. It is shown how these methods can lead to the discrimination between different pathways across single bonds: 4J through coplanar or gauche arrangement of the bonds and 5J through a zig‐zag pathway or bond proximity. Applications to configurational and conformational analysis of polycyclic compounds, a trimer of isophorone, two natural terpenoids (carotol and daucol) and four steroids, are presented.
13C and 31P NMR studies of some aminophosphonium chlorides
Authors: Krannich Larry K. , Kanjolia Ravindra K. , Watkins Charles L.
Published: May 2005

The multinuclear NMR spectral data for an homologous series of tertiary phosphines, R3‐nP(NMe2)n, aminophos‐phonium ions, [R3PNR′R″]+, and phosphonium ions, [R4‐nPMe]+, where R = Me, Et, n‐Pr and Ph, R′ and/or R″ = H, Me and n = 0 and 1 are reported and discussed. Quaternization by alkylation or chloramination causes an increase in the 31P chemical shift (Δ δP is positive), a decrease in the 13C chemical shift (Δ δC is negative) for all carbons, an increase in the magnitudes of 1J(PC), 3J(PC), 3J(PNCH) and 2J(PCH) and a decrease in the magnitude of 2J(PC). Substitution of a Me2N group for an alkyl or aryl group produces an increase in the 31P chemical shift and in the magnitude of 1J(PC). α‐ and β‐deshielding and γ‐shielding effects are noted in the 13C NMR spectra and β‐deshielding and γ‐shielding effects are noted in the 31P NMR spectra with substitution on the phosphorus and nitrogen atoms.
Concerted use of two‐dimensional NMR spectroscopy in the complete assignment of the 13C and 1H NMR spectra of globularin
Authors: Faure R. , Babadjamian A. , Balansard G. , Elias R. , Maillard C.
Published: May 2005

The complete assignment of the proton and carbon spectra of globularin is presented. 13C multiplicities were determined by the DEPT method; the interpretation of the spectra was achieved by comparison of heteronuclear 13C‐1H chemical shift correlation, 1H homonuclear correlation and 1H homonuclear J‐resolved two‐dimensional NMR spectra.
Identification of constituent sugar residues in oligosaccharides by two‐dimensional 1H NMR phase‐sensitive correlated spectroscopy
Authors: Dabrowski Janusz , Ejchart Andrzej , Kordowicz Maria , Hanfland Peter
Published: May 2005

Pure absorption phase‐sensitive shift‐correlated 1H NMR spectra were shown to furnish complete information on chemical shifts, their connectivities (including one‐ and two‐step remote connectivities) and coupling constants for oligosaccharides of considerable complexity. Therefore, a strategy using these spectra as a first step in ab initio structure elucidation of carbohydrates may require less effort and spectrometer time than alternative strategies exploiting J‐resolved, double quantum and relayed coherence transfer spectra. All these methods and also triple quantum filtered spectra were applied in order to compare their merits and to identify the constituent sugar residues of three peracetylated glycosphingolipids, viz. Galα(1–3)Galβ(1–4)GlcNAcβ(1–3)Galβ(1–4)Glcβ(1–1)Cer(Cer=ceramide),Galα(1–3)Galβ(1–4)GlcNAcβ(1–3)[Galα(1–3)Galβ(1–4)GlcNAcβ(1–6)]Galβ(1–4)GlcNAcβ(1–3)Galβ(1–4)Glcβ(1–1)Cer and GalNAcβ(1–3)Galα(1–4)Galβ(1–4)Glcβ(1–1)Cer(globoside).
Oxygen‐17 quadrupole coupling in liquid acetone
Authors: Ruessink B. H. , Maclean C.
Published: May 2005

17O NMR spectroscopy of liquid acetone, oriented in a strong applied electric field, was used to measure one of the principal components of the 17O quadrupole coupling tensor (qct). The component along the carbonyl bond was found to be (±)3.0±0.2 MHz. By comparison with other data in the literature concerning acetone and related molecules, it can be concluded that this value refers to the smallest of the principal components. The proposed NMR method is a powerful technique for obtaining information about qcts in normal liquids.
13C NMR spectra of new condensed tricyclic and tetracyclic pyrazole ring systems
Authors: Světlík Jan , Goljer Igor
Published: May 2005

The 13C NMR spectra of 1‐phenylpyrazolo[4,3‐e]pyrrolo[1,2‐a]pyrazine, its 5‐aza analogue and heterocycles with additional azolo ring annelations are reported.
13C NMR chemical shift assignments for some 2‐substituted cyclic 1,3‐diketones
Authors: Sammes Michael P. , Maini Prem Nath
Published: May 2005

Complete 13C NMR chemical shift assignments are reported for 32 cyclic and one acyclic 1,3‐diketones, either unsubstituted or having one or two substituents at the 2‐position. The first two classes exist exclusively in the enol form in (CD3)2SO and as mixed tautomers in CDCl3.
NMR investigation of lipophilic cage ligands 2—Structural assignments and conformational properties of the ligand 12‐hexadecyl ‐7,17,22,27‐tetraoxa‐1,4,10,14‐tetraazatricyclo[12.5.5.54,10] ‐nonacosane and of its sodium, potassium and silver complexes
Authors: Anelli Pier Lucio , Beringhelli Tiziana , Molinari Henriette , Quici Silvio
Published: May 2005

Two‐dimensional homonuclear (COSY, phase‐sensitive double quantum filtered COSY) and heteronuclear shift correlated experiments were employed to characterize fully the cylindrical cage ligand 12‐hexadecyl‐7,17,22,27‐tetraoxa‐1,4,10,14‐tetraazatricyclo[12.5.5.54,10] nonacosane (1) and its sodium, potassium and silver complexes. 13C NMR variable temperature experiments indicated that the free ligand 1 is a mobile molecule in a fast conformational equilibrium at room temperature, whereas its sodium complex is more rigid, some degrees of freedom being allowed in that part of the molecule featuring the longest bridge. The potassium derivative behaves similarly to its sodium counterpart. For the silver complex the differences observed have been attributed to a stronger interaction of the metal ion with nitrogen atoms.
Carbon‐13 chemical shifts assignment of (E)‐styryluracits. (E)‐styrylthiouracils and (E)‐3‐oxothiazolo[3,2‐a]‐6‐styryl‐pyrimidin‐5‐ones
Authors: Łapucha Andrzej , Wyrzykiewicz Elzbieta
Published: May 2005

The 13C NMR spectra of nine isomeric (E)‐styryluracils and (E)‐styrylthiouracils and those of five (E)‐3‐oxothiazolo[3,2‐a]‐6‐styrylpyrimidin‐5‐ones have been fully assigned. The Ai and AiK empirical parameters of p‐ and m‐hydroxystyryl, p‐N,N‐diethylaminostyryl, 5‐ and 6‐vinyl02,4‐diketopyrimidyl, 5‐ and 6‐vinyl‐2‐thio‐4‐ketopyrimidyl and 3‐oxothiazolo[3,2‐a]‐6‐vinyl‐5‐ketopyrimidyl groups were calculated for the prediction of the chemical shifts of substituted (E)‐styryluracils and (E)‐3‐oxothiazolo[3,2‐a]styrylpyrimidin‐5‐ones.
Carbon‐carbon [nJ(CO, C)] and carbon‐fluorine coupling constants [nJ(CF)] of ortho‐substituted benzoic acids and acid fluorides: INDO‐SOS calculations and evaluation of rotational effects
Authors: Hansen Poul Erik , Berg Arne , Schaumburg Kjeld
Published: May 2005

Carbon‐carbon coupling constants, nJ(CO, C) were determined for o‐alkylbenzoic acids and benzoyl fluorides and carbon‐fluorine coupling constants, nJ(CF), were determined for the fluorides. INDO‐SOS calculations showed promise for estimating factors that influence the coupling constants, and experimental and theoretical arguments were used in the evaluation of these factors. The coupling constants were investigated for use as parameters in determing the orientation of the acid fluoride group. Through‐space contributions to carbon‐carbon couplings were considered. 13C chemical shifts are briefly discussed in relation to the anisotropy and conformation of the carboxyl and alkyl groups.