bluuebunny/crossref_metadata_2025 huggingface dataset:
An alternative approach to multi‐dimensional NMR spectroscopy
Authors: Freeman Ray , Friedrich Jan , Davies Simon
Published: May 2005

Multi‐dimensional NMR spectroscopy must satisfy the Nyquist sampling condition in all frequency dimensions. This entails very long experiments and very large data arrays, and may mean that fine structure of cross‐peaks cannot be adequately digitized. This sampling restriction can be sidestepped in an alternative approach which explores the new frequency dimensions by scanning selective radiofrequency pulses in small steps over narrow frequency ranges. A pulse envelope shaped according to the first half of a Gaussian curve is particularly well suited to this task. Thus a form of double resonance experiment can be used to generate two‐dimensional correlation spectra that have all the features of the well known COSY experiment, with an additional ‘zoom’ capability that reveals the detailed fine structure information. For systems of three coupled spins the corresponding triple resonance experiment generates a three‐dimensional correlation specrum, the frequency scans being restricted to the region of interest (the 3D cross‐peak) based on information from the conventional NMR spectrum. For correlation spectroscopy of higher dimensionality no frequency search is employed, the selective pulses simply being set at predetermined chemical shift frequencies. A four‐dimensional correlation experiment is described which uses population transfer to establish that four non‐equivalent protons are coupled in a chain ISRP. It employs an initial ‘ZZ‐pulse’ applied at the I‐spin frequency to excite longitudinal two‐spin order (2IzSz) which is then propagated along the chain by the application of selective ‘ZZZ‐pulses’ to the intermediate spins S and R, creating an antiphase intensity perturbation (2RzPz) on the P multiplet. The procedure is recursive and can in principle be extended to N spins coupled pairwise in a ‘linear’ chain. This is a powerful diagnostic tool for structure determination and can be adapted to recognize other topological features such as chain branching and ring closure.
A practical guide to combined rotation and multiple‐pulse NMR spectroscopy of solids
Authors: Jackson Peter , Harris Robin K.
Published: May 2005

Technical details are given for the successful operation of CRAMPS techniques to obtain high‐resolution proton NMR spectra of solids. Matters addressed include probe construction, tunning procedures, optimization of pulses, spectral calibration and referencing. In practice, the MREV‐8 sequences is preferred to BR‐24. It is suggested that CRAMPS operation deserves more widespread application.
139La NMR as a tool for kineic studies
Authors: Ducommun Y. , Helm L. , Laurenczy G. , Merbach A. E.
Published: May 2005

The application of 139La NMR to study the kinetics of substitution reactions is described. Rate constants associated with fast substitution reactions on La3+ complexes in the presence of excess of the aqua‐ion can be obtained by measuring the line widths of the corresponding signals. Measurements as a function of temperature allow the separation of the kinetic and quardrupolar relaxation effects. The rate of aquation of La(2,6‐dicarboxy‐4‐hydroxypyridine)+ was measured in aqueous solution. The dissociation rate constant and the activation parameters obtained for this process are k298r = 207 ± 51 s−1, ΔH = 38.3 ± 3.1 kJ mol−1 and ΔS = −72 ± 8 J K−1 mol−1. The spin–spin relaxation rates of the lanthanum(III) in the two environments are described by 1/T = 550 ± 83 s−1 and EA = 26.4 ± 5.8 kJ mol−1 for the aqua‐ion and by 1/T = (2.00 ± 0.08) × 104 s−1 and EB = 16.3 ± 1.6 kJ mol−1 for the mono‐complex.
NMR of the methylene group: Artifacts in the proton–proton decoupled heteronuclear two‐dimensional chemical shift correlation experiment
Authors: Bain Alex D. , Hughes Donald W. , Hunter Howard N.
Published: May 2005

When the proton–proton decoupled heteronuclear two‐dimensional chemical shift correlation experiment is applied to a molecule containing methylene groups, the spectra show not only the expected signals at the two proton chemical shifts, but also a strong artifact. This artifact appears at the average of the two proton chemical shifts, and arises from coherence transfer between the two protons caused by the BIRD pulse. It is not caused by strong coupling between the protons, and so may appear in any spectrum. The dependence of this artifact on experimental conditions was analysed, and is illustrated with results obtained on the methylene groups from the cyclophane ring in N6′,N9‐octamethylenepurinecyclophane.
Unusual two‐bond 13C,13C coupling constants in sulphones
Authors: Rücker Christoph , Fritz Hans
Published: May 2005

A measurable coupling between carbon atoms through the SO2 group is observed in a series of structurally diverse sulphones. In open‐chain (single coupling path) sulphones this 2J coupling ranges from 5.5 to 27.2 Hz, while in cyclic (multiple coupling path) sulphones values ranging from 4.3 to 21.6 Hz are observed. Sulphides and sulphoxides do not exhibit a corresponding coupling of comparable magnitude. A positive sign for this coupling is derived from the data of cyclic sulphones. Whereas substituents and branching at the coupling termini exert minor influences on the coupling, the most important factor determining the magnitude of the 2J(CSC) coupling is the hybridization of the coupling carbon atoms. A linear relationship between the 2J value and the s character product of the CS bond forming C orbitals is estalished.
Application of data processing for sensitivity and resolution enhancement of 31P and 13C NMR spectra of humic substances
Authors: Kupka Teobald , Pacha Jerzy , Dziȩgielewski Jan O.
Published: May 2005

The application of various methods of data processing of a raw, untreated free induction decay (FID) to improve the quality of noisy and overcrowded spectra is shown. The use of complex interpolation of fragments of a typical 31P NMR spectrum of humic substances from forest soil in D2O, combined with two‐stage apodization of the FID, results in better defined signals and a higher accuracy of the integration of signals partially overlapped in the initial spectrum. Convolution difference resolution enhancement was used to enhance the spectral resolution of overlapped orthophosphate ion and orthophosphate monoester signals, while the noise was attenuated by a decreasing exponential.

An attempt to detect carbon signals buried in the noise by applying a rapidly decaying exponential (line broadening of 10 or 50 Hz) to a noisy FID, and the use of resolution enhancement, are also described for the 13C NMR signals from soil extracts.
NMR spectra of organogermanium compounds. 8—73Ge, 13C and 1H NMR spectra of methylvinylgermanes
Authors: Takeuchi Yoshito , Inagaki Hiroko , Tanaka Katsumi , Yoshimura Shin
Published: May 2005

A series of methylvinylgermanes were prepared and their 1H, 13C and 73Ge NMR spectra were determined. The chemical shifts were compared with those of the corresponding methylvinylsilanes and a very good correlation was found. The origin of the chemical shifts could not be simply attributed to the electron densities as estimated by MNDO calculations.
Reactions of silver(II) complexes with ketoxime, nitroso and isonitroso compounds: ESR spectroscopy of the radicals formed
Authors: Jezierski Adam
Published: May 2005

Reactions of silver(II) complexes with ketoxime, nitroso and isonitroso compounds in organic solvents were investigated by ESR. The oxidation yielded iminoxy radicals RR′CNO˙ and/or nitroxides R1R2NO˙. The silver(II) complexes with nitrogen ligands (mono‐, bi‐ and tri‐dentate) and AgO were used as oxidizing agents. The reaction products were analysed on the basis of the ESR spectra. The signs of the 14N hyperfine constants for the radicals were determined using the ESR spectra in an MBBA liquid nematic crystal as solvent. A linear correlation was found between the hyperfine 14N parameters and the Dimroth‐Reichardt ET(30) coefficients for the iminoxy radicals.
Definitive assignment of the 13C NMR signals of the indole C‐3 and C‐3a carbons of the ajmaline, picraline and sarpagine alkaloids
Authors: Morales‐Ríos M. S. , Joseph‐Nathan P.
Published: May 2005

Comparison of a 1H coupled natural abundance 13C NMR spectrum of 1‐oxo‐1,2,3,4‐tetrahydrocarbazole with a single‐frequency experiment in which the hydrogens three bonds away from C‐3 (indole numbering) were irradiated allowed the unambiguous distinction of the C‐3 and C‐3a signals. The results can be extrapolated for the assignment of the same signals in the ajmaline, picraline and sarpagine alkaloids, which also contain a carbonyl group as the substituent at the C‐2 position of the indole skeleton. The effect of this carbonyl group on the chemical shifts of the benzenoid carbons is also discussed.
13C NMR spectra of antiviral nucleosides' 3′‐azido‐3′‐deoxythymidine, 2′,3′‐dideoxyadenosine, 2′,3′‐dideoxycytidine and 2′,3′‐dideoxyinosine
Authors: Buchanan G. W. , Bourque K.
Published: May 2005

13C NMR chemical shifts and one‐bond 13C1H couplings are reported for 3′azido‐3′‐deoxythymidine, 2′,3′‐dideoxyadeno‐ sine, 2′,3′‐dideoxycytidine and 2′, 3′‐dideoxyinosine. Unambiguous assignments were made on the basis of results from 2D INADEQUATE experiments to establish the carbon–carbon connectivities.
13C and 1H NMR chemical shifts of 2‐substituted anthracenes
Authors: Berger Stefan , Diehl Bernd W. K.
Published: May 2005

The 1H and 13C NMR spectra of a series of eight 2‐substituted anthracene derivatives were measured and assigned using inverse 2D‐NMR C,H correlation spectroscopy.
Nuclear magnetic resonance study of gentiobiose octaacetate in solution
Authors: Marchettini Nadia , Ulgiati Sergio , Rossi Claudio
Published: May 2005

Gentiobiose octaacetate, a disaccharide molecule, was investigated in order to define (i) the proton and carbon assignments and chemical shift values, (ii) the carbon relaxation behaviour in DMSO solution and (iii) the dynamic properties of the molecule. It was found that in solution it behaves like a rigid molecule characterized by an unique isotropic correlation time. Scalar coupling constant analysis allowed the identification of the H‐6 axial and H‐6 equatorial protons for both sugar ring moieties.
Two‐bond deuterium isotope effects on 13C chemical shifts. A measure of carboncarbon bond lengths
Authors: Sardella D. J. , El‐Din Alyaa Emad
Published: May 2005

Two‐bond deuterium‐induced isotope effects (2Δ) have been studied in several neutral π‐systems (6,6‐dimethylfulvene, cyclohexene and cyclohexa‐1,3‐diene). Isotope effects on the 13C shifts of adjacent carbons are invariably to higher field, and vary from −84 to −139 ppb. In combination with literature data for a number of aromatic systems, these results establish that, for fragments of the type DC(sp2)13C(sp2) in five‐ or six‐membered rings, 2Δ correlates linearly with carboncarbon bond length, the average deviation between calculated and experimental bond lengths being 0.01 Å. The correlation embraces bridgehead and non‐bridgehead carbons in both five‐ and six‐membered rings. As a test of the utility of this empirical relationship, 2Δ in ferrocene‐d was determined to be −91 ppb, corresponding to a carboncarbon bond length of 1.42 Å, in good agreement with the experimental value of 1.43 Å.
13C NMR spectral studies of some methoxycoumarin derivatives. A re‐assignment for citropten (limettin) and an examination of Peri‐proximity effects for the methyl‐methoxy and methoxy‐methyl couples
Authors: Osborne Alan G.
Published: May 2005

The 13C chemical shifts and 13C1H coupling constants of some methoxycoumarins are reported. Some earlier spectral assignments, including those for citropten (limettin), require revision. Methoxy substituent effects on longrange 13C1H couplings in coumarins are highlighted. Peri‐proximity effects for the methyl‐methoxy and methoxy‐methyl couples are derived, and the value of these effects in the assignment of peri‐substituted compounds is illustrated.
NMR study of the monomer—dimer equilibria of dimethylnitrosobenzenes in solution. Identification of mixed azodioxy dimeric species
Authors: Orrell Keith G. , Stephenson David , Rault Thierry
Published: May 2005

The monomer‐dimer equilibria of 2,6‐ and 3,5‐dimethylnitrosobenzenes in CDCI3 solution were investigated by 1H and/or 13C NMR spectroscopy. The mixed systems nitrosobenzene + 2,6‐dimethylnitrosobenzene and 2,6‐dimethylnitrosobenzene + 3,5‐dimethylnitrosobenzene were also studied, and mixed azodioxy dimers were identified. In all systems exchange occurs exclusively between dimer and monomer species, rates and activation energies being calculated from time‐dependent 1H 1D spectra and/or 1H 2D‐EXSY spectra measured at different temperatures.
Nuclear spin relaxation of oxygen‐17, silicon‐29 and carbon‐13 in octamethylcyclotetrasiloxane
Authors: Kowalewski Jozef , Berggren Elisabet
Published: May 2005

17O, 13C and 29Si nuclear magnetic relaxation data are reported for neat liquid octamethylcyclotetrasiloxane in the temperature range 298–373 K. The electric field gradient at the site of the oxygen nucleus is estimated by ab initio calculations and the 17O relaxation data are interpreted in terms of isotropic rotational diffusion. The 13C dipole‐dipole relaxation rates are interpreted in terms of the Woessner model for internal methyl rotation superimposed on the isotropic overall tumbling. The 29Si spin‐lattice relaxation is composed of dipole‐dipole and spin‐rotation contributions, which are interpreted in a semi‐quantitative fashion.
Analysis of the 1H NMR spectra of the carboxylic ionophore narasin A in its Apo and cation‐bound forms
Authors: Caughey Byron W. , Gibbons William A. , Painter George R.
Published: May 2005

As a first step in the conformational analysis of the cation‐binding reactions of the carboxylic ionophore narasin A, 1H NMR spectra of narasin A in its apo and H+ ‐, K+ ‐ and Na+ ‐bound forms in CD3OD were assigned. In addition, new assignments for the spectrum of H+ ‐narasin A in CDCl3 were obtained. Two dimensional 1H−1H chemical shift correlation, one‐dimensional nuclear Overhauser effect and decoupling difference techniques were used to determine the chemical shifts and 1H1H coupling constants.
13C NMR study of the substituent effects on the internal steric hindrances in amidines
Authors: Wawer Iwona
Published: May 2005

13C NMR spectra of ten formamidines, five acetamidines and five butyramidines were recorded at low temperatures. The barrier to rotation around the CN1 bond for N2‐alkylformamidines is approximately 50 kJ mol−1 and for N2‐benzylformamidines approximately 52 kJ mol−1, and is thus ca. 10 kJ mol−1 lower than for N2‐phenylformamidines. The height of the barrier is related to Taft's substituent constants at N2, δG* = 49.25 + 8.08σ* −3.21Es. In the acetamidines the steric hindrance between the alkyl substituent at N2 with CFCH3 contributed to the decrease in δ* (lower than 40 kJ mol−1). The i‐C3H7 substituent at CF in butyramidines forces isomerization and these amidines become Z isomers. MNDO calculations indicate no significant changes of bond length on E/Z isomerization, and the low rotational barrier in butyramidines is probably caused by the steric interaction of the aromatic ring at N2 with the N1 (CH3)2 group.
Carbon‐13 NMR of the N‐substituents in 2,4,6‐trisubstituted pyridinium salts
Authors: Salman Salman R. , Khayat M. A. R.
Published: May 2005

The carbon‐13 chemical shifts of seven N‐substituted trimethylpyridinium and triphenylpyridinium salts and seven amines are reported.
Utilization of the selective pulse INEPT NMR experiment (INAPT) for the facile distinction of quaternary carbons attached to a trisubstituted alkene
Authors: Bernstein Michael A.
Published: May 2005

The INEPT experiment which uses selective 1H pulses (INAPT) was used to assign quaternary carbon NMR signals in trisubstituted alkenes. Given that 3J(CH) across the double bond is usually larger for the trans than the cis disposed nuclei, experimental conditions may be chosen such that more polarization transfer is effected in the case of the trans nuclei. We applied this approach to two important pharmaceutica Is, cyclobenzaprine and ami‐triptyline, and some structurally related compounds. In each case the INAPT experiment quickly afforded a stereochemical assignment. Assignments were corroborated with the data from two‐dimensional selective hetero‐nuclear J‐resolved and heteronuclear nuclear Overhauser effect experiments.
Complete assignment of the 13C and 1H NMR spectra of thyrsiferyl acetate
Authors: Blunt John W. , McCombs John D. , Munro Murray H. G. , Thomas Frank N.
Published: May 2005

The assignment of all reasonances in the 13C and 1H NMR spectra of thyrsiferyl acetate has been made through the application of 2D NMR experiments, together with the use of difference NOE spectroscopy.
Complete assignment of the 1H and 13C NMR spectra of 1,3‐diaza‐2,4‐diboranaphthalene derivatives by two‐dimensional NMR spectroscopy
Authors: Allaoud Smail , Bitar Hassan , Frange Bernard , Faure Robert
Published: May 2005

The total assignment of the 13C and the 1H NMR spectra of four derivatives of 1,3‐diaza‐2,4‐diboranaphthalene has been performed. The interpretation of the spectra was achieved from the concerted application of direct and long‐range heteronuclear chemical shift correlation and homonuclear COSY two‐dimensional NMR spectros‐copy. In addition, the 11B NMR chemical shifts of one of the compounds are reported and tentatively assigned.
Natural abundance carbon‐13 and deuterium NMR studies on the liquid and solid phases of tert‐butyl iodide
Authors: Aksnes D. W. , Ramstad Kari
Published: May 2005

Carbon‐13, deuterium and proton NMR line shapes of polycrystalline tert‐butyl iodide (1) have been studied between 200 K and the melting point (239 K). Carbon‐13 and deuterium spin‐lattice relaxation times (T1) were measured between 313 and 200 K in the liquid and solid phases of 1.

The NMR line shape data indicate the occurrence of two disordered phases of 1 between the melting point and 222 K. An analysis of the 13C and 2H T1 relaxation times is reported. The 13C and 2H T1 relaxation is governed by overall molecular tumbling in the liquid and disordered phases of 1, whereas the 13C T1 relaxation in the ordered solid is governed by uniaxial molecular reorientation of the tert‐butyl group. Rotational correlation times, activation energies and pre‐exponential factors were obtained from the T1 data by using the Arrhenius equation. Significantly different activation parameters were obtained for the two disordered solids. The effective correlation time at the melting point of 1 (ca. 5 ps) is 2–3 times longer than for other globular tert‐butyl compounds.
Structure of norbornene‐fused 3,1‐oxazine double cycloadducts
Authors: Sohár Pál , Bernáth Gábor , Stájer Géza , Szabo Angela E.
Published: May 2005

Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene‐azetidinone‐fused 3,1‐oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments.
1H and 13C NMR spectra of 4,4′‐substituted chalcones
Authors: Hayamizu Kikuko , Yanagisawa Masaru , Ishii Tetsuko , Yabe Atsuko , Yamamoto Osamu , Nakayama Masaharu , Hayashi Akio
Published: May 2005

1H and 13C NMR spectra of chalcone (trans‐benzylideneacetophenone) and 54 4,4′‐substituted chalcones were studied. The 400 MHz 1H NMR and the 13C NMR spectra were observed, analysed and assigned and the substituent constants were calculated by the least‐squares method.
A 1H and 13C NMR study of N‐formylmorphinans and their 6,14‐bridged derivatives; Comparison with N‐Me and NH analogues
Authors: Linders J. T. M. , Prazeres M. A. , Lie T. S. , Maat L.
Published: May 2005

The 1H NMR and 13C NMR spectra of N‐formylated morphinans were compared with those of the N‐methyl and N‐demethyl analogues. The magnitude of the changes in chemical shift of C‐9, C‐16 and C‐10 depended crucially on the nature of the substituent at nitrogen. For the 6α, 14α‐ethenoisomorphinans and 6β,14β‐ethenomorphinans, the proton chemical shifts of the 6,14‐etheno bridge across ring C are differently affected by the nitrogen atom. In the 6α,14α‐ethenoisomorphinans, the vinylic proton shifts are found between δ5.3 and 5.9, whereas in the 6β,14β‐ethenomorphinans these proton signals are found downfield from δ6.0. A similar, but opposite, anisotropy effect of the nitrogen is observed for the 8β‐proton. These results are important for the elucidation of the structures of these types of compounds.
1H and 13C NMR study of the adsorption of alcohols on charcoals with various pore structures
Authors: Du You‐Ru , Yuan Han‐Zhen , Wu Dong‐Hui , Kong Yu‐Hua
Published: May 2005

A 1H NMR study of methyl, ethyl, n‐propyl, isopropyl and allyl alcohols adsorbed on charcoals with various pore structures showed that the adsorption mechanism is by capillary condensation in pores with radii smaller than 30 Å, and by mono‐/multi‐layer adsorption on the solid surface of pores with larger radii. This mechanism is identical with that of adsorbed hydrocarbons. The 13C NMR parameters suggest that the adsorbed alcohols are preferentially oriented in the monolayer, with the methyl groups bonded to the solid surface. Longer chain alcohols are bent in capillaries with radii smaller than 10 Å. The broadening of the 13C resonances was partly eliminated in magic angle spinning experiments by using a spinning rate of 1.5–1.8 kHz.
Assignments of the 1H and 13C NMR resonances of C‐nucleoside analogues by means of two‐dimensional shift correlated NMR techniques
Authors: Dennin F. , Rousseaux O. , Blon‐Deau D. , Sliwa H.
Published: May 2005

Two‐dimensional 1H and 13C shift correlated NMR experiments were used for the unambiguous assignments for all proton and carbon chemical shifts of C‐nucleosides in [1,2,4]triazolo‐[1,5‐c]‐ and ‐[4,3‐c]‐pyrimidines.
Measurement of long‐range proton—carbon coupling constants in medium‐sized molecules
Authors: Hricovíni Miloš , Liptaj Tibor
Published: May 2005

A modified version of the two‐dimensional semiselective INEPT experiment is presented which allows the determination of long‐range proton‐carbon couplings in medium‐sized molecules. The difference in the T1 relaxation times is utilized for the reduction of the number of protons from which coherence is transferred. This results in a simplification of the 1D and 2D spectra obtained. The capability of the proposed pulse sequence is demonstrated by the determination of the long‐range couplings in a model molecule.
Complete spectral assignments of tatsidine by two‐dimensional NMR techniques
Authors: Snyder John K. , Zhang Xiaolin , Joshi Balawant S. , Pelletier S. William
Published: May 2005

Homonuclear 1H COSY, long‐range COSY and relay coherence transfer (RCT) correlation spectroscopy NMR experiments were used together with fixed‐evolution HETCOR and selective INEPT spectra for complete 13C and 1H spectral peak assignments for tatsidine. Stereochemical and conformational assignments were made from the two‐dimensional NOE spectrum. The results of these studies confirmed the location of the methylenedioxy group at C‐7/C‐8.
13C NMR spectra of some 4‐substituted N‐acetonyl ‐ N, N‐dimethyl‐N‐phenacyl‐ammonium bromides
Authors: Grandjean Jean , Laszlo Pierre , Canto Eduardo Leite Do , Rittner Roberto
Published: May 2005

The 13C NMR signals for some 4‐substituted N‐acetonyl‐N,N‐dimethyl‐N‐phenacylammonium bromides were assigned. The HETERCOSY and COLOC sequences allow an unambiguous distinction between the very similar signals of the methylene carbons. The chemical shifts observed for the aromatic ring carbons are in close agreement with those calculated from substituent increments.
59Co NMR of cobalt(III) porphyrin complexes. III. Data base on substituent and solvent effects
Authors: Bang H. , Cassidei L. , Danford H. , Edwards J. O. , Hagen K. I. , Krueger C. , Lachowitz J. , Schwab C. M. , Sweigart D. A. , Zhang Z.
Published: May 2005

A broad study of the 59Co NMR of cobalt(III) porphyrin complexes with axial amine ligands in a variety of solvents is reported. The data are presented in tabular form, as are the numerical correlations of chemical shift, δ, and line width, ω1/2, using the Kamlet‐Taft equation. The dependence of δ and ω1/2 on ligand substituents is discussed. Solvent data, including mixed solvent results, indicate that general factors such as acidity, basicity, polarity and hydrogen‐bonding capability are important, as are the specific nature of the functional groups on the ligands and the solvent.
13C NMR study of substituted 10,10‐diphenyl‐9‐phenanthrones. Structure determination and signal assignment using 2D NMR techniques
Authors: Mynott R. , Romão Maria J. , Herold B. J.
Published: May 2005

The 13C NMR spectrum of 10,10‐diphenyl‐9‐phenanthrone was assigned unambiguously using 2D 13C,1H shift correlated NMR spectra, optimized either for one‐bond or long‐range 13C1H couplings, and 2D RELAY NMR spectra. This information allowed the structures of a number of substituted 10,10‐diphenyl‐9‐phenanthrones to be deduced from their 13C NMR spectra. The results provide an insight into the mechanism of the reaction of 9‐fluorenone with chlorodiphenylmethyllithium.
Carbon‐13 NMR chemical shifts of 1‐alkyl‐3(5)‐cyano‐1H‐pyrazole‐4‐carboxylic acid esters
Authors: Babbitt George E. , Lynch Michael P. , Beck James R.
Published: May 2005

A compilation of 13C NMR chemical shifts for 13 pairs of 3‐ and 5‐cyano‐substituted pyrazole regioisomers is reported. All of the ring carbon and cyano carbon 13C chemical shifts show a regular, predictable correlation with the particular isomer, whether 3‐cyano or 5‐cyano. These shifts occurred in very narrow ranges, precluding any confusion of assignment within the group of compounds studied. x‐ray crystallographic analysis was performed on one of the samples.
Isolation of spatulenol and (−)‐caryophyllene oxide from Vernonia mollissima don and 1H and 13C reassignment by two‐dimensional NMR spectroscopy
Authors: Krebs H. C. , Rakotoarimanga J. V. , Habermehl G. G.
Published: May 2005

Two sesquiterpenoids, spatulenol and (−)‐caryophyllene oxide, were isolated from the hexane extract of the Brazilian plant Vernonia mollissima Don. The 1H and 13C NMR spectra of these compounds have been reassigned completely by COSY experiments and 13C/1H shift correlation diagrams.
Use of selective excitation techniques for the rapid analysis of 13C NMR data for enriched carbohydrates
Authors: Bossenne V. , Firmin P. , Perly B. , Berthault P.
Published: May 2005

One‐dimensional selective scalar transfer experiments are presented for the analysis of 13C NMR data for multilabelled molecules. ‘Classical’ 13C COSY experiments rapidly show limitations when a complete determination of remote coupling constants is required. Conversely, combination of 1D COSY and RELAY affords all the required information very rapidly and accurately. Three 13C‐labelled monosaccharides exhibiting different degrees of spectral complexity are used to illustrate the merits of these techniques.
Aromatic ring dynamics in crystalline molecular solids by one‐ and two‐dimensional exchange spectroscopy
Authors: Twyman J. Mark , Dobson Christopher M.
Published: May 2005

Variable‐temperature phase‐sensitive cross‐polarization/magic angle spinning magnetization transfer experiments in one and two dimensions, in conjunction with chemical shift line‐shape analyses, have been used in the quantitative characterization of slow aromatic ring dynamics in crystalline 4‐nitro‐1‐methoxybenzene and in crystalline penicillin G phenyl ester. The results obtained indicate the value of such approaches for investigating specific motional events in molecular solids.
α‐Nitroketones. Part 10.113C NMR spectra of alkylated 2‐nitrocyclohexanones
Authors: Zajac W. W. , Boyko W. J. , Gagnon J. L.
Published: May 2005

The 13C NMR spectra of 22 α‐nitrocyclohexanones were recorded and fully assigned. The one‐bond CH coupling constants for the nitromethine resonances of these compounds were also obtained and tabulated.
Carbon‐13 chemical shift assignment of (E)‐stilbenyloxyalkylthiouracils
Authors: Wybieralska Jadwiga , Wyrzykiewicz Elżbieta
Published: May 2005

The 13C NMR spectra of twelve isomeric 2‐and 4‐(E)‐stilbenyloxyalkylthiouracils have been calculated and fully assigned. The Ai and AiK empirical parameters of 4‐ketopyrimidyl‐2‐thioalkoxy, 2‐ketopyrimidyl‐4‐thioalkoxy, 2‐(E) ‐stilbenyloxyalkyl, 2‐(E)‐stilbenyloxyalkylthio, 4‐(E)‐stilbenyloxyalkyl and 4‐(E)‐stilbenyloxyalkylthio groups were calculated for the predictions of the chemical shifts of substituted uracils and benzenes.
17O NMR spectroscopic study of substituted benzoquinones and α,β‐unsaturated cyclic ketones
Authors: Boykin D. W. , Baumstark A. L. , Mehdizadeh A. , Venkatramanan M. K.
Published: May 2005

The17O NMR chemical shift data for a series of substituted benzoquinones and α,β‐unsaturated cyclic ketones in acetonitrile at 75°C are reported. In general, for the unsymmetrically substituted quinones two signals were observed, the assignments of which were made by17O enrichment and exchange experiments. For the benzoquinones, the effect of α‐methyl substitution (shielding) was greater on the signal for the 1‐carbonyl group than on that for the 4‐carbonyl group. α‐tert‐Butyl substitution resulted in deshielding of the proximate carbonyl group compared with that in the methyl analog. For the five‐ and six‐membered ring enones the shielding effect of β‐substituents was interpreted as electronic in origin. The large shielding effects observed for α‐substitution in the quinone and enone systems appeared to be the result of a combination of electronic and attractive van der Waals effects.
1H and 13C NMR conformational studies on quaternary nitrogen derivatives of the analgesic drug nefopam
Authors: Glaser Robert , Peleg Ariel , Geresh Shimona
Published: May 2005

Nitrogen quaternization in the analgesic nefopam [(±)‐3,4,5,6‐tetrahydro‐5‐methyl‐1‐phenyl‐1H‐2,5,‐ benzoxazocine hydrochloride] by either N‐trideuteriomethylation or N‐oxidation affords reaction product diastereomeric mixtures differing in N‐configuration. The axial to equatorial N‐CH3 product ratios were found to be ca. 3:2 (N‐trideuteriomethylation) and approximately equimolar (ca. 48:52, N‐oxidation). Both diastereomeric N‐oxides have boat‐(flattened chair) conformations of the octagonal ring in which the phenyl group is exo‐oriented. The quaternary ammonium salts showed considerable line broadening in the 1H NMR spectrum owing to rapid conformational equilibration. The same boat‐(flattened chair) conformation is clearly the preponderant contributor to the time‐averaged structure of nefopam methiodide in CD2Cl2 solution, similar to the case for the equatorial N‐methyl isomer of the parent hydrochloride salt. Conformational assignments were based on the vicinal coupling constants in the —OCH2CH2N—fragment and on the finding of an NOE intensity enhancement for the benzhydrylic‐H on irradiation of the equatorially oriented —OCH.
Multivariate investigation of 1H and 13C NMR shifts of 2‐ and 3‐substituted furans, thiophenes, selenophenes and tellurophenes
Authors: Ebert Cynthia , Gianferrara Teresa , Linda Paolo , Masotti Paola
Published: May 2005

The effect of substituents on 13C and 1H NMR chemical shifts in 2‐ and 3‐substituted furans, thiophenes, seleno‐phenes and tellurophenes was studied by means of principal components analysis (PCA) and partial least squares (PLS) analysis. The analysis of the data by PCA showed that for both series the substituents are grouped into four different classes depending on the heteroatom present in the ring, and that the substituent‐heteroatom interaction has the same nature for all the rings. PLS analysis of the data sets allowed the prediction of the chemical shift values of a different ring having the same substituents.
Fluorine NMR spectra of some 9α‐fluorosteroids
Authors: Smith Leland L. , Ezell Edward L.
Published: May 2005

Fluorine NMR spectra of 23 9α‐fluorocorticosteroid analogs established that the 9α‐fluorine is subject to deshielding effects by remote structural features (A‐ring olefinic unsaturation, A‐ring 1α‐ and 2β‐hydroxy and acetoxy features and D‐ring 16α‐methyl substitution) and to minor shielding effects by vicinal 11β‐alcohol dehydrogenation and acetylation, and by B‐ring olefinic unsaturation. Substitutions in the 6α‐, 6β‐, 16α‐ and 16β‐positions and D‐ring homoannulation do not alter the 19F chemical shift significantly. Coupling constants of the 9α‐fluorine to vicinal 8β‐ and 11α‐hydrogens are not altered appreciably by structural changes, except for introduction of a Δ6‐double bond or 11β‐alcohol dehydrogenation, indicating that the conformations of the tetracyclic ring system and particularly the B/C‐ring junction were very similar for these 9α‐fluorosteroids.
13C nuclear magnetic resonance studies on 1,3‐diphenylprop‐2‐enones
Authors: Parmar V. S. , Sharma Sunil , Rathore J. S. , Garg Meenu , Gupta Sandhya , Malhotra Sunita , Sharma V. K. , Singh Suddham , Boll P. M.
Published: May 2005

The 13C NMR spectra of 48 differently substituted chalcones (1,3‐diphenylprop‐2 enones) have been recorded and the results are discussed. The data will be useful in the identification of new/natural chalcones.
Spectroscopic analysis of (1‐α,2‐α′: η4‐quinodimethane)tris(trimethylphosphine)ruthenium(0)
Authors: Simpson Nigel J. , Mackie Raymond K. , Cole‐Hamilton David J.
Published: May 2005

The 1H, 13C and 31P NMR spectra of [Ru(CH2C6H4CH2)(PMe3)3], which contains a coordinated o‐xylidene moiety, have been analysed. Parameters such as the geminal coupling in the methylene groups, P,H couplings and the chemical shifts of the quaternary ring carbon atoms all point to a metal‐o‐xylidene binding that is intermediate between σ2,π and π2. Spectral assignment is assisted by P‐H correlation spectroscopy using the COLOC sequence. The best parameter for identifying the bonding mode is the chemical shift for the quaternary aromatic carbon atoms.
Structural analysis and complete assignment of the 1H and 13C NMR spectra of thiele's ester
Authors: Minter David E. , Marchand Alan P. , Lu Shao‐po
Published: May 2005

The 1H and 13C NMR spectra of ‘Thiele's ester,’ i.e. dimethyl 3α 4α, 7α, 7α‐tetrahydro‐4,7‐methano‐1H‐indene‐2,6‐dicarboxylate, have been assigned completely by using a combination of one‐ and two‐dimensional NMR techniques. The results thereby obtained afford the first unambiguous assignment of the structure of Thiele's ester that has been made solely on the basis of NMR spectral analysis. The structure obtained is fully consistent with that of Thiele's ester established previously by chemical methods.
Study of the hydrolysis of combined Al3+ and Ga3+ aqueous solutions: Formation of an extremely stable GaO4Al12(OH)24(H2O) polyoxycation
Authors: Bradley Susan M. , Kydd Ronald A. , Yamdagni Raghav
Published: May 2005

71Ga and 27Al NMR and clay mineral pillaring studies were used to investigate the hydrolysis of Al(H2O)–Ga(H2O) solutions, mixed in an Al:Ga mole ratio of 12:1, and confirmed the formation of the previously proposed GaO4Al12(OH)24(H2O) polyoxycation. This species has been found to be formed in marked preference to both AlO4Al12(OH)24(H2O) and the previously identified GaO4Ga12(OH)24(H2O) ions, and further to have a much higher thermal stability in solution than either of these. It is suggested that the reason for the increased stability of the ‘GaAl12’ species is that the substitution of a larger metal into the central tetrahedral position has resulted in the formation of a less distorted structure.
1H and 13C NMR analysis of D‐amygdalin: Oligosaccharide assignment and sequencing
Authors: Ribeiro Anthony A.
Published: May 2005

The 1H and 13C NMR spectra of D‐amygdalin, a cyanogenetic disaccharide accumulated in food plants, were assigned using a combination of NMR techniques. Methods applied include standard 1H–1H COSY, proton zero quantum coherence (ZQCOSY), 1D NOE, broad‐band decoupled 1H–13C chemical shift correlation and long‐range 1H–13C chemical shift correlation. ZQCOSY was especially useful in assigning the closely spaced sugar resonances, and long‐range 1H‐13C chemical shift correlation allowed sequencing of the monosaccharide rings. Coupling constants useful in conformational analysis are derived from highly digitized 1H 1D spectra and 2D J‐resolved spectroscopy. The 1H and 13C chemical shifts and coupling constants indicate that the β‐D‐glucopyranose rings of D‐amygdalin adopt a 4C1 chair conformation.
Carbon‐13 NMR spin–lattice relaxation time study of the molecular motions of 5‐nitro‐2‐(2‐pyridinylthio)pyridine
Authors: Amato Maria E. , Grassi Antonio , Perly Bruno
Published: May 2005

The motional behaviour of 5‐nitro‐2‐(2‐pyridinylthio)pyridine (NPTP) was ananlysed by 13C NMR spin‐lattice relaxation times (T1). The analysis of the experimental T1 data was performed by using an analytical model to describe the overall and internal motions fo the molecule. The results showed that on exchange exists between the two ‘enantiomeric’ preferred conformations of the molecule, which therefore assumes an enhanced conformationally rigid character in the liquid phase. The motional parameters, derived by the fitting procedure of the relaxation times, showed that strong intermolecular interactions occur in the liquid phase for NPTP and that, in particular, the dipole moment of the mitropyridine ring contributes greatly in determinating the motional dynamics of NPTP.
Disentangling coupling and NOE pathways involving poorly resolved proton signals: HMQC‐TOCSY and HMQC‐NOESY
Authors: Crouch Ronald C. , McFadyen Robert B. , Daluge Susan M. , Martin Gary E.
Published: May 2005

COSY and NOESY frequently fail when key proton signals are poorly resolved because of the proximity of the correlating off‐diagonal responses to the diagonal. Proton‐coupled heteronuclear multiple quantum relayed coherence spectroscopy (HMQC–TOCSY) and heteronuclear multiple quantum proton nuclear Overhauser effect (HMQC–NOESY) experiments to circumvent these problems are described. NMR data for a model carbocyclic nucleoside analog are presented for which assignments of resonances and stereochemistry were impossible by ‘conventional’ 2D NMR methods. Resonance and unequivocal stereochemical assignments were made, however, using the HMQC–TOCSY and HMQC–NOESY experiments, respectively.
Multinuclear NMR study of 1,3,3‐trimethylbicyclo[2.2.1]heptan‐2‐one (fenchone) and its six monochlorinated derivatives
Authors: Kolehmainen E. , Laihia K. , Korvola J. , Kauppinen R. , Pitkänen M. , Mannila B. , Mannila E.
Published: May 2005

1H, 13C and 17O NMR spectra of fenchone and six monochlorofenchones have been recorded. The second‐order 1H NMR spectra were analysed by an iterative computer program. The 1H and 13C chlorine‐induced substituent chemical shifts (SCS) were calculated. The vicinal coupling constants proved to be essential in the assignment of the chemical shifts of the geminal methyls. No clear correlation was observed between the chemical shifts of the carbonyl oxygen and the carbonyl carbon. All monochlorofenchones were previously unknown compounds and were synthesized for this work.
Carbon‐13 and proton spectra of tetracyclododecanes: Long‐range steric effects
Authors: Seidl P. R. , Leal K. Z. , Costa V. E. U. , Poli N. D.
Published: May 2005

The 1H and 13C spectra of endo‐endo‐tetracyclo[6.1.13,6.02,7]dodec‐4‐en‐10‐ol have been interpreted using shift reagents and HETCOR experiments. Carbon chemical shifts are compared with tetracyclic analogs and bicyclic model compounds. Evidence for upfield δ and ε effects of 3–5 ppm is presented.
39K NMR spectroscopy of potassium solutions in tetrahydrofuran containing 18‐crown‐6. Relaxation study
Authors: Sokól Maria , Grobelny Janusz , Jedliński Zbigniew J.
Published: May 2005

Blue potassium solution in THF containing 18‐crown‐6 was investigated by means of 39K NMR spectroscopy. The presence of potassium anions and complexed potassium cations was demonstrated. Spin‐lattice and spin‐spin relaxation times were measured in the temperature range 176–295 K. An attempt was made to explain the relaxation behaviour in the system.
SELRESOLV—inverse and selective detection of long‐range C,H spin coupling constants
Authors: Ochs Matthias , Berger Stefan
Published: May 2005

A pulse sequence (SELRESOLV) for the proton‐detected determination of long‐range C,H coupling constants is described. The 2D J(HH) resolved experiment with selective 13C excitation separates J(HH) from J(CH) couplings. Application is demonstrated using crotonaldehyde and β‐naphthol as examples.
13C NMR analysis of sultones and sulphonate–sulphate anhydrides
Authors: Castro V. , Boyer J. L. , Canselier J. P. , Terjeson R. J. , Mohtasham J. , Peyton D. H. , Gard G. L.
Published: May 2005

The 13C NMR spectra of 20 compounds belonging to several types of monocyclic sultones and related ‘carbyl sulphates,’ including a series of fluorinated β‐sultones (1,2‐oxathietane 2,2‐dioxides), are reported. Chemical shift increment systems with n‐alkanes as reference molecules are established for non‐fluorinated sultones: they show a much less pronounced deshielding effect on the carbon α to oxygen in β‐sultones than in the other series. Chemical shifts for the parent β‐sultone, predicted in two ways (linear or cyclic model compound), are found to be almost consistent with a purely additive scheme. In fluorinated β‐sultones the α‐substituent increments relative to perfluoroethanesultone are also derived.
Phosphorus‐31 and platinum‐195 NMR studies of carboxylato‐bridged dinuclear platinum(II) complexes
Authors: Kannan S. , Jain V. K.
Published: May 2005

Carboxylato‐bridged dinuclear platinum(II) complexes of the type [Pt2X2(μ‐OOCR′)2(PR3)2] [X = Cl, I; R′ = CH3, CF3; PR3 = PEt3n, PPr3n, PBu3n, PMe2Ph, PMePh2, PPh3, P(p‐Tol)3] were prepared and investigated by 31P and 195Pt NMR spectroscopy. The NMR data indicate that there is considerable platinum‐platinum interaction in these complexes.
Structure of a norbornane‐fused pentacyclic isoxazoline
Authors: Sohár Pál , Kövesdi István , Frimpong‐Manso Samuel , Stájer Géza , Bernáth Gábor
Published: May 2005

The steric structure of a pentacyclic adduct formed as a by‐product in a retro‐Diels‐Alder reaction was elucidated by 1H and 13C NMR spectroscopy, making use of double resonance and differential nuclear Overhauser effect measurements.
Identification of oplopanonyl acetate isolated from Chamaecyparis pisifera
Authors: De Bruyn André , De Pooter Herman L. , De Buyck Laurent , Jans Arnold W. H. , Buděšínský Miloš , Sedmera Petr
Published: May 2005

Oplopanonyl acetate was isolated from Chamaecyparis pisifera. Its structure and stereochemical features were established using NMR techniques.
NMR spectra of the porphyrins. Part 39. Paramagnetic shifts in cobalt(II) porphyrins
Authors: Abraham Raymond J. , Marsden Ian , Xiujing Lucy
Published: May 2005

A model of the paramagnetism in cobalt(II) porphyrin complexes has been developed which successfully calculates paramagnetic shifts for protons not affected by the contact term. The model utilizes a single large dipole positioned on the cobalt(II) atom, and calculates the pseudo‐contact shift using the dipole approximation.

With this model the angle of twist of the peripheral meso phenyl rings in tetraphenylporphyrin (TPP) derivatives was determined. In TPP and the meta‐ and para‐substituted derivatives studied the phenyl rings are at ca. 65° to the porphyrin plane, whereas in the ortho‐substituted derivatives the phenyl rings are essentially orthogonal. Similarly, the geometry for the β‐ethyl groups of octaethylporphyrin and etioporphyrin I was found to be 50° out of the plane of the porphyrin inclined to the meso proton, and that of the comparable propionate groups of coproporphyrin I to be 55°. Finally, the novel compound meso‐tetra(p‐phenoxyphenyl)porphyrin, an analogue of diphenyl ether, was prepared to determine the twist angles between the two phenyl rings. These were found to be 60° by correlating observed paramagnetic shifts with those calculated. This agrees well with MNDO studies, which gave a value of 59°.
Erroneous assignments of configuration around CC double bonds
Authors: Kamieńska‐Trela Krystyna
Published: May 2005

NMR studies on trans‐1‐trimethylsilyl‐1,2‐dibromoethene and cis‐secondary sulphinyl enamines were recently reported. However, it is shown that the assignment of the configuration should be reversed in both instances, i.e. the configuration of 1‐trimethylsilyl‐1,2‐dibromoethene should be cis and that of secondary β‐sulphinyl enamines should be trans..
Diacyl acid dihydrazides
Authors: Al‐Talib Mahmoud , Tashtoush Hasan , Odeh Nedal
Published: May 2005

N,N′‐Diacyl acid dihydrazides were prepaed by the reaction of acid dihydazides with two equivalents of acyl chlorides. The structures of these compounds were elucidated by 1H and 13C NMR spectroscopy.
High‐field multinuclear magnetic resonance relaxation studies of pivalic acid in liquid and solid phases
Authors: Aksnes Dagfinn W. , Kimtys Liudvikas L.
Published: May 2005

Proton, 13C, deuteron and 17O NMR line widths and spin‐lattice relaxation times (T1) were measured at a field strength of 9.4T over a wide temperature region in liquid and solid pivalic acid (PA). A striking feature of the NMR spectra is that the methyl proton signal is much wider than the carboxyl proton signal in solid I, whereas the opposite is true for the corresponding deuteron signals. Molecular self‐diffusion and overall molecular tumbling with activation energies of 59 and 31 kJ mol−1, respectively, are responsible for the considerable line narrowing observed for the methyl proton and deuteron resonances in solid I. The narrow carboxyl proton resonance and the low activation energy for the motional narrowing process (18 kJ mol−1) indicate that the acid hydrogen is moving through the lattice at a much faster rate than the rest of the molecule.

An analysis of the T1 relaxation times of PA is reported. Rotational correlation times and activation parameters for the overall tumbling, and also the internal methyl and tert‐butyl reorientations (C3 and C3′ motions) taking place in the liquid and solid phases of PA, have been obtained for the first time. The results show that the slower motion is overall tumbling with an activation energy of 20–32 kJ mol−1, while the faster motions are internal C3′ and C3 reorientations with activation energies of 10–15 kJ mol−1. On freezing, the rate of overall tumbling is reduced by a factor of 47 from 1.6 × 1010 to 3.3 × 108 s−1, whereas the rates of C3′ and C3 rotations (1.1 × 1011 and 3.2 × 1010 s−1, respectively) are hardly affected.
Solid‐state NMR studies of the structure and reactivity of molecular sieve catalysts
Authors: Klinowski Jacek , Anderson Michael W.
Published: May 2005

Insights into the structure of molecular sieves are provided by solid‐state NMR in ways which are herein reviewed and extended. The uses of 29Si, 27Al and 1H NMR are briefly discussed. Attention is then paid to recent work which examines, using 1H and 13C NMR, the chemical status of guest organic molecules and questions of shape selectivity, giving novel information relevant to catalytic reactions.
2D NOESY studies on [Pd(η3‐C10H15){(R)( + )‐BINAP}]+ defining the relative spatial orientation of the phenyl and π‐allyl moieties
Authors: Rüegger Heinz , Kunz Roland W. , Ammann Christian J. , Pregosin Paul S.
Published: May 2005

2D NOESY, COSY and 31P,1H correlation measurements have been carried out on the optically active β‐pineneallyl‐(R)(+)‐BINAP palladium complex, [Pd(η3‐C10H15){(R)(+)‐BINAP}](CF3SO3). The ortho protons of the four non‐equivalent phenyl rings have been assigned, as have the 15 protons of the β‐pineneallyl. The 2D NOE data show selective interactions of the phenyl ortho protons with different sections of the allyl ligand, thereby contributing to our knowledge of the three‐dimensional solution structure of this cationic complex.