bluuebunny/crossref_metadata_2025 huggingface dataset:
Conformational studies on pyranoid sugar derivatives by NMR spectroscopy. Correlations of observed proton—proton coupling constants with the generalized Karplus equation
Authors: Durette Philippe L. , Horton Derek
Published: May 2005

Proton spin‐spin coupling values measured for a wide range of tetrasubstituted tetrahydropyran ring‐systems obtained from aldopentopyranose sugars have been correlated with values calculated from a generalized version of the Karplus equation which takes into account the electronegativities of the various atoms in the molecule and the configurations of these substituents. Minor discrepancies between observed and calculated values can be attributed to slight flattening of the tetrahydropyran ring as a result of steric interactions of the substituents. The magnitude of the geminal coupling J5e,5a of these aldopentopyranose derivatives provides a rough measure of the conformational population; when H‐4 is axial [Cl(D) or 1C(L) conformation] J5e,5a is ∼10.9 Hz, and is ∼13.4 Hz when H‐4 is equatorial [1C(D) or Cl(L) conformation].
Etude par RMN des 2,2′‐Dihalogeno‐Diethylethers—I: Effet de Température
Authors: Haloui Ezzeddine , Canet Daniel , Granger Pierre
Published: May 2005

Les spectres RMN d′éthers disubstitués de formule (XCH2CH2)2O avec X = Cl, Br, I, d′une part, à température ambiante et à l′état pur et, d′autre part, en solution dans CS2 et à différentes températures, ont été analysés avec précision. Les déplacements chimiques de chacun des groupements CH2 ont pu ětre attribués. Les rotaméres prépondérants ont été déterminés à l′état pur et à différentes températures. De plus, il est montré que pour ces trois halogénures dissous dans CS2, les formes gauches relatives à chaque branche deviennent plus stables en refroidissant. Les auteurs ont mis au point une procédure permettant, par décomposition de raies, de traiter les spectres de type AA′BB′ ayant l′aspect de spectres de type A2B2.
The effect of cyclopropyl groups on chemical shifts and coupling constants
Authors: Anderson J. E.
Published: May 2005

Some shielding and deshielding effects by an adjacent cyclopropyl ring and the effect of the ring on geminal coupling constants α‐ to the ring are reported and discussed.
NMR‐Untersuchungen bei Prolin‐enthaltenden Diketopiperazinen
Authors: Siemion Ignacy Z.
Published: May 2005

Bei NMR‐Untersuchungen der cis‐ und trans‐Reihe Prolin‐enthaltender Diketopiperazine konnten Unterschiede zwischen den Signalen pseudoaxialer und pseudoäquatorialer Substituenten (α‐Proton, α‐Methylgruppe, α‐iso‐Propylgruppe) festgestellt werden.
Nuclear magnetic resonance studies of internal rotation—III Rotational barriers in META‐ and PARA‐substituted N, N‐dimethylcinnamamides
Authors: Spassov S. L. , Dimitrov V. S. , Agova M. , Kantschowska I. , Todorova R.
Published: May 2005

The rotational barriers about the CN bond of eight m‐ and p‐substituted N, N‐dimethyl cinnamamides have been determined by the iterative total line shape NMR method. The ΔG values have been correlated with the substituent constants σ, σn and σ+. By comparison of the results with literature data, some conclusions about the accuracy of the barrier determination as well as the transmittance of polar effects in conjugated amides have been drawn.
A semi‐empirical MO calculation of 13C chemical shifts—I: Alkanes
Authors: Solkan V. N. , Mamayev V. M. , Sergeyev N. M. , Ustynyuk Yu. A.
Published: May 2005

13C shielding constants have been calculated for a series of alkanes, methane to pentane. The quantities σd and σp have been obtained, using an average excitation energy approximation and the extended Hückel MO wave functions in terms of the Pople method. The results fit the experimental data and the VB results of Grant et al. fairly well. The quantity σd varies within a wide range for carbon atoms of various degrees of substitution. Two conformations of the hydrocarbons studied have been calculated. The results show that the 13C chemical shifts may be used for conformational analysis.
Tris(dipivaloylmethanato)europium induced shifts of proton resonances in π‐deficient nitrogen heterocycles
Authors: Armarego W. L. F. , Batterham T. J. , Kershaw J. R.
Published: May 2005

Tris(dipivaloylmethanato)europium [Eu(DPM)3]induced shifts of the proton resonances of pyridine and its 2‐methyl, 3‐methyl, 2,3‐dimethyl and 2,5‐dimethyl derivatives, pyridazine, pyrimidine, pyrazine, quinoline, isoquinoline, 1,6‐, 1,7‐ and 1,8‐naphthyridine, cinnoline, phthalazine, quinazoline, quinoxaline, 1,4,5‐ and 1,4,6‐triazanaphthalene, pteridine, acridine, phenanthridine and 1, 10‐phenanthroline, have been measured for solutions containing 0·1, 0·3 and 0·5 molar equivalents of Eu(DPM)3. Differences in the behaviour of these heterocycles are discussed in terms of the steric relationship between the heterocycle and the complex. The 3 cos2 ϕ term, present in the expression for calculating pseudo‐contact shifts, is shown to be important. The order of basicity of these heterocycles, as measured by their pKa values, cannot be used to predict the order of Eu(DPM)3 induced chemical shifts.
Proton magnetic resonance spectrum of thiophen dissolved in a nematic solvent
Authors: Dereppe Jean‐Marie , Morisse Jean‐Pierre , Van Meerssche Maurice
Published: May 2005

The PMR spectrum of thiophen dissolved in a nematic phase is reported. This spectrum has been analysed iteratively. The ratios of the various inter‐proton distances determined in this study are in good agreement with those previously reported.
14N chemical shifts in the enamino ketone quaternary ammonium salts
Authors: Dąbrowski Janusz , Kamieńska‐trela Krystyna , Sadlej Andrzej J.
Published: May 2005

The 14N chemical shifts were measured for a series of quaternary ammonium salts of enamino ketones. An upfield shift of the 14N resonance signals upon quaternization has been observed. The interpretation in terms of the approximate theory of nuclear magnetic shielding is given. The calculations for some model systems result in a general agreement with the experimental data.
Spectroscopic studies on N, N‐dimethylamides—IV An NMR total line shape study of substituent effects and medium effects on amide‐rotational barriers of N,N‐dimethylbenzamides and ‐cinnamamides
Authors: Spaargaren K. , Korver P. K. , Van Haak P. J. Der , de Boer Th. J.
Published: May 2005

Amide‐rotational barriers obtained with a total line shape analysis of a series of para‐substituted N,N‐dimethylbenzamides and ‐cinnamamides are correlated with the result of an H. M. O. (Ω = 1·4) calculation. There is no difference in the activation parameters at a concentration of 0·25 M and 1 M in CDCI3 as a solvent.

Despite the lower solvent polarity of chloroform (ε = 4·7) compared with acetonitrile (ε = 37·5) the rotational barriers in both solvents are about equal, probably due to hydrogen bonding in chloroform.

The amide rotation rate appears to be very sensitive to traces of hydrochloric acid in a non‐basic solvent like chloroform.
Conformational analysis of 1,2:5,6‐diepithio‐3,4‐di‐o‐acetyl‐hexitols
Authors: Sohár P. , Kuszmann J.
Published: May 2005

Conformational studies of acetylated open chain hexitol derivatives, possessing similar structures but differing in their configuration have been made by analysing their NMR spectra. It is shown, that the carbon chain of all three (manno‐, ido‐and gluco‐) isomers is present in a non planar non zig‐zag conformation, containing the acetoxy groups at C‐3 and C‐4 in a trans relation.
Constantes de Couplage en Serie Pyridinique. Application de la Theorie des Orbitales Moleculaires
Authors: Dorie J. P. , Martin M. L. , Barnier S. , Blain M. , Odiot S.
Published: May 2005

Les constantes de couplages relatives à un ensemble de 35 pyridines substituées sont discutées en relation avec les propriétés électroniques des substituants et le mécanisme du couplage. Un calcul de J est réalisé, sur la base de la théorie de Pople, à l′aide des valeurs de polarisabilités mutuelles obtenues par la méthode CNDO/2 et la méthode d'Hoffmann. L'influence d′une inclusion des intégrales bicentriques est examinée.
Carbon‐13 chemical shifts of monosubstituted cyclohexanes
Authors: Pehk T. , Lippmaa E.
Published: May 2005

The carbon‐13 chemical shifts of monosubstituted cyclohexane derivatives are compared with those of aliphatic compounds. The polar substituents exert a similar influence on the α‐, β‐ and γ‐carbons in both series of compounds. The δ‐effect is shown to be characteristic mainly to the cyclic compounds, however. The appearance of a δ‐effect is discussed as a possible consequence of electron delocalization in alicyclic molecules. A correlation of these δ‐effects with inductive parameters of the substituents is presented.
A new N‐alkylation reaction—V: NMR investigations
Authors: Sohár P. , Reiter J. , Toldy L.
Published: May 2005

The structure elucidation of some isomeric imidazo(1,2‐a)pyrimidones by NMR spectroscopy is described. The tautomerism of the compounds with non‐substituted nitrogen is also discussed.
Dimers from α‐alkoxybenzyl radicals. An NMR study
Authors: Goh S. H. , Ong S. H. , Sieh Iling
Published: May 2005

meso and dl Dimers (ArCHOR)2 where R is Me, Et, iPr, tBu, cyclohexyl and 1‐adamantyl may readily be differentiated by their NMR spectra; the benzylic protons of the meso isomer always absorb at a slightly higher field than those of the dl isomer in each of the solvents used. Differences in chemical shift are discussed in terms of preferences in conformer distribution. The formation of equal amounts of both dimers from the corresponding radical ArCHOR shows that steric and polar factors are not important in influencing the dimerization. Magnetic non‐equivalence due to the presence of asymmetric centres was found in some of the compounds discussed above.
The accidental equivalence of protons in 3‐hydroxy‐3‐methylbutyrolactone: Solvent and temperature dependence
Authors: Firth Bruce E. , Singh S. P. , Kagan Jacques
Published: May 2005

The temperature or the nature of the solvent selectively affects the NMR equivalence of the protons at C‐2 and C‐4 in 1.
Hindered rotation in thioamides—II
Authors: Ramey Kermit C. , Louick David J. , Whitehurst Philip W. , Wise William B. , Mukherjee Rabindranath , Rosen John F. , Moriarty Robert M.
Published: May 2005

The NMR spectra for a series of amides and thioamides of type magnified image where R = CH3, C6H5 and C6H5CH2, were investigated from −60° to 150°C. The Arrhenius activation energies, Ea, for the normal amide equilibration were determined by the W½ method and the values range from 15.4 to 20.9 Kcal/mole.

The three thioamides, compounds (2), (4) and (6) yield spectra showing a second, low temperature, equilibration. This exchange was first studied by Siddall and co‐workers and they interpreted the spectral changes in terms of population changes of the conformational isomers about the NCH bonds. They assumed strong interaction of nitrogen alkyl groups which gave rise to three low energy dl pairs of isomers. Their results, however, as well as those obtained for similar compounds reported herein, show only two sets of patterns at low temperatures. These spectra suggest a first order, A⇄B, type equilibration where PA≠PB. An alternative assignment based upon the following classification of steric effects of S, R, R′ and R″, magnified image is suggested; (1) a strong interaction of the sulfur atom with the adjacent alkyl group on the nitrogen atom, R′, (2) a somewhat weaker interaction of R with the adjacent nitrogen alkyl group R″ and (3) a still weaker interaction of the two nitrogen alkyl groups, R′ and R″. This leads to four isomers, two dl pairs, C1T4, C6T3 and C1T6, C6T3, which are expected to have a lower energy than the rest and the first pair is preferred.

The W½ method of measuring exchange rates was extended to cover A⇄B equilibrations, where PA≠PB. The results indicate an accuracy that is not significantly lower than that obtained by the more elaborate total line shape analysis.
The molecular structure and unusual orientation of phenol in a liquid crystal solevent as determined by NMR spectroscopy
Authors: Diehl P. , Henrichs P. M.
Published: May 2005

The NMR spectrum of phenol, dissolved in a nematic solvent, is explainable in terms of two averaging planar structures for each of which the principle axis of orientation in the ring is on the opposite side of the oxygen atom from the hydroxyl proton. External hydrogen bonding to the solvent seems to be an important factor in determining the orientation. The molecular structure obtained is compared with those found by microwave spectroscopy and X‐ray diffraction.
Chemical polarization of nuclei. Proton polarization during thermal decomposition reaction of dimethyl perdiglutarate
Authors: Ignatenko A. V. , Kessenikh A. V.
Published: May 2005

Proton chemical polarization was observed in methyl butyrate, γ‐butyrolactone and in some other products of the dimethyl perdiglutarate decomposition reaction. The polarization pattern of the α‐CH2 and β‐CH2 groups in butyrolactone is just as one would expect in the products of the CH3OCH2CH2ĊH2 radical which has left the pair of identical radicals. Thus butyrolactone is formed from the CH3OCH2CH2ĊH2 radical by means of intramolecular cyclization and elimination of the methyl radical.
Determination of the rate of intramolecular exchange between two complex spin systems from the NMR spectra
Authors: Derendyaev B. G.
Published: May 2005

Reversible 1,2‐shifts of the ethyl group in the 9‐ethyl‐9, 10‐dimethylphenanthrenonium ion lead to a reversible change of the ring hydrogen states (A′B′C′D′ ⇄ A″B″C″D″). Line shape analysis for the determination of the exchange rate was performed for this case of intramolecular exchange between the two multi‐spin systems. The calculations are based on density matrix formalism.
AB‐based NMR systems. Choice of bounds for θ in trigonometric forms of co‐factors in mixed wave‐functions
Authors: Batterham T. J. , Bigum C. J.
Published: May 2005

Labelling problems associated with the choice of bounds for the angle θ in the trigonometric forms of the co‐factor expressions for levels in AB‐based NMR spectra have been investigated. It has been shown that any pair of octants within the 0 → 2π range can be specified as bounds, provided that appropriate linear combinations of wave functions are chosen. The range 0 ⩽ θ ⩽ π/2 is preferred for simplicity in calculation.
NMR‐spectra of 1‐[2,4,5‐triphenylcyclopentenyl] phenyl ketones
Authors: Wawzonek S. , Bennett W. E.
Published: May 2005

NMR‐Spectra of 1‐[2,4,5‐triphenyl‐2‐cyclopentenyl]phenyl ketone and 1‐[2,4,5‐triphenyl‐1‐cyclopentenyl]phenyl ketone indicate that the coupling constants of vicinal hydrogens in the cyclopentene ring vary with structure.
Barriers to internal rotation in 1,3,5‐trineopentylbenzenes—II: Unsymmetrically halogen‐substituted compounds
Authors: Nilsson Bertil , Carter Robert E. , Dahlqvist Kjell‐Ivar , Márton József
Published: May 2005

The temperature dependence of the three different methylene AB spectra due to the 1‐, 3‐ and 5‐neopentyl groups in 2‐chloro‐4‐iodo, 2‐bromo‐4‐iodo and 2‐bromo‐4‐chloro‐1,3,5‐trineopentyl‐benzene was studied by proton magenetic resonance measurements at 60 MHz. The identification of the lines of the AB quartets at low temperature was carried out on an HA‐100 spectrometer by means of the INDOR technique. The activation parameters for all three barriers in each compound were found to be approximately the same, which perhaps reflects the interdependence of the rotations, with the smaller of the two halogens determining the size of the barrier. An explanation in terms of magnetic nonequivalence induced in the 1‐ and 5‐methylenes by the 3‐neopentyl group is considered to be most plausible.
Conformational effects in cyclic imino acids—I: The NMR spectra and conformations of l‐azetidine‐2‐carboxylic acid and its N‐acetyl derivative
Authors: Thomas W. A. , Williams M. K.
Published: May 2005

The complete analysis of the PMR spectrum of azetidine‐2‐carboxylic acid is reported and conclusions made regarding the conformation of the molecule in aqueous solution. the effect of N‐acetylation on chemical shifts, coupling constants and hence conformation is investigated, and the geometric isomer ratio and energy barrier to rotation about the amide bond determined.
13C, 14N, 15N and 17O NMR spectra of the charged species of nitropyrroles and nitroimidazoles
Authors: Lippmaa E. , Mägi M. , Novikov S. S. , Khmelnitski L. I. , Prihodko A. S. , Lebedev O. V. , Epishina L. V.
Published: May 2005

Changes in 13C and 14N chemical shifts of the nitro derivatives of nitrogen heterocycles upon ionization (anion or cation formation) are twofold—first a uniform paramagnetic or in the case of protonation, a uniform diamagnetic shift of all the ring resonances that parallels the changes in the respective ultraviolet spectra and must be caused by changes in the molecular excited states, and second—the influence of the conjugated nitro group. About one third of the total negative anion charge may be localized on the nitro group, which causes unusually large shifts of the ring 13C resonances in this case.
v‐Triazolines—IV: NMR configuration assignment of 5‐dialkylamino‐v‐triazolines
Authors: Stradi Riccardo , Pocar Donato , Bianchetti Giuseppe
Published: May 2005

A series of 1‐aryl‐5‐amino‐4,5‐dihydro‐v‐triazoles bearing at least one hydrogen atom at the C‐4 position has been prepared. The NMR features of the above compounds have been studied with the purpose of differentiating the triazolines with a trans configuration from those with a cis configuration. It has been shown that the hydrogen atom at C‐4 lying on the same side of the amine group at C‐5 always resonates at lower field than the hydrogen atom on the opposite side. This rule can be applied for identifying the configuration of the 5‐amino‐v‐triazolines.
Conformational studies by nuclear magnetic resonance—III: ASIS and protonation studies of the rotational isomerism of enamino aldehydes and ketones
Authors: Kozerski Lech , Dąbrowski Janusz
Published: May 2005

Thes‐cis⇌s‐transequilibrium of several enamino ketones and aldehydes,equation imagehas been evaluated based on the results of aromatic solvent induced shift measurements and of protonation of the title compounds. In contrast to α,β‐unsaturated ketones bearing no heteroatom, the Δδ3,cisvalue but not the Δδ3,trans, proved to be useful in conformational assignments. Protonation, which occurs mainly on oxygen, enhances the rotational barrier, thus enabling the observation of both rotamers at room temperature. Steric hindrance to conjugation enhances the rate of protonation at the carbon C2.
C‐13 chemical shifts of the carbonyl group—VI: Transannular interactions in mesocyclic compounds
Authors: Nakashima Thomas T. , Maciel Gary E.
Published: May 2005

The utility of C‐13 NMR in detecting transannular interactions of a carbonyl group with O, S and N in eight‐membered ring compounds has been studied. The C‐13 carbonyl chemical shifts were determined in two solvents, employing frequency‐sweep and pulse/Fourier transform techniques. The results confirm earlier conclusions based upon other physical methods and indicate that C‐13 NMR should prove useful in studies of such interactions.
Chemical shift assignments in N,N‐disubstituted trifluoroacetamides
Authors: Graham Laurine L.
Published: May 2005

Due to hindered rotation about the central CN bond in N,N‐disubstituted trifluoroacetamides, CF3CONR1R2, two resonance peaks are usually observed for each proton in R1 and R2. Chemical shift assignments are made for the following amides: 1, R1 = R2 = Me; 2, R1 = R2 = Et; 3, R1 = Me, R2 = 2‐Propyl; 4, R1 = Me, R2 = 1‐Butyl; 5, R1 = Me, R2 = Cyclohexyl; 6, R1 = R2 = 2‐Propyl; 7, R1 = 2‐Propyl, R2 = Cyclohexyl. Amides 6 and 7 show an inversion of the relative chemical shift for both the methine and methyl protons of the 2‐propyl group as compared with 3. For non‐fluorinated amides, aromatic solvents shift the trans alkyl peaks to higher field faster than those cis (to the carbonyl oxygen atom); however, this generalization does not apply to all trifluoroacetamide proton peaks.
Conformational studies by nuclear magnetic resonance—IV: Restricted rotation in vinylogous thioamides
Authors: Dabrowski Janusz , Kamieńska‐Trela Krystyna
Published: May 2005

Enamino ‐thial and ‐thiones R1C(S)CHCHNR (R1 = H or alkyl; R2 = Me or Et) have been shown by NMR spectra to exist in two rotational forms, s‐cis and s‐trans, the populations of the latter being approximately the same as in the case of the parent oxa analogues. An increase of the order of 2 to 4 Kcal/mole in the heights of CC and CN rotation barriers (ΔG*) was found on comparing the title compounds with their oxa analogues. IR spectra failed as a tool to establish the rotational equilibrium. IR absorption bands of the νCC, νCH (in the NMe2 group) and γHCCH vibrations have been found, but the νCS band could not be assigned unambiguously. Anomalies concerning the frequency and intensity of the νCC band are discussed.
The conformation of meso and racemic 2,3,4‐trichloropentanes—model compounds for polymers derived from 1,2‐dichloroethylenes
Authors: Clifford R. P. , Ewing D. F.
Published: May 2005

On the basis of coupling constants and chemical shifts the conformation of meso and racemic 2,3,4‐trichloropentanes have been determined. The meso isomer exists as an equilibrium between the expected rotameric forms but the racemic isomer is anomalous and exists almost entirely as a distorted form of a rotamer which has parallel 1:3 interactions. The significance of these conformations is discussed in relation to the likely conformation and stability of the corresponding stereoregular polymers, which may be derived from cis‐ and trans‐1, 2‐dichloroethylene.
Barriers to rotation about CN bonds—I: Rotation about the CN bond in mono‐, di‐ and trifluoroacetamide, and deuterium isotope effects upon 19F shielding
Authors: Pendlebury M. H. , Phillips L.
Published: May 2005

The 19F NMR spectra of mono‐ and difluoroacetamide are used to derive the activation parameters for rotation about the CN bond; it is not possible to obtain useful results for trifluoroacetamide. A total line shape analysis is used.

Unusually large deuterium isotope effects upon the shielding of the 19F nucleus are observed for N‐deuterated derivatives. The magnitude of the isotope effect is different for mono‐, di‐ and trifluoroacetamides, and in the mono‐deuterated species the isotope effect is different for cis and trans rotational isomers.
Stereochemistry of the addition of DCl to acetylene
Authors: Rigo Adelio , Gurato Giorgio
Published: May 2005

The stereochemical distribution of the addition products of DCl to acetylene was studied by proton magnetic resonance. The NMR parameters of cis and trans isomers of vinylchloride‐βd1 are reported.
Lanthanide induced paramagnetic shifts—derivation of equilibrium constants and absolute shifts in Eu(DPM)3 systems
Authors: Mackie R. K. , Shepherd T. M.
Published: May 2005

Relationships between the magnitude of induced 1H NMR shifts and the equilibrium conditions in solutions containing lanthanide shift reagents are discussed and applied to the shifts induced in several organic molecules by Eu(DPM)3. Evidence that monoadduct formation is the predominant equilibrium in these solutions, and values of absolute shifts and equilibrium constants are reported. The results indicate that a contact mechanism makes the major contribution to the observed shifts in 4‐methylpyridine. In the case of 2,4,6‐trimethylpyridine the observed shifts are largely pseudocontact in origin.
The decomposition of 1‐phenyl‐3‐chloro‐nortricyclene and 1‐phenylnortricyclene on reduction in 1,2‐dimethoxyethane. The EPR spectra of the radical ions
Authors: Eloranta Jorma , Paasivirta Jaakko , Moilanen Reijo , Vesterinen Raili
Published: May 2005

Radical anions of 1‐phenyl‐3‐chloronortricyclene and 1‐phenylnortricyclene were produced by reduction with potassium in 1,2‐dimethoxyethane under a high vacuum. The initially formed radical anion of 1‐phenyl‐3‐chloronortricyclene was very unstable, and decomposed finally to the anions of naphthalene and biphenyl. The only product of the reduction of 1‐phenylnortricyclene was the biphenyl anion. The EPR spectra of the reaction mixtures were measured at temperatures from —80°C to room temperature.
Hydrogen exchange in benzamidoximes studied by NMR spectroscopy
Authors: Alexandrou N. E. , Nicolaides D. N.
Published: May 2005

The hydrogen exchange process in benzamidoximes (1 and 2) was studied over a range of temperature and a determination of the activation parameter ΔG‡ for this process was made.
Characterization of di‐ and trimethoxybenzaldehydes by analysis of deshielding gradients obtained with Eu(fod)3 shift reagent
Authors: Neville G. A.
Published: May 2005

Eu(fod)3 shift reagent was used to simplify PMR spectra from isomeric mono‐, di and trimethoxybenzaldehydes. Deshielding gradients, obtained by plotting induced shift vs. molar ratio of [Eu(fod)3]/[substrate] made it possible to assign methoxyl proton signals to the correct positional substituent in polymethoxylated benzaldehydes. Anomalous upfield shifts for the aldehydic protons of 2,6‐dimethoxy‐ and 2,4,6‐trimethoxybenzaldehyde were observed with Eu(fod)3 Various instances of long‐range (5J) proton coupling between the aldehydic proton and a meta‐proton provide insight to the geometry of the substrate in the complexed state with Eu(fod)3. Di‐ and trimethoxybenzaldehydes are important precursors for the synthesis of the correspondingly methoxylated amphetamines which are of pharmacological and forensic interest because of abuse and illicit manufacture.
Heterocycles Contenant du Phosphore—XII: Etude par Resonance Magnetique Nucleaire des Oxo‐ et Thio‐2 Phenoxy‐2 Trimethyl‐3,5,5 Oxazaphosphorinanes‐1,3,2. Un Cas Particulier de Systeme ABXY
Authors: Durrieu Josiane , Kraemer Raymond , Navech Jacques
Published: May 2005

Les deux oxazaphosphorinanes‐1,3,2 étudiés ici donnent des spectres de RMP qui, après élimination des couplages entre les protons et le phosphore, peuvent e'tre analysés comme des ABXY dans lesquels certaines constantes de couplage sont nulles. Le cas particulier de système ABXY où JAY = JBX = 0 est étudié et on donne l'expression des niveaux d'énergie E7, E8, E9 et E10 et de la fréquence des transitions qui leur sont liées. Des expériences d'INDOR permettent de déterminer le signe relatif des constantes de couplage 3JP–OCH et 3JPNCH. Les résultats expérimentaux permettent de montrer que ces deux oxazaphosphorinanes‐1,3,2 se présentent dans une conformation chaise et que, si équilibre il y a, cet équilibre est très nettement en faveur d'un conformère privilégié.
Nuclear magnetic resonance spectra of codeine and isocodeine derivatives
Authors: Jacobson Arthur E. , Yeh Herman J. C. , Sargent Lewis J.
Published: May 2005

The NMR spectra of a spiro oxirane (1) derivative of codeinone, codeine (2), isocodeine (3), 6‐methylcodeine (4) and 6‐methylisocodeine (5) were compared. NOE and double‐resonance experiments were used to confirm the conformation of 1, and the configuration about C‐6 of 6‐methylcodeine and 6‐methylisocodeine. An interchange of the chemical shifts of the olefinic protons in 1 was noted, as compared with those in all of the other compounds. This interchange could be attributed to the bond anisotropies of the oxirane moiety.
Two‐frequency spin echo in molecular crystals
Authors: Grechishkin V. S. , Shishkin E. M.
Published: May 2005

The two‐frequency pulse response of a multilevel system in NQR is investigated. Additional spin echo signals are shown to appear. The application of the two‐frequency spin echo method to some of the crystals is demonstrated. The method is of great value for the investigation of local fields in crystals.
Dioxidobutane: A comparison between high field and Eu‐shifted PMR spectra
Authors: Gatti G. , Demoarco A.
Published: May 2005

Complete analysis of the high field spectrum of the title compound gives well determined parameters in all cases; the value of the CHCH coupling is in agreement with free rotation around this bond. In contrast, the Eu‐shifted spectrum does not allow such a complete analysis because of lack of resolution. Shift dependence on concentration and temperature is reported and discussed.
Electronic distribution in protonated eucarvone
Authors: Cornélis André , Laszlo Pierre
Published: May 2005

Carbon and proton chemical shifts are used, together with interproton coupling constants, to establish the preferred localisation of charge in protonated eucarvone. Comparison with the Hückel values suggests predominant residence of the FSO3‐counter ion near C‐3.
Stereochemical studies‐XIV: Cyclic amino alcohols and related compounds‐VII
Authors: Sohár P. , Bernáth G.
Published: May 2005

1,3‐Tetrahydro‐oxazine‐2‐ones were prepared by the reaction of cis‐ and trans‐2‐hydroxymethylcyclohexylamine, as well as cis‐ and trans‐2‐aminomethylcyclohexanol with carbamide. Their structure and stereochemical purity were proved by IR and NMR investigations. With the help of the NMR spectra the conformation of these compounds was established. The trans isomers exist in stable chair‐chair conformation. Two chair‐chair conformations are possible in the case of the cis isomers; one in which the heteroatom and the methylene group of the heteroring are axial and equatorial, respectively and the second in which their positions are reversed. It was proved that the cis isomers are conformationally homogeneous, having the hetero atom in axial position.
Processus de rotation empéchée autour de la liaison CN dans les anilines
Authors: Filleux‐Blanchard M. L. , Fieus J. , Hallé J. C.
Published: May 2005

Dans les anilines une non équivalence des protons aminés, due à la rotation empêchée autour de CN apparait à basse température. Les relations entre les paramètres d'activation et les effets électroniques des substituants sont étudiés et les paramètres RMN sont discutés.
13C CIDNP effects in the decomposition products of acetylbenzoyl peroxide
Authors: Kessenikh A. V. , Petrovskii P. V. , Rykov S. V.
Published: May 2005

13C CIDNP effects in the decomposition of acetylbenzoyl peroxide in cyclohexanone are described. A comparison between our data, and those on the 1H CIDNP effects and the 13C CIDNP observed in the decomposition of ABP in C2Cl41 leads to definite conclusions on the signs of the HFI constants of the benzoyl radical and to an identification of the separate products of the radical‐induced reactions with the solvent.
Proton‐proton coupling constants in the unsubstituted pyrylium cation
Authors: Radics L. , Kardos Julia
Published: May 2005

An iterative analysis of the PMR spectrum of the title compound was performed and the calculated values of spectral parameters, relative chemical shifts, proton‐proton and direct carbon‐proton couplings are compared with those of pyridine.
The use of chiral solvents to distinguish meso from d or 1 diastereoisomers
Authors: Abraham R. J. , Siverns T. M.
Published: May 2005

The 56·4 MHz 19F spectrum of a mixture of meso and dl 1,2‐difluoro‐1,2 dichloroethane in L‐bornyl acetate resolved the 19F resonances of the separate d and l stereoisomers, thus identifying the dl spectrum, but not those of the meso isomer.

These observations are considered with other examples of the use of chiral solvents to distinguish meso and dl isomers.
Recherches sur la stéréochimie des diènes fonctionnnels—XI: Interprétation théorique des déplacements chimiques de stéréoisomères D'éthoxybutadiènes‐1,3
Authors: Tonnard F. , Odiot S. , Dorie J. P. , Martin M. L.
Published: May 2005

Une analyse théorique des déplacements chimiques protoniques de stéréoisoméres alcoxydiéniques est proposée. La contribution diamagnétique est évaluée à partir des indices théoriques π et σ obtenus par un calcul de type CNDO/2; ce terme qui dépend de la stéréochimie ne suffit pas à expliquer les écarts expérimentaux, bien que l'alternance des charges refléte celle des déplacements chimiques; la contribution paramagnétique est importante mais reste mal expliquée dans le cadre des méthodes approchées de calcul des effects d'anisotropie et de champélectrique. Cependant l'analyse des résultats apporte des informations sur la nature des équilibres conformationnels au niveau de la liaisonCO.
Die Konstitutionsabhängigkeit und die benzolinduzierten Effekte der chemischen Verschiebungen der Methoxyprotonen einiger Carbonsäuremethylester
Authors: Brink Maud , Larsson Erik
Published: May 2005

Die chemischen Verschiebungen der Methoxyprotonen in etwa 60 verschiedenen Carbonsäuremethylestern wurden in CCl4 und C6D6 bestimmt. Ihre Abhängigkeit von Konstitution und Lösungsmittel wird diskutiert. Ferner wird gezeigt, dass sie für ein bestimmtes Molekül als eine Summe von Parametern ausgedrückt werden, die für die Substituenten charakteristisch sind.
Proton chemical polarisation, autocatalysis and frontal kinetics of the oxidation of dialkylsulphides with nitric acid
Authors: Rudakov E. S. , Mastikhin V. M. , Popov S. G. , Rudakova R. I.
Published: May 2005

The oxidation of dimethyl sulphide to dimethylsulphoxide with nitric acid displays CIDNP effects of protons and the phenomenon of frontal kinetics. The process is autocatalytic, with N2O4 as the catalyst and the primary oxidant of sulphide. In the presence of the inhibitor (methylmercaptan) the frontal reaction takes place: in purified samples—the usual volume reaction. The interaction of ethyl, n‐propyl and n‐butyl sulphides with NO2 is accompanied by integral polarisation of the α‐CH2‐protons. In all the cases sulphide is negatively polarised and sulphoxide positively polarised. The reaction mechanism proposed includes the formation of a radical pair during the interaction of sulphide with N2O4. Disproportionation of the radical pair leads to the formation of polarised sulphoxide and the decay results in re‐generation of sulphide. The rate of oxidation of sulphide during the volume reaction is proportional to the product polarisation.
Analyse conformationnelle de pyrazolines‐1 substituées
Authors: Danion‐Bougot R. , Carrié R.
Published: May 2005

L'analyse conformationnelle de pyrazolines‐1 diversement substituées sur les carbones 3 et 4 a été réalisée à l'aide de la RMN. L'utilisation de l'équation de Karplus pour interpréter les valeurs des constantes de couplage 3J(H4H5) permet de vérifier l'existence d'un équilibre entre deux formes enveloppes. L'angle d'ouverture de l'enveloppe, calculé sur un composé modèle figé dans une seule conformation, est voisin de 36°. Les pourcentages relatifs des deux conformères à la température ambiante sont calculés pour les divers pyrazolines étudiées.
Conformational studies by nuclear magnetic resonanceVI: CC and CN rotation barriers in various enamine derivatives
Authors: Dabrowski Janusz , Kozerski Lech
Published: May 2005

Delocalisation of the nitrogen lone electron pair by an acyl and acylvinylogue group simultaneously, results in a lowering of both CN rotational barriers. MeC(O)CBrCHNMe2 and MeC(O)C(OCOMe)CHNMe2 exhibit restricted rotation around what is formally a double bond CC.
31P CIDNP in the free radical reactions of dialkyl phosphites
Authors: Levin Ya. A. , Il'yasov A. V. , Goldfarb E. I. , Vorkunova E. I.
Published: May 2005

The polarisation of phosphorus nuclei (31P CIDNP) takes place during the homolytic reactions of dialkyl phosphites. The mechanisms of 31P CIDNP and the corresponding chemical reactions are discussed.
Kinetics of chemical polarisation of 31P nuclei in the reactions of phosphites
Authors: Pobedimsky D. G. , Kirpichnikov P. A. , Samitov Yu. Yu. , Goldfarb E. I.
Published: May 2005

Chemical polarisation of 31P nuclei was discovered and quantitatively measured in the peroxide‐phosphite system. The qualitative interpretation of the net polarisation of 31P nuclei and of its sign in the products of the radical reactions in the presence of phosphites is given within the frame of the radical pair model.
Effects of magnetic field on chemical reactions
Authors: Sagdeev R. Z. , Molin Yu. N. , Salikhov K. M. , Leshina T. V. , Kamha M. A. , Shein S. M.
Published: May 2005

The effect of the magnetic field on CIDNP can be found in many chemical reactions. It is considered to result from the fact that the probability of singlet‐triplet transitions in a radical pair is determined by magnetic interactions in the pair and is field strength dependent. In the present communication we wish to demonstrate that for the same reason the external magnetic field can also markedly affect the rates of chemical reactions involving free radicals.
Nuclear magnetic resonance and the conformation of some derivatives of Michler's ketone
Authors: Bartle K. D. , Hallas G. , Hepworth J. D.
Published: May 2005

1H NMR spectra are reported for Michler's ketone and twenty of its derivatives, along with 13C chemical shifts for five of the compounds. 1H chemical shifts show only small changes with increasing substitution at the sterically hindered 2‐position. Estimates of the dihedral angle between the benzene ring and CCOC planes have been obtained from the chemical shifts of CO and 4‐C for ketones 1, 3, 5, 15 and 16. These angles are both internally consistent and very similar to dihedral angles determined by other methods for corresponding compounds in the benzophenone series.
Etude conformationnelle de formyl‐2 aroyl‐3 furannes et formyl‐3 aroyl‐2 furannes
Authors: Fournié‐Zaluski M. C. , Roques B. P. , Chatain‐Cathaud C.
Published: May 2005

L'étude des constantes de couplage stéréospécifiques 4J et 5J ainsi que l'interprétation des déplacements chimiques en termes d'effets électroniques de substituants et d'anisotropie ont permis de montrer que les formyl‐2 aroyl‐3 furannes existent sous une conformation OO cis des deux groupements carbonylés et les formyl‐3 aroyl‐2 furannes sous une conformation OO trans.
Molecular motions in alicyclic compounds
Authors: Levy G. C. , Komoroski R. A. , Echols R. E.
Published: May 2005

Carbon‐13 spin‐lattice relaxation times and chemical shifts are reported for a number of cyclic alcohols and the corresponding methyl ethers. The overall rotation of the alcohols was found to be considerably more anisotropic than that of the methyl ethers. Anisotropic motion becomes less pronounced in both series as ring size increases.
Proton transfer in the 1,1‐dinitroethane/n‐dibutylamine complex
Authors: Borodin P. M. , Golubev N. S. , Denisov G. S. , Ignatiev Yu. A.
Published: May 2005

The 1H NMR spectra of 1,1‐dinitroethane/n‐dibutylamine solutions in CCl4 have been investigated. It is shown that two types of complexes, the CH … N hydrogen bond complex and the ion pair are present in the solution simultaneously, with slow exchange through proton transfer between them. The exchange rates, activation energy and enthalpy of proton transfer are determined. It can be concluded that the act of proton transfer from carbon to nitrogen and back is kinetically determined.
An example of hydrate‐keto equilibrium
Authors: Dhingra M. M. , Tatta K. R.
Published: May 2005

The hydrate of 1,1,1,5,5,5‐hexafluoro‐2‐hydroxy‐2‐methylpentan‐4‐one has been shown to exist in a hydrate‐keto equilibrium in acetone and ether solutions using 1H and 19F magnetic resonance. The equilibrium percentages of the keto and hydrate forms as determined from 19F resonance are 30 and 70, respectively.
Selektive unterdrückung von NMR signalen mit hilfe von T1 Pulssequenzen
Authors: Roth Klaus
Published: May 2005

Die Anwendung der ‘inversion‐recovery’ und ‘progressive saturation’ Techniken erlaubt unter geeigneten experimentellen Bedingungen die selecktive Unterdrückung von NMR‐Signalen. Mit Hilfe beider Techniken können verdeckte Signale nachgewiesen werden, wie am Beispiel des 13C Spektrums des Phthalsäurediäthylesters und dem 1H Spektrum des Indenylanions gezeigt wird.
Some calculations of the local diamagnetic contribution to nuclear screening constants
Authors: Jallali‐Heravi M. , Webb G. A. , Witanowski M.
Published: May 2005

Some INDO/S parameterized calculations of local diamagnetic contributions to some carbon and nitrogen screening constants are reported. It is shown that Pople's local term model provides data which are in satisfactory agreement with X‐ray photoelectron results. The restricted atom‐dipole model also provides reasonable agreement. However the complete atom‐dipole expression is found to be incompatible with the experimental data due to the presence of a non‐local contribution.
Spectra–structure relationships in carbon‐13 nuclear magnetic resonance spectroscopy. Results from a large data base
Authors: Milne G. W. A. , Zupan J. , Heller S. R. , Miller J. A.
Published: May 2005

A link between a substructure searching system and a 13C NMR data base has been established and permits the retrieval and examination of the chemical shifts associated with specific substructures. The means by which these searches are accomplished is described and the results from the searches are presented and discussed. The system is interactive, and can be used to locate in the data base the chemical shifts of carbon atoms in precisely defined environments. Alternatively, it may be used to learn the range of the chemical shifts possessed by particular types of carbon atoms, such as N‐methyl or O‐methyl carbons.
Conformational Analysis. XIX properties and reactions of 1,3‐oxathianes VIII A 1H NMR conformational study of methyl‐substituted derivatives
Authors: Pihlaja Kalevi , Pasanen Paavo , Wähäsilta Jukka
Published: May 2005

The addition of thioacetic acid to unsaturated alcohols or acids was utilized to obtain mercaptoalkanols which were condensed with suitable carybonyl compounds to prepare 24 methyl‐substituted 1,3‐oxathianes. The 1H NMR spectra of the 1,3‐oxathiane products were recorded at 60, 100 and/or 300 MHz and fully analysed. The results are best explained by a chair form which is completely staggered in the C‐4C‐5C‐6 moiety ψ45 or (ψ56=60±1°). 1,3‐Oxathianes having syn‐axial 2,4‐ (and/or 2,6‐) methyl‐methyl interactions exist appreciably, if not exclusively, in twist forms. The vicinal coupling constants lead to the conformational free energies of axial methyl groups at C‐4, ΔG°=7.4±0.4 kJ mol−1, and at C‐5, ΔG°=3.7±0.3 kJ mol−1, in good agreement with previous estimates. They also show that both r‐4,cis‐5,trans‐6‐ and r‐4,trans‐5,trans‐6‐ trimethyl‐1,3‐oxathianes greatly favour the chiar form where the methyl group at C‐4 is axial. The chair‐twist energy parameters are reestimated at ΔH°CT 27.0 kJ mol−1, ΔS°CT 11.6J mol−1K−1, and ΔG°CT(298) 23.5 kJ mol−1 for a 2,5‐twist form.
Structural studies of metalloporphyrins. VI—13C relaxation time, T1, measurements and the nature of the axial N—metal bond in some macrocyclic complexes
Authors: Huet J. , Gaudemer A.
Published: May 2005

Rotation barriers around the metal—pyridine bond of various macrocyclic complexes of cobalt(III), rhodium(III), zinc(II) and magnesium(II) have been studied using the 13C longitudinal relaxation times, T1, of the carbon atoms of pyridine and the macrocycle. The data have been rationalized on the basis of steric and electronic factors. The influence of π back‐donation on the rates of rotation around the axial CoN and RhN bonds is discussed. The agreement found between the conclusions drawn from this study and X‐ray data reported for complexes of identical or closely related structure demonstrates the validity of this method.
One‐bond C‐α,H coupling constants in amino acids and peptides pH dependence and substituent increments
Authors: Egli Huldrych , von Philipsborn W.
Published: May 2005

One‐bond C‐α,H coupling constants are reported for glycine, alanine, sarcosine and related di‐ and tripeptides. A detailed study of the pH dependence of 1J(C‐α,H) has led to a determination of additive increments, ζ, for the functional groups NH3, NHCO, COO−, and CONH which can be used, together with known values for NH2, COOH and alkyl substituents, to calculate 1J(C‐α,H) in amino acids and peptides.
13C NMR spectral studies of zoapatanol and montanol, novel diterpenes from Montanoa tomentosa (zoapatle), and their chemical derivatives
Authors: Cotter Mary Lou
Published: May 2005

Zoapatanol and montanol are biologically active compounds isolated from the leaves of Montanoa tomentosa (zoapatle), and represent an unusual diterpenoid structural type. The 13C NMR of these compounds, and of several of their chemical derivatives, have been assigned by the use of off‐resonance decoupled experiments, internal comparisons within this series of related compounds and also by the use of model compounds.
The NMR spectrum and total geometry of selenophene determined in the liquid crystal medium ZLI 1167
Authors: Bechtold William , Magruder G. Brock , Goldstein J. H.
Published: May 2005

The calculated 12C, 13C and 77Se spectra of selenophene have been reproduced from the observed proton NMR spectrum in the orienting medium Merck ZLI 1167, and the entire ring structure computed. The effects on structure of vibration, solvent dependence of couplings and temperature have been explored. Most notable was the observation of a substantial increase in the SeC bond length, comparable to that previously reported for selenophene in Merck Phase IV.
trans–cis Isomerization of schiff's bases (N‐benzylideneanilines) on addition of lanthanide shift reagents
Authors: Saleem L. M. N.
Published: May 2005

Application of the lanthanide shift reagent Eu(fod)3 to a series of benzylideneanilines causes isomerization of the stable trans form to the less stable cis form. A linear relationship was obtained between the % cis isomer with the mole ratio of Eu(fod)3/substrate.
Proton magnetic resonance spectra of 2,6‐disubstituted naphthalenes
Authors: Salman S. R.
Published: May 2005

The spectra of several 2‐methyl‐6‐R‐disubstituted naphthalenes (R=H, Me, I, NO2, Cl, SO2Cl, OH, OMe, COMe, Br, F and NHCOMe), have been analysed. Chemical shift and coupling constant values of these compounds are presented. The proton chemical shifts have been found to correlate with the ortho parameter, Q.
A 13C and 1H NMR study of some aryltellurium tris(diethyldithiocarbamates)
Authors: Khadim Mohammad A. , Kumar Vijay , Bird Peter H. , Pant Bhuvan C. , Colebrook Lawrence D.
Published: May 2005

Carbon‐13 and proton NMR spectra are reported for phenyl‐,4‐methoxyphenyl‐, 4‐ethoxyphenyl‐ and 3‐methyl‐4‐methoxyphenyltellurium tris(diethyldithiocarbamate). Both the 1H and the 13C spectra are typical of compounds undergoing a fast exchange process, only the N‐methylene proton signals and the thiocarbonyl carbon signals showing evidence for exchange broadening. The phenyl C‐1 carbon signal is deshielded relative to benzene (by 12.0 ppm), and shows solvent dependence. The thiocarbonyl carbon atoms absorb at 197.5‐199.1 ppm, showing solvent dependence but little sensitivity to the aryl group substituents.
Carbon‐13 NMR study of (20,24)‐epoxydammarane triterpenes
Authors: Francisco Cosme G. , Freire Raimundo , Hernández Rosendo , Salazar José A. , Suárez Ernesto , Cortés Manuel
Published: May 2005

Assignments of the 13C NMR signals of the dammarane triterpenes, 3β,25,30‐trihydroxy‐(20R,24R)‐epoxydammaran‐16‐one 3,30‐diacetate (trevoagenin A diacetate) (2), its 20S‐isomer (trevoagenin B diacetate) (3) and their related (20R)‐3β,30‐diacetoxy‐16‐oxo‐25,26,27‐trisnordammarane‐24,20‐lactone (4) and its 20S‐isomer (5) have been achieved. Suitable tetrahydrofuran models have been synthesized in order to aid the 13C NMR assignments of the side‐chain carbons of the above‐mentioned compounds. The remarkable chemical shift differences observed for C‐21 and C‐22 between each pair of the C‐20 epimers (2, 3 and 4, 5) allowed the confirmation of the C‐20 stereochemistry of these ocotillol‐type dammarane triterpenes.
A 13C13C spin–spin coupling matrix for 1‐ and 2‐methylnaphthalene by the two‐dimensional INADEQUATE method. Correlation with π‐bond orders
Authors: Berger Stefan
Published: May 2005

All resolvable 13C13C Spin–Spin Coupling constants in 1‐ and 2‐methylnaphthalene have been measured in natural abundance by the two‐dimensional INADEQUATE method. The results have been interpreted in terms of HMO theory.