bluuebunny/crossref_metadata_2025 huggingface dataset:
ESR, ENDOR and TRIPLE resonance studies on radical reactions of 1,4‐benzoquinone and 1,4‐hydroquinone in alkaline methanol and liquid ammonia
Authors: Joela H. , Kasa S. , Mäkelä R. , Salo E. , Hannonen K.
Published: May 2005

The relative signs and absolute values of the hyperfine coupling constants of different methoxy‐1,4‐benzoquinones were measured by ESR, ENDOR and TRIPLE resonance spectroscopy. Reactions of 1,4‐benzoquinone and 1,4‐hydroquinone with methanol took place in alkaline methanol, giving rise to methoxy‐substituted 1,4‐benzoquinones. The same substitution reaction occurred in a mixture of ammonia and methanol. The reactions depended on temperature and the alkali concentration. Coupling constants were assigned by the modified additivity relationship method. An extremely small line width of 0.014 G was measured in the ESR spectrum of deuterated 2,5‐dimethoxy‐1,4‐benzoquinone.
Stable conformations and energy barriers to rotation in perfluoro(4‐sec‐butylpyridine)
Authors: Sandall John P. B. , Sutcliffe Leslie H.
Published: May 2005

All‐valence‐electron MNDO–SCF–MO calculations were carried out on perfluoro(4‐sec‐butylpyridine) in order to calculate the stable conformations of the perfluoroalkyl group and the energy barrier to rotation of this group around the CalkylCaryl, bond. Both the AM1 and PM3 Hamiltonians were used. The results were compared with the value obtained from a variable‐temperature study of the 19F NMR spectrum of the compound. The PM3 method is shown to give a significant improvement compared with AM1.
Carbon‐13 chemical shift assignments of derivatives of benzoic acid
Authors: Wnuk Stanisław , Wyrzykiewicz Elżbieta , Kaczmarek Elżbieta , Kinastowski Stefan
Published: May 2005

The 13C NMR spectra of 23 di‐ and tri‐substituted derivatives of esters, thioesters and amides of benzoic acids have been calculated and fully assigned. The Ai empirical parameters of the (alkoxy)(dialkoxycar‐bonyl) methylamino, (alkoxy)(alkoxycar‐bonyl)(cyano)methylamino, (alkylamino) (dialkoxycarbonyl) methylamino and (alkylthio) (dialkoxycarbonyl) methylamino groups have been calculated for use in the prediction of the chemical shifts of substituted benzenes.
Conformational and dynamic investigation in solution of inosine and its molecular complex, inosiplex, by proton and carbon NMR spectroscopy
Authors: Rossi Claudio , Picchi Mariapia , Tiezzi Enzo , Corbini Gianfranco , Corti Piero
Published: May 2005

The conformational and dynamic properties of inosine and two other components of inosiplex (p‐acetamidobenzoic acid and dimethylaminoisopropanol) were analysed. For inosine, the most interesting molecule of the complex, the rotamer populations of all six allowed structures related to the N ⇌ S puckering and the 5′‐exocyclic conformation were calculated. Analysis of different NMR spectra and/or parameters, i.e. 2D‐NOE, saturation transfer, spinlattice relaxation rates and scalar coupling constants, suggests that a distribution of several inosine structures occurs in solution, with the inosine syn conformation predominating.
Cycloheptatrienyl radicals: An EPR study of substituent effects
Authors: MacCorquodale Finlay , Walton John C.
Published: May 2005

Cycloheptatrienyl radicals with donor and acceptor substituents were generated by hydrogen abstraction from the corresponding cycloheptatrienes and studied by EPR spectroscopy. The barrier to rotation about the C‐1CO bond in ethoxycarbonylcycloheptatrienyl radicals was found to be ca. 7.5 kcal mol−1 (31.4 kJ mol−1). The observed hyperfine splittings of the ring hydrogens were interpreted in terms of a model in which the substituent causes an energy separation ΔE between the frontier orbitals. Populations of the symmetric and antisymmetric orbitals were deduced, and ΔE values were estimated. A similar analysis was carried out from EPR data for substituted benzene radical anions. These energy separations show a linear correlation with Hammett constants. The p‐values from plots of this type for [n]annulene radicals decrease in magnitude as the size of the ring increases.
1H NMR structural analysis of a series of naphthalene‐hydroxymethyl‐and ‐mercaptomethyl‐carboxylic acids and derivatives
Authors: Tsatsakis A. M. , Dais Photis
Published: May 2005

1H NMR chemical shifts allow the determination of some structural properties of a series of naphthalene‐hydroxymethyl‐ and ‐mercaptomethyl‐carboxylic acids and their derivatives used as potential pesticides.
13C NMR chemical shifts of 2,4,5,‐ tri‐substituted 2H‐pyridazin‐3‐ones
Authors: Liptaj T. , Konečny V. , Kovác Š
Published: May 2005

The 13C NMR spectra of a series of 2‐X‐4‐Y‐5‐Z‐substituted 2H‐pyridazin‐3‐ones were measured and assigned on the basis of results from one‐dimensional semi‐selective INEPT or one‐dimensional relayed coherence transfer (HICUUP) experiments.
15N, 13C and 1H NMR spectra of the 2:1 cobalt(III) complexes of some azo dyes
Authors: Lyčka Antonín , Jirman Josef , Cee Aleš
Published: May 2005

The 15N, 13C and 1H NMR spectra of 2:1 cobalt(III) complexes of azo dyes and their 15N isotopomers, derived from substituted 2‐hydroxyaniline azo coupling products with acetoacetanilide, were measured. It was found that, in contrast to precursors existing fully in their hydrazone forms, 2:1 cobalt(III) complexes exist in (E)‐azo configurations, cobalt being bound to oxygens which originate in hydroxy and amide groups and nitrogen from substituted anilines as starting material.
Stereochemistry of benzannelated 1,6‐diazabicyclo[4.2.1]octadienes and the conformation of substituents on the methylene bridge
Authors: Kleinpeter E. , Hartmann J. , Werner B. , Schroth W.
Published: May 2005

The stereochemistry of benzannelated 1,6‐diazabicyclo[4.2.1]octa‐3,7‐dienes (the conformation of the eight‐membered ring and of the variable substituents on the methylene bridge) was determined by means of NOE enhancements and stereospecific long‐range H,H coupling constants in the relevant NMR spectra.
Compounds with bridgehead nitrogen. 62—NMR spectra and stereochemistry of perhydropyrido[1,2‐c][1,3]thiazepines and related systems
Authors: Crabb Trevor A. , Fallah Asadollah
Published: May 2005

Perhydropyrido[1,2‐c][1,3] thiazepine adopts (CDCl3 solution, 25°C) an equilibrium containing > 98% trans‐fused conformer, in contrast to perhydropyrido[1,2‐c][1,3]oxazepine, which adopts a ca. 74% trans‐fused ⇌ 26% O‐inside‐cis‐fused conformational equilibrium. The cis‐(H‐5a, H‐8)‐8‐ethyl‐substituted derivatives of both systems show increased preference for the S/O inside cis conformations. The related 2‐tert‐butylperhydropyrido[1,2‐c][1,3]diazepine adopts predominantly the trans‐fused conformation.
Liquid‐ and solid‐state (CP‐MAS) 13C and 207Pb nuclear magnetic resonance study of two triorganolead methoxides and a stabilized triorganolead cation
Authors: Wrackmeyer Bernd , Horchler Klaus , Sebald Angelika , Merwin Lawrence H.
Published: May 2005

Liquid‐ and solid‐state NMR data (13C, 207Pb) are reported for three organolead compounds, Me3PbOMe (1) and two comparable heterocycles, 5,5,4‐tricyclopentyl‐2,5‐dihydro‐1,2,2,3‐tetramethyl‐1,2,5‐oxoniaplumbaboratol (2) and (E)‐2‐dimethyl‐3‐diisopropyl(propinyl)borata‐4‐methyl‐2‐pentene (3); 2 contains a bridging methoxy group, and a triorganolead cation is stabilized by a bridging alkynyl group in 3. Compound 1 is shown to be associated in solution and forms chains in the solid state with bridging methoxy groups. The 207Pb CP‐MAS NMR spectrum of 1 shows that there is a single lead site with near‐axial symmetry. Two‐dimensional heteronuclear 13C/1H shift correlations were used to obtain the relative signs of numerous J(207Pb13C) and J(207Pb1H) coupling constants. In the case of 2 and 3 the 1J(207Pb13CMe) coupling constants have a negative sign. This indicates an extremely distorted tetrahedral surrounding of the lead atom. The isotropic 207Pb chemical shifts of 2 and 3 are almost identical in the solid state and in solution. Therefore, the structures in the solid state are fully retained in solution. Quantitative analysis of the spinning side‐band pattern of the 207Pb CP‐MAS spectra gave similar chemical shift anisotropies, Δσ(207Pb‐1133) ppm (2) and ‐1223 ppm (3), and also similar tensorial components of σ(207Pb), indicating that the basic structures of the two heterocyclic systems are comparable except for the bridging unit.
Rotational isomerism in 5‐amino‐6‐(N‐methylformamido)‐as‐triazin‐3(2H)‐one
Authors: Riand Jacques , Tanguy Michel , Chenon Marie‐Thérèse , Tzeng Cherng‐Chyi , Panzica Raymond P.
Published: May 2005

A 1H dynamic NMR study of the hindered rotation in 5‐amino‐6‐(N‐methylformamido)‐as‐triazin‐3(2H)‐one was conducted. Signals for two rotamers were observed and their proton chemical shifts were assigned. It was found that the rotamer in which the as‐triazine ring is cis to the formyl hydrogen predominates. The free energies of activation for hindered rotations about the N CHO and C NH2 bonds were determined by 1H NMR line‐shape analysis.
Sign and magnitude of the phosphorus–phosphorus coupling constant in the [cyclopentadienyltris(trimethylphosphine)iron]+ cation of [(η5‐C5H5)(Me3P)3Fe]BF4and the 13C/12C isotope effect on the 31P chemical shift
Authors: Buchner Wolfgang , Ries Wolfgang , Malisch Wolfgang
Published: May 2005

The 13C NMR methyl group multiplet of the [cyclopentadienyltris(trimethylphosphine)iron]+ cation was simulated to obtain the sign and magnitude of the phosphorus‐phosphorus coupling constant and the 13C/12C isotope effect on the 31P chemical shift.
77Se and 15N NMR investigation of some cycloalkeno‐1,2,3‐selenadiazole derivatives
Authors: Duddeck Helmut , Wagner Petra , Müller Dieter , Jászberényi Joseph Csaba
Published: May 2005

The 13C, 15N and 77Se NMR data (chemical shifts and coupling constants) of some cycloakeno‐1,2,3‐selenadiazoles are presented. Extremely large 77Se chemical shifts are found. 15N, 77Se coupling constants, obtained at natural abundance, are reported for the first time. Strong signal shifts due to different sizes of the cycloakeno rings can be qualitatively rationalized in terms of electron transfer between the nitrogen and selenium atoms. A positive γ‐syn effect of the methyl group on N‐3 is found in 4‐methyl‐4,5,6,7‐tetrahydrobenzo‐1,2,3‐selenadiazole.
13C and 15N NMR study of derivatives of N‐unsubstituted pyrrolidines
Authors: Barbry Didier , Hasiak Bruno , Couturier Daniel
Published: May 2005

13C and 15N NMR data for twelve N‐unsubstituted pyrrolidines are reported and cis and trans stereomers are assigned for 2,3‐, 2,4‐ and 2,5‐disubstituted compounds.
13C NMR spin–lattice relaxation mechanisms of carbocations in superacids
Authors: Kelly David P. , Leslie D. Ralph
Published: May 2005

The contributions to the 13C NMR spin–lattice relaxation rates of both protonated and non‐protonated carbons of a range of carbocations in superacids were determined from the analysis of T1 values measured over a range of temperatures and at different field strengths. From the data for 1‐adamantyl, 2‐methyl‐2‐norbornyl, 3‐methyl‐3‐nortricyclyl, 2‐phenyl‐2‐norbornyl, cumyl (1‐methyl‐1‐phenylethyl) and methylphenylcyclopropylcarbinyl (1‐cyclopropyl‐1‐phenylethyl) cations, dipole–dipole interactions (both intra‐ and inter‐molecular) were found to be entirely responsible for the relaxation of protonated carbons. However, for the cationic carbons, chemical shift anisotropy contributes significantly to their relaxation at low field strengths (2.3 T) and predominantly at high field strengths (5.8 T). The shielding anisotropies (Δσ) of the cationic carbons were determined as 410–540 ppm, which are amongst the largest reported for any carbon atoms.
Substituent effects in the 13C NMR spectra of 17α‐ethinyl‐19‐nortestosterone derivatives
Authors: Hammann Peter E. , Wöbbecke Elke , Hoppen Hans‐Otto
Published: May 2005

The 13C NMR spectra of eight norethisterone derivatives are presented. Substituent chemical shifts for the methyl group at C‐18, the methylene group at C‐11 and the Δ15 double bond are evaluated and discussed.
13C NMR spectra of (E)‐2‐pyridinecarbaldehyde pyridin‐2′‐ylhydrazone and eight analogues
Authors: Casey Allan T. , Traverso Ivan P.
Published: May 2005

The total assignment of the 13C NMR spectra of (E)‐2‐pyridinecarbaldehyde pyridin‐2′‐ylhydrazone and eight analogues is reported. The assignment of the spectra was achieved by comparison with data from the hydrazone precursors and other similar compounds.
Characterization of cyclonerodiol isolated from corn infested by fusarium moniliforme sheld.: One‐ and two‐dimensional 1H and 13C NMR study
Authors: Laurent D. , Goasdoue N. , Kohler F. , Pellegrin F. , Platzer N.
Published: May 2005

A metabolite extracted from maize culture was identified as cyclonerodiol. Its 1H and 13C NMR spectra have been fully analysed, and some literature assignments have been reversed.
31P and 13C NMR studies on the phase structures of the binary barium ethyl octyl phosphate–water system
Authors: Yoshida Tadayoshi , Miyagai Kiyotaka , Taga Keijiro , Okabayashi Hirofumi , Matsushita Kazuhiro
Published: May 2005

31P nuclear magnetic resonance (NMR) studies of the four phases (I, II, II′ and III) in the barium ethyl octyl phosphate‐water system were carried out. The concentration dependence of the 31P chemical shift, half‐height width and line shape provided information on the phase structures. For phase I the critical micelle concentration (CMC) is found at 1.2 wt.%, and above this concentration there is a monomer ⇌ micelle equilibrium. Phase II has a monomer ⇌ micelle equilibrium system, similar to phase I. Phase II′ is an aggregate system and is structurally organized. The structure of phase III is more organized than that of phase II′ and depends strongly on concentration. The 3J(POCC) values were also used to establish the restricted state of the POCC single bond in the phases.
19F NMR study of fluoro‐substituted tetracyclo[6.3.0.02,4.03,7]undec‐5‐enes
Authors: Osselton E. M. , Erkelens C. , Krijnen E. S. , Lempers E. L. M. , Cornelisse J.
Published: May 2005

19F and 1H NMR data are reported for fluoro‐substituted tetracyclo[6.3.0.02,4.03,7]undec‐5‐enes, which are products of the meta photocycloaddition reaction of fluorobenzenes to cyclopentene. Hetero‐ and homo‐nuclear decoupling techniques were used to identify the adducts.
HMQC‐NOESY: Application to a polynuclear aromatic at natural abundance
Authors: Ronald  , Crouch C. , Andrews C. Webster , Martin Gary E. , Luo Jiann‐Kuan , Castle Raymond N.
Published: May 2005

Orientation of proton spin systems relative to one another in polynuclear aromatics through the use of 1H homo‐nuclear nuclear Overhauser effects (NOE) detected by heteronuclear multiple quantum correlation (HMQC‐NOESY) at natural abundance is reported. The experiment was explored as a potential alternative for problems in which a solution cannot be obtained by more conventional methods. Optimization of the HMQC‐NOESY experiment is discussed.
13C NMR spectra of some substituted furo[3,2‐b] pyrroles
Authors: Dandárová Miloslava , Krutošíková Alžbeta , Aalföldi Juraj
Published: May 2005

13C chemical shifts for 16 derivatives of furo[3,2‐b] pyrrole substituted at positions 2, 4 and 5 are reported. The J(CH) values were determined for some derivatives. Heterocorrelated 2D 1H‐13C NMR spectra, selective heteronuclear decoupling and selective INEPT experiments were used for signal assignment.
Analysis of the 1H and 13C NMR spectra of the novel macrolide antibiotic roxithromycin. Structure and conformation in solution
Authors: Gharbi‐Benarous Josyane , Delaforge Marcel , Artaud Isabelle , Girault Jean‐Pierre
Published: May 2005

A complete assignment of the 1H and 13C NMR spectra of roxithromycin in deuteriochloroform, methanol‐d4 and D2O was made using different two‐dimensional (2D) chemical shift correlation methods. The coupling constants observed by 1H NMR and the NOEs show that the predominant conformation of roxithromycin in CDCl3 solution is very similar to that in the crystalline state. However, variable‐temperature and variable‐solvent NMR experiments show that the major conformation of roxithromycin presents a conformational flexibility in the C‐2–C‐8 region and, particularly, in the C‐4–C‐5 bond of the molecule. The NOE data indicate that the 9‐[O‐(2,5‐dioxahexyl)oxime] chain is directed towards the 6‐OH, certainly involving an intramolecular hydrogen bond. This results in a globular structure for roxithromycin with less freedom for the macrolactone ring and the sugar units.
A multinuclear magnetic resonance study of protonation in imidazo[1,2‐a]pyrazine
Authors: Sanderson P. N. , Farrant R. D. , Lindon J. C. , Barraclough P.
Published: May 2005

1H and 13C NMR spectra are reported and assigned for imidazo[1,2‐a] pyrazine and for N‐1‐methyl‐ and N‐7‐methyl‐imidazo[1,2‐a] pyrazinium iodides. The effect of protonation on the chemical shifts of the parent molecule is demonstrated, and through the use of 13C and 15N NMR spectra the site of protonation is deduced to be at N‐1, in contrast to 2‐aryl substituted compounds synthesised as potential cardiotonic agents where protonation occurs at N‐7.
Molar paramagnetic solvent NMR shifts of galvinoxyl in toluene. Kinetics of the reaction between galvinoxyl and tertiary amines at high radical concentrations
Authors: Screttas Constantinos G. , Heropoulos Georgios A.
Published: May 2005

The molar paramagnetic solvent NMR shifts of galvinoxyl (1, G′) in toluene were measured at 34°C and found to be 2.21 and 2.39 ppm mol−1 for the aliphatic and the aromatic proton signals of toluene, respectively. The implications of the inequality of the two molar shifts are discussed. The paramagnetic solvent shift of G. in toluene in the presence of tertiary amines decays according to a first‐order rate law. The apparent first‐order rate constants were found to be linearly related to the initial concentration of the amine. The kobs vs. [R3N]0 regression lines in some cases exhibit a positive intercept, indicating the involvement of the solvent in the reaction. The logarithms of the second‐order rate constants are shown to be linear with respect to the ionization potentials of the amines. The reaction products of galvinoxyl with n‐Bu3N are hydrogalvinoxyl, GH and the enamine n‐Bu2NCH=CHEt whereas, with N/N‐dimethylaniline. the products are hydrogalvinoxyl and the hemiaminal ether of formaldehyde, derived from the combination of the radical PhN(Me)CH2. with G. through the oxygen of the latter. A mechanistic scheme is proposed involving a rate‐determining electron‐transfer step.
Accurate determination and analysis of the temperature dependence of long‐range spin–spin couplings in 2‐chlorobenzaldehyde
Authors: Laatikainen Reino , Tuppurainen Kari , Hiltunen Yrjö , Lötjönen Simo
Published: May 2005

The proton‐proton spin‐spin couplings of 2‐chlorobenzaldehyde were determined accurately for acetone‐d6 and CD3CN solutions at several temperatures. The sign and temperature dependence of the para‐benzylic six‐bond coupling, 6Jα4, was also obtained, although the observed value of this indicator of the formyl–ring co‐planarity was in the range −24 to −31 mHz. The fitting of the temperature dependence suggests that 6J0 (the value of the coupling when the formyl‐ring dihedral angle is 0°) is very small and probably positive, in contrast, for example, to styrene. The results are discussed on the basis of some modified INDO/FP calculations. A simple resolution enhancement technique is also described.
Spectroscopic electronegativities correlated with the 13C NMR shifts of metal (Ia, IIa, IIIa) 2‐ethoxyethoxides
Authors: Micha‐Screttas Maria
Published: May 2005

Spectroscopic electronegativities of Li, Na, K, Mg, Ca, Sr and Al bear a linear relationship with the C‐1 chemical shifts in the corresponding sequence of metal 2‐ethoxyethoxides. The unusual feature of this correlation is that it accommodates data for derivatives of metals belonging to different groups. The observed correlation implies that there is a linearity between χspec and the mean excitation energy.
29Si and13C NMR spectra of 4‐substituted 2‐methoxytrimethylsiloxybenzenes. Factors determining the chemical shifts in models of lignin constituents
Authors: Schraml Jan , Kvíčalová Magdalena , Chvalovský Václav , Elder Thomas , Brežný Robert
Published: May 2005

29Si and13C NMR chemical shifts are reported for a series of twenty 4‐substituted 2‐methoxytrimethyl‐siloxybenzenes; the set of substituents incorporates a basic set of ten substituents differing in their relative polar and resonance effects and ten other substituents which model substituents encountered in lignins. The factors affecting the chemical shifts are discussed using a comparison with the NMR data for a similar series of compounds, correlations with substituent parameters and electronic charges calculated by a quantum chemical method (MNDO calculations on force‐field optimized molecular geometries) for the basic set. It is concluded that the methoxy group in theorthoposition to the trimethylsiloxy group takes, for most of its time, the conformation in which the methyl group lies in the plane of the benzene ring and is turned away from the trimethylsiloxy group which assumes a perpendicular conformation. Proximity deshielding effects observed on both the methoxy and trimethylsiloxy groups are influenced by the substituents in position 4, which is in agreement with the notion that these effects are due to an interaction of the vicinal oxygen atoms or their unshared electrons. The dependence of the29Si chemical shifts on σpis not substantially affected by the presence of theorthomethoxy group.
Assignment of carbonyl carbon and acetyl methyl proton resonances of acetylated saccharides by the use of two‐dimensional NMR techniques
Authors: Uhrínová Stanislava , Petráková Eva , Ruppeldt Juraj , Uhrín Dušan
Published: May 2005

Carbonyl carbons in peracetylated saccharides are coupled via three‐ and two‐bond couplings with ring protons and acetyl methyl protons, respectively. Using their mean values, the optimum setting for 2D heterocorrelated experiments (Freeman–Morris and COLOC sequences) designed for the assignment of carbonyl carbon and acetyl methyl proton resonances is presented. Selective inversion of the methyl proton resonances in the middle of the refocusing period is introduced. This modification eliminates the effect of 2J(CO,CH3) on the intensity of the carbonyl carbon‐ring proton cross‐peaks, which is essential in the assignment procedure. The carbonyl carbon, acetyl methyl and ring proton resonances can be used for the determination of the primary structure of complex saccharides.
Study of solvent effects on the nitrogen NMR shieldings of some indolizines
Authors: Witanowski M. , Sicińska W. , Grabowski Z. , Webb G. A.
Published: May 2005

Solvent effects on the nitrogen NMR shieldings of indolizine and three azaindolizines are presented for a range of thirteen solvents. The results are discussed in terms of hydrogen‐bonding an solvent polarity effects. ‘Pyridine‐type’ nitrogen atoms show a much larger range of solvent effects than do ‘pyrrole‐type’ nitrogens; solvent to solute hydrogen bonding is the dominant contribution to the changes in shielding for the ‘pyridine‐type’ nitrogen atoms as the solvent is varied. Solvent polarity effects are important for both types of nitrogen atom in azaindolizines and can be attributed to a solvent‐induced electronic charge separation between the nitrogen atoms concerned.

Quantum chemical calculations involving the solvaton model are used to provide supporting evidence for the importance of solvent polarity effects on nitrogen shieldings in azaindolizines.
A question of assignments in the 13C NMR of estrone and related structures
Authors: Smith William B.
Published: May 2005

The initial assignments for C‐6 and C‐8 in the carbon spectrum of estrone [3‐hydroxyestra‐1,3,5(10)‐triene‐17‐one] were reversed by a subsequent group of investigators. Recent respected reference publications have reproduced these conflicting sets of data, reflecting an uncertainty regarding the correct assignments. The implied question has been answered with the aid of APT, 2D COSY and HETCOR experiments.
13C NMR study of polyaryl‐ and poly‐C‐heteroaryl‐carbinols and their carbonium salts
Authors: Avendaño Carmen , de Diego Carmen , Elguero José
Published: May 2005

The carbon‐13 chemical shifts of a series of trisubstituted methanols with phenyl, p‐dimethylaminophenyl, 9‐fluorenyl, 2‐N‐methylpyrrolyl, 2‐furyl, 2‐thienyl, 2‐N‐methylindolyl, 2‐benzofuryl and 2‐benzothienyl substituents (26 compounds) are discussed. Those of the sp3 carbon atoms bearing the OH group, and the ipso carbons carrying the COH group, follow additive models with high accuracy. The corresponding central carbon atom of the carbonium ions, which were stable enough to be studied in chloroform (eight compounds), also follows an additive pattern which allows the prediction of the chemical shifts of derivatives not studied in this work.
1H and 13C NMR spectra of pseudomorphine and dimethylpseudomorphine
Authors: Graden D. W. , Caldwell G. W. , Villani F. J. , Maryanoff C. A. , Grant A.
Published: May 2005

The 1H and 13C NMR spectra of 7,7′,8,8′‐tetradehydro‐4,5:4′,5′‐diepoxy‐17,17′‐dimethyl‐[2,2′‐bimorphinan]‐3,3′,6,6′‐tetrol; [2,2′‐bimorphine] (pseudomorphine) and 7,7′,8,8′‐tetradehydro‐4,5:4′,5′‐diepoxy‐17,17′‐dimethyl‐[2,2′‐bimorphinan]‐3,3′‐dimethoxy‐6,6′‐diol; 2,2′‐bimorphine (dimethylpseudomorphine) were measured and assigned using DEPT, COSY, HETCOR, NOESY, NOE difference techniques and selective proton decoupled carbon NMR experiments.
13C cross‐polarization/magic angle spinning and 2H NMR studies of the structure and dynamics of the (deoxycholic acid)2–ferrocene inclusion compound
Authors: Heyes Stephen J. , Dobson Christopher M.
Published: May 2005

The channel‐type inclusion complex, (deoxycholic acid)2–ferrocene [(DCA)2–;ferrocene], was studied by 13C cross‐polarization/magic angle spinning NMR spectroscopy. The spectra indicate that two different DCA molecules are present in the crystalline structure. Relaxation data indicate a relatively restricted degree of reorientational freedom of the included ferrocene molecules. 2H NMR spectra of the inclusion complex with perdeuterated ferrocene reveal rapid, anisotropic librations of the principal axes of the ferrocene molecules about their mean positions, varying from <ca. ± 1° at 160 K to ca. ± 28° at 350 K. The anisotropic, librational nature of this molecular reorientation may be rationalized in terms of the packing features of the sheet‐like nature of the structures of such deoxycholic acid compounds.
Silicon‐29 MAS NMR investigations of Na2O · SiO2 glasses: Refinement of the binary distribution model
Authors: Grimmer Arnd‐RÜDiger , Thomas Berthold , Seifert Gudrun , Sarv Priit
Published: May 2005

Silicon‐29 MAS (9 kHz) NMR spectra at 11.7 T, combined with an improved deconvolution procedure, are used to refine the Qn/Qn‐1 distribution model for binary glasses x Na2O · SiO2 (0.18 < x < 0.49). Using the fictitious temperature concept the binary distribution is shown to be the low‐temperature limiting case for the distribution of structural units Qn, Observed deviations from the strict model tending to random distribution can be explained by the model of Dorfeld. Additional structural information can be derived from 29Si chemical shift and line‐width data.
Complete 1H and 13C NMR spectral assignment of some polynitropolycyclic cage molecules by 2D NMR spectroscopy
Authors: Axenrod T. , Liang B. , Dave P. R.
Published: May 2005

The 1H and 13C NMR spectra of several saturated polynitropolycyclic molecules were unambiguously assigned using aromatic solvent‐induced shifts, NOE difference spectra, 1H–1H COSY spectra and 2D 13C–1H shift correlated spectra, optimized either for one‐bond or long‐range 13C–1H couplings.
1H NMR investigation of selected heptafulvenes
Authors: Bönzli Peter , Neuenschwander Markus
Published: May 2005

The 1H NMR spectra of selected heptafulvenes 2a–e were analysed under high‐resolution conditions. The results are in agreement with a symmetrical boat conformation for 2a and with a nearly planar conformation of 2e. Within the series 2a–e, ring planarization and π‐delocalization increase. Substituent effects on NMR parameters are discussed.
1H NMR structural analysis of isomeric tetrazole‐substituted spirostan steroids: Shielding effects and conformational study
Authors: Silwood Christopher J. L. , Davies David B.
Published: May 2005

The structures of two pairs of tetrazole‐substituted spirostan steroids were characterized by the use of one‐ and two‐dimensional 1H NMR measurements. The conformation of the seven‐membered spirostan ring A of the steroid was determined by analysis of proton spin coupling constants and confirmed by 1D and 2D NOE experiments showing interactions between the methyl group and ring protons. The conformation of the tetrazole‐substituted ring A was found to be the same for the four isomers, allowing them to be differentiated by the analysis of the effect of tetrazole‐ring isomerization on the chemical shifts of neighbouring protons.
Influence of the phosphorus lone pair on coupling constants in vinylphosphines
Authors: Mitchell Terence N. , Heesche‐Wagner Kerstin , Belt Heinz‐Joachim
Published: May 2005

Multinuclear NMR data are presented and discussed for a variety of vinylphosphines in which the vinyl group bears one, two or three substituents; these include organic and trimethylstannyl residues. The orientation of the phosphorus lone pair can be determined from two‐bond phosphorus‐carbon coupling constant values. The magnitudes of the 3J(PCCSn), 4J(PCCSnC) and 5J(PCCSnCH) coupling constants are clearly determined by a throughspace interaction when P and C are in a cis configuration.
Multinuclear magnetic resonance study of 1,3,3‐trimethylbicyclo [2.2.1]heptan‐2‐one (fenchone) oxime, its five monochloro derivatives and a dehydrochlorination product
Authors: Kolehmainen Erkki , Laihia Katri , Korvola Jorma , Kauppinen Reijo , Mänttäri Pia , Rissanen Kari
Published: May 2005

Fenchone oxime, 5‐exo‐chlorofenchone oxime, 6‐exo‐chlorofenchone oxime, 7‐anti‐chlorofenchone oxime, 8‐chlorofenchone oxime, 9‐chlorofenchone oxime and a dehydrochlorination product of 10‐chlorofenchone oxime were synthesized from fenchone and the corresponding chlorofenchones. The 1H, 13C and 17O NMR spectra of the oximes and the dehydrochlorination product were recorded. The NMR data were compared with the corresponding parameters obtained earlier for fenchone and monochlorofenchones in order to determine the differences between the carbonyl and oxime substituents from the NMR spectroscopic point of view, and to assign the stereochemistry of the oxime group. This stereochemistry could not, however, be assigned solely by NMR spectroscopy.
1H NMR spectra of some 5‐substituted‐thianthreniumyl perchlorates
Authors: Lochynski Stanislaw , Hoque A. K. M. M. , Shin Seung Rim , Shine Henry J.
Published: May 2005

1H NMR spectra of 21 5‐substituted‐thianthreniumyl perchlorates are reported that allow chemical shift and structural assignments to be made.
Carbon‐13 NMR spectral investigation of organosulfur compounds. Substitutent‐induced chemical shift (SCS) effects in acyclic saturated organosulfur compounds
Authors: Dyer John C. , Evans Slayton A.
Published: May 2005

The 13C NMR shielding effects on proximal carbon atoms caused by oxidation of sulfenyl sulfur to sulfinyl, sulfonyl and sulfonium species are diagnostic indicators and extremely useful in the structural characterization of organosulfur compounds.
Determination of polyaminocarboxylate ligand denticity by 13C NMR paramagnetic line broadening
Authors: Popov K. , Vendilo A. , Djatlova N.
Published: May 2005

The 13C NMR characteristics of sodium acetate and complexes of ethylenediaminetetraacetic acid (EDTA, H4edta) with La3+ and VO2+ in the presence of the paramagnetic relaxant [Gd(H2O)n edta]− are reported. The observed selective paramagnetic line broadening of the uncoordinated glycinate arms in [VO2edta]3− permits an assignment of the 13C resonances and independent ligand denticity determination. For COO resonances the selectivity was found to be ca. 18. A large difference was also observed between the 13C transverse relaxation times for the uncoordinated COO groups of CH3COO− and the coordinated COO groups of [La(H2O)3edta]−. The magnitude of the selectivity provides clear advantages in aiding the 13C NMR assignment and the establishment of the true denticity for the complexes of polydentate ligands.
Loss in conformational rigidity of bradykinin on replacement of the Phe‐8 by tyrosine
Authors: Srivastava Sudha , Haram S. , Phadke Ratna S.
Published: May 2005

The complete resonance assignments and the conformation of the hormone [Tyr8]‐bradykinin, a nonapeptide, in DMSO‐d6 have been determined using 2D 1H NMR techniques. NMR parameters such as the chemical shifts, coupling constants, temperature coefficients of the backbone NH protons and NOEs have been analysed in the light of the known conformation of the native peptide. The results indicate that the peptide loses conformational rigidity on the replacement of Phe‐8 by Tyr.
NMR analysis of fluorinated corticosteroids related to fluocinonide: Detection of long‐range 1H–19F couplings using the heteronuclear equivalent of the COSY experiment
Authors: Hughes Donald W. , Bain Alex D. , Robinson Valerie J.
Published: May 2005

The analysis of the 1H and 19F NMR spectra of the corticosteroid fluocinonide and five related steroids is reported. The 500 MHz 1H NMR spectra revealed several previously undetected long‐range 1H–19F coupling constants. These couplings were assigned by the application of the heteronuclear equivalent of the COSY pulse sequence. The fluorine substituent effects and long‐range heteronuclear couplings were examined in relation to structures derived from molecular mechanics (MMX) calculations.
Correlation of the crystal structure and solid‐state 13C NMR spectrum of pyromellitic dianhydride
Authors: Wolfe Roger A. , Schwartz Willis T. , Dinan Frank J.
Published: May 2005

The interatomic distances for crystalline pyromellitic dianhydride (PMDA) were calculated from x‐ray crystallographic data. The CP‐MAS 13C NMR spectrum of PMDA was found to be consistent with and accountable for in terms of these distances after literature assignment errors were corrected. An anomalous peak was observed in the differential scanning calorimetry thermogram of PMDA. The entropy change associated with this transition indicates that a two‐fold change in symmetry occurs approximately 60°C below the melting point of PMDA. Attempts to observe this transition by CP‐MAS 13C NMR were unsuccessful.
Liquid‐phase stereochemistry of cationic [Rhbisphosphinediene]+ and neutral [RhbisphosphinedieneCl] complexes. 1H, 31P and 13C NMR and molecular mechanics study
Authors: Szalontai Gábor , Sándor Péter , Bakos József
Published: May 2005

The liquid‐state stereochemistry of cationic [Rh(I)dienebisphosphine]+ and neutral [Rh(I)dienebisphosphineCl] complexes is reported on the basis of their 1H, 13C and 31P NMR spectra. In solution the 400‐MHz 1H spectra indicate C2 symmetry for the cationic species and a strongly solvent‐ and temperature‐dependent equilibrium for the neutral five‐coordinated species. Gas‐phase molecular mechanics calculations on the cationic complexes predict local energy minima for the skew(diequatorial), chair and boat conformations of the six‐membered phosphine chelate. The 2D exchange spectra of the neutral complex prove a slow exchange between identical forms of the bidentate chelate, but no such exchange exists between the diene atom pairs; the origin of the observed pairwise identify of the diene atoms is therefore not fully understood. In principle, several stereoisomers can exist in such complexes, depending on the actual conformation of the bisphosphine chelate and/or on the cis or trans relationship of the fifth coordinating point and the rest of the phosphine. The existence of the traditionally asssumed trigonal‐bipyramidalsquare‐pyramidal equilibrium is unlikely. As an alternative, the fluxional nature of the aliphatic part of the phosphine chelate could explain the phenomena. This motion, however, should be restricted to a chair—boat equilibrium which does not significantly change the axial—equatorial positions of the phenyl rings.
Molecular modelling, NOED and spin—lattice relaxation study of the stereochemistry of some terpenoids
Authors: Qing Ning , Colebrook Lawrence D. , Commodari Fernando
Published: May 2005

NOED, COSY and HETCOR experiments in conjunction with molecular mechanics calculations, were used to assign the 1H and 13C NMR spectra of the terpenoids α‐ionone and methyl O‐methylpodocarpate and to investigate their stereochemistry. These compounds were used as models to investigate the ability of molecular mechanics and associated calculations to predict 1H spin—lattice relaxation rates in molecules of this type.
133Cs, 1H two‐dimensional heteronuclear Overhauser effect spectroscopy (HOESY): Structural analysis of organic caesium compounds by detection of short Cs,H contacts
Authors: Bauer Walter
Published: May 2005

Transient heteronuclear Overhauser effects were observed between 133Cs and 1H by two‐dimensional heteronuclear Overhauser effect spectroscopy (HOESY). In caesium tetraphenylborate (CsBPh4) dissolved in pyridine‐d5, Cs+ is tightly attached to the BPh4− anion, thus forming a contact ion pair (CIP). By contrast, after addition of one equivalent of the crown ether 18‐crown‐6, caesium is located intimately at the site of the crown ether whereas the tetraphenylborate anion is remote (solvent‐separated ion pair, SSIP). The results are in agreement with experiments described earlier by Mei et al. Similar observations were made for caesium 3‐methylpentyl 3‐oxide in tetrahydrofuran‐d8 solution. 133Cs, 1H HOESY indicates the presence of a contact ion pair. Steady‐state 133Cs {1H} experiments on the latter compound reveal weak fractional enhancements of 0.2%.
13C CP‐MAS NMR spectra and fluxional behaviour of [M2(ηHCCCMe2)(CO)4(ηC5H5)2]+ [BF4]− (M = Mo, W) complexes in the solid state
Authors: Galakhov M. V. , Bakhmutov V. I. , Barinov I. V.
Published: May 2005

Internal rotation about the C‐2–C‐3 bond was observed in the 13C CP‐MAS NMR spectra of the solid complexes [M2(ηHC1C2C3Me2)(CO)4(ηC5H5)2]+ [BF4]− where M = Mo or W.
Direct determination of proton‐exchange kinetics by 320‐MHz tritium NMR spectroscopy
Authors: Dixon Richard E. , Williams Philip G. , Saljoughian Manouchehr , Long Mervyn A. , Streitwieser Andrew
Published: May 2005

The first application of tritium NMR spectroscopy to the direct observation of proton‐exchange kinetics is described; this technique allows the study of milligram amounts of substrates and for substrates with multiple exchangeable positions. The examples include benzene and the ring and methyl positions of p‐xylene reacting with cesium cyclohexylamide in cyclohexylamine, and the enolate positions of cyclohexanone and methyl 7,12‐dihydroxy‐3‐ketocholan‐24‐oate reacting with heptafluorobutyric acid in dioxane.
Carbon‐13 NMR study of 5‐triphenyl‐phosphoranilydeneaminopyrazoles
Authors: Arques Antonio , Molina Pedro , Vinader María Victoria , Elguero José
Published: May 2005

13C chemical shifts and 13C–31P coupling constants are reported for nineteen pyrazoles bearing an NPPh3 substituent at position 5. The three heterocyclic carbons are coupled with the phosphorus (2J, 3J and 4J). These couplings are very sensitive to the nature of the subtituent at position 4 [CHO, CHCHCOMe, CH(CH2NO2)2, CHNR, CH2NHR and CH2N(COR)Ar].
Protonated XH heteroatom (X = O, N, S) analysis in oil fractions from morocco oil‐shale using 29Si multiple‐pulse NMR
Authors: Béguin Claude G. , Bennouna Chakib , Bitar Hassane , Dahbi Abderrahman , Léna Louis
Published: May 2005

The characterization and determination of the protonated heteroatom content of the XH type (X = O, N, S) in oil fractions was carried out using 29Si NMR on silylated derivatives of the heteroatomic compounds. The analysis was achieved on a mixture of standard compounds and on two oil fractions from Morocco oil‐shale: asphaltenes and the aromatic and polar components.
Conformational study of somatostatin analogues in methanol at low temperature
Authors: Verheyden Patricia M. F. , Coy David H. , Van Binst Georges
Published: May 2005

The conformations of three somatostatin analogues were compared in methanol at 193 K. A biologically active cyclic analogue, DC13‐116 (D‐Nal5‐Cys6‐Tyr7‐D‐Trp8‐Lys9‐Val10‐Cys11‐Thr12‐NH2), and two linear analogues, one biologically active, DC25‐24 (D‐Phes5‐Cpa6‐Tyr7‐D‐Trp8‐Lys 9‐Val10‐Phe11‐Thr12‐NH2), and one with poor biological activity, DC23‐89 (D‐Phe5‐Ala6‐Phe7‐D‐Trp8‐Lys9‐Thr10‐Ala11‐Thr12‐NH2), were compared. The predominant conformation of the linear active analogue is shown to be the same as that of the active cyclic analogue; they both adopt a β11 turn/β‐sheet structure. The linear analogue with low activity has a similar conformation, which, however, is less stable.
1H and 13C NMR data for the basic naturally occurring isoxazolin‐5‐one derivatives
Authors: De Bruyn André , Verhegge Georges , Lambein Fernand
Published: May 2005

The 1H and 13C NMR data of the basic isoxazolin‐5‐one derivatives occurring in the Lathyrus species are reported.
Structural changes in the complexation of benzo‐crown ethers—NOESY and variable‐temperature 13C NMR study
Authors: Mariappan S. V. Santhana , Gomathi L. , Subramanian S.
Published: May 2005

The structural changes during the complexation of benzo‐crown ethers with Cs+, K+ and Na+ were studied by NOESY and variable‐temperature 13C NMR spectroscopy. It was found that, on complexation, the distance between the CH‐α and 1‐CH2 is reduced in dibenzo‐24‐crown‐8 (DB24C8), dibenzo‐18‐crown‐6 and benzo‐15‐crown‐5. Two mechanisms have been proposed for the distance reduction, the fluttering motion of the benzo group and the elongation of the crown moiety. However, it is concluded that both of these mechanisms seem to play a role in the distance reduction. In the complexed state of DB24C8 with Cs+, Cs+ is predicted to be slightly above the plane of the crown oxygens with respect to DB24C8.
Secondary metabolites by chemical screening. 12. 13C NMR studies of Elaiophylin derivatives
Authors: Hammann Peter , Kretzschmar Gerhard
Published: May 2005

The 13C chemical shifts of elaiophylin and 21 of its derivatives are described and discussed.
Determination of Z and E configurations in trifluoromethylated vinyl compounds: 3J(CF) coupling constants as a criterion for configurational assignments
Authors: Bégué Jean‐Pierre , Bonnet‐Delpon Danièle , Mesureur Dany , Ourévitch Michèle
Published: May 2005

NOE and T1 proton measurements were carried out in order to determine unambiguously the Z and E configurations of some CF3‐trisubstituted vinylic compounds (HCRCR′CF3). The β‐ethylenic carbon in olefins, enol ethers and enamines is always more strongly coupled to CF3 in the cis compound (CF3 and the vinylic proton cis to each other): |3J(CF)|cis > |3J(CF)|trans. This observation, in addition to the already known higher shielding of 19F NMR signal in the cis isomer, allows the safe assignments of Z and E isomers even when only one is obtained, regardless of the nature of R and R′.
Synthesis and steric structure of alicycle‐fused 1,3‐thiazine‐β‐lactams
Authors: Sohár Pál , Szabó János , Simon Lajos , Talpas Gizella S. , Szücs Erzsébet , Bernáth Gábor
Published: May 2005

2 + 2‐Cycloaddition reactions of cis‐ and trans‐cyclopenta‐, ‐cyclohexa‐ and ‐cyclohepta‐ and trans‐cycloocta [e]‐2‐phenyl‐4H‐1,3‐thiazines gave new types of hydrated tricyclic 1,3‐thiazino‐β‐lactam derivatives having the 2‐phenyl substituent and H‐9 in cis positions. The configurations and conformations of the new compounds were determined by 1H and 13C NMR spectroscopy, including double resonance, DNOE and 2D HSC measurements.
1H NMR spectra of a series of disperse azo dyes
Authors: Fedorov L. A. , Savarino P. , Dostovalova V. I. , Viscardi G. , Carpignano R. , Barni E.
Published: May 2005

The 1H NMR spectra of a series of disperse monoazo dyes in solution are reported and analysed in terms of electronic effects of the substituents, rotational isomerism and hydrogen bonding.
Carbon‐13 NMR signals of some substituted indanones, tetralones and benzo‐α‐pyrones, β‐substituted β‐phenylpropionic acids and related compounds
Authors: Patra Amarendra , Misra Swapan K.
Published: May 2005

13C spectral assignments for 3‐methyl‐1‐indanone, 3‐ethyl‐1‐indanone, 3‐n‐propyl‐1‐indanone, 3‐phenyl‐1‐indanone, 3‐phenyl‐1‐tetralone, 3‐ and/or 4‐substituted benzo‐α‐pyrones and dihydrobenzo‐α‐pyrones, together with those for 3‐phenylbutyric acid, 3‐phenylvaleric acid, 3‐phenylcaproic acid, 3,3‐diphenylpropanoic acid, 3,4‐diphenylbutyric acid, their 2‐carboxy derivatives and the ethyl esters of the 2‐carbethoxy derivatives are reported.
1H and 13C NMR studies on the conformation of E,Z‐diastereomers of N‐desmethyl‐N,O‐diacetyl‐α‐metazocine (sp2‐hybridized nitrogen derivatives of a benzomorphan narcotic analgesic)
Authors: Glaser Robert , Bernstein Michael A. , Balan Ayala
Published: May 2005

The 1H (300 MHz) and 13C (75.5 MHz) NMR spectra (CDCl3) of N‐desmethyl‐N,O‐diacetyl‐α‐metazocine showed two (E,Z)‐amide diastereomers (ratio ≈︁ 1 : 2, respectively). All four vicinal proton‐proton coupling constants in each NCH2CH2C moiety were readily measured owing to effective chemical shift dispersion caused by the acetamido function. All vicinal coupling constants were also measured in the E. COSY 2D NMR spectrum. Comparison of the vicinal coupling constants involving sp2‐N piperidine ring protons in the (E,Z)‐amides and the corresponding values involving sp3‐N piperidine ring protons in morphine free base and hydrochloride N‐methyl diastereomers shows them to be similar. The R‐factor method was used to estimate a 54(1)° value for the NCH2CH2C dihedral angle in the sp2‐N piperidine ring for both solution‐state E,Z‐diasteromers. The corresponding dihedral angle within the sp3‐N piperidine ring in solid‐state (±)‐6‐desmethyl‐8‐deoxy‐α‐metazocine · HCl was found to be 53.8° by x‐ray crystallography. Both sp2 and sp3 N‐hybridrization seem to afford basically the same slightly flattened chair‐type conformations for the piperidine‐ring.
Conformational studies of caprylolactam
Authors: Borgen Gerd
Published: May 2005

The equilibrium mixture of the cis and trans isomers of caprylolactam (1‐azacyclononan‐2‐one), was studied by 1H and 13C NMR spectroscopy at various temperatures. The exchange between corresponding carbons in the two isomers in solution was studied by 2D NOE. Assignments were made for all 13C lines of the cis and trans isomers in CDCl3, CD3OD and C5D5N by 2D NMR. The conformations and conformational processes were studied by low‐temperature NMR. The trans isomer was shown to exist in at least two different conformations in solution. In addition to the high barrier interconversion between the cis and trans isomers, two different conformational processes were found for the trans isomer in the temperature range −140 to +60°C and one for the cis isomer. The conformational processes in solution are identified as (1) geminal 1H exchange in the cis and the trans isomers: for the cis isomer with a coalescence temperature of ca. −70°C a free energy of activation of 40 kJ mol−1 and for the trans isomer with a coalescence temperature of ca. +40°C a free energy of activation of 61 kJ mol−1; and (2) a low‐temperature process interconverting two trans conformations with a coalescence temperature of ca. −120°C and a free energy of activation of 29 kJ mol−1, observed in both the 1H and the 13C spectra.