bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereochemical studies‐XIV: Cyclic amino alcohols and related compounds‐VII
Authors: Sohár P. , Bernáth G. 
Published: May 2005

Abstract1,3‐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

AbstractDans 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

Abstract13C 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.
The use of chiral solvents to distinguish meso from d or 1 diastereoisomers
Authors: Abraham R. J. , Siverns T. M. 
Published: May 2005

AbstractThe 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

AbstractUne 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

AbstractDie 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

AbstractThe 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

AbstractL'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

AbstractDelocalisation 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

AbstractThe 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

AbstractChemical 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

AbstractThe 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

Abstract1H 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

AbstractL'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

AbstractCarbon‐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

AbstractThe 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

AbstractThe 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

AbstractDie 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

AbstractSome 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

AbstractA 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

AbstractThe 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

AbstractRotation 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

AbstractOne‐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

AbstractZoapatanol 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

AbstractThe 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

AbstractApplication 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

AbstractThe 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

AbstractCarbon‐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

AbstractAssignments 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

AbstractAll 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.
A novel use of cobalt(III) meso‐tetraphenylporphyrin as a chiral shift reagent
Authors: Abraham Raymond J. , Plant James , Bedford Geoffrey R. , Wright Brian 
Published: May 2005

AbstractThe NMR spectra of the diastereomeric complexes formed by the coordination of nitrogenous enantiomeric bases with cobalt(III) meso‐tetraphenylporphyrin (CoTPP) allow the immediate differentiation of these complexes. The spectra are interpreted on the basis of symmetry (RR and SS) and pseudo‐chirality (RS and SR) considerations. The effects are observed in both the proton and carbon spectra and the complexes are stable in both CDCl3 and DMSO‐d4 solution. This technique, in principle, allows the ready determination of the optical purity of multifunctional ligands.
Regeneration of the antennules in the Australian freshwater crayfish, Cherax destructor
Authors: Sandeman D. C. , Luff Susan E. 
Published: May 2005

AbstractRemoval of one eye from the Australian freshwater crayfish, Cherax destructor, results in the growth of a heteromorph appendage which re‐ sembles the outer flagellum of the antennule. The heteromorph is con‐ sistently uniramous.Transplanting part of the animal's own antennule into the eye stalk after removal of the ipsilateral eye results in a significant number of biramous appendages being developed in the eye socket. Biramous appendages when they possess fully differentiated hairs, can be identified as being the external and internal flagella of the antennule. Triramous appendages were never observed.The specificity of the antennular sensilla was tested in relation to the cleaning behavior released by stimulating them electrically. Sensilla on the external flagellum of the antennule produce depression of the antennule and cleaning using the maxillipeds. This behavior is also produced when the heteromorph appendage is stimulated although in this case it is misdirected. Stimulation of the hairs in the eye socket releases cleaning of the eye socket with the 2nd and 3rd walking legs. Eye socket cleaning is not released by stimulation of the heteromorph indicating that the antennular sensilla retain their specificity in relation to the cleaning behavior released.Removal of the antennule results in the ipsilateral olfactory lobe becoming smaller than the contralateral lobe. No change was observed in the accessory lobes.
Cyclic AMP and amine effects on phosphorylation of specific protein in abdominal ganglion of Aplysia californica; localization and kinetic analysis
Authors: Levitan Irwin B. , Madsen Carol J. , Barondes Samuel H. 
Published: May 2005

AbstractIncubation of abdominal ganglia, obtained from Aplysia californica weighing 120‐‐260 g, with octopamine or serotonin led to marked increases in cAMP (cyclic adenosine 3′,5′‐monophosphate) levels after 10 min of incubation; these increases were blocked by phentolamine and methysergide, respectively. Incubation for 21 hr with octopamine also produced an elevation in cAMP levels but prolonged incubation with serotonin did not. Both these amines increased incorporation of 32P or 33P into a specific protein with apparent molecular weight of 118,000, upon incubation with the ganglion for 21 hr. The selective effect on this phosphoprotein was previously shown to be blocked by phentolamine (for octopamine effect) or methysergide (for serotonin effect) and could be mimicked by addition of dibutyryl cAMP to the medium.Incubation for more than 15 hr was required to generate a stable phosphoprotein pattern in which 5 phosphoprotein peaks could be reliably identified on polyacrylamide gels. With shorter incubations there was marked variability between ganglia with respect to the proteins which incorporated radioactive phosphate. The dibutyryl cAMP effect on phosphorylation of specific protein could not be demonstrated with incubations shorter than 15 hr.The specific effect on the phosphoprotein with molecular weight 118,000 was not observed in a number of large identified cells removed from the ganglion after 21 hr of incubation with radioactive phosphate and dibutyryl cAMP. The effect was also not observed in connective nerves and the bag cell clusters, but was consistently present in that portion of the ganglion remaining after these dissections. Upon subcellular fractionation the phenomenon was not observed in a crude nuclear fraction but was consistently present in a crude mitochondrial fraction. All these results are consistent with the possibility that the change in phosphoprotein metabolism produced by dibutryl cAMP may be localized in the neuropil, which contains all the synaptic contacts in this ganglion.