共查询到20条相似文献,搜索用时 15 毫秒
1.
The solvent/solute interactions of four isomeric benzothienopyridines (parent compounds) have been investigated by 1H n.m.r. A close study of the second-order spectra shows: (i) a preferential orientation of the solvent molecules (acetone) surrounding the pyridine ring; (ii) large variations in the coupling constants of the benzenic part of the benzothienopyridines as a function of the solvent; (iii) a preferential interaction of the pyridine ring in collision complexes with benzene. These results can be applied to a comparative study of the complexes between DNA base pairs and intercalating derivatives. 相似文献
2.
Lanthanide-induced shifts provide a convenient method for total assignment of 1H nmr spectra of benzothienopyridines and determination of the substitution sites. Evidence of the effect of steric hindrance around the site of complex formation on the spatial localization of the lanthanide ion is given. 相似文献
3.
Phosphorus chemical shifts have been evaluated by means of the perturbation theory using CNDO/S wave functions in phosphine, phosphite, phosphonate and phosphate derivatives. The necessity of introducing 3d orbitals of phosphorus and of using Zeff3d as an adjustable parameter for each family of compounds is shown. Calculated values agree with experimental ones. 相似文献
4.
Pierre Maroni Louis Cazaux Jean-Pierre Gorrichon Pierre Tisnes Jean-Grard Wolf 《Magnetic resonance in chemistry : MRC》1973,5(11):517-522
In order to calculate empirically proton chemical shifts in methyl 1,3-dioxans, the basic values for each proton of 1,3-dioxan itself are estimated. Then, using methyl derivatives in the chair conformation, the Δδ primary effects of methyl groups in any position are given. Modifications take place in molecules with butane gauche interactions and these secondary effects are evaluated. Analogous Δδ in both the cyclohexane and dioxane series are related to similar cyclic geometry. The presence of oxygen atoms however, introduces important discrepancies. 相似文献
5.
P. Maroni L. Cazaux J. P. Gorrichon P. Tisnes J. G. Wolf 《Magnetic resonance in chemistry : MRC》1973,5(11):523-528
The empirical calculation of chemical shifts of methyl-1,3-dioxans leads to consistent results. Deviations from the experimental value are correlated with ring deformation. This method is applied to 4 or 6-ethyl, -isopropyl and tertiary butyl-1,3-dioxans. With no substituent at C5, the 4-tertiary butyl group causes no more deformation than at the 2 or 5 position. Interactions of this group with one or two methyl groups at C5 are examined. 相似文献
6.
Measurements of the 13C chemical shifts of monosubstituted cyclopropanes (C3H5X, X = CH3, Br, ? C?CH) enabled us to determine the direct additivity parameters which depend solely on the nature of the substituent. In the case of polysubstituted derivatives, complementary effects due to pairwise contributions of the substituents superpose upon the direct effects. A systematic study of cyclopropanes polysubstituted by bromine atoms, and methyl and ethynyl groups shows these different contributions and permits us to propose a simple interpretation for the majority of cases. Pairwise interaction has been ascribed either to electron transfer or to symmetric or dissymmetric steric interactions between the different substituents, as is shown by the comparison of the theoretical with the experimental shift values. 相似文献
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8.
The study of this series of compounds proves the usefulness of shift increments for the identification of proton and carbon-13 resonances. These increments may be obtained as a first approximation from the study of the monosubstituted derivatives or by comparison with the corresponding benzene derivatives. 相似文献
9.
Various complexes (RnMO·BF3) of boron trifluoride with sulphoxides, aminoxides, phosphinoxides and arsinoxides have been prepared and investigated using proton, fluorine (at variable temperature) boron and phosphorus resonance. A comparison with similar adducts containing a co-ordinative O? B bond is presented. 相似文献
10.
A. Bobst 《Helvetica chimica acta》1967,50(6):1480-1491
HMO and semi-empirical SCF calculations on pterine systems of biochemical interest have been performed. The most basic center of each molecule has been determined by correlating the perturbation effect on the transition energy and the spectroscopic data. Additional calculations attempt to show why the redox-system which interfers in hydroxylation reactions consists of 5,6,7,8-tetrahydropterine and a quinoidic form. Finally the formation of radicals in the oxidation step of hydrogenated pterines is discussed. 相似文献
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12.
Jean-Pierre Vidal Jean-Pierre Girard Jean-Claude Rossi Jean-Pierre Chapat Robert Granger 《Magnetic resonance in chemistry : MRC》1974,6(10):522-524
The configuration of conformationally homogeneous epoxides in trans bicyclo-(n.3.0) alkanes is established by progressive complexation with Eu(dpm)3. The examples described demonstrate the importance of this method which is superior to all the other physicochemical methods already used to determine the cyclopentane epoxide configuration. 相似文献
13.
Reaction of 2-t-butylthiobenzaldehyde with N-(2-dialkylaminoethyl)-cyanacetamides followed by heating of the resulting 3-(2-t-butylthiophenyl)-2-cyanoacrylamides in polyphosphoric acid leads to the formation of 3-carboxamido-2-imino-2H-benzo[b][l]thiopyrann intermediates which afford thiocoumarins on hydrolysis. The authors postulate the intermediate formation of a thiophenate ion by an electronic mechanism involving six centers. 相似文献
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15.
The Hantzsch thiazole synthesis from α-haloketones and thioamides, proceeds via intermediates that can be isolated under certain conditions. These have been identified, mainly by nmr spectroscopy, as thioimidate derivatives. The chain or cyclic structures of these compounds depend upon the nature of the substituents. Their dehydration gives together with the expected thiazole, secondary products which have also been isolated and identified as α-mercaptoketones and α-ketothiolesters. 相似文献
16.
J. P. Moliton C. Boutinaud J. C. Vareille J. L. Decossas J. L. Teyssier B. Delaunay 《Journal of Polymer Science.Polymer Physics》1982,20(7):1313-1326
The kinetic interpretation of the damage produced by heavy ions (Kr and Cl from 1 MeV/amu) and γ radiation in cellulose triacetate leads to an exponential dependence on the ion fluence. A comparison of the fading effect produced by heavy ions and γ rays shows that the heavy ions, unlike γ rays, cause irreversible damage. Finally, a nonlinear dependence on the flux of ions and γ rays is found in the kinetics of radiation damage. This result is contrary to the usual assumption that heavy-ion flux, like γ-ray flux, is additive, at least for the fluxes of 109?2 × 1010 ions/cm2s and dose rates of 103–104 Gy/h used in this work. 相似文献
17.
G. Gacel M. C. Fourni-Zaluski B. P. Roques 《Magnetic resonance in chemistry : MRC》1976,8(10):525-529
The preferential conformation of 3-formyl and 3-acetyl furans, thiophenes, pyrroles and some 3-acyl furans are determined by use of simulated lanthanide induced shifts. The ratios of the different rotamers are similar to those obtained by other n.m.r. methods. This result shows that the complexation does not induce any change in the conformational preference, and thus validates the use of the foregoing method for the conformational analysis of heteroaromatic aldehydes and ketones. In the three heterocycles studied, the carbonyl group shows an X? O trans preferential conformation for the aldehydes and a mixed equilibrium in the case of acetyl groups. 相似文献
18.
19.
J. Bertran J. J. Dannenberg R. Leute C. Ponce O. Chalvet R. Daudel 《Theoretical chemistry accounts》1970,17(4):249-258
Résumé En suivant la méthode dite du «cycle de Förster», on détermine au moyen des méthodes de la Chimie Quantique les valeurs des P
K
des états excités singulet et triplet de la -naphtylamine et du -naphtol. Dans le cas de cette dernière molécule, on propose un modèle pour décrire l'ion -naphtolate intervenant dans les équilibres classiques étudiés.
J. J. Dannenberg tient à remercier le National Institute of General Medical Science de l'attribution d'une bourse post-doctorale. 相似文献
Calculation of the P k values of the first excited singlet and triplet states of -naphthol and -naphthylamine
On the basis of the cycle of Förster the P K values of the excited singlet and triplet states of -naphthylamine and -naphthol are determined. In the case of the latter molecule a model is proposed in order to calculate the anion of -naphthol, which is found in classical equilibriums.
Zusammenfassung Ausgehend vom Försterzyklus werden auf quantenmechanische Weise die P K -Werte der angeregten Singulett- und Triplettzustände des -Naphthylamins und des -Naphthols bestimmt. Im Fall des letzteren Moleküls wird ein Modell zu Berechnung des -Naphtholations, das bei dem untersuchten Gleichgewicht auftritt, vorgeschlagen.
J. J. Dannenberg tient à remercier le National Institute of General Medical Science de l'attribution d'une bourse post-doctorale. 相似文献
20.
Starting from 3-bromo-, 1-iodo- and 4-iodo-9-oxo-fluorene three symmetrical bifluorenonyls and the corresponding hydrocarbons 3,3′-, 1,1′- and 4,4′-bifluorenyls are prepared. An attempt to obtain the non-symmetrical 1,2′-bifluorenyl is also described. 相似文献