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791.
A new mechanism is suggested for the anionic polymerization of isoprene. The key moment of this mechanism is thermal electron excitation of the complex of a living polymer with a monomer to the low lying S1 (T1) state involving a charge (electron) and (Li+) cation transfer from the terminal unit to the monomer molecule. It is stated that the probability of chemical bonding depends on the spin density on the radical centers of reactant molecules and on the geometry of the reaction complex. The semiempirical AM1 and ab initio 6-31G* quantum-chemical calculations revealed strong interaction for the ground electronic state of the complex (5-10 kcal/mole) and low energies of the excited triplet levels (<10 kcal/mole). 相似文献
792.
The title substances, derivatives of two new heterocyclic ring systems, were synthesized by intramolecular cyclisations of diazonium compounds, prepared from derivatives of 2-amino-thiophene-3-carboxamide and of 2-amino-benzo[b]thiophene-3-carboxamide. By-reactions and substitution reactions are mentioned. 相似文献
793.
I. F. Makarevich 《Chemistry of Natural Compounds》1971,7(1):36-39
Summary Another two cardiac glycosides have been isolated from the seeds ofCheiranthus allioni Hort. It has also been established that in cheiroside A the D-glucose is attached at C4 of the D-fucose. The second glycoside, which we have called glucoalliside, is new, and has the structure of bipindogenin 3-O-[O--D-glucopyranosyl-(1 » 4)--L-glucomethylopyranoside].For Communication V, see [2].Khar'kov Chemical and Pharmaceutical Scientific-Research Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 40–45, January, 1971. 相似文献
794.
The reactions between rubidium carbonate and vanadium pentoxide were performed at different high temperatures. Four reaction products of the compositions: I. Rb2O · V2O5; II. 2 Rb2O · V2O5; III. 3 Rb2O · V2O5; and IV. Rb2O · 4 V2O5 were obtained. According to the determination of Rb and the X-ray powder photographs of the products the existence of rubidium metavanadate (RbVO3) and rubidium pyrovanadate (Rb4V2O7) was confirmed. On the other hand, the preparation of a pure rubidium orthovanadate (Rb3VO4) and rubidium tetravanadate (Rb2O · 4 V2O5) was not successful. The diffraction pattern of Rb2O · V2O5 obeys hexagonal indexing with lattice dimensions a = 7.347 and c = 13.608 Å. 相似文献
795.
K. Dimroth A. Berndt F. Br A. Schweig R. Volland 《Angewandte Chemie (International ed. in English)》1967,6(1):34-40
The distribution of the unpaired electron over the oxygen and the 24 carbon atoms in the free 2,4,6-triphenylphenoxy radical was determined by electron spin resonance spectroscopy and quantum-mechanical approximation methods. The hyperfine splitting was evaluated with the aid of the spectra of triphenylphenoxyls deuterated in some or all of the substituent phenyl groups. The results of the quantum-mechanical approximations were checked by recording the ESR spectra of triphenylphenoxyls labeled with 13C in positions 1,2,3, or 4 of the central ring. The spin density distribution permits a first discussion of the 17O-coupling constants of correspondingly labeled triphenylphenoxyl and other organic free radicals. 相似文献
796.
797.
Strong adhesion and smooth conductive surface via graft polymerization of aniline on a modified glass fiber surface 总被引:1,自引:0,他引:1
The goal of this paper is to prepare surface-conductive glass fibers. The fibers were first hydroxylated, after which they were reacted with 3-bromopropyltrichlorosilane to form a bromopropylsilane monolayer, which was further reacted with aniline to substitute the bromine atoms. The surface-bound aniline molecules were used as active sites for the graft polymerization of polyaniline (PANI). The composition, structure and the morphology of the modified glass fiber surface were examined by X-ray photoelectron spectroscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. The method generated a smooth and homogenous thin layer of PANI on the surface of the glass fiber with a surface conductivity of about 6 S/cm, hence larger than the usual value ( approximately 1 S/cm) of the bulk polyaniline. 相似文献
798.
F. M. Bobonich G. Forbek Yu. G. Voloshina 《Theoretical and Experimental Chemistry》1994,29(2):120-123
A method is proposed for calculating the heat of immersion of zeolites in water from data on the composition and density of the zeolite framework. The phenomenon of localization of some of the zeolite cations in the unhydrated crystallographic positions is explained. For ferrisilicates with the ZSM-5 structure, the fraction of iron atoms in the framework has been estimated from data on the energy of hydration.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 2, pp. 174–179, March–April, 1993. 相似文献
799.
S. N. Karyagin V. F. Kiselev G. S. Plotnikov Yu. D. Fomin 《Theoretical and Experimental Chemistry》1990,25(5):504-509
Electrophysical methods and ESR measurements have been used to investigate the changes, photosensitized by molecules of rhodamine B (RB), in the charge states of electron traps created by molecules of p-benzoquinone (pBQ) in the Ge/GeO2 system. The results obtained in studying the quenching of fluorescence of RB molecules indicate that the photodestruction of electron traps is due to transfer of electronic excitation energy traps is due to transfer of electronic oxidation energy from the RB molecules to charged complexes formed upon adsorption of the pBQ. In order to select optimal conditions for recharging of such complexes, a study has been made of the relationship between the relative change in ESR signal and the concentration of adsorbed RB molecules.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 545–550, September–October, 1989. 相似文献
800.
Conclusions The esterification of amido- and ester-amidophosphites with 1-(2-thienyl)-2,2,2-trichloroethanol gave the l-(2-thienyl)-2,2,2-trichloroethyl dialkyl- and 1-(2-thienyl)-2,2,2-trichloroethyl alkylamidophosphites, which easily add sulfur or are oxidized to the corresponding thiophosphates and phosphates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 182–187, January, 1981. 相似文献