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131.
M. R. Darafsheh Y. Farjami A. R. Ashrafi M. Hamadanian 《Journal of mathematical chemistry》2007,41(3):315-326
The non-rigid molecule group theory (NRG) in which the dynamical symmetry operations are defined as physical operations is
a new field in chemistry. Smeyers and Villa computed the r-NRG of the triple equivalent methyl rotation in pyramidal trimethylamine
with inversion and proved that the r-NRG of this molecule is a group of order 648, containing a subgroup of order 324 without
inversions (see J. Math. Chem. 28(4) (2000) 377–388). In this work, a computational method is described, by means of which it is possible to calculate the
symmetry group of molecules. We study the full non-rigid group (f-NRG) of Sponge and Pina molecules with C
2 and C
i point groups, respectively. It proved that these are groups of order 162 and 13122 with 54 and 3240 conjugacy classes, respectively.
The character tables of these groups are also computed. 相似文献
132.
Joanna Gajewiak 《Tetrahedron letters》2006,47(43):7607-7609
Lysophosphatidic acid (LPA) and phosphatidic acid (PA) are potent bioactive lipid mediators of signal transduction and are inactivated by phosphatases. To obtain receptor-isoform selective ligands with neutral phosphomimetic head groups, we performed the stereoselective synthesis of LPA and PA analogues with trifluoromethanesulfonamide and trifluoromethanesulfonamidoxy moieties replacing the phosphomonoester. 相似文献
133.
Production of submicron-sized multihollow polymer particles by alkali/cooling method 总被引:5,自引:0,他引:5
Submicron-sized styrene-methacrylic acid copolymer particles, which were produced by emulsion copolymerization, were changed to those having multihollow structure by treating stepwise the emulsion as follows. First alkali treatment was carried out at higher temperature than the glass transition temperature and subsequently the emulsion was cooled by keeping it at room temperature. This was named alkali/cooling method. The effects of methacrylic acid content, pH, time and temperature in the alkali treatment on the formation of multihollow structure were clarified.Part CLV of the series Studies on suspension and emulsion 相似文献
134.
A. M. Churakov O. Yu. Smirnov S. L. Ioffe Yu. A. Strelenko V. A. Tartakovsky 《Russian Chemical Bulletin》1994,43(9):1532-1535
2-(tert-Butyl-NNO-azoxy)aniline was prepared by selective reduction of 2-(tert-butyl-NNO-azoxy)nitrobenzene. Its bromination yielded the correspondingpara-bromo- andortho, para-dibromoanilines (3a,b).meta-Bromoanilines (6a,b) were synthesized by selective replacement of theortho-bromine atoms in ortho,para-bromo(tert-butylazoxy)benzenes (5a,b) by ammonia in toluene under pressure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1620–1623, September, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-18461). 相似文献
135.
O. N. Litvinenko A. N. Kuznetsov A. V. Olenev B. A. Popovkin 《Russian Chemical Bulletin》2007,56(10):1945-1947
Three new mixed tellurides of nickel and group 13–14 metals Ni3−δMTe2 (M = Sn, In, Ga) were prepared by high-temperature ampoule synthesis and studied by powder X-ray diffraction analysis. The
compound Ni3−δSnTe2 was also studied by single crystal X-ray diffraction analysis. The structural model of this phase and two analogs was described
as consisting of layers with nickel-main group metal bonds confined from the above by tellurium atoms. The van der Waals gap
formed through contacts between the tellurium atoms of neighboring layers is partially occupied by nickel atoms.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1879–1881, October, 2007. 相似文献
136.
邢凤鸣 《中国科学B辑(英文版)》1991,(11)
It is considered that the early Jinning period granitoids from southern Anhui Province belong to the continental crust transformation (S) type and have their own characteristics which are different from those for general continental crust transformation type granitoids. They were formed at the early stage of the late Proterozoic era when that region was at an island-arc stage of the continental margin environment. By that time the continental crust was just formed and had a nature of juvenile crust. It is this juvenile crust that determined a series of characteristics of that type granitoids and made them a relatively independent rock type. They are the products formed by the continental crust in a certain stage of development. 相似文献
137.
L. A. Sviridova G. A. Golubeva S. V. Shorunov 《Chemistry of Heterocyclic Compounds》2006,42(9):1185-1189
3-Nitromethylpyrazolidine reacts with derivatives of unsaturated acids and reducing agents with the formation of polyfunctional
compounds of the pyrazolidine nucleus.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1365–1369, September, 2006. 相似文献
138.
Chen-Hui Li Wen-Wei Lai Keh Ying Hsu Teh-Chou Chang 《Journal of polymer science. Part A, Polymer chemistry》1993,31(1):27-34
A series of semi-aromatic poly(ether-ester)s containing cinnamic group was prepared from 4,4′-diacrylic acid-α,ω-phenoxyalkanes with diols in the presence of diphenylchlorophosphate (DPCP) and pyridine as a catalyst and solvent. The phase behavior of these polymers was studied by differential scanning calorimetry (DSC), optical polarizing microscopy equipped with a heating stage, and wide-angle x-ray diffraction (WAXD). All of the poly(ether-ester)s, except P3 , show nematic or smectic thermotropic liquid crystalline behaviour under optical polarizing microscopic observation. These polymers can undergo photocrosslinking reaction upon heating, as examined by IR, solubility, and DSC analysis. © 1993 John Wiley & Sons, Inc. 相似文献
139.
Boris A. Trofimov Ol’ga V. Petrova Lyubov’ N. Sobenina Igor’ A. Ushakov Al’bina I. Mikhaleva Yurii Yu. Rusakov Leonid B. Krivdin 《Tetrahedron letters》2006,47(22):3645-3648
Functionalized pyrrolic enols, 2-(2,2-dicyano-1-hydroxyethenyl)-1-methylpyrroles, synthesized from 2-ethenylpyrroles by a nucleophilic SEt-OH exchange, upon heating (75-142 °C) are readily rearranged to their 3-isomers in near to quantitative yield. The inter or intramolecular auto-protonation of a pyrrole ring by the acidic enol hydroxyl to form a mesomeric pyrrolium cation or zwitterion is suggested to be a key step in the rearrangement. 相似文献
140.
We prove Borel summability of the perturbation series for the dielectric constant and the free energy density for the hierarchical ()4 lattice model. Our methods are based on nonperturbative renormalization group analysis of the model.On leave from the Department of Mathematical Methods of Physics, Warsaw University, Poland.Supported in part by the Center for Interdisciplinary Research, Bielefeld University, Germany. 相似文献