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21.
Zora M 《The Journal of organic chemistry》2005,70(15):6018-6026
Transition structures, energetics, and nucleus-independent chemical shifts (NICS) for Cope rearrangements of cis-2,3-divinylaziridine (1N), cis-2,3-divinyloxirane (1O), cis-2,3-divinylphosphirane (1P), and cis-2,3-divinylthiirane (1S), leading to 4,5-dihydro-1H-azepine (3N), 4,5-dihydrooxepine (3O), 4,5-dihydro-1H-phosphepine (3P), and 4,5-dihydrothiepine (3S), respectively, are reported at the (U)B3LYP/6-31G level and compared to those of cis-1,2-divinylcyclopropane (1C). The minimum energy path for all rearrangements proceeds through an endo-boatlike, aromatic transition structure. The predicted activation barriers increase in the order of 1C < 1N < 1O < 1P < 1S, which agrees qualitatively with the decreasing ring strain order of reference compounds (cyclopropane > aziridine > oxirane > phosphirane > thiirane). The exothermicities for these rearrangements decrease in the order of 1N > 1O > 1C > 1P > 1S. If the place of 1C in this sequence is ignored, the decreasing reaction exothermicity order correlates well with the increasing activation barrier order and with decreasing strain order of reference compounds. NICS values calculated for transition structures are typical of highly aromatic transition structures of thermally allowed pericyclic reactions. 相似文献
22.
Perjessy A Fabian WM Parik P Ludwig M Loos D Sustekova Z 《Molecules (Basel, Switzerland)》2004,9(4):213-222
The wavenumbers of the IR absorption bands of the C=O, S=O and N-H stretching vibrations for a series of p-substituted N-phenylsulfonylbenzamides were measured in trichloromethane. The bond orders, Mulliken charges, charge densities and heats of formation were calculated using the PM3 method. Fifty significant mutual mono parameter (MP) and six dual parameter (DP) correlations were found for the IR spectral, theoretical structural data, substituent constants and previously reported dissociation constants in five polar organic solvents. The transmission of the substituent effects has been discussed and the solvent effect on the slopes of some linear correlations was evaluated using different solvent parameters. The results showed that the factors describing the electronic structure and controlling the dissociation equilibrium and the IR spectra properties of p-substituted N-phenylsulfonylbenzamides must be the same. 相似文献
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Boris-Marko Kukovec Zora Popović Gordana Pavlović Marijana Vinković Dražen Vikić-Topić 《Polyhedron》2008
Cadmium(II) complexes of 3-hydroxypicolinic acid, namely [CdI(3-OHpic)(3-OHpicH)(H2O)]2 (1), [Cd(3-OHpic)2(H2O)2] (2) and [Cd(3-OHpic)2]n (3) were prepared and characterized by spectroscopic methods (IR, NMR) and their molecular and crystal structures were determined by X-ray crystal structure analysis. Complexes 1 and 2 were prepared in similar reaction conditions using different cadmium(II) salts: cadmium(II) iodide and cadmium(II) acetate dihydrate, respectively, while 3 was prepared by recrystallization of 2 from N,N-dimethylformamide solution. Various coordination modes of 3-OHpicH in 1–3 were established in the solid state: bidentate N,O-chelated mode in 1 and 2, monodentate mode through the carboxylate O atom from zwitterionic ligand in 1 and bidentate N,O-chelated and bridging mode in 3. In the DMF solution of all prepared complexes, only monodentate mode of 3-OHpicH binding to cadmium(II) through the carboxylate O atom was established by 1H, 13C, 15N and 113Cd NMR spectroscopy. 相似文献
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Ivica ?ilovi Dubravka Matkovi‐alogovi Zora Popovi Vibor Roje 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(7):m351-m352
In the crystal structure of the title compound, [Zn(C18H14NO2)2]·C2H6O, the Zn atom displays a highly distorted octahedral coordination involving the O and N atoms of two molecules of the Schiff base 1‐[N‐(2‐methoxyphenyl)iminomethyl]naphthalen‐2(1H)‐one, which acts as an O,N,O′‐tridentate ligand. The ethanol molecule is bound to the methoxy group of one ligand molecule via a hydrogen bond. 相似文献
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Gordana Mili? Bajram Jakupi Shinji Tokonami Radmila Trajkovi? Tetsuo Ishikawa Igor ?elikovi? Predrag Uji? Olivera ?ukni? Ilia Yarmoshenko Katica Kosanovi? Feriz Adrovi? Sarat K. Sahoo Nenad Veselinovi? Zora S. ?uni? 《Radiation measurements》2010,45(1):118-121
This paper deals with the results of indoor radon and thoron concentrations and exposure doses obtained for 63 dwellings out of the 14 rural communities of Central Kosovo, North Kosovo and Prizren region. These research activities are part of overall radiological research that has systematically been carried out since 1986, particularly in Kosovo and Metohija regions. Passive radon/thoron discriminative detectors, exposed for three months, were used. The arithmetic mean concentrations of indoor radon and thoron are CRn = 429 Bq m?3 CTn = 85 Bq m?3. 相似文献
28.
Decio Levi Miguel A. Rodríguez Zora Thomova 《Journal of Nonlinear Mathematical Physics》2019,26(2):281-293
Nonlinear PDE’s having given conditional symmetries are constructed. They are obtained starting from the invariants of the conditional symmetry generator and imposing the extra condition given by the characteristic of the symmetry. Series of examples starting from the Boussinesq and including non-autonomous Korteweg–de Vries like equations are given to show and clarify the methodology introduced. 相似文献
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Dubravka Matkovi‐alogovi Zora Popovi Vesna Trali‐Kulenovi Livio Racan Grace Karminski‐Zamola 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o190-o191
The title compound, C8H8N3S+·Cl−·2H2O, has been synthesized and characterized both spectroscopically and structurally. The structure consists of 1,3‐benzothiazole‐6‐carboxamidinium cations, chloride anions and water molecules, all interconnected by hydrogen bonds into a three‐dimensional network. The 1,3‐benzothiazole moiety is inclined to the 6‐amidine group by 36.71 (9)°. 相似文献
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Zora Popovi Gordana Pavlovi Boris‐Marko Kukovec 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):m181-m183
The title compound, [Cu(C9H5N2O3)2(C2H6OS)2], consists of octahedrally coordinated CuII ions, with the 3‐oxo‐3,4‐dihydroquinoxaline‐2‐carboxylate ligands acting in a bidentate manner [Cu—O = 1.9116 (14) Å and Cu—N = 2.1191 (16) Å] and a dimethyl sulfoxide (DMSO) molecule coordinated axially via the O atom [Cu—O = 2.336 (5) and 2.418 (7) Å for the major and minor disorder components, respectively]. The whole DMSO molecule exhibits positional disorder [0.62 (1):0.38 (1)]. The octahedron around the CuII atom, which lies on an inversion centre, is elongated in the axial direction, exhibiting a Jahn–Teller effect. The ligand exhibits tautomerization by H‐atom transfer from the hydroxyl group at position 3 to the N atom at position 4 of the quinoxaline ring of the ligand. The complex molecules are linked through an intermolecular N—H...O hydrogen bond [N...O = 2.838 (2) Å] formed between the quinoxaline NH group and a carboxylate O atom, and by a weak intermolecular C—H...O hydrogen bond [3.392 (11) Å] formed between a carboxylate O atom and a methyl C atom of the DMSO ligand. There is a weak intramolecular C—H...O hydrogen bond [3.065 (3) Å] formed between a benzene CH group and a carboxylate O atom. 相似文献