排序方式: 共有46条查询结果,搜索用时 15 毫秒
31.
A. I. Vokin V. A. Lopyrev A. M. Shulunova T. N. Komarova V. K. Turchaninov 《Russian Chemical Bulletin》1997,46(4):834-836
The dependence of the energies of intramolecular charge-transfer electron transitions in 1,3,5-trimethyl-4-nitropyrazole,
4-nitropyrazole, and its anion on the dielectric and acidbase properties of solvents was analyzed. The dipole moments of these
species in the excited state are larger than those in the ground state. The nonspecific solvation is accomplished through
dipole-dipole interactions. 4-Nitropyrazole, which possesses acidic properties, is also solvated by the mechanism of hydrogen
bonding with the solvent, which acts as a base. The strength of the hydrogen bond increases on going from the ground to the
electron-excited state. The 4-nitropyrazole anion is a base, and its hydrogen bonds with the solvent are stronger in the ground
state. The mechanism of specific solvation of the molecule and the anion of 4-nitropyrazole during electronic excitation is
discussed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 867–869, April, 1997. 相似文献
32.
A. I. Vokin A. M. Shulunova T. N. Aksamentova G. V. Bozhenkov V. K. Turchaninov 《Russian Journal of General Chemistry》2006,76(4):596-614
Examination of the UV spectra of a large series of solvatochromic indicators of the general formula 1-X-4-NO2-C6H4 in aprotic solvents confirmed the proportionality between the dipole moments of these compounds in the ground (μg) and first electronically excited (1 A 1, μe) states: μe = r μμg. The coefficient r μ was determined by applying the equation of the Bakhshiev-Bilot-Kawski solvatochromism theory both to nonspecifically solvated molecules and to their H complexes with aprotic protophilic solvents. An anisotropy of the electron redistribution was revealed for low-symmetry 1-substituted 2,4-dinitrobenzenes. The r μ value obtained allowed the calculation of the Kamlet-Taft empirical solvatochromic parameter π* on the basis of generalized characteristics of the solvent. 相似文献
33.
34.
35.
36.
Murzina N. M. Vokin A. I. Fedorov S. V. Demenev A. P. Sobenina L. N. Mikhaleva A. I. 《Russian Journal of General Chemistry》2002,72(6):945-948
The effect of aprotic inert media on the conformational structure of 2-(2,2-dicyanovinyl-1-methylthio)-5-methylpyrrole was studied by UV, NMR, and IR spectroscopy. Chloroform and less polar solvents stabilize only one of the four conformers. In more polar media, there is a dynamic equilibrium between all the possible conformers of the title compound. The state of the equilibrium depends both on the solvent and on the temperature. 相似文献
37.
Krivoruchka I. G. Vokin A. I. Turchaninov V. K. 《Russian Journal of Organic Chemistry》2002,38(10):1456-1461
According to the results of HF/6-31G* and B3LYP/6-31G* nonempirical calculations, N-(4-methyl- 2-nitrophenyl)acetamide in the synperiplanar and antiperiplanar conformations gives stable complexes with protophilic solvents, which are stabilized by bifurcated (three-center) hydrogen bond. The complexes are characterized by (1) opposite variations of the interatomic distances and angles corresponding to intra- and intermolecular components of the bifurcated hydrogen bond, (2) extension of the intramolecular component and a more pronounced shortening of the intermolecular component with increase in the strength of the three-center H-complex, and (3) nonlinear and nonmonotonic relation between the NH stretching vibration frequency and the energy of complex formation. 相似文献
38.
Vokin A. I. Gavrilova G. A. Shulunova A. M. Krivoruchka I. G. Aksamentova T. N. Turchaninov V. K. 《Russian Journal of General Chemistry》2004,74(2):239-249
2-Nitrophenol and 2,4,6-trinitrophenol form with protophilic solvents complexes with a bifurcate (three-center) hydrogen bond. Their O-H stretching vibration frequencies nonlinearly and unsteadily vary with the H-bond acceptor ability of the medium, which is a spectroscopic evidence for three-center H-complex formation. 相似文献
39.
Ionization energies of four model compounds with known conformations,i.e., benzo-1,3-dioxole, 2-methoxyphenol, benzo-1,3-dioxole-5-carbaldehyde (piperonal), and 4-hydroxy-3-methoxybenzaldehyde, have been calculated by theab initio AM1 method, using the formalized scheme of configuration interactions. It has been demonstrated that this method is adequate for the study of photoelectronic spectra of methoxy(hydroxy)-substituted benzenes. The ionization energies of 1,2-dimethoxybenzene, 3,4-dimethoxybenzaldehyde, and 4-hydroxy-3,5-dimethoxybenzaldehyde have been calculated for various orientations of theo-methoxy(hydroxy) groups. It has been revealed that three first ionization potentials corresponding to the states with vacancies on the -MO depend on the torsion angle. It has been established by comparison of calculated and experimental ionization potentials that in gas the compounds with adjacent methoxy groups have one O-Me bond parallel with the plane of the benzene ring, while another group is nearly perpendicular to this plane. Conformations of the heavy-atom framework are planar for gaseous molecules with adjacent methoxy and hydroxy groups.For Part 7, see Ref. 1.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2365–2368, December, 1995. 相似文献
40.
T. N. Aksamentova I. G. Krivoruchka V. N. Elokhina A. I. Vokin V. A. Lopyrev V. K. Turchaninov 《Russian Chemical Bulletin》1999,48(11):2176-2177
The dipole moments of 3(5)-nitropyrazole, its methyl-substituted derivatives, and H-complexes with dioxane were measured experimentally
and estimated byab initio calculations (6-31G* basis set). Comparison of the experimental and calculated dipole moments suggests a shift of the tautomeric equilibrium toward
the 3-nitroisomer.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2202–2203, November, 1999. 相似文献