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1.
The hydrolysis of 1,2-dichlorotetramethyldisilane was studied at different temperatures. At reduced temperatures, the hydrolysis
gave permethylcyclo(oxadisilanes) [(Me2Si)2O]n (n = 2 and 3) and α,ω-dihydroxypermethyloligo(oxadisilanes) HO[(SiMe2)2O]mH (m = 1–5). The formation of the latter was proved by the GC-MS method.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 722–724, April, 2006. 相似文献
2.
Fully relativistic, four-component Dirac–Fock calculations and quasirelativistic pseudopotential calculations at different
ab initio levels are used to study the bonding trends among the naked, triatomic [OAnO]
q+
groups or the oxyfluorides [AnO
n
F
m
]
q
with f
0 configurations. The triatomic f
0 series is suggested to range from the bent ThO2 via the linear OPaO+ to at least NpO2
3+, a possible new gas-phase species. The neutral oxyfluoride molecules include the experimentally unknown NpO2F3 and PuO2F4. The latter is a candidate for the so far unknown oxidation state Pu(VIII), which is found to lie considerably above Pu(VI),
but to be locally stable. Their all-oxygen isoelectronic analogues are NpO5
3−, known in the solid state, and the unknown PuO6
4−. Further possible candidates for Pu(VIII) are PuO4(D
4h
) and the cube-shaped PuF8(O
h
). Isoelectronic UF8
2− is calculated to be D
4d
, in agreement with experiment.
Received: 18 May 2001 / Accepted: 21 June 2001 / Published online: 11 October 2001 相似文献
3.
4.
G. Kh. Khisamutdinov G. G. Rozantsev V. I. Slovetsky A. A. Fainzilberg 《Russian Chemical Bulletin》1998,47(8):1605-1606
Difluoroamine does not react with tetranitromethane and fluoro-, chloro-, and bromotrinitromethanes in DMF and in acidic media
(CF3COOH, ClSO3H, FSO3H, and oleum), but reacts with α-fluoro- and α-(difluoroamino)-α,α-dinitrotoluenes to give substitution products of the difluoroamino
group for both the nitro groups,viz., PhC(NF2)2F and PhC(NF2)3, respectively.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1647–1649, August, 1998. 相似文献
5.
W. A. de Jong R. J. Harrison J. A. Nichols D. A. Dixon 《Theoretical chemistry accounts》2001,107(1):22-26
A complete set of fully-relativistic benchmark results for the bond lengths and vibrational frequencies of uranyl at various
levels of correlation treatment are presented. It is shown that the relativistic and correlation effects are of the same magnitude
and should be treated on an equal footing. Results of uranyl calculations using various relativistic effective core potentials
(RECP) are presented. Appropriate choices for RECPs for use in density functional theory (DFT) calculations in the local density
approximation (LDA) and with the gradient-corrected B3LYP exchange-correlation functional are discussed. The conclusion is
reached that small-core RECPs need to be used and that the best results as compared to the benchmark values are obtained by
using a DFT functional that includes some fraction of Hartree-Fock Exchange.
Received: 18 May 2001 / Accepted: 25 July 2001 / Published online: 30 October 2001 相似文献
6.
W. Li M. Wang Z. H. Li X. F. Shang H. Wang Y. W. Wang Y. B. Xu 《Russian Journal of Electrochemistry》2007,43(11):1279-1283
The lithium-ion-conducting inorganic solid electrolytes in the oxide systems Li2O-SiO2-P2O5 and Li2O-TiO2-SiO2-P2O5 were prepared by the solid-state reaction, and the electrolyte pellet made by cold-pressing method had diameter of 13 mm
and was about 1 mm thick. Phase identification and surface morphology of the products were carried out by X-ray diffraction
and scanning electron microscopy. Ionic conductivity of the pellets was investigated through ac impedance. The results show
that the adding of other cations can improve the ionic conductivity of the solid electrolyte, and the sintering temperature
and duration can influence the ionic conductivity. The maximum ionic conductivity in the samples is 9.9 × 10−4 S/cm in the Li2O-TiO2-SiO2-P2O5 system.
Original Russian Text ? W. Li, M. Wang, Z.H. Li, X.F. Shang, H. Wang, Y.W. Wang, Y.B. Xu, 2007, published in Elektrokhimiya,
2007, Vol. 43, No. 11, pp. 1341–1345. 相似文献
7.
The electron affinities of Ti, V, Cr, Fe, Co, Ni, and Cu are computed using the density function theory and CCSD(T) approaches.
Overall the CCSD(T) approach yields the best results. For this property, the B3LYP, BLYP, and BP86 functionals perform better
than the BPW91, PBEPBE, and PBE1PBE ones. The accuracy of all the methods is higher if the number of 3delectrons is the same in the neutral atom and the anion. This is especially true for the density functional theory methods.
Received: 23 January 2002 / Accepted: 1 April 2002 / Published online: 24 June 2002 相似文献
8.
Coupled-cluster calculation of dispersion contributions to interaction energies and polarizabilities
The induced dipole dispersion-type contributions to the two-body and nonadditive three-body energies and electric dipole
polarizabilities are studied for long-range interactions involving the He, Ne, Ar and Kr atoms and the H2 and N2 molecules. The coupled-cluster singles and doubles model and large basis sets are used. Comparison of the energy contributions
with data derived from experiment shows in most cases the deviations to be less than 1%; therefore, it may be expected that
the calculated polarizability increments are accurately determined and can be used to estimate the accuracy of approximate
methods.
Received: 20 March 2001 / Accepted: 5 April 2001 / Published online: 27 June 2001 相似文献
9.
In the present study the derivatization of two water-soluble and synthetic polymers, such as α,β-poly(N-hydroxyethyl)-DL-aspartamide
(PHEA) and α,β-polyasparthydrazide (PAHy), with glycidylmethacrylate (GMA) is described. This reaction allowed the introduction
of double bonds in the macromolecular chains of PHEA and PAHy in order to make easier the crosslinking by a radical mechanism.
Different parameters affected the reaction of derivatization, such as reaction pH, GMA concentration and reaction time. As
far as PHEA is concerned the amount of GMA linked to the polymer increased until reaching a plateau. On the contrary, the
reaction of PAHy with GMA proceeded with a zero order kinetics and the GMA amount in the polymer increased regularly. Some
aqueous solutions of PHEA-GMA and PAHy-GMA copolymers at various GMA content were submitted to gamma radiation processing,
thus obtaining crosslinked structures. The derivatization of PHEA and PAHy with GMA was a convenient method to introduce insaturations
in their chains and it allowed to obtain gels at lower doses with respect to the starting polymers.
Received: 2 April 1996 Accepted: 30 June 1996 相似文献
10.
R. Q. Topper K. Chung C. M. Boelke D. Louie J. S. Kang R. Hannan T. Kiang L. H. Chan 《Theoretical chemistry accounts》2003,109(4):233-238
2-(Acetylamino)fluorene (AAF), a potent mutagen and a prototypical example of the mutagenic aromatic amines, forms covalent
adducts to DNA after metabolic activation in the liver. A benchmark study of AAF is presented using a number of the most widely
used molecular mechanics and semiempirical computational methods and models. The results are compared to higher-level quantum
calculations and to experimentally obtained crystal structures. Hydrogen bonding between AAF molecules in the crystal phase
complicates the direct comparison of gas-phase theoretical calculations with experiment, so Hartree–Fock (HF) and Becke–Perdew
(BP) density functional theory (DFT) calculations are used as benchmarks for the semiempirical and molecular mechanics results.
Systematic conformer searches and dihedral energy landscapes were carried out for AAF using the SYBYL and MMFF94 molecular
mechanics force fields; the AM1, PM3 and MNDO semiempirical quantum mechanics methods; HF using the 3-21G*and 6-31G* basis
sets; and DFT using the nonlocal BP functional and double numerical polarization basis sets. MMFF94, AM1, HF and DFT calculations
all predict the same planar structures, whereas SYBYL, MNDO and PM3 all predict various nonplanar geometries. The AM1 energy
landscape is in substantial agreement with HF and DFT predictions; MMFF94 is qualitatively similar to HF and DFT; and the
MNDO, PM3 and SYBYL results are qualitatively different from the HF and DFT results and from each other. These results are
attributed to deficiencies in MNDO, PM3 and SYBYL. The MNDO, PM3 and SYBYL models may be unreliable for compounds in which
an amide group is immediately adjacent to an aromatic ring.
Received: 26 May 2002 / Accepted: 12 December 2002 /
Published online: 14 February 2003 相似文献
11.
The ground and excited states of 1,4-di (2-phenylvinyl)benzene (PPV3) were studied theoretically and compared with experimental
results. The equilibrium geometries of the ground states were found to be nonplanar despite the π conjugation in PPV3; however,
the equilibrium geometry of the first excited state of PPV3 is planar, due to the increased π character between the benzene
and ethylene units. The electronic structures of the excited state were investigated using the INDO/S-CIS method. The lack
of a mirror-image relationship between the absorption and fluorescence spectra of PPV3, obtained experimentally, was analyzed
theoretically. It was demonstrated that structural inhomogeneity might be the reason for the particular spectral band shape.
Received: 12 April 1999 / Accepted: 15 June 1999 / Published online: 4 October 1999 相似文献
12.
A. V. Aksenov A. V. Sarapii O. A. Antonova I. V. Borovlev V. I. Goncharov 《Chemistry of Heterocyclic Compounds》2005,41(8):1031-1035
The reaction of 1-alkyl-3-(2-quinolyl)quinolinium iodides with excess zinc in THF gives a diastereomeric mixture of 1,1′-dialkyl-3,3′-di(2-quinolyl)-1,1′,4,4′-tetrahydro-4,4′-biquinolyls.
An excess of lithium in THF gives a mixture of 1′,2′-dihydro-2,3′-biquinolyl and 1′-alkyl-1′, 4′-dihydro-2,3′-biquinolyl with
the former predominating. The reduction by lithium in THF of 1,1′-dialkyl-3,3′-di(2-quinolyl)-1,1′,4,4′-tetrahydro-4,4′-biquinolyls
leads to analogous products. Reduction of 1-alkyl-3-(2-quinolyl)quinolinium iodides by metallic potassium gives 1-alkyl-1′,4′-dihydro-2,3′-biquinolyls.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1208–1212, August, 2005. 相似文献
13.
14.
15.
T. P. Vasil'eva A. F. Kolomiets E. I. Mysov A. V. Fokin 《Russian Chemical Bulletin》1997,46(6):1181-1183
α-(Trifluoromethyl)acrylic acid (1) and γ,γ,γ-trifluorocrotonic acid (2) add AcSH (exothermally and at 100 °C, respectively) in the absence of a catalyst to form products of β-thiolation, which
can be easily hydrolyzed to the corresponding β-mercaptoalkanoic acids. Thiols also add regiospecifically to acids1 (in the absence of a catalyst) and2 only in the presence of trifluoromethanesulfonic acid as the catalyst) when heated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1230–1232, June, 1997. 相似文献
16.
Lixin Zhou 《Theoretical chemistry accounts》2000,105(1):86-92
Results of ab initio self-consistent-field (SCF) and density functional theory (DFT) calculations of the gas-phase structure,
acidity (free energy of deprotonation, ΔGo), and aromaticity of 1,2-diseleno-3,4-dithiosquaric acid (3,4-dithiohydroxy-3-cyclobutene-1,2-diselenone, H2C4Se2S2) are reported. The global minimum found on the potential energy surface of 1,2-diseleno-3,4-dithiosquaric acid presents a
planar conformation. The ZZ isomer was found to have the lowest energy among the three planar conformers and the ZZ and ZE
isomers are very close in energy. The optimized geometric parameters exhibit a bond length equalization relative to reference
compounds, cyclobutanediselenone, and cyclobutenedithiol. The computed aromatic stabilization energy (ASE) by homodesmotic
reaction (Eq 1) is −20.1 kcal/mol (MP2(fu)/6-311+G** //RHF/6-311+G**) and −14.9 kcal/mol (B3LYP//6-311+G**//B3LYP/6-311+G**).
The aromaticity of 1,2-diseleno-3,4-dithiosquaric acid is indicated by the calculated diamagnetic susceptibility exaltation
(Λ) −17.91 (CSGT(IGAIM)-RHF/6-311+G**//RHF/6-311+G**) and −31.01 (CSGT(IGAIM)-B3LYP/6-311+G**//B3LYP/6-311+G**). Thus, 1,2-diseleno-3,4-dithiosquaric
acid fulfils the geometric, energetic and magnetic criteria of aromaticity. The calculated theoretical gas-phase acidity is
ΔGo
1(298K)=302.7 kcal/mol and ΔGo
2(298K)=388.4 kcal/mol. Hence, 1,2-diseleno-3,4-dithiosquaric acid is a stronger acid than squaric acid(3,4-dihydroxy-3-cyclobutene-1,2-dione,
H2C4O4).
Received: 11 April 2000 / Accepted: 7 July 2000 / Published online: 27 September 2000 相似文献
17.
O. A. Antonova V. I. Goncharov A. V. Aksenov 《Chemistry of Heterocyclic Compounds》2006,42(2):197-199
1,1′-Dialkyl-3,3′-di(2-quinolyl)-1,1′,4,4′-tetrahydro-4,4′-biquinolines react with organolithium and organo-magnesium compounds
to form 1′-alkyl-2′-R-1′,2′-dihydro-2,3′-biquinolines.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 224–226, February, 2006. 相似文献
18.
G. P. Girina N. M. Alpatova L. G. Feoktistov 《Russian Journal of Electrochemistry》2006,42(1):102-105
In the cyclic voltamograms for electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene at its concentrations of 5 and 10 mM in dimethylformamide solution of 0.1 M Bu4NBF4, taken at glassy-carbon electrode, four current peaks corresponding to consecutive stages of the reduction process are observed for the first time. The many times repeated potential cycling from 0 V (SCE) to the value approaching the 2nd peak potential results in the electrode passivation; a film of the intermediate product of the α,α,α′,α′-tetrabromo-p-xylene reduction is deposited at the electrode, whose composition may be-(BrCH-C6H4-CHBr-BrCH-C6H4-CHBr)n-. When the electrode covered with the deposited film is transferred to a solution of the same composition, in which the primary cycling was performed, yet free from α,α,α′,α′-tetrabromo-p-xylene, and underwent to potential cycling up to ?2V, the first cycle demonstrates a current peak that is due to the film reduction. A redox-active poly(p-phenylenevinylene) forms at the electrode. 相似文献
19.
The electrochemical behavior of a film, which consists of intermediate products of the α,α,α′,α′-tetrabromo-para-xylol (TBX) reduction and is deposited on a glassy-carbon electrode from 5 × 10?2 M TBX solutions, is studied in 0.1 M Bu4NBF4 solution in DMFA by cycling the potential from 0 to ?1.4 V with respect to an aqueous saturated calomel electrode. When the potential is cycled from 0 to ?2.1 V in a cell filled with the supporting electrolyte, the film, which is assumed to have the (-BrHC-C6H4-CHBr-)n composition, can be reduced to form poly(para-phenylenevilylene) (PPV). This film exhibits redox activity in the cathodic range in solutions of Bu4NBF4 in DMFA and in both cathodic and anodic ranges in solutions of Bu4NBF4 in AN. It is observed for the first time that, if the cathodic limit of the potential cycling range is extended to ?2.5 V, the cathodic doping of PPV at potentials below ?2 V disappears and a new reversible redox process takes place at more negative potentials. 相似文献
20.
The self-interaction error (SIE) of commonly used density functional theory (DFT) exchange functionals mimics long-range
(nondynamic) pair correlation effects in an unspecified way. Slater exchange suffers from a larger SIE and, therefore, covers
more nondynamic correlation effects than Becke exchange, which is the reason why exchange–correlation (XC) functionals based
on Slater exchange lead to stabler restricted DFT solutions than those based on Becke exchange. However, the stability of
an XC functional does not guarantee higher accuracy. On the contrary, if system-specific nondynamic correlation effects have
to be introduced via the form of the wave function, these will be suppressed by nondynamic correlation effects already covered
by the exchange functional. Hybrid functionals suffer less from the SIE and, therefore, cover a smaller number of nondynamic
electron correlation effects. Accordingly, they are better suited when nondynamic electron correlation has to be introduced
by the form of the wave function. It is shown that, for example, broken-symmetry unrestricted DFT calculations are more accurate
when carried out with B3LYP than BLYP contrary to claims made in the literature.
Received: 8 November 2001 / Accepted: 30 January 2002 / Published online: 8 April 2002 相似文献