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91.
A. A. Balandina V. A. Mamedov E. A. Khafizova Sh. K. Latypov 《Russian Chemical Bulletin》2006,55(12):2256-2264
The combined use of 2D NMR correlation methods and ab initio chemical shift calculations is efficient and, in some cases, virtually the only way to determine the structures of new organic
compounds. This approach enabled us to establish the structure of the major unusual product of the three-component reaction
of imidazo[1,5-a]quinoxalin-4-one, bis(2-chloroethyl)amine hydrochloride, and potassium carbonate in DMF.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2172–2179, December, 2006.
Dedicated to Professor A. V. Il’yasov on the occasion of his 70th birthday. 相似文献
92.
Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important
concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal
substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits,
CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify
a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation,
which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way
for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass
Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.
Community Reference Laboratory for Antimicrobial Veterinary Drug Residue Control in Food from Animal Origin 相似文献
93.
Yuji Naruse Atsushi Takamori Itsuki Nagasawa 《Phosphorus, sulfur, and silicon and the related elements》2020,195(7):523-525
AbstractWe previously designed and prepared the first molecules to exhibit observable CD spectra by n-σ* excitation, 2,6-dithiaspiro[3.3]heptane 2,6-dioxide. Spiro[3.3]heptane frameworks possess axial asymmetry due to puckering of 2 four-membered rings; the ring bonds are rich in p-character due to acute bond angles, which lowers the σ* energy levels. In contrast, the lone pairs are rich in s-character, which results in a good donor with conformational fixation. We expected that, instead of lone pairs as donating orbitals, the use of σ-electron-donating Si-Si bonds should result in UV absorption in the observable range (>180?nm), so that the Cotton effect could appear, at least partially, in that range. We designed 2,6-disilyl-2,6-disilaspiro[3.3]heptanes as models, and performed theoretical calculations to confirm our idea. 相似文献
94.
The reaction path, the dynamical properties along the reaction path and CVT rate constants are computed by the ab initio MO method, the reaction path Hamiltonian theory and the variational transition state theory. The results show that the effect of the electron correlation energy on activation barrier is large, the recrossing and tunneling effects exist in the reaction. 相似文献
95.
N. Nandi D. Vollhardt R. Rudert 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):279-287
In the present work, the pair potential of enantiomeric N-palmitoyl aspartic acid amphiphile monolayer at the air/water interface is calculated based on an atomistic model. The molecular structure and partial charges are calculated using two semi empirical (PM3, AM1) and one empirical (Gasteiger and Marcili) methods. A distance-dependent dielectric function is used to represent the interfacial dielectric constant at the aqueous subphase. The present study indicates that a pair of molecules have favorable interaction at specific ranges of mutual orientations. Other orientations are favorable but at larger separations. Favorable electrostatic interaction at a specific combination of orientation and short separations of the head groups significantly contribute to the total energy. The curvature of the domain boundary is suggested to be driven by the favorable arrangement which is dependent on the pair potential of molecules. The use of charges obtained by the PM3 and GM do not lead to a significant variation of the orientation-dependent features, while the AM1 predicts higher partial charges and interactions are stronger than the former two methods. However, orientation-dependent features remain the same. The variations in the LJ parameters and charges indicate that the conclusions made are insensitive to the choice of parameters. The mutual favorable interaction predicted by calculation agree with the handedness of curvature of domains. 相似文献
96.
97.
邻氯苄基氯与锡反应合成三(邻氯苄基)氯化锡,经x射线方法测定了新化合物 的晶体结构,化合物属三方晶系,空间群为R-3,晶体学参数:α=b=1.3583(4) mn,c=2.1147(8)am,v=3.3790(19)nm~3,Z=6,μ(Mo kα)=16.11cm~-1, r (000):1572,R_1=O.0755;Sn-C键长分别为0.2148(13)和0.220(2)nm,Sn-C1 键为0.2528(15)和0.2477(13)Bill.中心锡原子与亚甲基碳和氯原子构成畸型四 面体.并对其结构进行量子化学从头计算,探讨化合物的稳定性、分子轨道能量、 原子净电荷布居规律以及一些前沿分子轨道的组成特征. 相似文献
98.
严继民 《中国科学B辑(英文版)》1990,(7)
An ab initio calculation of the hydrogen bond complex (HF)_2 is given with the 6-311 G~(**) basis set, according to which the potential surface around the balance point of the distancès and the orientations between two HF molecules is obtained. The atomic charges in the system are calculated with the PD/LSF method (potential-derived/least-square-fitting method) and then an analysis of the hydrogen bond interaction between two HF molecules is given with the (exp-6-1) potential function, by means of which it is shown that the main interaction between them is not an electro-static but a charge transfer one. The potential curve between two HF molecules is like a Morse function. 相似文献
99.
Moreno M. M. Torres Santos R. H. A. Gambardella M. T. P. Camargo A. J. da Silva A. B. F. Trsic M. 《Structural chemistry》1998,9(5):365-373
The crystal and molecular structures of the following molecules have been determined: 1-acetyl-indoline, 1-acetyl-5-nitro-indoline, l-acetyl-5-nitro-7-bromo-indoline, 1-acetyl-5-bromo-7-nitroindoline, and l-acetyl-5-bromo-7-nitro-indol. Molecular orbital calculations are performed for these compounds and two related species. 相似文献
100.
Density functional calculations were performed on bonding and structural features of [(ηn-BH4)TM(CO)4]− (n = 1, 2, 3; TM = Cr, Mo) complexes. Calculations show that the ground state is bidentate which is in good agreement with experimental results. It has been found that the bridge and terminal hydrogen atoms will interchange by two pathways: (i) twist of BH4 about one of the bridge B-H and (ii) twist of BH4 about one of the terminal B-H. The molecular orbital calculations and natural bond orbital methodologies for different isomers of these complexes have been evaluated. The final results indicate that case (i) is more preferable relative to another case. 相似文献