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91.
P. I. Dem'yanov E. M. Myshakin D. P. Krut'ko V. S. Petrosyan 《Russian Chemical Bulletin》1997,46(12):1996-2005
The results of calculations for benzyl chlorides and benzyl bromides that contain substituents in the ring by different quantum-chemical
methods are compared. The electron density on the benzyl carbon atom increases as the electron-withdrawing properties of substituents
are enhanced due to the shift of the electron density from the benzyl halogen atom to the adjacent carbon atom. A topological
analysis according to Bader confirmed the main reason for the change in the paramagnetic shielding of the benzyl13C nuclei. The results of calculations provide, for the first time, an explanation for the resonance upfield13C shift of this atom as the Hammett constant of a substituent increases in compounds of the series under consideration.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2111–2119, December, 1997. 相似文献
92.
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
93.
Ab initio calculations (RHF) of EtX molecules (X=F, Cl, Br, I, or OTs) were carried out with the use of different basis sets. Total
charges on the atoms in the compounds under study were determined by Mulliken's, NPA, and Bader's methods, and a comparison
of these values was performed. For all EtX compounds, a topological analysis of the electron density was carried out within
the framework of Bader's theory, and the global and relative local hardnesses of the above-mentioned ethylating agents were
estimated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 608–612, April, 1998. 相似文献
94.
JIANG Qi-Jun 《结构化学》2005,24(10):1140-1144
1 INTRODUCTION The electron-transfer reaction of C60 derivatives, especially light-induced electron-transfer reaction, has been an active research field for a long time. Many researches are focused on the long-live charge- separated state caused by electron-transfer[1]. And several electron-transfers between electron donor and C60 or intramolecular electron-transfer have been confirmed. As an example, TTF-C60 is proved to be a short-live charge-separated compound[2].Due to the excelle… 相似文献
95.
用 CNDO/2方法在 586微机上计算了 C57X3C56X4(X=B、N、P)的 234个位置异构体的电子结构。在C57X3(X=B、N、P)位置异构体中,C57X3(1,2,9)(X=B、N、P)分别是最稳定的。对于C56X4(X=B、N、P)位置异构体,C56B4(1,2,9,8),C56N4(1,2,9,12)和C56P4(1,2,9,12)分别是最稳定的,但稳定性都比C60差。其氧化或还原性都比 C60好,将它们和 C60比较,与 X相距一个或两个键的 C原子电荷密度增加或减少较多,其余电或亲核反应性增加;X与 X,X与 C原子之间 Wiberg Order都减少较多,其键的强度削弱;邻近杂原子的 C与 C原子之间 Wiberg Order减少或增加很少,其键的强度稍有削弱或增强。 相似文献
96.
97.
《Arabian Journal of Chemistry》2022,15(11):104302
Traditional Chinese medicine (TCM) is the key to unlock treasures of Chinese civilization. TCM and its compound play a beneficial role in medical activities to cure diseases, especially in major public health events such as novel coronavirus epidemics across the globe. The chemical composition in Chinese medicine formula is complex and diverse, but their effective substances resemble “mystery boxes”. Revealing their active ingredients and their mechanisms of action has become focal point and difficulty of research for herbalists. Although the existing research methods are numerous and constantly updated iteratively, there is remain a lack of prospective reviews. Hence, this paper provides a comprehensive account of existing new approaches and technologies based on previous studies with an in vitro to in vivo perspective. In addition, the bottlenecks of studies on Chinese medicine formula effective substances are also revealed. Especially, we look ahead to new perspectives, technologies and applications for its future development. This work reviews based on new perspectives to open horizons for the future research. Consequently, herbal compounding pharmaceutical substances study should carry on the essence of TCM while pursuing innovations in the field. 相似文献
98.
Differential scanning calorimetry (DSC) is the most widely used thermal analytical technique in food research and it has a great utility in quality assurance of food. Proteins are the most studied food components by thermal analysis including studies on conformation changes of food proteins as affected by various environmental factors, thermal denaturation of tissue proteins, food enzymes and enzyme preparations for the food industry, as well as effects of various additives on their thermal properties. Freezing-induced denaturation of food proteins and the effect of cryoprotectants are also monitored by DSC. Polymer characterization based on DSC of polysaccharides, gelatinization behaviour of starches and interaction of starch with other food components can be determined, and phase transitions during baking processes can be studied by DSC. Studies on crystallization and melting behaviour of fats observed by DSC indicate changes in lipid composition or help characterizing products. Thermal oxidative decomposition of edible oils examined by DSC can be used for predicting oil stability. Using DSC in the freezing range has a great potential for measuring and modelling frozen food thermal properties, and to estimate the state of water in foods and food ingredients. Research in food microbiology utilizes DSC in better understanding thermoadaptive mechanisms or heat killing of food-borne microorganisms. Isothermic microcalorimetric techniques provide informative data regarding microbial growth and microbial metabolism. 相似文献
99.
Yu. B. Vysotsky V. S. Bryantsev O. A. Gorban 《Chemistry of Heterocyclic Compounds》2002,38(12):1451-1468
The effects of benzannellation, phenyl substitution at the nitrogen atom, protonation at the carbene carbon, ionization, and the state of the carbene center (2 or 2) on the electronic structure, diamagnetic susceptibility, induced -electron ring currents, the 1H, 13C, and 14N chemical shifts, and the energies of the lowest electronic transitions of imidazol-2-ylidenes and their oxo and thio analogs were examined in the bound version of -electron perturbation theory. The calculated and experimental data are compared. 相似文献
100.
The infrared spectra of 4-Cl 2-Me, 4-Cl 3-Me and 6-Cl 3-Me phenols have been recorded. The vibrational spectrum has been analysed
assuming that the molecules belong toC
s
point group and a tentative assignment of the observed frequencies to various modes of vibration has been proposed. The near
ultraviolet absorption spectrum of these compounds has also been recorded. Assuming the transition to be electronically allowed
the strongest band on the longer wavelength side has been assigned as the (0, 0) band in each case. The spectrum has been
analysed in terms of several excited state frequencies which have been correlated with the ground state frequencies observed
in the infrared spectrum. 相似文献