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191.
Dipankar Datta 《Journal of Chemical Sciences》1988,100(6):549-557
A correspondence betweenab initio calculations, the principle of electronegativity equalisation and group electronegativity has been established within the
framework of Mulliken population analysis. Using this we have calculated electronegativities of some 37 groups/atoms. These
electronegativities show excellent linear correlation with1
J
CC coupling constants in monosubstituted benzenes and Inamoto’si scale and a satisfactory one with Wells’ group electronegativity data. The correspondence however required a scaling of charge
(obtained byab initio calculations) and a proportionality between the electronegativity of the neutral group and its hardness. It is shown that
using these electronegativity values it is possible to calculate group charges in molecules where groups under consideration
interact with each other through σ bond only. 相似文献
192.
Through the application of the atom–bond electronegativity equalization method (ABEEM) to the calculation of the hardnesses of more than 300 tautomers, it can be seen that the maximum hardness principle is nearly useless to account for their relative stabilities. Moreover, by calculating the energies of these tautomers with the HF, B3LYP, B3PW91, and MP2 methods at the 6‐31G, 6‐31G*, 6‐31G**, 6‐31+G**, 6‐311G**, or 6‐311++G** level, it is found that all these methods may not be always reliable in predicting their relative stabilities. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
193.
应用ABEEM/MM模型研究水分子团簇(H2O)n (n=11~16)的性质 总被引:3,自引:0,他引:3
应用ABEEM/MM 模型计算了较大的水分子团簇(H2O)n (n=11~16)的各种性质,如:优化的几何构型, 氢键个数, 结合能, 稳定性, ABEEM 电荷分布, 偶极矩, 以及结构参数、平均氢键个数和强度, 增加的团簇结合能等.结果表明,从立方体结构到笼状结构的过渡出现在n=12的水分子团簇中,随着类似于笼状结构特点的不断增强,五元环的富集程度有所增加. 相似文献
194.
Dependence of surface-enhanced Raman scattering (SERS) from Calf thymus DNA on anions is investigated.With the silver colloid,the bands at 732,960 and 1333 cm-1 for adenine (A),1466 cm-1 for deoxyribose,and 1652 cm-1 for the C=O group of thymine (T) are observably enhanced.With the presence of the Cl- or SO42- anions,the bands at 732 and 1326/1329 cm-1 for the symmetric stretching and skeletal vibrational modes of adenine (A) are dramatically enhanced,and the enhancement effect with the SO24- ion is more than that with the Cl- ion.The experimental results show that the DNA molecule can be adsorbed on the silver colloid particles through the C6N and N7 of adenine (A),the C=O of thymine (T) and deoxyribose.Moreover,the formed hydrogen bonding of the Cl- or S2O4- ions to the C6NH2 group of adenine (A) can induce larger C6N electronegativity,which is favor for the C6N/N7 cooperative adsorption on the (Ag) n colloid particles. 相似文献
195.
利用探针辅助的脉冲激光诱导负离子剥离诊断技术对掺入5%O_2的容性耦合Ar等离子体电负特性进行了诊断研究.首先详细解析了脉冲激光剥离后探针的电信号,分析了探针偏压在低于或高于空间电位下的探针收集信号特征;根据探针偏压与探针收集信号之间的依赖关系,用来描述Ar+O_2等离子体电负特性的等离子体电负度被定义为脉冲激光剥离出的电子电流与偏压高于空间电位的探针收集到的背景电子电流的饱和比值,并对等离子体电负度随放电气压、射频功率以及轴向位置的变化进行了诊断测量.实验结果表明等离子体的电负度随着射频功率的增加而减小、随着放电气压的上升而变大;由于非对称电极的分布特性,在轴向方向上靠近功率电极时等离子体电负度有升高的趋势,这种趋势可能与鞘层边界附近二次电子的动力学行为以及负离子的产生与消失过程有关. 相似文献
196.
Tomoyuki Watanabe Susumu HasegawaNaoki Wakiyama Fusao UsuiAkira Kusai Tetsuhiko IsobeMamoru Senna 《Journal of solid state chemistry》2002,164(1):27-33
A composite of indomethacin (IM) and SiO2 was prepared in a solid state by cogrinding. Dehydration was observed as a consequence of a chemical reaction between silanol groups of SiO2 and carboxyl groups of IM. Several specific radical species found on separately ground SiO2 disappeared preferentially after cogrinding as a result of their recombination. These chemical interactions under mechanical stress bring about a charge transfer, as confirmed by X-ray photoelectron spectroscopy, leading to Si-O-C bridging bond formation at the IM/SiO2 interface. 相似文献
197.
本文建立了一种只利用pauling电负性数据直接计算各类非共轭共价基团的电负性的方法,并讨论了用电负性解释分子物理性质和化学性质的一些例子. 相似文献
198.
D. N. Kravtsov A. S. Peregudov A. I. Krylova Yu. Yu. Gorelikova 《Russian Chemical Bulletin》1997,46(6):1167-1170
Compounds (4-FC6H4)3SnSEPh3 (E=C, Si, Ge, Sn, or Pb) were synthesized or generated in solution. The data on the comparative electronegativity of the
Ph3E groups were obtained from the results of19F NMR spectroscopy. It was established that, except for E=C, the electronegativity changes in parallel with the absolute electronegativity
of the central atom. Possible reasons for the deviation observed are discussed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1215‐1218, June, 1997. 相似文献
199.
用紫外光谱研究了等离子点时1:1Co(Ⅱ)-HSA配合物金属中心的结构,结果表明:该配合物的中心钴在低浓度时以Co(Ⅱ)和Co(Ⅲ)两种氧化态共存,高浓度时(>3.0×10-4mol·L-1)仅以Co(Ⅲ)氧化态存在;且金属中心随着浓度增大发生"八面体→四方锥→四方平面"的构型变化。与生理pH时金属中心的结构存在显著差别,可用pH效应加以解释。 相似文献
200.
Pablo R. Dalmasso Raúl A. Taccone Jorge D. Nieto Pablo M. Cometto Silvia I. Lane 《Journal of Physical Organic Chemistry》2008,21(5):393-396
Rate constants for the reactions of Cl atoms with CH3OCHCl2 and CH3OCH2CH2Cl were determined at (296 ± 2) K and atmospheric pressure using synthetic air as bath gas. Decay rates of these organic compounds were measured relative to the following reference compounds: CH2ClCH2Cl and n‐C5H12. Using rate constants of 1.33 × 10?12 and 2.52 × 10?10 cm3 molecule?1 sec?1 for the reaction of Cl atoms with CH2ClCH2Cl and n‐C5H12, respectively, the following rate coefficients were derived: k(Cl + CH3OCHCl2) = (1.05 ± 0.11) × 10?12 and k(Cl + CH3OCH2CH2Cl) = (1.14 ± 0.10) × 10?10, in units of cm3 molecule?1 s?1. The rate constants obtained were compared with previous literature data and a correlation was found between the rate coefficients of some CH3OCHR1R2 + Cl reactions and ΔElectronegativity of ? CHR1R2. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献