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1.
A new formulation of the Lindemann mechanism of unimolecular reactions in gaseous phase is presented, without the use of steady state hypothesis. It is hereby shown that the nature of applicability of steady state hypothesis in the regime of high reactant gas pressure is different from that in the regime of low gas pressure. In the former case it is an equilibrium approximation, while in the latter case it is a highly reactive intermediate approximation in no connection with a steady state. Furthermore for the latter case it is shown that in the classical formulation of Lindemann mecbRnism the use of steady state hypothesis is an ad hoc assumption. A highly reactive intermediate in the sense that its concentration is very small during the whole course of reaction is a necessary condition for the applicability of very reactive intermediate approximation. When the two distinctive nature of the applicability of steady state hypothesis is mlxed-up, wrong or useless conclusion may be arrived at. The only possible case of realizing a true steady state in a complex reaction is pointed out. 相似文献
2.
Lian De ZHU Ying Xiu LI Guo Yi ZHU* State key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 《中国化学快报》2002,13(11)
Histidine is one of the necessary basic amino acids in biological bases, which often controls the catalytic activity of enzymes and acts in holding the higher structure of proteins. Furthermore, it is also an important ingredient in pharmaceutical preparations used for treatment of hetpatosis and nephropathy. Therefore, the determination of histidine in biological fluids and pharmaceutical preparations is of great importance. Various methods have been proposed for the detection of histidine … 相似文献
3.
Jin-zhi Zhang Li Xie Shi-gan Chai Qi-chao Zou 《化学物理学报(中文版)》2014,27(3):307-314
The interaction between N, N′-bis(dimethyldodecyl)-1,6-hexanediammoniumdibromide (G12-6-12) and cetyltrimethylammonium bromide (CTAB) in D20 aqueous medium has been investigated by NMR at 298 K. The G12-6-12 and CTAB are about 0.773 and measured critical micelle concentration (cmc) of 0.668 mmol/L, respectively. The cmc^* (cmc of mixture) values are less than CMC^* (cmc of ideally mixed solution) in the mixed system, and the interaction parameter βM〈0 at different molar fractions α of G12-6-12 in the mixed systems, but just when α≤0.3, cmc^* values are much smaller than CMC^*, and βM satisfies the relation of |βM|〉|ln(cmc1/cmc2)| (cmcl: cmc of pure G12-6-12 and cmc2: cmc Of pure CTAB). The results indicate that there exists synergism between G12-6-12 and CTAB, and they can form mixed micelles, which is further proven by 2D NOESY and self-diffusion coefficient D experiments. There are intermolecular cross peaks between G12-6-12 and CTAB in 2D NOESY, and the radius of micelles in mixed solution is bigger than that in G12-6-12 pure solution in D experiments, indicating there are mixed micelles. However, when α〉0.3, we find that cmc^*≈CMC^*, βM≈0, obviously, the two surfactants are almost ideal mixing fitting the pseudo-phase separation model and regular solution theory. 相似文献
4.
The reactivation of trace elements in source rocks is fundamental in the formation of many economic deposits. Although transport by fluid flow and infiltration is very effective along visible fractures, the migration of trace elements from the inner part of solid cells to the weaknesses is much less efficient, and so becomes the bottleneck in the migration of these elements from their initial positions in the source rock to the final deposition site in an ore body. Diffusion may play a key role in the reactivation of trace elements. The overall migration pattern of trace elements in source rocks is characterized by an embedded sink mosaic structure, which possesses the self-similarity of a fractal. There are two general migration tendencies of trace elements. One is from within solid cells, such as mineral grains, toward the sink, consisting of weaknesses in the source rock. The other is from high-temperature fields toward low-temperature ones. High temperature favors the realization of these two tenden 相似文献
5.
Xia Guo Ling Lin Rong Guo 《中国化学快报》2007,18(10):1265-1268
In this study,the photoisomerization of trans-sfilbene was carried out in water in oil (W/O) microemulsions by using sodium dodecyl sulfate (SDS),dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) as surfactant,respectively.The catalytic effect of microemulsion on this reaction is closely related to the structure of surfactant.When there is no photosensitizer 9,10-dicyanoanthracene (DCA),the surfactant with shorter hydrophobic chain is preferred,while in the presence of DCA,the surfactant with anionic polar group is preferred. 相似文献
6.
The distribution and forms of phosphorus (P) were investigated in the tidal flat sediments of the Yangtze Estuary and coast. The total P contents in surface sediments range from 18.0 to 31.4 μmol · g-1 along the southern coast. The spatial and temporal distribution of P in tidal flats is closely related to the location and pollution resources, especially in association with the variation of hydrodynamic conditions. Significant variations in the forms of P in different sites were observed. P bonded with Ca(Ca-P) is the dominant mineral form in all surface sediments, organic P(Org-P) is lower. Most P is of unstable form, suggesting that P has larger potential activity. P accumulation is the main behavior process between water and sediment in the coastal environment of the Yangtze Estuary. 相似文献
7.
The migration mechanism of ionizable compounds in capillary electrochromatography (CEC) is more complicated than in high performance liquid chromatography (HPLC) due to the involvement of electrophoresis and the second chemical equilibrium. The separation mechanism of ionizable compounds in CEC has been studied theoretically. The electrochromatographic capacity factors of ions (k~*) in CEC and in the pressurized CEC are derived by phenomenologicai approach. The influence of pH, voltage, pressure on k~* is discussed. In addition, the k~* of weak acid and weak base are derived based on acid-base equilibrium and the influence of pH on k~* is studied theoretically. 相似文献
8.
JieHU BaiLingLIU 《中国化学快报》2004,15(4):459-462
The free radical polymerization of styrene in water in the presence of β-cyclodextrin (β-CD) is described.It is found that β-CD could greatly accelerate the polymerization,enhance the final conversion of monomer.The particle-size distribution of the final polymer is also improved than that without β-CD in the system. 相似文献
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Mercaptans in petroleum products wreck the quality of finished products, so it is necessary to remove them in petroleum refining industry. Merox fixed-bed process is widely used in which mercaptans are converted by contacting feedstock with a metal phthalocyanine catalyst in the presence of air and an alkaline agent. However, use of caustic brings a spent caustic disposal problem so that novel caustic-free catalysts are highly desired to meet environment requirements1-3. It is not just simply … 相似文献
10.
HE Nong-Yue BAO Shu-Lin XU Qin-HuaDepartment of Chemistry Nanjing University Nanjing Jiangsu China 《中国化学》1997,(1)
Zeolite L with Fe in lattice position is prepared from the gel with Fe/(Fe+Al) ratio up to 0.4 using ferric nitrate as Fe source. The incorporation of Fe(Ⅲ) in framework is characterized by XRD, IR, TG/DTA, BET and Mossbauer spectroscopy. Zeolite L is destabilized by Fe(Ⅲ) in framework and the reduction of Fe(Ⅲ) in framework of (Al,Fe )KL was first reported. 相似文献
11.
The expansion coefficient CD|L| of Coulomb potential 1/r12 of atomic system in hyper‐spherical harmonics is derived and the explicit expression is given. 相似文献
12.
研究了500~750℃富氧条件下RuO2|M|YSZ|Pd(M=Ag,Pd,Pt,Au)固体电解质电解池在0~4V直流电压下对NO的分解性质.600℃下,O2-在Pd|YSZ阴极界面处的传导是O2-在RuO2|Pd|YSZ|Pd固体电解质电解池中传导过程的速控步骤.反应温度越低,RuO2|Pd|YSZ|Pd电解池上NO电催化分解相对于氧分解的选择性因子α越大.600℃下O2-在M|YSZ阴极界面处的传导阻力按Ag2|Ag|YSZ|Pd电解池上分解率为15.3%,NO选择性因子达到13.4. 相似文献
13.
研究了在O_2存在条件下,NO在Pd |YSZ| Pd固体电解质电池和RuO_2 |Pd|YSZ| Pd固体电解质电池上的分解性质,在O_2存在条件下650 ~ 700 ℃之间 ,在0 ~ 4.4 V直流电压作用下,NO在Pd |YSZ| Pd电池和RuO_2|Pd|YSZ| Pd电池 上的分解不以电解机制进行,而以电催化机理进行的。即在直流电压下,阴极催化 剂上的O~(2-)被直流电压通过YSZ固体电解质转移到阳极,以O_2的形式放出,以此 保持催化剂的活性状态。在Pd|YSZ|Pd 固体电解质电池上,Pd金属表面是催化NO分 解的主要活性位。RuO_2 |Pd|YSZ| Pd固体电解质电池上,某特定还原态的RuO_x (0 < x < 2)是NO分解的主要活性位。在O_2存在下,该电池在1 ~ 4 V间合适的电 压下,在650 ~ 700 ℃能选择性地对NO进行电催化分解。 相似文献
14.
The electric dipole moment in the ground state (vp = 0) and the first five excited states (vp = 1 … 5) of the ring puckering vibration of thietane have been determined from Stark shifts of rotational transitions. The results are: 0|μa|0 = 1.87583(16) D, 1|μa|1 = 1.87341(18) D, 2|μa|2 = 1.89759(28) D, 3|μa|3 = 1.88688(29) D, 4|μa|4 = 1.90036(18) D, 5|μa|5 = 1.88596(59) D. The dependence of these values on vp shows the zig-zagging behaviour typical of modes with double minimum potentials. A combined analysis of the ground and first excited states yielded also a precise value for the transition moment, 0|μc|1 = 0.24023(49) D.
A potential and electric dipole moment function has been derived from ab initio calculations, using MP2 and the 6–31G** basis set. Expectation values of the dipole and transition moments were determined from these data. Absolute values are about 5% in error, but the variation with vibrational state is reproduced excellently by the theoretical values. 相似文献
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16.
溶胶-凝胶法制备光学杂化功能材料 总被引:9,自引:0,他引:9
在简述溶胶-凝胶法基本原理的基础上,介绍了设计杂化材料的原则及预掺杂法、后掺杂法和原位化学合成法三种溶胶-凝胶法制备光学杂化功能材料的途径;综述了稀土发光材料、波导材料和光致变色材料三种光学杂化功能材料,并结合国内外的研究提出开展光学杂化功能材料研究的重要方向. 相似文献
17.
The hyperfine coupling constant (A in units of energy or A' in units of magnetic field) and zero-field splitting (D in units of energy or D' in units of magnetic field) in the ESR spectrum of Mn(2+) in calcite were determined. The spreading of the non-central allowed transitions |3/2, m --> |5/2, m, |1/2, m --> |3/2, m, |-3/2, m --> |-1/2, m and |-5/2, m --> |-3/2, m was analysed and the experimental transitions were attributed. Particular relevance was given to the difference between the two types of resonances, shoulder or divergence, and to their origin (M, m). The analysis explains the presence of a weak shoulder between each of the five central doublets |-1/2, m --> |1/2, m. Six independent methods for calculating the hyperfine coupling constant and five methods for calculating the zero-field splitting, based on the analysis of the allowed and forbidden transitions, were provided. The values of the hyperfine coupling constant range from -93.9 to -94.6 G and those of the zero-field splitting range from -79.5 to -80.5 G. A critical evaluation of the advantages and drawbacks of the 11 methods is included: the best value for A' is -94.30 G and that for D' is -79.95 G. 相似文献
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Electrochemical studies on hydrolytically unstable complex fluorides have been shown to be possible in highly purified acetonitrile. The techniques of study will be described briefly. A survey of the results obtained to date wille given.MoF6 is a stronger oxidising agent than WF6 by 1.06 volts. Neither |MoF6|? nor |WF6|? can be reduced below |MF6|? in acetonitrile. |UF6|? can be reduced to the transient species |UF6|2? which is unstable in solution. |OsF6|? undergoes successive reduction to |OsF6|2? and |OsF6|3?.|MF6L|? undergoes complex electrochemical behaviour involving reduction to |MF6L|2? with subsequent dissociation to |MF6|? and L?. Reoxidation is in the presence of L? and hence none of the redox steps are fu]ly reversible. The relation between the electrode potentials and the ligand L will be discussed.We thank NATO for a grant in support of this work. 相似文献
20.
Matsumura T Ohoyama H Watanabe D Yasuda K Kasai T 《The journal of physical chemistry. A》2007,111(16):3069-3073
Atomic orbital alignment effect was observed for the CN (B2Sigma+) formation in the reaction of oriented Ar (3P2) with CH3CN (CD3CN). The relative cross-sections for each magnetic MJ' substrate in collision frame sigmaH|MJ'| for CH3CN and sigmaD|MJ'| for CD3CN, were determined to be sigmaH0:sigmaH|1|:sigmaH|2|:sigmaD0:sigmaD|1|:sigmaD|2| = 1.00:0.81:0.84:2.01:1.92:1.87. A significant atomic orbital alignment effect was observed. In addition, a notable deuterium isotope effect was observed on both the cross-section and the atomic orbital alignment effect. 相似文献