Activation in chemical reaction

The description of single enzyme activity in chemical reactions, together with the activity of other biomolecules, is typical for biochemical models of alkaloid biogenesis. There is no contradiction between chemical and biochemical, which serve to enrich one another. In many cases, typical chemical and biochemical models are unified in papers today ". ... 

Despite its bulk inertness, Au nanoparticles with diameters smaller than 5nm on UO2 supports have shown high catalytic activity in chemical reactions... 

Now perhaps you can see that a protein is an assembly of many different kinds of group attached to a polyamide backbone. Some of the groups are purely structural, some control the shape of the protein, some help to bind other molecules, and some are active in chemical reactions. 

Three phase systems have been the main focus of activities in chemical reaction engineering, and the many novel aspects of them are too numerous to cover here, hence only a few examples will be referenced. In the case of gas-1iquid-sparingly soluble solid, it has been demonstrated that particles substantially smaller than the diffusion film thickness of film model can enhance the specific rates of mass transfer if the reaction is sufficiently fast (45). Work in this area has been persistently pursued by Sada and coworkers (46,47). Recently Alper et al. (24) has pointed out and demonstrated that in catalytic slurry reactors similar enhancement can be observed if the catalyst particles are sufficiently small. There is however some dispute on the order of magnitude of the enhancement (48,49). Another aspect is complex reactions and in the case of slurry reactors the product distribution may well depend on the degree of diffusional resistance (50). Dynamic methods have been ingeniously employed to obtain physicochemical parameters in slurry reactors (51). 

Application of perovskite oxides have been extensively studied [6-13] in sueh as, solid state chemistry, physics, advanced materials, and catalysis. Because of these diverse applications and special requirements in each application, perovskite-type oxides with speeial properties are required depending on the ultimate end use. For example, materials-oriented applications require densification by high temperature sintering to minimize both surfaee area and surface free energy in order to maximize meehanieal strength. In eontrast, eatalytie materials have to maintain sufficiently high surface area in order to maximize their participation and activity in chemical reactions.[14]... 

Eyring H 1934 The activated complex in chemical reactions J. Chem. Phys. 3 107... 

Eyring H 1935 The activated complex in chemical reactions J. Chem. Phys. 3 107-15 Hofacker L 1963 Quantentheorie chemischer Reaktionen Z. Naturf. A 18 607-19 Robinson P J and Holbrook K A 1972 Unimolecular Reactions (New York Wiley)... 

In chemoinformatics, chirality is taken into account by many structural representation schemes, in order that a specific enantiomer can be imambiguously specified. A challenging task is the automatic detection of chirality in a molecular structure, which was solved for the case of chiral atoms, but not for chirality arising from other stereogenic units. Beyond labeling, quantitative descriptors of molecular chirahty are required for the prediction of chiral properties such as biological activity or enantioselectivity in chemical reactions) from the molecular structure. These descriptors, and how chemoinformatics can be used to automatically detect, specify, and represent molecular chirality, are described in more detail in Chapter 8. 

In this book the discussion has been restricted to the structure of the normal states of molecules, with little reference to the great part of chemistry dealing with the mechanisms and rates of chemical reactions. It seems probable that the concept of resonance can be applied very effectively in this field. The activated complexes which represent intermediate stages in chemical reactions are, almost without exception, unstable molecules which resonate among several valence-bond structures. Thus, according to the theory of Lewis, Olson, and Polanyi, Walden inversion occurs in the hydrolysis of an alkyl halide by the following mechanism ... 

Natural mobilization includes chemical, mechanical, and biological weathering and volcanic activity. In chemical weathering, the elements are altered to forms that are more easily transported. For example, when basic rocks are neutralized by acidic fluids (such as rainwater acidified by absorption of CO2), the minerals contained in the rocks can dissolve, releasing metals to aqueous solution. Several examples are listed below of chemical reactions that involve atmospheric gases and that lead to the mobilization of metals ... 

In different places in the outlines of teachers reflective diaries there are statements indicating that students interest in learning about chemical reactions has increased in comparison to previous years. Teachers mentioned the increase of students interest in the context of all three main factors that are incorporated in the LON approach, i.e. (1) Eveiyday life situations as the foundation of the learning process. (2) The learning process involves many students activities. (3) Chemical reactions are consistently presented in all three types of representation. Consequently, we assnme that those three factors are the main reasons for the increased interest of students in learning about chemical reactions. Each of the listed factors is described in detail below ... 

Students interest in learning about chemical reactions increased, which is due to three main factors that ate incorporated in the LON approach (1) Everyday life situations ate the foundation of the learning process. (2) The learning process involves mat r students activities. (3) Chemical reactions are consistently presented in all three types of representation. 

Chemical reactions in boundary lubrication are different from static reactions even if the reactive substances involved are the same. The temperature to activate a chemical reaction on rubbing surfaces is usually lower than that required in the static chemical process. Some believe this is because of the naked surfaces and structural defects created by the friction/wear process, which are chemically more active. Kajdas proposed a new concept that accumulations of stress and strain in friction contacts could cause emission of low-... 

Quantum tunnelling in chemical reactions can be visualised in terms of a reaction coordinate diagram (Figure 2.4). As we have seen, classical transitions are achieved by thermal activation - nuclear (i.e. atomic position) displacement along the R curve distorts the geometry so that the... 

Microwave irradiation of catalysts before their use in chemical reactions has been found to be a new promising tool for catalyst activation. Microwave irradiation has been found to modify not only the size and distribution of metal particles but probably also their shape and, consequently, the nature of their active sites. These phenomena might have a significant effect on the activity and selectivity of catalysts, as found in the isomerization of 2-methylpentene on a Pt catalyst [2],... 

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