Homogeneous catalysis involving

Homogeneous catalysis involves transition metal complexes. The presence of transition metal atoms, with their valence d shells, introduces serious demands in the type of quantum chemical methods that can be applied. While methods like Hartree-Fock (HF) and local density functional... 

In the strictest sense, homogeneous catalysis involves catalytic reactions occurring in a single phase. However, as currently used, the term implies only that at least a portion of a particular reaction is known or suspected strongly to occur in the coordination sphere of a metal (most frequently a transition metal). Activation of substrates and likely the steric course of the reaction are then consequences of bonding in an in-... 

Hydrogenation with homogeneous catalysis involves a soluble catalyst rather than the more common heterogeneous catalysis with, say, Pd metal dispersed on an insoluble charcoal support as in Chapter 24. In general terms homogeneous catalysts are those that are soluble in the reaction mixture. 

Homogeneous catalysis involves a much broader area than will be presented here, but a selection was necessary in order to remain within the scope of this book. The aim of this chapter is to give an impression of the current status of the field of homogeneous catalysis, expectations concerning the future developments of the crucial concepts and techniques, and all this in relation to present and potential industrial applications. 

Unlike conventional homogeneous catalysis involving relatively low oxidation state transition metals, the proposed mechanism involves successive... 

This article mainly focuses on the two major and recent breakthroughs in the area of low-coordinate group 13 chelates (1) tri-coordinate cationic group 13 chelates and (2) monovalent group 13 chelates. Recent advances in homogeneous catalysis involving more classical tricoordinate Al(III) complexes are also briefly mentioned. 

Nonlinear mechanisms are very common in heterogeneous catalytic reactions. They are also characteristic of chain reactions and, perhaps, of homogeneous catalysis involving metal complexes. Because of this, the classification of these mechanisms is of considerable interest. 

The Wacker-Smidt process—hereafter known simply as the Wacker oxidation, reaction, or process—enjoyed considerable success, yet its use has declined dramatically over the past 10 years for at least two reasons.49 First, manufacturing plants are expensive to build and maintain because they must be constructed to withstand a corrosive environment. Second, another procedure that yields acetic acid directly from synthesis gas was developed and now supplants the Wacker-Smidt process. This newer route also uses homogeneous catalysis involving Rh and Ir complexes and will be described in Section 9-5. 

Catalytic cylcles in homogeneous catalysis involve changes in the state of the central ion during the reaction. At the same time the initial state of the central ion could be the same or different from the final state. 

Homogeneous catalysis involving transition metal hydride complexes is such a large subject that several monographs have been devoted to Table 2 shows some typical homogeneous... 

The development of a mechanistic model for a homogeneous reaction requires constructing a catalytic cycle, which is quite difficult. On the other hand, simple kinetic expressions of both the power law and hyperbolic types can be readily derived. These are usually adequate for reactor design. Thus in the analysis of homogeneous catalysis involving a gas-liquid reaction, the following general hyperbolic form of the rate equation may be used ... 

Hydrogen gas is adsorbed onto the surface of these metal catalysts, and the catalyst weakens the H—H bond. In fact, if H2 and D2 are mixed in the presence of a platinum catalyst, the two isotopes quickly scramble to produce a random mixture of HD, H2, and D2. (No scrambling occurs in the absence of the catalyst) Hydrogenation is an example of heterogeneous catalysis, because the (solid) catalyst is in a diffo-ent phase from the reactant solution. In contrast, homogeneous catalysis involves reactants and catalyst in the same phase, as in the acid-catalyzed dehydration of an alcohol. 

Enantioselective Homogeneous Catalysis Involving Transition-Metal-Allyl Intermediates. 

Recall that there are a number of reactions where homogeneous catalysis involves two phases, liquid and gas, for example, hydrogenation, oxidation, carbonylation, and hydroformylation. The role of diffusion becomes important in such cases. In Chapter 6, we considered the role of diffusion in solid catalyzed fluid-phase reactions and gas-liquid reactions. The treatment of gas-liquid reactions makes use of an enhancement factor to express the enhancement in the rate of absorption due to reaction. A catalyst may or may not be present. If there is no catalyst, we have a simple noncatalytic gas-liquid heterogeneous reaction in which the reaction rate is expressed by simple power law kinetics. On the other hand, when a dissolved catalyst is present, as in the case of homogeneous catalysis, the rate equations acquire a hyperbolic form (similar to LHHW models discussed in Chapters 5 and 6). Therefore, the mathematical analysis of such reactions becomes more complex. 

Another well-studied example of homogeneous catalysis involves the decomposition of hydrogen peroxide in aqueous solution ... 

Catalysis involves an alternative mechanism in which the catalyst is involved. Catalysis is divided into three classes heterogeneous catalysis, homogeneous catalysis, and enzyme catalysis. Heterogeneous catalysis at the surfaces of solids involves adsorption of the reactants. We discussed the Langmuir theory of adsorption and applied it to heterogeneous catalysis. Homogeneous catalysis involves mechanisms with steps that occur in a single phase, and example reactions were analyzed. 

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