Reactions parallel Type

These values of the reaction rate constants differ from those cited by Pannetier and Souchay (6) because these individuals erroneously treated the two reactions as if they were of the simple parallel type instead of as if there were a competition between the acrolein and butadiene molecules for other butadiene molecules. 

The waste minimisation reaction related examples in this text are represented mainly by combinations of consecutive and parallel type reactions. Although the major details of such problems are dealt with in conventional textbooks, it may be useful to consider the main aspects of such problems from the viewpoint of solution by digital simulation. 

This parallel change in the electrical conductivity and in the activity may take place in the same or in opposite directions depending on the type of reaction (n-type or p-type) and on the type of semiconductor (n-type or p-type). In the case of an 7i-type reaction on an n-type semiconductor or of a p-type reaction on a p-type semiconductor, the electrical conductivity and the activity vary in the same direction. On the contrary, in the case of an n-type reaction on a p-type semiconductor or a p-type reaction on an n-type semiconductor, they vary in opposite directions. 

The necessity for postulating combination steps raises questions regarding the nature of the intermediates which may be formed from acetylene and then reacted to form carbon. Various types have been suggested, such as aromatics, fulvene-type cyclic compounds, and highly unsaturated aliphatics. There is evidence for formation of all such types in thermal reactions of acetylene, but not enough is known of their chemistry to determine which might be of most significance as an intermediate under combustion conditions. It is probable that no one type actually controls the reaction. Parallel with the chemical question here, there is an important physical question of whether the nucleus for the ultimate carbon particle is a droplet of liquid polymer or a small bit of solid. 

The series-parallel type of reaction outlined in Section 1.10.1 is quite common among industrial processes. For example, ethylene oxide reacts with water to give monoethylene glycol, which may then react with more ethylene oxide to give diethylene glycol. 

Another early success in biomimetic chemistry concerns reactions promoted by thiamin. In 1943, more than 35 years ago, Ukai, Tanaka, and Dokowa (12) reported that thiamin will catalyze a benzoin-type condensation of acetaldehyde to yield acetoin. This reaction parallels a similar enzymic reaction where pyruvate is decarboxylated to yield acetoin and acetolactic acid. Although the yields of the nonenzymic process are low, it is clearly a biomimetic process further investigation by Breslow, stimulated by the early discovery of Ugai et al., led to an understanding of the mechanism of action of thiamin as a coenzyme. 

This ubiquitous role for electrified interfaces throughout many aspects of science suggests that electrochemistry should not be regarded as only a branch of chemistry. Rather, while most chemists have concentrated upon thermally activated reactions and their mechanisms, with electrochemical reactions as some special academic subcase, there is a parallel type of chemistry based not on the collisions of molecules and the energy transfers that underlie these collisions but on interfacial electron transfers. It is this latter chemistry that seems to underlie much of what goes on in the world around us, for example, in photosynthesis, in metaboiism, and in the... 

In many cases, parallel pathways exist for photochemical loss of ligands, particularly for CO. In addition, many of the radicals have appreciable lifetimes and can also undergo photochemical reactions. This type of reactivity can be used in designed synthesis and, possibly, photocatalysis. It also has to be guarded against since many metal-metal bonded complexes that are relatively stable, even in solutions in the presence of oxygen in the dark, are rapidly oxidized in the presence of stray light. 

When the main reaction consists of a sequence of steps involving intermediates and coke is formed out of a con nent appearing before the rate limiting step, the coking behaves as if it were of the parallel type and the numerator of the rate equation for coke formation is proportional to Coke formation from a con onent appearing beyond the rate determining step leads to a rate equation... 

Type I selectivity occurs between two different products formed in parallel reactions that differ by at least one reactant. Type II selectivity involves selectivity of one product over another in parallel reactions involving the same reactants. And, Type III selectivity involves the selectivity between products in a series reaction. Both Type I and III selectivities are affected by mass transport rates (22). 

The stoichiometric chemical equation. Reactions may be divided in this manner into five major types simple reactions, parallel reactions, series reactions, complex series reactions, and reversible reactions. 

In Section 2,4.1 further reactions were mentioned. Their combination results in further systems with two independent parallel reactions. These types of reaction characteristically yield Jacobi matrices, which are diagonal. According to eq. (2.87) a -diagram is obtained, which is shown in Fig. 2.4. 

Several of the parallel-type Milestone microwave reactor systans have been used for scale-up of reactions, including the pharmaceutically valuable Biginelli and Hantzsch multi-component reactions. The work showed reproducibility throughout a set of small reaction vessels run in parallel, and also the applicability of one set of conditions across a range of substrates. 

The simplest is that of parallel, independent reactions (Wheeler Type I) ... 

These types of equations can be applied to more complex reaction schemes such as sequential reactions,parallel reactions and solid state reactions.Table 1 shows some of the reaction schemes where such equations can be written. 

Kinetic measurements show that the simple rate laws known from the last chapter are often not sufficient for a correct description of the temporal course of a reaction or the composition of a reaction mixture. Many reactions take place by mechanisms that involve several elementary steps. Three fundamental types of composite reactions are discussed in this chapter opposing or equilibrium reactions, parallel reactions, and consecutive reactions. Composite reactions not only play a large role in industrial applications (e.g., heterogeneous catalysis) but are also very important in nature (e.g., enzyme reactions). 

A chemical reaction is a process that results in the interconversion of chemical species Table 4.3 summarizes the base reaction types. Chemical reactions might be elementary reactions or stepwise reactions. A stepwise reaction consists of at least one reaction intermediate and involves at least two consecutive elementary reactions. Parallel reactions are several simultaneous reactions that form different respective products from a single set of reactants (Svehla 1993, Muller 1994). 

In order to understand the complexity in oscillatory reactions, it would be worthwhile to examine their relationship with different types of chemical reactions [10], which have been summarized in Fig. 9.8 in increasing order of complexity viz., irreversible reactions -> reversible reactions parallel reaction consecutive reaction -> autocatalytic reactions damped oscillations aperiodic oscillations spatio-temporal oscillations chaotic oscillations. Further, Fig. 9.8 shows the concentration... 

The two cobalt centers in dicobalt cofacial diporphyrins have been reported to act in concert in order to achieve four-electrrMi reduction of oxygen [51,52], One of the sites reportedly functions as a Lewis acid to stabilize the intermediate(s) in the cavity, ensuring that it does not dissociate before completion of the reaction [53], To corroborate the dual-site postulate and specificity of the reaction site, a parallel type of mechanism involving both the two- and four-electron reduction was observed when one of the Co(III) centers in C02FTF4 was replaced by A1(III) [53]. A simplified scheme of the proposed mechanism of oxygen by dicobalt cofacial porphyrins is shown in Fig. 7.10 [48]. 

In this chapter, the dynamics of ideally stirred tank reactors will be analyzed. First, the assumptions, required to limit model complexity, will be discussed. Next, various types of reaction will be considered such as simple first-order reactions, equilibrium reactions, parallel reactions, etc. Subsequently, the analysis will be expanded to include non-isothermal reactors. Numerical examples of chemical reactors are given and the non-linear model descriptions are compared with the linearized model descriptions. 

Although this is described as fundamentally different from the situation with parallel reactions, both types of problems can be solved by defining two extents of reaction and... 

The conditions under which various types of compounds encountered in tracer work exchange with water are given in Tables IV, V, VI, VII, and VIII. These tables can be used as a guide in planning experiments, but in the last analysis, particularly in biocherhical reactions, parallel control experiments must be run to examine the possibility of isotopic... 

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