Multi step reaction

Reaction databases additionally contain information on chemical reactions, giving the reaction participants and reaction conditions of both single- and multi-step reactions. 

CASREACT The CASREACT Eile (The Chemical Absiracts Reaction Search Service) is a chemical reaction database with reaction inlormatioii derived from journal documients from 1974 to the present and from patent documeiiis from 1982 to date. Thie document-based file conlains both 3 million single-step and 3.0 million multi-step reactions (Pcbiniaiy, 2003). 

CASREACT (Chemical Abstracts Reaction Search Service) is a reaction database started in 1985 with more than 6.7 million reactions (3 million single-step and 3.7 million multi-step reactions) (March, 2003) derived from 400 000 documents (journals, patents, etc.). The records contain the following information ... 

Chemln- formRX FIZ CHEMIE GmbH, Germany chemical reactions reaction, biblio., struc- ture 1.0 mio substances, 113859 records, 689029 single-step reactions, 377491 multi-step reactions 250 journals FIZ commercial online quarterly www.mdli.com... 

The expression template reaction indicates mostly a reaction in which a complexed me) ion holds reactive groups in the correct orientation to allow selective multi-step reactions. T1 template effect of the metal is twofold (i) polymerization reactions are suppressed, since th local concentration of reactants around the metal ion is very high (ii) multi-step reactions are possible, since the metal holds the reactants together. In the following one-step synthesis eleven molecules (three ethylenediamine — en , six formaldehyde, and two ammonia molecules) react with each other to form one single compound in a reported yield of 95%. It is ob vious that such a reaction is dictated by the organizing power of the metal ion (I.I. Creasei 1977),... 

An efficient carboannulation proceeds by the reaction of vinylcyclopropane (135) or vinylcyclobutane with aryl halides. The multi-step reaction is explained by insertion of alkene, ring opening, diene formation, formation of the TT-allylpalladium 136 by the readdition of H—Pd—I, and its intramolecular reaction with the nucleophile to give the cyclized product 137[I08]. 

Rate-determining step (Section 4.9) Slowest step of a multi-step reaction mechanism. The overall rate of a reaction can be no faster than its slowest step. 

Many other multisubstrate examples abound in metabolism. In effect, these situations are managed by realizing that the interaction of the enzyme with its many substrates can be treated as a series of uni- or bisubstrate steps in a multi-step reaction pathway. Thus, the complex mechanism of a multisubstrate reaction is resolved into a sequence of steps, each of which obeys the single- and double-displacement patterns just discussed. 

VlL-l-Deoxy-l-fluoro-myo-inositol (393) and (+)-lD-l-deoxy-l-fluoro-m> oinositol (394) have been prepared from myo-inositol through multi-step reactions involving DAST treatment. 

F. G. Helfferich, Kinetics of Homogenous Multi-step Reactions, Elsevier, (2001). H.-J. Kreuzfeld, etal.. Tetrahedron Asymmetry, 4(9), 2047 (1993). 

This section contains a brief survey of NMR spectroscopic investigations of chemical reaction kinetics and mechanisms. One of the goals of reaction kinetics studies is to measure the rate of the reaction (or rate constant) - the rate at which the reactants are transformed into the products. Another goal is to determine the elementary steps that constitute a multi-step reaction. Finally, and perhaps the most important goal is to identify transitory intermediate species. NMR, in common with other spectroscopic techniques, is especially valuable in achieving this... 

This reaction could be one of the steps in a more complicated series of reactions, in a so-called multi-step reaction. If this reaction is the ratedetermining step of the overall complicated series, then this rate law still holds see p. 357. 

The numerical value of the rate of reaction is obtained from a rate equation, which is obtained by first multiplying together the concentrations of each reactant involved in the reaction. (Before we do this, we must be sure of the identities of each reactant - in a complicated multi-step reaction, the reacting species might differ from those mentioned in the stoichiometric equation.) The following simple equation defines exactly the rate at which the reaction in Equation (8.1) occurs ... 

The kinetic treatment of multi-step reactions, and the rate-determining step... 

Each step in a multi-step reaction sequence proceeds at a different rate. 

When we write k(i) with the subscripted T in brackets, we mean the rate constant of the first step in a multi-step reaction. When we write k with a subscripted T but no brackets, we mean the rate constant of a first-order reaction. We adopt this convention to avoid confusion. 

Most organic reactions occur in multi-step reactions, with only a small minority of organic reactions proceeding with a single step. We find, experimentally, that it is extremely unlikely for any two steps to proceed with the same rate constant, which means that we can only follow one reaction at a time. And the reaction that can be followed is always the slowest reaction step, which we call the rate-determining step - a term we often abbreviate to RDS. 

We call the slowest step in a multi-step process its ratedetermining step, often abbreviated to RDS. The overall (observed) rate of a multi-step reaction is equal to the rate of the ratedetermining reaction. 

The multi-functionality of metal oxides1,13 is one of the key aspects which allow realizing selectively on metal oxide catalysts complex multi-step transformations, such as w-butane or n-pentane selective oxidation.14,15 This multi-functionality of metal oxides is also the key aspect to implement a new sustainable industrial chemical production.16 The challenge to realize complex multi-step reactions over solid catalysts and ideally achieve 100% selectivity requires an understanding of the surface micro-kinetic and the relationship with the multi-functionality of the catalytic surface.17 However, the control of the catalyst multi-functionality requires the ability also to control their nano-architecture, e.g. the spatial arrangement of the active sites around the first centre of chemisorption of the incoming molecule.1... 

Starting with 11, we followed a multi-step reaction path that roughly parallels the mechanism shown in Figure 2 ... 

New research and conceptual tools to allow chemo- and biocatalysis to work efficiently in tandem and to perform complex multi-step reactions... 

TSA (Transition state analogue) Frequently a stable analogue of an unstable, high-energy reaction intermediate that is close to related energy barriers in a multi-step reaction. 

In the present paper we describe the catalytic mechanisms of synthetic polymer-Cu complexes a catalytic interaction between the metal ions which attached to a polymer chain at high concentration and an environmental effect of polymer surrounding Cu ions. In the latter half, the catalytic behavior is compared with the specific one of tyrosinase enzyme in the melanin-formation reaction which is a multi-step reaction. To the following polymers Cu ions are combined. 

In reality, it is believed that the oxidation of carbonaceous surfaces occurs through adsorption of oxygen, either immediately releasing a carbon monoxide or carbon dioxide molecule or forming a stable surface oxygen complex that may later desorb as CO or C02. Various multi-step reaction schemes have been formulated to describe this process, but the experimental and theoretical information available to-date has been insufficient to specify any surface oxidation mechanism and associated set of rate parameters with any degree of confidence. As an example, Mitchell [50] has proposed the following surface reaction mechanism ... 

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