Single reactant replacement

Fig. 14 Variations of the trisubstituted oxazole MCR using the single reactant replacement approach...

Abstract In the past decade, it has been extensively demonstrated that multicomponent chemistry is an ideal tool to create molecular complexity. Furthermore, combination of these complexity-generating reactions with follow-up cyclization reactions led to scaffold diversity, which is one of the most important features of diversity oriented synthesis. Scaffold diversity has also been created by the development of novel multicomponent strategies. Four different approaches will be discussed [single reactant replacement, modular reaction sequences, condition based divergence, and union of multicomponent reactions (MCRs)], which all led to the development of new MCRs and higher order MCRs, thereby addressing both molecular diversity and complexity. 

Fig. 6 Schematic representation of the single reactant replacement (SRR) strategy to scaffold diversity...

FIGURE U Single reactant replacement method for MCRs. 

One of the best strategies for discovering new reactions in the MCR field is the replacement of one of the components, which is also called single reactant replacement (SRR) [92], This strategy requires a detailed analysis of the mechanism reaction. Following the accepted mechanism for the Ugi-4CR (see Scheme 7.15), the last step is the nonreversible Mumm-type... 

An explanation which is advanced for these reactions is that some molecules collide, but do trot immediately separate, and form dimers of dre reactant species which have a long lifetime when compared with the period of vibration of molecules, which is about 10 seconds. In the first-order reaction, the rate of tire reaction is therefore determined by the rate of break-up of tirese dimers. In the thud-order reaction, the highly improbable event of a tluee-body collision which leads to the formation of tire products, is replaced by collisions between dimers of relatively long lifetime widr single reactant molecules which lead to tire formation of product molecules. 

The simplest model of a bubbling fluidized bed, with uniform bubbles exchanging matter with a dense phase of catalytic particles which promote a continuum of parallel first order reactions is considered. It is shown that the system behaves like a stirred tank with two feeds the one, direct at the inlet the other, distributed from the bubble train. The basic results can be extended to cases of catalyst replacement for a single reactant and to Astarita s uniform kinetics for the continuous mixture. 

Without limiting the validity of the approach we may simplify the situation by replacing reactants, intermediates and products by a single molecule each ... 

Predicting Use the diagram to predict if a single-replacement reaction will occur between the following reactants. Write a chemical equation for each reaction that will occur. 

In a single displacement reaction, one element switches places with another element in a compound. The reactants in a single displacement reaction are an element and a compound, and the products are a different element and a different compound. A single displacement reaction can also be called a single replacement reaction. Look at this example of a single displacement reaction ... 

Nonetheless, understanding high-pressure phase behavior is vitally important to evaluating C02 as a potential replacement solvent for reactions. Certainly, commercial reactions are not run at dilute conditions, so the solubility of the reactants, products, and catalysts in the C02 (if one desires to run the reaction as a single-phase system) will frequently be the key factor in determining the economic viability of the C02-based reaction system. 

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