Fast consecutive-competing reactions

The idea was to use a system of fast consecutive-competing reactions, the yield of which may be very sensitive to micromixing, as pointed out by Bourne et al. 0). However, instead of the sophisticated reactions used by these authors, we designed the following system ... 

David, R. and Villermaux, J. (1987), Interpretation of micromixing effects on fast consecutive competing reactions in semi batch stirred tanks by a simple interaction model, Chem. Eng. Commim., 54, 333-352. 

Examples of such consecutive competing reactions are chlorination, nitration of hydrocarbons, or the addition of alkene oxides (e.g., ethylene oxide) to amines or alcohols. If the mixing is fast enough, so that the reacting fluid is homogenous before the reaction takes place, the maximum yield of the desired intermediate A3 will be controlled by the ratio of k2/ky Let us suppose irreversible second order reactions, so the following relations describe the transformation rates of the involved reactants. 

The mechanism of oxidative dyeing involves a complex system of consecutive, competing, and autocatalytic reactions in which the final color depends on the efficiency with which the various couplers compete with one another for the available diimine. In addition, hydrolysis, oxidation, or polymerization of diimine may take place. Therefore, the color of a mixture caimot readily be predicted and involves trial and error. Though oxidation dyes produce fast colors, some off-shade fading does occur, particularly the development of a red tinge by the slow transformation of the blue indamine dye to a red phenazine dye. 

Regime 2 slow reactions. The reaction rate is fast enough that significant reaction occurs in the film between the reactants, but the consecutive or competing reactions are slow relative to the primary reaction. In this case, the conversion rate would be slower than expected, but selectivity would be unaffected. 

The cathodic pinacolisation of 2- and 4-acetylpyridine, which had been investigated by one of the present authors (231-233), offered the chance for a complete kinetic analysis as the respective current voltage curves are of reversible character. They allow for evaluation of the kinetics of consecutive reactions, and one can show that at low pH reaction, Eq. (45c) is only possible if strong surfactants are absent. Such surfactants, by occupying the electrode surface, displace ketyl radicals, RiR2(OH)C , from the electrode surface because the latter are relatively weakly adsorbed and cannot compete with strong surfactants in adsorption. Ketyl radicals dissolved in aqueous or organic solvents of low pH are protonated in a fast almost diffusion-controlled reaction. After protonation they are further immediately reduced to form the monomeric carbinol instead of the hydrodimer—the pinacol ... 

Phases gas with mixer as catalyst, gas-liquid, liquid, liquid-liquid. Fast competing parallel or consecutive reactions that are highly exothermic. For gas-liquid fast reactions in the liquid phase. 

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