Generation of Reactions

Generation of reaction networks with RAIN resonance structures and tautomerism Solid-state NMR studies of reversible 1,5-H shifts Tautomeric equilibria (AMI, MNDO, PM3)... 

Similarly Silica-Bound Co(salen) 37 (Scheme 10) [69] was also effectively used in the HKR of styrene oxide (Scheme 11) and 4-hydroxy-1-butene oxide (Scheme 12). The immobilized catalysts were adapted to a continuous flow process for the generation of reaction products in high yield and ee, requiring only very simple techniques for product purification (Scheme 13). 

A major difference to mass transfer is that now the real reaction rate can be higher than the apparent one. The concentration in the particle is always lower or equal to the concentration in the bulk fluid phase and therefore, from this perspective, the real rate is always lower or, at best, equal to the apparent rate. However, in strong exothermic reactions heat transfer cannot cope with the high rates of generation of reaction heat and the temperature in the catalyst particle can be much higher than in the fluid phase, resulting in a much higher reaction rate than the apparent one. 

Fontain E, Bauer J, Ugi I (1987) Computer-assisted bilateral generation of reaction networks from educts and products, Chem Letters, S. 37 Fontain E, Bauer J, Ugi 1 (1987) Computerunterstiitzte mechanische Analyse der Streith-Reaktion mit dem Pro-gramm RAIN, Z Naturforsch 42B 889... 

Reitsam K, Fontain E, (1991) The generation of reaction networks with RAIN. 1. The reaction generator, J Chem Inf Comp Sci, 31 96... 

Bauer J, Fontain E, Ugi I (1988) Computer-assisted bilateral solution of chemical problems and generation of reaction networks, Anal Chim Acta 210 123 Ugi I, Bauer J, Fontain E (1990) Reaction pathways on a PC, in Personal computers for chemists. J Zupan ed, Elsevier, Amsterdam, p 135... 

Baltanas, M. A., and G. F. Froment, Computer generation of reaction networks and calculation of product distributions in the hydroisomerization and hydrocracking of paraffins on Pt-containing bifunctional catalysts, Comput. Chem. Eng., 9. 71-81 (1985). 

The GRI mechanism lies somewhere between an elementary and empirical mechanism. The latter type of mechanisms will be described in detail in Section 4.4.9. Given the above precautions, the approach used in the GRI mechanism is an important and novel advance of the mathematically-assisted generation of reaction mechanisms. 

C. Chevalier, J. Warnatz and H. Melenk, Automatic Generation of Reaction Mechanisms for the Description of the Oxidation of Higher Hydrocarbons, Ber. Bunsenges. Phys. Chem. 94 (1990) 1362-1367. 

C. Chevalier, W.J. Pitz, J. Wamatz, C.K. Westbrook and H. Melenk, Hydrocarbon Ignition Automatic Generation of Reaction Mechanisms and Application to Modeling of Engine Knock, 24th Symp. (Int.) Comb. (1992) pp. 93-101. 

E.S. Blurock, Reaction System for Modelling Chemical Reactions I. Generation of Reaction Mechanisms, Version 2.0. Program Manual (1995). 

We arrive to the conclusion that in order to maximize selectivity the generation of reaction by-products needs to be as small as possible. The most obvious way to achieve this is to make the hot surface in the reactor as small as possible. This is the driving force for using cold wall reactors for selective tungsten. Such reactors can show superior selectivity when compared to hot wall batch systems. 

With high concentrations of starting materials, the mode MIX is selected. This mode ensures that all combinations of starting materials are considered in the generation of reactions. For instance, if three starting materials. A, B, and C are given, nine reactions will be considered three for monomolecular or pseudo-monomolecular reactions of the reactants (decomposition) three for the combinations A + B, A + C, and B + C and three for potential dimerization or polymerization of the reactants. 

Two different approaches are commonly referred to in the literature when it comes to the automatic generation of reaction mechanisms. The first approach involves combinatorial algorithms based mainly on the pioneering work of Yoneda (1979). These generate the whole set of possible reactions by only taking into account the congruence of the electronic configuration of reactants and products. Bond electron matrices are used to represent the chemical species and matrix operators describe all the possible reactions. 

Clymans, P. J., and Froment, G. F., Computer generation of reaction paths and rate equations in the thermal cracking of normal and branched paraffins, Comp. Chem. Png. 8(2), 137-142 (1984). 

The additions of S04 results in a sharp rise in the activation energy for the generation of reaction products, while in the presence of K and Na the activation energy for the formation of acrolein, aldehydes, and acids falls off. 

Warth, V, Battin-Leclerc, F., Fournet, R., Glaude, P.A., C6me, G.M., Scacchi, G. Computer based generation of reaction mechanisms for gas-phase oxidation. Comput. Chem. (Oxford) 24(5), 541-560 (2000)... 

The more intense heat generation of reaction (13.2) causes the temperature and moisture in the plates to reach more quickly the critical values at which vigorous oxidation starts. 

The second generation of reaction retrieval systems were more specifically tailored to the problem of efficient reaction retrieval, and specifically stored information relating to the atom-to-atom correspondences in going from reactants to products. Searches which made use of these correspondences were fast and essentially free from false drops. In addition these systems permitted extensive use of searches based on keywords or phrases, which are particularly useful when associated with a hierarchically structured thesaurus. 

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