Computer-assisted design of reaction mechanisms

The design of a complex reaction mechanism can also be helped by the computer. This is obviously very close to that of the organic synthesis assisted by the computer, which has given rise to an abundant literature (see, for example, refs. 228—233 and references therein). Studies dedicated to organic synthesis are not concerned with the problems of the kinetic modelling and simulation of reactions and reactors. Only two investigations directed towards chemical kinetics will be briefly mentioned. 

Yoneda [189] has devised a program which generates elementary reaction networks for reactions involving free radicals, ions or active sites on heterogeneous catalysts. Reactants and products are represented by connectivity tables and reactions by matrices equal to the difference of the matrices of products and reactants, respectively. As soon as a set of reaction matrices has been defined, by applying them to the initial reactants, a new set of intermediates and products is obtained, which are themselves submitted to reactions and so on. Restrictions are necessary to avoid the appearance of unrealistic steps or compounds. 

Vogin et al. [235] have created a program for the computer design of a free radical reaction mechanism in the gas phase, in agreement with the rules formulated in Sect. 2.5.3. An algorithm has been devised to transform by the computer the formula of a compound, written in the linear notation described in Sect. 6.2.1 [182], into a canonical notation. Thus, the system both preserves the flexibility of a simple natural language and gains the sophistication of a canonical notation. 

The state of the art of the mathematical, numerical, statistical, optimizing, and processing methods available nowadays for solving problems in chemical kinetics allows the mechanistic approach to reach its full potential in two directions (i) to contribute to the elucidation of the mechanisms of complex reactions and to the determination of the kinetic parameters of elementary processes (ii) to permit the design of, calculations on, the optimization of and control of an industrial chemical reactor from the results of a previous mechanistic study. This calls for two requirements (i) to improve the numerical and processing methods (some directions of research have been indicated above) (ii) to improve the data bases of fundamental kinetic parameters as well as our understanding of general reaction mechanisms. 

Aj pre-exponential factor of the rate coefficient fe, Aj reactant number j 

Qij index of the element in the formula of Cj coefficient of a one-step algorithm A reactant 

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