Chapter 2

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1 Notes of Applied Chemical Kinetics course Carlo Cavallotti Chapter 1. Introductory aspects and classification of chemical reactions Chapter 2. Kinetic schemes and reaction mechanisms Chapter 3. Kinetic theory of Gases Chapter 4. Fundamentals of Statistical Thermodynamics and Molecular Quantum Mechanics Chapter 5. Transition State Theory and further developments 2 Chapter 2. Kinetic schemes and reaction mechanisms 2.1 Introduction The schematization of reaction mechanisms introduced in the previous chapter seems to indicate a well-defined path to predict the kinetics of any reagent system. Given any reagent system, it seems possible to study its reactivity in a systematic way by applying a protocol that consists in the definition of all the chemical species that can be reasonably formed during the reaction, and in the construction of a kinetic scheme that includes all the reactions that can occur between them. Thus, the problem is reduced to the estimation of the kinetic constants of every single elementary act. This approach is endearing for many reasons. At least because it seems to suggest the existence of a universal method to study any reagent system. Actually it is a path followed by some research groups in the kinetics field, whose aim is the creation of an ‘automatic generator of kinetic schemes’. Basically it would be a software capable of generating automatically a kinetic scheme given any reactive system, and of estimating the kinetic constants of every reaction that appears automatically (e.g. using the methods described in chapter 5 of these notes). However, the few examples reported in literature are unconvincing. The problems are essentially two. The first is the a priori identification of the chemical intermediates that can be formed during the…