The Thermodynamic Conjugation of Processes

Let two stoichiometric stepwise reactions, which involve some combi nation of elementary chemical reactions, be concurrent in the system. Indicate these stepwise reactions by indices 21 and 22. It is evident that for stoichiometric stepwise transformations, the elementary reactions can be omitted in the equation for djS/dt  

Note that the thermodynamically necessary inequahty equation (1.22) can 

The latter inequality contradicts the condition of the spontaneous mode of stepwise reaction 22. Therefore, in this case the two stepwise reactions under consideration must be interdependent, or conjugate. The former reaction, which is thermodynamically allowed to be spontaneous, is referred to as conjugating, while the latter reaction is referred to as conju gated to the former one. Chapter 2 will demonstrate that the conjugation occurs only in cases when the stepwise processes encompass elementary stages with common (for the stepwise reactions) intermediates omitted in the equation to describe these stoichiometric stepwise transformations. 

This is namely a thermodynamic conjugation of two processes that allows the conjugated stepwise reaction 22 to proceed in a forbidden direction when K y.2 and V22 are of opposite signs, and thus, the stepwise reaction 22 leads, formally, to a decrease in the entropy. Typical examples of the conjugating and conjugated reactions are, respectively, a reaction catalyzed by some catalyst and the closed chain of chemical transformations of the catalyst active center. The simplest combination of such reactions is the catalyzed stepwise reaction 

Actual catalytic processes are described in a much more complex way than the reaction sequence (1.24) (see, e.g.. Chapter 4). Yet, a more com plex example of conjugation of chemical reactions is, indeed, the vital activity of living species based on the metabolic cycles driven by transfer mations of an energy rich food. 

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