Definition of Pseudoatoms

So certain atoms in Eq. (13.9) reaction can be combined into groups. For example, as a result of the substitution of Q = CO, Eq. (13.10) is obtained  

For example, the group of Q = KO permits a mechanism, with which Q will be transferred or attached to CO2, and then from the CO2 an oxygen atom will be split off, which emerges eventually in the water group. If we introduce the two substitutes Q=OH and Q=KH, then the introduction of these respective radicals is not valid. We can conclude that bonds must be opened within these radicals in the course of the particular reaction. 

On the other hand, the gradual enlargement of Q gives a reference to the group of CO up to the reactant CO2. Obviously, this means that this group (Q = CO2) does not split in the course of the reaction. 

By a combination of such statements, we can arrive in the best case conclusively at a restriction of possible reaction mechanisms. Even we may exclude some reaction mechanisms by a critical examination of such a procedure. 

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