Reaction Coordinate Diagrams of Catalytic Reactions

A catalyst decreases the activation energy of a reaction, relative to that of the uncatalyzed reaction, by stabilizing the transition state. Because the transition state is an unstable species and is fleeting, the catalyst cannot affect the transition state alone. Instead, the catalyst binds one or more of the reactants and remains bound through the transition state 

Greater stabilization of ground state than transition state-no catalysis 

Reaction coordinate for a reaction mediated by C, where C is a reagent not a catalyst 

Reaction coordinate diagram for an uncatalyzed reaction, a reaction catalyzed by A, a reaction promoted by an additive B, and a reaction involving a reagent C. 

All three reaction coordinates show the formation of an adduct (S A, S B, or S C) between the substrate and the additives that, for the purpose of illustration, is lower in energy than the reactants. This lower energy is unnecessary for catalysis, and the same principles could be illustrated with a reaction coordinate in which these adducts lie uphill of the reactants. 

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