The Hammond postulate elucidates the connection between the energy of a reaction’s transition state and its associated reactants or products.

According to the Hammond postulate, the structure of a transition state is more similar to the species (either reactants or products) with which it shares a closer energy level. Specifically, if the transition state is energetically closer to the reactants, it will resemble the reactants more closely. Conversely, if it is closer in energy to the products, it will bear a greater resemblance to the products.

This postulate is crucial for understanding reaction kinetics, as it sheds light on why certain reactions proceed at different rates. When the transition state is closer in energy to the reactants, it requires less energy to attain that transition state, resulting in a faster reaction rate. On the other hand, if the transition state is energetically closer to the products, reaching that state demands more energy, which can slow down the reaction.

In summary, the Hammond postulate serves as a valuable framework for comprehending the relationship between the energy of a reaction’s transition state and its reactants or products, as well as how this relationship influences the kinetics of the reaction.