It is derived from the idea that the transition state is always the point of highest energy on a reaction-energy diagram, and that in an endothermic reaction the transition state is closer to the products in energy and structure, while in an exothermic reaction the transition state is closer to the reactants in energy and structure.
It explains why exothermic processes tend to be less selective than similar endothermic processes. It is derived from the idea that the transition state is always the point of highest energy on a reaction-energy diagram, and that in an endothermic reaction the transition state is closer to the products in energy and structure, while in an exothermic reaction the transition state is closer to the reactants in energy and structure. FTP, identify this postulate that states the structure of a transition state resembles the structure of the closest stable species.
It explains why exothermic processes tend to be less selective than similar endothermic processes.
{Hammond} postulate