the Hammond postulate

The Hammond postulate states that if two similar chemical reactions have similar transition states (the high-energy configurations during a reaction), then these transition states will also resemble each other in structure and energy. Essentially, when comparing reaction steps that are near each other in energy, the transition state of one can be inferred based on the other. This helps chemists predict how changes in a molecule or reaction conditions might affect the speed and pathway of a reaction, by understanding how the transition states shift as the reaction progresses.