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Hammond Postulate (Polanyi-Hammond Postulate)

ChemieOrganische ChemieReaktionsmechanismen

In this learning unit, the Hammond postulate (Polanyi-Hammond postulate) is explained in detail. The concept of early and late transition states is described and its use for estimating the transition state structure is depicted. In addition, the theoretical fundamentals of estimating the influence of substituents on the reaction rate are illustrated.


  • Prof. Dr. Gregor Fels
  • Dr. Carsten Biele


  • Dr. Carsten Biele

Learning objective

  • Basic understanding of the Hammond postulate.
  • Concept of early and late transition states.
  • Fundamentals of estimating the substituents' influence on the reaction rate.
  • Correlation between the transition state structure and the structure of starting products, products, and intermediates.

Important Keywords in this Learning Unit

transition state, activation energy