The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate. At this point, assuming a perfectly irreversible reaction, colliding reactant molecules will always go on to form products. It is often marked with the double dagger ‡ symbol. It is also related to enzymes.
As an example, the transition state shown below occurs during the SN2 reaction of bromoethane with a hydroxyl anion.
Read more about Transition State: History of Concept, Explanation, Observing Transition States, Locating Transition States By Computational Chemistry, The Hammond–Leffler Postulate, The Structure-correlation Principle, Implications For Enzymatic Catalysis
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