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Transition state

Not to be confused with Transition of state.

In chemistry, 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 potential energy along this reaction coordinate.[1] It is often marked with the double dagger (‡) symbol.

As an example, the transition state shown below occurs during the SN2 reaction of bromoethane with a hydroxide anion:

The DFT-determined geometry for the transition state of the above reaction.[2] Distances are listed in angstroms. Note the elongated C-Br and C-O bonds, and the trigonal bipyramidal structure.

The activated complex of a reaction can refer to either the transition state or to other states along the reaction coordinate between reactants and products, especially those close to the transition state.[3]

According to the transition state theory, once the reactants have passed through the transition state configuration, they always continue to form products.[3]

  1. ^ Solomons, T.W. Graham & Fryhle, Craig B. (2004). Organic Chemistry (8th ed.). John Wiley & Sons, Inc. ISBN 0-471-41799-8.
  2. ^ The calculation used a B3LYP functional and a 6-31+G* basis set.
  3. ^ a b Peter Atkins and Julio de Paula, Physical Chemistry (8th ed., W.H. Freeman 2006), p.809 ISBN 0-7167-8759-8

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