Transition State
The highest-energy configuration along the reaction coordinate, at which bonds are partly broken and partly formed.
Formula / equation
denoted ‡
Unit
kJ/mol
In depth
The transition state exists for only about one bond vibration and cannot be isolated. Its structure determines the activation energy and hence the rate, so understanding what stabilises it — solvent, substituents, catalysts — is the key to controlling reaction speed.
Examples in the real world
The trigonal bipyramidal arrangement in an SN2 reaction, with partial bonds to both leaving group and nucleophile.