Concerted reaction - Definition

In chemistry, a concerted reaction is one that takes place in a single step. For instance in the Sn2 reaction a concerted reaction takes place. S is substitution, n is nucleophilic, 2 is the number of molecules involved, hence a bimolecular reaction. Because the reaction rate is bimolecular there are two molecular species controlling the rate of the reaction. Because the rate is dependant on two molecules the reaction does not have any intermediate steps, only a transition state. This means that all the bond making and bond breaking takes place in a single step. In order for the reaction to occur both molecules must be situated correctly. Therefore, the reaction is said to be concerted because it occurs in one step. Analogous to a concerted action, everything occurs in one step.

Example Usage of Concerted