In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step. Reactive intermediates or other unstable high energy intermediates are not involved. Concerted reaction rates tend not to depend on solvent polarity ruling out large buildup of charge in the transition state. Pericyclic reactions are concerted reactions.
In the SN2 reaction a concerted reaction also takes place. Because the reaction rate is bimolecular there are two molecular species controlling the rate of the reaction. Because the rate is dependent 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.
Famous quotes containing the words concerted and/or reaction:
“Civil strife is as much a greater evil than a concerted war effort as war itself is worse than peace.”
—Herodotus (c. 484–424 B.C.)
“Christianity was only a very strong and singularly well-timed Salvation Army movement that happened to receive help from an unusual and highly dramatic incident. It was a Puritan reaction in an age when, no doubt, a Puritan reaction was much wanted; but like all sudden violent reactions, it soon wanted reacting against.”
—Samuel Butler (1835–1902)