Concerted reaction

In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step.

[1][2] Concerted reaction rates tend not to depend on solvent polarity ruling out large buildup of charge in the transition state.

The rate of the SN2 reaction is second order overall due to the reaction being bimolecular (i.e. there are two molecular species involved in the rate-determining step).

The reaction does not have any intermediate steps, only a transition state.

In order for the reaction to occur both molecules must be situated correctly.