Bimolecular Reaction
An elementary step in which two species collide and react.
Formula / equation
A + B → products, rate = k[A][B]
Unit
L/(mol·s)
In depth
Bimolecular steps are always second order overall and are by far the commonest type of elementary reaction, since simultaneous collisions of more than two particles are statistically rare. The reacting species must collide with sufficient energy and in the correct orientation.
Examples in the real world
The SN2 attack of hydroxide on bromomethane; H₂ colliding with I₂ in the gas phase.