Induced Reaction

Induced Reaction 

a chemical reaction that occurs only in conjunction with another reaction and only in the presence of at least one common reagent. The reaction (A + B → products) inducing other reactions is called the primary reaction, and the one induced by the primary reaction (A + C → products) is called the secondary reaction. Reagent A, which participates in both reactions, is called the actor. Reagent B, whose interaction with A induces the secondary reaction, is called the inductor, while reagent C is called the acceptor. Inductors in induced reactions, in contrast to catalysts in catalytic reactions, are consumed.

An example of an induced reaction is seen in the joint oxidation of carbon monoxide and hydrogen: 2H₂ + O₂ = 2H₂O and 2CO + O₂ = 2CO₂. The second reaction, in the absence of hydrogen, does not proceed except at very high temperatures but takes place readily with the introduction of H₂ into the system. The induction factor I, which is equal to the ratio of the quantities of reacted acceptor and inductor expressed in moles (gram molecular weight) or gram equivalents, is used as a quantitative index for induced reactions. In the above case, I = n_co/n_H2.

The principal features of the mechanism and certain kinetic characteristics of induced reactions were established in the investigations of oxidative reactions in solutions by N. A. Shilov. The basis for the phenomenon of induced reactions and chemical induction is the formation of intermediates, which arise in the primary reaction and transmit the inductive effect of the primary reaction to the secondary reaction. As a rule, induced reactions are considered chain reactions: after the formation of a primary radical under the action of the inductor, a chain develops involving transformations of acceptor molecules without the participation of inductor molecules. In many cases, induced reactions are similar to autocatalytic reactions.