Reaction inhibitor

A reaction inhibitor is a substance that decreases the rate of, or prevents, a chemical reaction.

Examples:

• Added acetanilide slows the decomposition of drug-store hydrogen peroxide solution, inhibiting the reaction
  

2H₂O₂ → 2H₂O + O₂, which is catalyzed by heat, light, and impurities.

Inhibition of a catalyst

An inhibitor can reduce the effectiveness of a catalyst in a catalysed reaction (either a non-biological catalyst or an enzyme). E.g., if a compound is so similar to (one of) the reactants that it can bind to the active site of a catalyst but does not undergo a catalytic reaction then that catalyst molecule cannot perform its job because the active site is occupied. When the inhibitor is released, the catalyst is again available for reaction.

Inhibition and catalyst poisoning

Inhibition should be distinguished from catalyst poisoning. An inhibitor only hinders the working of a catalyst, whilst in catalyst poisoning the catalyst is destroyed by an irreversible reaction with a chemical substance (the active catalyst in the latter case may be regained by a separate process).

See Also

• Enzyme inhibition
• Catalyst poisoning