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What are Radical inhibitors and their role in a reaction?

A radical reaction usually happens in three steps- Initiation (creation of free radicals), Propagation (multiplication and growth of radical reaction), and Termination (stopping of the free radical reaction).

Radical inhibitors are chemical species that inhibit radical reactions by halting the chain propagation step.

Examples of such inhibitors are Hydroquinone, BHT (2,6-di-t-butyl-4-methylphenol), etc.

An inhibitor like BHT, a sterically hindered phenol, forms stable, non-reactive radicals that do not react further. The radical is entirely flanked by two bulky t-butyl groups blocking its reactivity. The radical is also stabilized by resonance with the aromatic ring.

 

role of radical inhibitors, example

 

Hydroquinone inhibitors pick up the radical to form a stable nonradical compound, quinone. 

 

Hydroquinone radical inhibitor role free radical reaction

 

Such radical inhibitors are very useful in slowing or stopping the reaction since the radical chain reactions are fast and uncontrolled. The inhibitors must be consumed before the reaction can proceed at the initial rate. 

 

Related Reading- Free Radicals (Introduction, Structure, and Types)

 

Reactive Intermediates
Organic Chemistry - Drawing Structures, Concepts, and Examples

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