Azobisisobutyronitrile is a toxic compound often used as a foamer in plastics and rubber and as a radical initiator. It is commonly known as AIBN. Its most common chemical reaction is one of decomposition, eliminating a molecule of nitrogen gas to form two 2-cyanoprop-2-yl radicals:

These radicals can be used to to initiate free radical polymerizations and other radical reactions. For instance a mixture of styrene and maleic anhydride in toluene will react if heated, forming the polystyrene polymer, only very slowly unless an initiator such an AIBN is present. Another example of a radical reaction that can be initiated by AIBN is the anti-Markovnikov hydrohalogenation of alkenes.

AIBN is safer to use than benzoyl peroxide (another radical initiator) because the risk of explosion is far smaller. However, it is considered a flammable solid. It is soluble in methanol and ethanol, but is insoluble in water. It can explode if dissolved in acetone. AIBN is highly toxic. Wear a respirator/dust mask, protective gloves, & safety glasses when handling AIBN.

Several water-soluble azo initiators similar to AIBN are manufactured by DuPont^[1] and Wako.^[2]

• 1,1′-Azobis(cyclohexanecarbonitrile) or ABCN is another free radical initiator

de:Azo-bis-(isobutyronitril)

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