Azobisisobutylonitrile

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Azobisisobutyronitrile, also azobisisobutylonitrile, is a toxic white crystalline compound often used as a foamer in plastics and rubber. It is commonly known as AIBN, it decomposes by the elimination of a molecule of nitrogen gas to form two 2-cyanoprop-2-yl radicals.

These radicals can be used to start up free radical polymerizations. For instance a mixture of styrene and maleic anhydride in toluene will react if heated very slowly to form the polystyrene polymer unless an initiator such a AIBN is present. Another example of free radical polymerization is the 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. The melting point of AIBN is 103-105°C. It is soluble in methanol & ethanol, but 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.