22azobisisobutyronitrile

2,2'-Azobis(isobutyronitrile), commonly abbreviated as AIBN, is an azo compound used as a radical initiator in polymerization and organic synthesis. It decomposes thermally to produce free radicals that initiate chain growth in a variety of vinyl monomer polymerizations.

Its structure consists of two isobutyronitrile groups connected by an azo (-N=N-) bond. The molecular formula is C8H12N4. AIBN appears as a white to pale yellow crystalline solid and is soluble in many organic solvents, while only sparingly soluble in water.

Upon heating, AIBN undergoes homolytic cleavage of the azo bond, giving two 2-cyanoprop-2-yl radicals and nitrogen gas. This process typically starts at temperatures around 60–70°C and provides a controlled source of radicals for initiating polymerizations or other radical reactions.

It is used to initiate free radical polymerizations of vinyl monomers such as styrene, acrylates, and methacrylates, in bulk, solution, or emulsion processes. In organic synthesis, AIBN serves as a convenient radical source for various transformations and cascade reactions.

AIBN is considered hazardous: it can be explosive when dry or finely divided and should be stored in a cool, dry place away from heat and oxidizers. Appropriate safety precautions, including ventilation and personal protective equipment, should be used when handling and disposing of this compound.