Aliphatic azo compounds (R and/or R′ = aliphatic) are less commonly encountered than the aryl azo compounds. A commercially important alkyl azo compound is azobisisobutyronitrile (AIBN), which is widely used as an initiator in free-radical polymerizations and other radical-induced reactions. It achieves this initiation by decomposition, eliminating a molecule of nitrogen gas to form two 2-cyanoprop-2-yl radicals:
For instance a mixture of styrene and maleic anhydride in toluene will react if heated, forming the copolymer upon addition of AIBN.
A simple dialkyl diazo compound is diethyldiazene, , which can be synthesized through a variant of the Ramberg–Bäcklund reaction. Because of their instability, aliphatic azo compounds pose the risk of explosion.
AIBN is produced by converting acetone cyanohydrin to the hydrazine derivative followed by oxidation: