Effect of stannous octoate on the thermal decomposition of 2,2?-azobis(isobutyronitrile)

The thermal decomposition rate constant kd of 2,2′-azobis(isobutyronitrile) (AIBN) in ethyl acetate was determined at 60 °C in the presence of various amounts of stannous octoate (SnOc2). The kd values were found to be dependent on the concentration of SnOc2 in the solution. This dependence is not a linear function of the concentration because kd goes through a maximum when [SnOc2]/[AIBN] = 1. These features were explained by assuming the formation of a 1:1 cyclic complex between the nitrile groups of AIBN and the tin atom of SnOc2. This complex induces steric constraints in the azo bond of AIBN, thus increasing its rate of decomposition.