PHOTO- AND THERMAL INITIATOR EFFICIENCY OF 2,2'-AZOBISISOBUTYRONITRILE AT 25 DEGREES

Using thiols as free-radical scavengers and exceedingly long reaction times, the fraction of kinetically free radicals produced in the thermal decomposition of 2,2′-azobisisobutyronitrile (ABN) has been measured in benzene and cyclohexane at 25°. Using a chain reaction as a radical counter, a similar fraction is obtained for the photodecomposition of ABN thereby providing, for the first time, a comparison of these efficiencies at a common temperature. The photoprocess is found to be somewhat more efficient in both solvents but both photo- and thermal decompositions are less efficient in cyclohexane than in benzene.