Die radikalausbeute beim thermischen zerfall von azoisobuttersäuredinitril in gegenwart von sauerstoff und in methylmethacrylat als lösungsmittel

The efficiency ε of the thermal radical formation from bisazoisobutyronitrile (AIBN) in oxygen-containing solutions, was determined by two direct analytical methods, which complement one another. The first consists in the gaschromatographic determination of tetramethyl succinodinitrile, which originates from combination of the primarily formed 2-cyanoisopropyl radicals; it yields a value for (1-ε). The second method consists in the jodometric determination of 2-cyanoisopropyl hydroperoxide and p-benzoquinone which originate from those radicals which have escaped from the primary combination reaction and which latterly undergo a seavengering-reaction with hydroquinone; it yields value for ε. For the system methylmethacrylate/AIBN/O₂/hydroquinone and for 90°C both methods correspondingly result ε + 0.810 ± 0.005. Between 70 and 100°C ε increases linearely from 0.785 ± 0.005 to 0.833 ± 0.005. For n-propyl acetate and toluene as the solvents and at 90°C the same ε-value as for methyl methacrylate was found, i.e. 0.813 ± 0.005 and 0.810 ± 0.005, respectively.