A brief study on the effect of addition of cumene hydroperoxide (II

CHP

in text) without or with simultaneous addition of an alkaline additive (sodium carbonate or calcium oxide) on the reduction of the induction period in the autoxidation of cumene (I) showed that the heterogeniety inherent in the latter systems resulted in poor reproducibility. Sodiumsalt of cumene hydroperoxide (III) was introduced as an oilsoluble system in which the initiator and the alkaline additive are in combination. Experiments with various amounts of III at 110° 120°and 130°that the induction period and the autocatalysis were either completely or practically eliminated. The reproducibility of the experiments accompanying the use of III was extremely good. The rate of accumulation of II was 16±0.7% (wt.)/hr. at. 130° at 120° the rate was 8.7%/hr. except when the amount of III was 3.33% (7.3%/hr.); at 110° the rate varies more pronouncedly with the amount of III (3.0-5.0%/hr.). Oxygen-absorption in a closed system was observed in order to examine more closely the phenomena of the elimination of the induction period. It was found that a rapid absorption of oxygen took place in the first minutes

followed by a somewhat slower absorption. Kharaschs conceptions on the alkaline catalyzed decomposition of II and the subsequent

reactions between the resulting dimethylphenylcarbinol and II

yielding free radicals

were considered to be adequate in explaining the instantaneous initiation of the reaction chain. Water of crystallization in II facilitates the ionic reaction. Addition of solid sodium hydroxide also caused a rapid initial oxygen absorption

only that a very brief induction period was observed. This is thought to follow the same course of reaction as outlined above

with traces of II in I participating. The efficiency of the autoxidation of I with respect to II-accumulation when III was used was found to be 92-97%. The use of cobalt stearate in promoting the rate of autoxidation of I was investigated. At 110°

addition of the cobalt-salt indeed increased the initial rate of accumulation of II (11.5-12.5%/hr.)

yet the same mechanism that induced the reaction chain and subsequently brought about the faster rate of reaction prevented the accumulation of II (25%) to a higher degree. The destruction of II by cobalt ions was evidenced by the fact that

with the highest concentration of cobalt-salt used

there was actually no accumulation of II.at the beginning of the reaction. Addition of II together with cobalt-salt did not further promote the reaction. It is concluded that traces of II in I was sufficient to be responsible for the chain-initiation processes. The lower accumulation of II with use of cobalt-salt was remedied by simultaneously adding III. The result was that the rate of accumulation of II at 110°?corresponded to that at 130?with addition of II or III alone. The degree of accumulation of II was also high (40%).