Cumene polar decomposition

Effects other than those of purely viscometric origin were seen to be significant in a schematic study by McHugh and co-workers of the free radical decomposition of cumene hydroperoxide [48], and subsequent oxidation of cumene (isopropyl benzene) [49, 50] in a range of supercritical and liquid solvents. The effective non-catalysed rate coefficients for cumene hydroperoxide decomposition in non-polarisable supercritical fluids (krypton, xenon) were greater than that for non-polar liquid cyclohexane, as expected a priori on the basis of viscosities. Yet, liquid 1-octene and 1-hexanol gave similar... 

Several solvents have been tested in the epoxidation of a- isophorone with t-butyl hydroperoxide (TBHP). The best performance of the aerogel was observed in low polarity solvents such as ethylbenzene or cumene (Table 1). In these solvents 99 % selectivity related to the olefin converted was obtained at 50 % peroxide conversion, independent of the temperature. Rasing temperature resulted in increasing initial rate and decreasing selectivity related to the peroxide. The low peroxide efficiency is explained by the homol5d ic peroxide decomposition. Protic polar solvents were detrimental to the reaction due to their strong coordination to the active sites. There was no epoxide formation in water. 

Table III. Polar and Radical Decomposition of Cumene Hydroperoxide Induced by Organic Sulfur Compounds (16)...

Thiolsulfinates and their reaction products play an important role in the preventive antioxidant activity observed with organic sulfides and disulfides. An investigation of the decomposition of cumene hydroperoxide in benzene at 25°C in the presence of tert -butyl tert-butanethiolsulfinate has shown that the actual peroxide decomposer is an acidic species whose activity is affected by the basic character of the S-O group in the parent thiolsulfinate and in the sulfoxides. Alternative mechanisms for generating the acidic species are discussed. Although hydroperoxide decomposition occurs primarily by a polar process, the results also indicate the involvement of radical generating processes. 

The polar nature of the catalytic decomposition of cumene hydroperoxide with added terf-butyl terf-butanethiolsulfinate has been clearly established (I). The thiolsulfinate is converted into an active peroxide decomposer capable of destroying many moles of hydroperoxide per mole of sulfur compound. The acidic character of the active species was demonstrated by its effective neutralization with the added base calcium carbonate. Formation of the active peroxide decomposer may be envisaged as involving one or more of the following three reaction types concerted process, ionic processes, and free-radical processes. 

It has been established that the decomposition of cumene hydroperoxide in the presence of thiolsulfinate occurs primarily via a polar process (1). However, a homolytic process may be involved in the conversion of the thiolsulfinate to the active peroxide decomposer. This was probed by adding the radical inhibitors /2-naphthol and 2,6-di-tert-butyl-4-methylphenol (see Figure 5). The inhibitors totally suppressed the decomposition of hydroperoxide by thiolsulfinate. In contrast to /3-naphthol and 2,6-di-terf-butyl-4-methylphenol, the addition of cyclo-hexanol had no significant effect. Similarly, the addition of methanol only reduced the decomposition of hydroperoxide by the thiolsulfinate by 1% after 186 hr. 

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