Isooctane photooxidation products

Characterization of Photooxidation Products Formed in Isooctane. Among the lodometncally titratable species formed in the photooxidation of isooctane, a substance, developed in appreciable amounts, was observed which was easily distinguishable from ordinary alkyl-hydroperoxides. This substance is, at room temperature, readily destroyed by addition of olefins to the reaction medium. This is a reaction which is typical and specific for peracids (10) and can be employed for quantitative assessment of peracids in the presence of alkylhydroperoxides. In contrast to alkylhydroperoxides, peracids react with olefins forming the corresponding epoxide, according to the equation... 

Figure 3. Relative initial rate of formation of photooxidation products other than peracids in isooctane against -log Iq.

Quantitative assessments turned out to be much more difficult in 2,4-dimethylpentane than in isooctane, due to formation of relatively unstable photooxidation products. 

Products reacting in this way in photooxidized isooctane have therefore been assigned to peracids. Their rate of formation has been determined in our photooxidation experiments by use of 7-tetradecene, which turned out to be a convenient olefin for peracid-analysis. The results obtained for different rates of radical initiation are shown in Figure 2. 

After removal of peracids by tetradecene addition, substantial amounts of iodometrically titratable oxidation products remained in photooxidized isooctane. Their relative rate of formation did not depend markedly on the rate of radical initiation and was found to be in the order of 40 to 45% of I. This is shown in Figure 3. Although the chemical composition of these products has not been identified, it is, however, assumed that these products were mainly hydroperoxides and probably dialklyperoxides other than those formed by self-recombination of tertiary peroxy radicals. 

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