Indene photooxidation

The observed ambient organic aerosol formation rates are also consistent with those estimated by extrapolation of smog-chamber kinetic data. Other heavy unsaturates, such as styrene and indene, are present in the atmosphere and may contribute, in part, to the formation of benzoic acid and homophthalic acid, respectively. Diesel exhaust and industrial emission are possible sources of such heavy unsaturates. Diolefins of C6+ are not present in gasolines and exhaust gases and have not been found in the atmosphere, and their possible role as precursors of the Cs-7 difiinctional acidic compounds is seriously challenged. Lower diolefins are emitted in automobile exhaust. Examination of vapor-pressure data indicates that the bulk of their expected photooxidation products remains in the gas phase, including most of the less volatile C3-4 dicarboxylic acids. 

For the kinetics and mechanisms of the gas-phase reactions of other 2- to 4-ring PAHs with OH radicals, N03 radicals, and 03, see, e.g., phenanthrene, Kwok et al. (1994a), and indan, indene, fluorene, and 9,10-dihy-droanthracene, Kwok et al. (1997) for dibenzo-thiophene, a volatile S-PAC that is ubiquitous in polluted ambient air environments and forms mutagenic photooxidation products, see Kwok et al. (1999) see also Kwok et al. (1994b) for a review of gas-phase NO-, radical reactions with aromatics. 

In some instances the primary product of alkene photooxidatitxi is not the allylically rearranged hydroperoxide, but the dioxetane addition product, e.g. (56), which may or may not formed by concerted [2 + 2] cycloaddition. Some of these dioxetanes, e.g. (57), ate relatively stable, although most suffer cleavage to produce carbonyl compounds or other materials. For example, photooxidation of indene gives homophthaldehyde (58) which was not produced under identical reaction conditions from hydroperoxide (59). Isomeric hydroperoxides (60) and (61) were also isolated when the oxidation was carried out in methanolic solution (Scheme 14). 

Zhang, J. and Foote, C. S., Photooxidation of substituted indenes at low temperature. Tetrahedron... 

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