Quinones as sensitizers

Rabek [498, 505] examined the rapid degradation of cis-1,4-polyisoprene on exposure to light in the presence of p-quinones p-quinone, chloranil, 1,4-naphthoquinone, anthraquinone, phenanthrene-quinone and 1,2-benzanthraquinone (Fig. 20). Later, Rabek [504] also found that p-quinone sensitizes the photo-oxidation of polystyrene in benzene in the presence of UV radiation. 

Other derivatives of p-quinones, such as anthraquinone, mono- and di-sodium sulphonates are photosensitizers of the oxidation of isopropanol [Refs. 84, 105, 106, 158, 662, 663]. Lock and Sagar [377] have suggested that a similar mechanism may occur in the photosensitized oxidation of JV-alkylamides which they studied as a model system simulating the photo-sensitized degradation of polyamides. They suggest that the AT-alkyl radical initially produced may add molecular oxygen to give peroxy radicals which are the precursors of the observed oxidation reaction. 

Egerton [200] found that 1-piperidinoanthraquinone sensitized the photo-oxidation of polyamides and 1,5-diaminoanthraquinone sensitized the photo-oxidation of nylons and cellulose. Kujirai et al. [354] reported sensitized photo-oxidation of cellulose by anthraquinone and its derivatives. 

The primary photodissociation of alkyl peroxides takes place in the first absorption region. The weak RO—OR bond is disrupted  

At wavelengths below 2300 A alkyl peroxides dissociate in another way namely, 

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