Hydroxyl radicals, lignin degradation

K Tatsumi and N Terashima. Oxidative degradation of lignin. (7) Cleavage of P-O-4 linkage of guaiaclglycerol-P-ether by hydroxyl radicals [from hydrogen peroxide]. Mokuzai Gakkaishi 31 316-317,1985. 

The lignin-degrading peroxidases operate by generating hydrogen peroxide, which dissociates into hydroxyl radicals that react with lignin by free radical substitution reactions to break down the network structure of the highly crosslinked, three-dimensional polymer. This reaction sequence is illustrated below for a representative section of the complex lignin macromolecule ... 

Chauaqui et al (10) show that y irradiation of two types of kraft lignin with about 2.4 Mrad of dose leads to polymerization materials. High dose of 10 Mrad are required to induce degradation reactions with loss of methoxyl groups. Their results indicate that the most important free radicals formed involved phenolic hydroxyl groups, a carbonyl groups and a ethylenic double bonds. Unfortunately the dose rate used was not reported. 

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