Detection of Mechanoradicals in Lignin

Milled wood lignin is carefully packed into a quartz sample tube and inserted into the ESR cavity. Turn on the instrument and by following the procedure described above, a singlet signal with a g-value of 2.0023 and a line width of 16 gauss will be detected (Fig. 5.5.5) The concentration of this particular lignin 

3 Detection of Free Radicals in a Photoirradiated Lignin Model Compound 

260 nm at 77 K Heating of the irradiated sample at 298 K for 3 mm reduces the spec trum to a singlet signal (dotted line) 

Many free radicals generated in lignin have been studied Because of the structural complexity of lignin, multiplet spectra are obtained The analysis and interpretation of the spectrum can be performed by different techniques depending on the experimental conditions (Hon 1982, 1987, Zavoiskn 1945) 

ESR studies of lignin model compounds, on the other hand, have yielded information on the detailed structures of phenoxy radicals that are involved in some homolytic splitting reactions of lignin Such information has proven useful in elucidating the mechanisms of these reactions As with other spectrometnc methods, ESR also suffers from its inability to shed light on the true nature of free radicals, phenoxy or otherwise, that exist in lignin macromolecules 

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