Lignin-derived phenolic species phenols

Many oxidative degradations also have been carried out to break coal down into simpler species (10, 18-21) however, isolation and identification of phenols such as p-hydroxybenzene (I), vanillic (II), and syringic (III) derivatives, which are considered as characteristic lignin oxidation products (1, 4, 17, 22, 23), have not yet been confirmed definitely. 

Lignin, one of the major polymeric constituents of wood, is a highly crosslinked phenolic polymer derived from the free-radical coupling of substituted phenylpropa-noids (Figure 5.9). It reacts with aqueous chlorine to form oxidized and chlorinated species. This is a key reaction in the bleaching of wood pulp by the kraft process... 

---