Lignins structural units

The presence of lignin structural units was confirmed by retention time data and by comparisons of mass spectra to library spectra, to spectra of authentic standards, and to published mass spectra of lignin phenols Fill. 

The analysis of lignitic woods by analytical pyrolysis has shown that lignin structural units can be preserved as biomaikers in samples as old as Carboniferous age, or approximately 300 million years. At least half or more of the pyrolysis products in lignitic wood of Cretaceous age are methoxyphenols characteristic of lignin. The pn uct distributions in these Cretaceous samples indicate that the lignin is mainly altered in the 3-carbon side chains. Phenols, cresols, catechols, and other methylated phenols account for most of the remaining pyrolysis products. It is likely diat these products are also derived frx>m li in, especially lignin that has been altered by coalification reactions. 

Fig.6.6.4. Lignin structural units giving rise to monomeric products (NEP) by NE method...

Hatcher P. G. (1988) Dipolar dephasing C NMR studies of decomposed wood and coaUfied xylem tissue evidence for chemical structural changes associated with defunctionalization of lignin structural units during coalification. Energy Fuels 2, 48-58. 

Kaneko et al. [79] have prepared hyperbranched structures from the copolymerization of 4-hydroxycinnamic acid with 3,4-dihydroxy cinnamic acid i.e. monomers bearing some resemblance to lignin structural units). These... 

---