Lignin structure guaiacyl

Although, the ultraviolet spectroscopy of softwood lignin and guaiacyl model compounds has been thoroughly studied, the same cannot be said about hardwood lignins. It has been shown that the absorptivity of hardwood milled wood lignins at 280 nm decreases linearly with the methoxyl/carbon ratio (Sarkanen et al. 1967), but the effects of side chain structures on the ultraviolet absorption properties of hardwood lignins have yet to be determined. 

Different phenolic derivatives with lignin-related structures were also released. Among them, we note the presence of some benzenecarboxylic acids, some of them being lignin structures with p-hydroxycoumaryl, guaiacyl and syringyl skeletons, peaks (1) 4-methoxybenzenecarboxylic acid methyl ester, (4) 3,4-dimethoxybenzenecarboxylic acid methyl ester, (7) 3,4,5-... 

Many grasses have mostly guaiacyl structures. Which monomer forms the guaiacyl lignin structure ... 

Akiyama, T. Goto, H. Nawawi, D. S. Syafii, W. Matsumoto, Y. Meshitsuka, G. Erythro/threo ratio of P-O-4-structures as an important structural characteristic of lignin. Part 4 variation in the erythro/threo ratio in softwood and hardwood lignins and its relation to syringyl/guaiacyl ratio. Holzforschung 2005, 59, 276-281. 

Fig. 2.2 A. Chemical structure of the three types of lignin monomer units H, p-hydroxyphenyl- G, guaiacyl and S, syringyl. Note the methyl groups (boxed) in the methoxy moieties of the G and S monomers. B. Pie chart showing the proportions of pine xylem ESTs that putatively encode enzymes of Ci metabolism, glycolysis, and the TCA cycle.

Condensed Structures in p-Hydroxyphenyl-Guaiacyl Type DHP. It has been difficult to determine the exact amount of p-hydroxyphenylpropane units in lignin. This can best be illustrated by an example nitrobenzene oxidation of a DHP prepared by the Zutropfverfahren method from a mixture of p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol, gave no detectable p-hydroxybenzaldehyde on alkaline nitrobenzene oxidation... 

---