Linear structure of lignin :

structure of vegetables

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The chemists knew very early that the organic matter which structures the plants was essentially, made up of 3 distinct parts by attacking it in various basic mediums in which :

Cellulose insoluble and is lightly degraded, even at high temperature, under pressure and very strong concentration of soda. It is the principle of the Kraft process of production of paper pulp which did not move conceptually since its discovery at the end of the 19th century and which one makes today industrially 95% more of the chemical paper pulp in the world. Admittedly the chemists knew quickly that it consisted of molecules of polymerized glucose but it is only in the Sixties, with the first structures obtained by x-rays that the cellulose was identified like regular stereo linear polymer ß -1,4 of the D-glucose, organized in crystalline units constituting the fibres responsible for its astonishing mechanical properties.

Hemicelluloses as for them are partially solubilized in basic medium with weak concentration with the atmospheric pressure. In fact these connected regular polymers do not have mechanical properties and easily release by hydrolysis their constitutive sugars which are, for the straw, primarily D xylose with, according to varieties, a small proportion of D glucose and D arabinose.

Lignins appeared very quickly as composed of variously substituted phenolic cores whose structural arrangement appeared irregular and particularly complex. It is thus by hypothetical structural models that the chemists explain so far the structure of lignin.