Lignin is a macromolecule that is located in plant cell walls. It is the most abundant component of lignocellulosic biomass, right after cellulose and hemicellulose. There are many reasons why it is better to study smaller lignin models instead of lignin as a whole. First, lignin has a high molecular weight, so it is a large biomolecule. Therefore, its structure and functions can be more easily understood if smaller lignin structures are studied first (monomeric, dimeric and polymeric lignin models). Second, it becomes even more difficult to study lignin as a whole when the biomass is fractionated into cellulose, hemicellulose and lignin, because the lignin structure becomes different. Finally, lignin structure as a whole also varies greatly depending on plant species, plant age and many other environmental factors.
This diploma thesis contains an overview of the syntheses of the most common lignin models. Most syntheses include reaction schemes and descriptions of experimental work from the scientific literature. Syntheses of monomeric lignin models are described first. Syntheses of dimeric lignin models are overviewed next in a longer part of the thesis. Finally, there is a brief overview of biomimetic and non-biomimetic syntheses of polymeric lignin compounds.
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