Quantification of Lignin Hydroxyl Containing Functional Groups via 31P{1H} NMR Spectroscopy and Synthesis of Lignin Degradation Standards

摘要

The focus of this thesis is on the structural characterization of lignin, a complex phenol-based heteropolymer. In the first part of the study, functionalization of lignin and its known degradation products by 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (TMDP) and analysis by 31P NMR spectroscopy was investigated. Chemical shifts of derivatized alcohols, phenols, and carboxylic acids were determined that allowed for qualitative characterization of lignin. This approach was further applied for the quantitative analysis of OH-containing groups present in lignin employing the internal standard. Lignin samples, fractionated by gel permeation chromatography (GPC) based on molecular weights, were derivatized by TMDP and characterized by 31P NMR spectroscopy. It was determined that the number of hydroxyl-containing functional groups quantified in lignin samples increased by 366% after GPC.;In the second part of the study, six possible lignin degradation products were synthesized. It was confirmed that one of them, (E)-4,4'-(ethane-1,2-diyl)bis(2-methoxyphenol), was present in lignin degradation samples.