木素分子氧化性氨化反应过程中的结构变化

Structural Changes of Lignins Caused by Oxidative Ammonolysis

在一定压力和温度条件下,木素大分子和氨发生反应,生成一些氮修饰木素.为了解反应过程中木素分子结构的变化,用13C和1H-13C 2D-NMR HMQC技术检测了反应前后的分子谱图,结果显示反应过程中木素分子的碎裂化现象十分明显,很可能在氧化性氨化反应过程中,木素大分子表面基团发生了氧化性修饰,如一些侧链CH3被氧化形成CHO和COOH等,然后这些基团与氨结合等;此外,芳香环结构可能通过粘康酸单体断裂形成一些酰胺类产物,但木素分子内部的高度缩合性结构没有明显的变化.

Nitrogen-modified lignins was produced from the reaction of ammonia and lignins under proper conditions. C-13 and H-1-C-13 2D-NMR HMQC spectroscopy was applied to detect the changes of lignin molecule during oxidative ammonolysis. Results showed that fragmentation of lignins molecule was highly drastic during oxidative ammonolysis. Probably oxidative modifications of moieties on the surface of lignin molecule (such as formation of CHO and COOH from CH3 or CH2) took place. Then nitrogen was incorporated into the lignin. However, no obvious changes was found in the highly-condensed lignin inner structures.