Wu Jie, Liu Chao, Li Qinbin
Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, School of Energy and Power Engineering, Chongqing University, Chongqing, 400030, China.
J Mol Model. 2019 Jul 22;25(8):234. doi: 10.1007/s00894-019-4117-1.
O-acetyl-4-O-methylglucurono-xylan is selected as a model compound because of its abundant O-acetyl and 4-O-methylglucuronic acid groups as side chains of hemicellulose. The detailed decomposition pathways of O-acetyl-4-O-methylglucurono-xylan are investigated by using density functional theory (DFT) and transition state theory. In addition, the possible pyrolysis pathways of 4-O-methylglucuronic acid, based on the Mayer bond order values, are predicted. The results indicate that the most energetically favored initial reaction of O-acetyl-4-O-methylglucurono-xylan is the cleavage of the 4-O-methylglucuronic acid unit. Furfural can be obtained through the ring-opening of 4-O-methylglucuronic acid in three different pathways. The O-methyl group is predominantly responsible for the generation of CHOH. In addition, the formation pathways of a special furan-derived product 2-hydroxymethylene-tetrahydrofuran-3-one are first validated by DFT calculation. The rate-determining steps to form 2-hydroxymethylene-tetrahydrofuran-3-one are the cyclization reaction and enol-keto tautomerization. Anhydroxylopyranose and dianhydroxylopyranose can be produced through intramolecular dehydration and glycosidic bond cleavage reactions. Graphical abstract The main pyrolysis products distribution of O-acetyl-4-O-methylglucurono-xylan.
由于O-乙酰基-4-O-甲基葡糖醛酸木聚糖作为半纤维素侧链含有丰富的O-乙酰基和4-O-甲基葡糖醛酸基团，因此被选为模型化合物。利用密度泛函理论（DFT）和过渡态理论研究了O-乙酰基-4-O-甲基葡糖醛酸木聚糖的详细分解途径。此外，基于迈耶键级值预测了4-O-甲基葡糖醛酸可能的热解途径。结果表明，O-乙酰基-4-O-甲基葡糖醛酸木聚糖在能量上最有利的初始反应是4-O-甲基葡糖醛酸单元的裂解。糠醛可通过4-O-甲基葡糖醛酸的三种不同开环途径获得。O-甲基主要负责生成CHOH。此外，首次通过DFT计算验证了一种特殊的呋喃衍生产物2-羟基亚甲基-四氢呋喃-3-酮的形成途径。形成2-羟基亚甲基-四氢呋喃-3-酮的速率决定步骤是环化反应和烯醇-酮互变异构。通过分子内脱水和糖苷键裂解反应可以生成脱水吡喃糖和二脱水吡喃糖。图形摘要：O-乙酰基-4-O-甲基葡糖醛酸木聚糖的主要热解产物分布。
