Zhu Youtao, Han Zhe, Fu Lijun, Liu Chengbu, Zhang Dongju
Advanced Material Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, 250014, People's Republic of China.
Key Lab of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, Shandong University, Jinan, 250100, People's Republic of China.
J Mol Model. 2018 Oct 24;24(11):322. doi: 10.1007/s00894-018-3854-x.
Understanding the mechanism for the catalyzed cleavage of the β-O-4 ether linkage in lignin is crucial to developing efficient strategies for depolymerizing lignin. In this work, veratrylglycerol-β-guaiacyl ether (VG) was used as a lignin model compound in a theoretical investigation of the mechanism for the cleavage of the β-O-4 bond as catalyzed by the acidic ionic liquid (IL) 1-H-3-methylimidazolium chloride ([HMIM]Cl). The reaction was found to involve two processes-dehydration and hydrolysis-in which the cation functions as a Brønsted acid (donating a proton) and the anion acts as a nucleophile (promoting dehydration) or interacts with the substrate through hydrogen bonding, stabilizing the intermediate. These roles of the anion and cation of [HMIM]Cl explain why the [HMIM]Cl medium catalyzes the depolymerization of lignin. In addition, calculations predict that adding formaldehyde during the depolymerization of VG prevents the condensation of VG without significantly altering the mechanism of depolymerization, thus suggesting a method for potentially improving the efficiency of lignin depolymerization.
了解木质素中β - O - 4醚键催化裂解的机制对于开发高效的木质素解聚策略至关重要。在这项工作中，藜芦醇甘油 - β - 愈创木酚醚（VG）被用作木质素模型化合物，对酸性离子液体（IL）1 - H - 3 - 甲基咪唑氯盐（[HMIM]Cl）催化的β - O - 4键裂解机制进行理论研究。发现该反应涉及脱水和水解两个过程，其中阳离子作为布朗斯特酸（提供质子），阴离子作为亲核试剂（促进脱水）或通过氢键与底物相互作用，稳定中间体。[HMIM]Cl的阴离子和阳离子的这些作用解释了[HMIM]Cl介质催化木质素解聚的原因。此外，计算预测在VG解聚过程中添加甲醛可防止VG缩合，而不会显著改变解聚机制，从而提出了一种可能提高木质素解聚效率的方法。
