Significance of Phenolic Hydroxy Group in Lignin Acidolysis

合成了非酚类C6-C2型模型化合物(V‘g、烯醇醚、V’g-a-OMe和V‘g-a-BR)，并在HBr、HCl和H_2SO_4中进行了反应。V‘g-a-OMe的酸解表明，在H_2SO_4体系中，苯基阳离子几乎完全进行H2O加成反应返回起始化合物，而在HBr或HCl体系中，它部分反应生成烯醇醚产物。这一结果极大地解决了自20世纪80年代以来提出的为什么反应路线取决于酸的类型和消失率顺序为HBr&gt；HCl&gt；H2SO4的问题。对酚类和非酚类化合物也进行了定量研究。酚类化合物与非酚类化合物的比较表明酚羟基的存在具有重要意义。

Non-phenolic C6-C2-type model compounds (V’G, Enol ether, V’G-a-OMe and V’G-a-Br) were synthesized and reacted in HBr, HCl and H2SO4. The acidolysis of V’G-a-OMe indicated the intermediate compound, benzyl cation almost fully undergoes H2O addition reconverting to the starting compound in the H2SO4 system while it partially reacts into enol ether product in the HBr or HCl system. This result greatly solved the question which has been proposed since 20th why the reaction route depends on the type of acid and the disappearance rate in the order of HBr> HCl > H2SO4. Quantitative study on phenolic and non-phenolic compounds has also been carried out. The comparison between phenolic and non-phenolic compounds could suggest the significance of presence of phenolic hydroxyl group.