This paper theoretically investigated a large number of reaction pathways and kinetics to describe the vapor-phase pyrolytic behavior of several syringol-type monolignol compounds that are derived from the primary pyrolysis of lignin: 1-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-en-1-one (HDPP), sinapyl alcohol, 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (HHDPP), 1-(4-hydroxy-3,5-dimethoxyphenyl)propane-1,3-diol (HDPPD), and syringol. The possible pyrolytic pathways involving unimolecular decomposition, addition, and abstraction reactions were investigated by comparing the energy barriers calculated at the B3LYP/6-311++G(d,p) level. In the proposed pathways, all syringol-type monolignols containing a side chain undergo its cleavage to form syringol through the formation of syringaldehyde or 4-vinylsyringol. Syringol is then converted into two products: (a) pyrogallol via the homolysis of the O–CH₃ bond and hydrogenation or (b) guaiacol via addition of an H atom with a carbon bearing methoxyl group in syrignol and the subsequent demethoxylation. The pyrolytic pathways of pyrogallol are classified into two processes: (a) the concerted dehydrogenation of the two hydroxyl H atoms and the unimolecular decomposition to produce acetylene (C₂H₂), ethynol (C₂HOH), and CO or (b) the displacement of an OH with H to produce catechol and resorcinol. Additionally, HDPP undergoes O–CH₃ bond cleavage to form but-1-en-3-yne. The high-pressure limit rate constants for all the proposed elementary reaction steps were evaluated on the basis of transition state theory.

中文翻译：

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丁香酚型单木质酚化合物热分解过程中基本反应步骤的理论研究

本文理论上研究了大量的反应途径和动力学，以描述几种木质素的一次热解衍生的丁香酚型单木质醇化合物的气相热解行为：1-（4-羟基-3,5-二甲氧基苯基）丙-2-烯-1-酮（HDPP），芥子醇，3-羟基-1-（4-羟基-3,5-二甲氧基苯基）丙-1-酮（HHDPP），1-（4-羟基-3 1,5-二甲氧基苯基）丙烷-1,3-二醇（HDPPD）和丁香酚。通过比较在B3LYP / 6-311 ++ G（d，p）水平计算的能垒，研究了涉及单分子分解，加成和抽象反应的可能的热解途径。在提出的途径中，所有含有侧链的丁香酚型单木香酚均通过其丁香醛或4-乙烯基丁香酚的裂解而形成丁香酚。₃键和氢化或（b）愈创木酚，其通过在Hyrignol中添加带有带有碳原子的甲氧基的H原子并随后进行脱甲氧基化来实现。邻苯三酚的热解途径分为两个过程：（a）两个羟基H原子协同脱氢和单分子分解生成乙炔（C ₂ H ₂），乙炔醇（C ₂ HOH）和CO或（b）用OH取代OH以产生邻苯二酚和间苯二酚。另外，HDPP经历O–CH ₃键裂解形成but-1-en-3-yne。在过渡态理论的基础上，对所有拟议的基本反应步骤的高压极限速率常数进行了评估。