乙醛氧化生成乙酸反应机理的分子模拟

采用基于密度泛函理论(DFT)的量子化学方法研究了乙醛氧化生成乙酸的反应过程。结果表明：无氧条件下链引发过程最难发生，反应能垒达到380.78 kJ/mol，但氧气可将此过程的反应能垒降至116.26 kJ/mol；乙酰基自由基生成过氧乙酸以及链终止反应的各步骤的反应能垒均较低，反应较快；过氧乙酸转化为乙酸的反应较难发生，为整体反应过程的速率控制环节。此过程有2个可能的反应路径，速率控制步骤分别为过氧乙酸均裂生成乙酸自由基和羟基自由基的过程和过氧乙酸和乙醛反应生成乙醛单过氧乙酸酯中间化合物的过程，反应能垒分别为147.18、137.21 kJ/mol。

Molecular Simulation on the Reaction Mechanism of Acetaldehyde Oxidization to Acetic Acid

Density functional theory (DFT) simulation method was applied to study the oxidization process of acetaldehyde to acetic acid. Simulation results suggest that, chain initiation step should be the most difficult step under anaerobic condition with a reaction energy barrier 380.78 kJ/mol. However, with the presence of oxygen, the reaction energy barrier could be decreased to116.26 kJ/mol. It has been found that reaction energy barriers in each step of acetyl free radicals reacting to peracetic acid are quite low, and also in chain termination step. It is also noticed that the reaction of peracetic acid to acetic acid is difficult to take place, and it should be the rate control step in the overall reaction process. There are two possible reaction paths in the process. The reaction rate control steps could be homolytic cleavage of peracetic acid to generate acetic acid free radical and hydroxyl free radical, or the reaction of acetaldehyde with peracetic acid to produce acetaldehyde monooxyacetate. The reaction energy barriers of the above two reactions are 147.18 kJ/mol and 137.21 kJ/mol, respectively.