Abdel-Rahman Mohamed A, Shiroudi Abolfazl, Czub Jacek, Zhao Hao
Chemistry Department, Faculty of Science, Suez University, Suez 43518, Egypt.
Department of Physical Chemistry, Gdańsk University of Technology, Narutowicza 11/12, Gdańsk 80-233, Poland.
J Phys Chem A. 2024 May 23;128(20):4068-4082. doi: 10.1021/acs.jpca.4c01338. Epub 2024 May 10.
The thermo-kinetic aspects of 3-hydroxybutyric acid (3-HBA) pyrolysis in the gas phase were investigated using density functional theory (DFT), specifically the M06-2X theoretical level in conjunction with the cc-pVTZ basis set. The obtained data were compared with benchmark CBS-QB3 results. The degradation mechanism was divided into 16 pathways, comprising 6 complex fissions and 10 barrierless reactions. Energy profiles were calculated and supplemented with computations of rate coefficients and branching ratios over the temperature range of 600-1700 K at a pressure of 1 bar using transition state theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) methods. Thermodynamics results indicated the presence of six stable conformers within a 4 kcal mol energy range. The estimated chemical kinetics results suggested that TST and RRKM approaches are comparable, providing confidence in our calculations. The branching ratio analysis reveals that the dehydration reaction pathway leading to the formation of HO and CHCH═CHCOH dominates entirely at ≤ 650 K. At these temperatures, there is a minor contribution from the simple homolytic bond fission reaction, yielding related radicals [CHCHOH + CHCOH]. However, at ≥ 700 K, this reaction becomes the primary decomposition route. At = 1700 K, there is a minor involvement of a reaction pathway resulting in the formation of CHCH(OH)CH + CHO(OH) with an approximate contribution of 16%, and a reaction leading to [CH + CHOHCHCOH] with around 9%.
利用密度泛函理论（DFT），特别是M06 - 2X理论水平结合cc - pVTZ基组，研究了气相中3 - 羟基丁酸（3 - HBA）热解的热动力学方面。将所得数据与基准CBS - QB3结果进行比较。降解机理分为16条途径，包括6个复杂裂变和10个无势垒反应。使用过渡态理论（TST）和赖斯 - 拉姆齐格 - 卡塞尔 - 马库斯（RRKM）方法，计算了能量分布，并补充了在1 bar压力下600 - 1700 K温度范围内的速率系数和分支比计算。热力学结果表明在4 kcal mol能量范围内存在6种稳定构象。估计的化学动力学结果表明TST和RRKM方法具有可比性，这为我们的计算提供了信心。分支比分析表明，导致形成HO和CHCH═CHCOH的脱水反应途径在≤650 K时完全占主导。在这些温度下，简单均裂键裂变反应产生相关自由基[CHCHOH + CHCOH]的贡献较小。然而，在≥700 K时，该反应成为主要分解途径。在= 1700 K时，导致形成CHCH(OH)CH + CHO(OH)的反应途径的参与度较小，贡献约为16%，以及导致[CH + CHOHCHCOH]的反应贡献约为9%。
