美国阿贡国家实验室Kirill Prozument研究组在研究中取得进展。团队通过模拟、实验、理论范式揭示了丙酮热解中的取代反应。 相关研究成果发表在2021年2月22日出版的《美国化学会杂志》。

化学反应体系高保真机制的发展是一个具有挑战性的过程，需要为一个大的、有点不明确的反应集合汇编速率描述。目前建模、实验和理论的统一结合为改进这种机制的开发工作提供了范例。

该文中，研究人员基于从自动从头算过渡态理论为主方程计算和高级热化学参数化获得的速率常数，将宽带旋转光谱学与详细的化学建模相结合。宽带旋转光谱提供定量和异构体特异性检测，通过它可以获得极性反应产物的分支比。

利用这项技术，研究人员观察和表征了丙酮（CH3C（O）CH3）在1800K的快速热解过程中氢原子取代反应的产物，主要产物是烯酮（CH2CO）。次要产物包括乙醛（CH3CHO）、丙炔（CH3CCH）、丙烯（CH2CHCH3）和水（HDO）。

丙酮热解的文献记载的机制没有充分描述副产物。从自动从头算动力学预测和活性热化学表分析获得的速率常数和热化学，包括各种取代反应证明了这类过程的重要作用。生成乙醛的途径是丙酮的甲基被自由氢原子取代，而丙烯的形成是由一个自由的H原子取代丙酮的烯醇形式的OH形成的。

附：英文原文

Title: Substitution Reactions in the Pyrolysis of Acetone Revealed through a Modeling, Experiment, Theory Paradigm

Author: Daniel P. Zaleski, Raghu Sivaramakrishnan, Hailey R. Weller, Nathan A. Seifert, David H. Bross, Branko Ruscic, Kevin B. Moore, III, Sarah N. Elliott, Andreas V. Copan, Lawrence B. Harding, Stephen J. Klippenstein, Robert W. Field, Kirill Prozument

Issue&Volume: February 22, 2021

Abstract: The development of high-fidelity mechanisms for chemically reactive systems is a challenging process that requires the compilation of rate descriptions for a large and somewhat ill-defined set of reactions. The present unified combination of modeling, experiment, and theory provides a paradigm for improving such mechanism development efforts. Here we combine broadband rotational spectroscopy with detailed chemical modeling based on rate constants obtained from automated ab initio transition state theory-based master equation calculations and high-level thermochemical parametrizations. Broadband rotational spectroscopy offers quantitative and isomer-specific detection by which branching ratios of polar reaction products may be obtained. Using this technique, we observe and characterize products arising from H atom substitution reactions in the flash pyrolysis of acetone (CH3C(O)CH3) at a nominal temperature of 1800 K. The major product observed is ketene (CH2CO). Minor products identified include acetaldehyde (CH3CHO), propyne (CH3CCH), propene (CH2CHCH3), and water (HDO). Literature mechanisms for the pyrolysis of acetone do not adequately describe the minor products. The inclusion of a variety of substitution reactions, with rate constants and thermochemistry obtained from automated ab initio kinetics predictions and Active Thermochemical Tables analyses, demonstrates an important role for such processes. The pathway to acetaldehyde is shown to be a direct result of substitution of acetone’s methyl group by a free H atom, while propene formation arises from OH substitution in the enol form of acetone by a free H atom.

DOI: 10.1021/jacs.0c11677

Source: https://pubs.acs.org/doi/10.1021/jacs.0c11677