Abstract Understanding and predicting the formation of polycyclic aromatic compounds (PACs) and their role in the formation of high molecular mass compounds is still an unresolved topic in combustion. PACs characteristics, such as chemical composition, size, and presence of side chains, play an important role not only in terms of environmental and health impact, but also when developing models that describe the formation of nanoparticles and soot. In this paper, we report on a detailed analysis of the reaction pathways describing the chemistry of furan-embedded PACs using ab initio G3-type electronic structure calculations leading to the formation of benzofuran and dibenzofuran from benzene and biphenyl. The 82 elementary reactions, identified in this work, contain unexplored pathways involving triplet oxygen atom and hydroxyl radical addition reactions. A protocol for improving the calculations of reaction energetics from ab initio compound methods is proposed, which consists of the thorough usage of IRCmax scheme to identify the transition state structure and an energy correction ( ~ 0.2 kcal/mol) to the empirical term in G3 formula for systems with open-shell singlet type of electronic configurations. Based on these ab initio calculations, temperature dependent reaction rate constants are calculated according to statistical theories, together with thermodynamics data. Branching ratio analysis based on steady-state approximation is carried out to illustrate the relative importance of the new pathways in an ethylene premixed flame. Results show that the newly discovered benzofuran formation pathways can play a relative important role when in presence of phenol or phenoxyl radicals at various locations in the flame.

中文翻译：

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燃烧中形成苯并呋喃和二苯并呋喃的化学途径

摘要 了解和预测多环芳族化合物 (PACs) 的形成及其在高分子量化合物形成中的作用仍然是燃烧中未解决的话题。PAC 的特性，例如化学成分、大小和侧链的存在，不仅在环境和健康影响方面发挥着重要作用，而且在开发描述纳米颗粒和烟尘形成的模型时也发挥着重要作用。在本文中，我们报告了使用 ab initio G3 型电子结构计算导致苯和联苯形成苯并呋喃和二苯并呋喃的反应途径的详细分析，描述了嵌入呋喃的 PAC 的化学过程。在这项工作中确定的 82 个基本反应，包含未探索的途径，涉及三线态氧原子和羟基自由基加成反应。提出了一种从 ab initio 复合方法改进反应能量计算的协议，该协议包括彻底使用 IRCmax 方案来识别过渡态结构和对 G3 公式中的经验项进行能量校正 (~ 0.2 kcal/mol)用于具有开壳单线态电子配置的系统。基于这些从头计算，根据统计理论以及热力学数据计算依赖于温度的反应速率常数。进行了基于稳态近似的支化比分析，以说明乙烯预混火焰中新路径的相对重要性。