Ketohydroperoxides are important in liquid-phase autoxidation and in gas-phase partial oxidation and pre-ignition chemistry, but because of their low concentration, instability, and various analytical chemistry limitations, it has been challenging to experimentally determine their reactivity, and only a few pathways are known. In the present work, 75 elementary-step unimolecular reactions of the simplest γ-ketohydroperoxide, 3-hydroperoxypropanal, were discovered by a combination of density functional theory with several automated transition-state search algorithms: the Berny algorithm coupled with the freezing string method, single- and double-ended growing string methods, the heuristic KinBot algorithm, and the single-component artificial force induced reaction method (SC-AFIR). The present joint approach significantly outperforms previous manual and automated transition-state searches - 68 of the reactions of γ-ketohydroperoxide discovered here were previously unknown and completely unexpected. All of the methods found the lowest-energy transition state, which corresponds to the first step of the Korcek mechanism, but each algorithm except for SC-AFIR detected several reactions not found by any of the other methods. We show that the low-barrier chemical reactions involve promising new chemistry that may be relevant in atmospheric and combustion systems. Our study highlights the complexity of chemical space exploration and the advantage of combined application of several approaches. Overall, the present work demonstrates both the power and the weaknesses of existing fully automated approaches for reaction discovery which suggest possible directions for further method development and assessment in order to enable reliable discovery of all important reactions of any specified reactant(s).

中文翻译：

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结合自动反应发现方法的应用，γ-酮基氢过氧化物的单分子反应途径

酮氢过氧化物在液相自动氧化和气相部分氧化和预燃化学中很重要，但由于它们的浓度低、不稳定性和各种分析化学限制，因此很难通过实验确定它们的反应性，并且只有少数途径是已知的。在目前的工作中，通过将密度泛函理论与几种自动过渡态搜索算法相结合，发现了最简单的 γ-酮氢过氧化物，3-氢过氧丙醛的 75 个基本步骤单分子反应：伯尼算法与冷冻弦法相结合，单端和双端增长字符串方法、启发式 KinBot 算法和单分量人工力诱导反应方法 (SC-AFIR)。目前的联合方法明显优于之前的手动和自动过渡态搜索——这里发现的 68 个γ-酮氢过氧化物反应以前是未知的，完全出乎意料。所有方法都找到了最低能量过渡态，这对应于 Korcek 机制的第一步，但除 SC-AFIR 之外的每个算法都检测到了其他任何方法都没有发现的几个反应。我们表明，低阻隔化学反应涉及可能与大气和燃烧系统相关的有前途的新化学。我们的研究突出了化学空间探索的复杂性和多种方法联合应用的优势。全面的，