Nozière Barbara, Vereecken Luc
IRCELYON, CNRS, Université Claude Bernard Lyon 1, 2 avenue Albert Einstein, 69626, Villeurbanne, France.
Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
Angew Chem Int Ed Engl. 2019 Sep 23;58(39):13976-13982. doi: 10.1002/anie.201907981. Epub 2019 Aug 21.
The autoxidation of organic peroxy radicals (RO ) into hydroperoxy-alkyl radicals (QOOH), then hydroperoxy-peroxy radicals (HOOQO ) is now considered to be important in the Earth's atmosphere. To avoid mechanistic uncertainties these reactions are best studied by monitoring the radicals. But for the volatile and aliphatic RO radicals playing key roles in the atmosphere this has long been an instrumental challenge. This work reports the first study of the autoxidation of aliphatic RO radicals and is based on monitoring RO and HOOQO radicals. The rate coefficients, k (s ), were determined both experimentally and theoretically using MC-TST kinetic theory based on CCSD(T)//M06-2X quantum chemical methodologies. The results were in excellent agreement and confirmed that the first H-migration is strongly rate-limiting in the oxidation of non-oxygenated volatile organic compounds (VOCs). At higher relative humidity (2-30 %) water complexes were evidenced for HOOQO radicals, which could be an important fate for HOO-substituted RO radicals in the atmosphere.
有机过氧自由基（RO ）自动氧化为氢过氧烷基自由基（QOOH），进而生成氢过氧 - 过氧自由基（HOOQO ），如今这一过程在地球大气中被认为是重要的。为避免机理上的不确定性，最好通过监测自由基来研究这些反应。但对于在大气中起关键作用的挥发性脂肪族RO自由基而言，长期以来这一直是一个仪器方面的挑战。这项工作报道了对脂肪族RO自由基自动氧化的首次研究，且基于对RO和HOOQO自由基的监测。速率系数k（s ）通过基于CCSD(T)//M06 - 2X量子化学方法的MC - TST动力学理论，分别通过实验和理论确定。结果吻合得非常好，并证实了首次氢迁移在非氧化挥发性有机化合物（VOCs）氧化过程中是强烈的速率限制步骤。在较高相对湿度（2 - 30 %）下，有证据表明HOOQO自由基存在水络合物，这可能是大气中HOO取代的RO自由基的一个重要归宿。
