Schöne Luisa, Schindelka Janine, Szeremeta Edyta, Schaefer Thomas, Hoffmann Dirk, Rudzinski Krzysztof J, Szmigielski Rafal, Herrmann Hartmut
Leibniz-Institute for Tropospheric Research, Permoserstraße 15, 04318 Leipzig, Germany.
Phys Chem Chem Phys. 2014 Apr 7;16(13):6257-72. doi: 10.1039/c3cp54859g.
Kinetic and mechanistic studies were conducted on the isoprene oxidation products methacrolein, methyl vinyl ketone, methacrylic and acrylic acid reacting with hydroxyl and nitrate radicals and sulfate radical anions in aqueous solution by use of the laser flash photolysis technique and a reversed-rate method for kinetics. High-performance liquid chromatography/mass spectrometry was applied for product analysis. The kinetic investigations show the highest reactivity of the hydroxyl radical followed by sulfate and nitrate radicals. For methacrolein and methyl vinyl ketone the following rate constants have been determined at 298 K: k(OH+methacrolein) = (9.4 ± 0.7) × 10(9) M(-1) s(-1), k(OH+methyl vinyl ketone) = (7.3 ± 0.5) × 10(9) M(-1) s(-1), k(NO3+methacrolein) = (4.0 ± 1.0) × 10(7) M(-1) s(-1), k(NO3+methyl vinyl ketone) = (9.7 ± 3.4) × 10(6) M(-1) s(-1), k(SO4(-)+methacrolein) = (9.9 ± 4.9) × 10(7) M(-1) s(-1) and k(SO4(-)+methyl vinyl ketone) = (1.0 ± 0.2) × 10(8) M(-1) s(-1). Temperature and pH dependencies of the reactions of OH, NO3 and SO4(-) with methacrolein, methyl vinyl ketone, methacrylic and acrylic acid as well as Arrhenius parameters have been obtained and discussed. Product studies were performed on the OH radical induced oxidation of methacrolein and methyl vinyl ketone. In the reaction of methacrolein + OH methylglyoxal and hydroxyacetone were identified as first oxidation products with yields of 0.099 and 0.162. Methylglyoxal was primarily produced in the oxidation of methyl vinyl ketone with a yield of 0.052. For both precursor compounds the formation of glycolaldehyde was observed for the first time with yields of 0.051 and 0.111 in the oxidation of methacrolein and methyl vinyl ketone, respectively. Furthermore, highly functionalised C4 compounds were determined from the oxidation of both precursor compounds, but for the first time for methyl vinyl ketone. Reaction schemes were developed based on known peroxyl radical reaction mechanisms. The aqueous phase conversion of the first generation isoprene oxidation products can potentially contribute to tropospheric aqueous phase budgets of important carbonyl and dicarbonyl components which are expected to be conducive to the formation of aqSOA.
采用激光闪光光解技术和动力学的逆速率方法，对异戊二烯氧化产物甲基丙烯醛、甲基乙烯基酮、甲基丙烯酸和丙烯酸在水溶液中与羟基、硝酸根自由基及硫酸根阴离子的反应进行了动力学和机理研究。应用高效液相色谱/质谱进行产物分析。动力学研究表明，羟基自由基的反应活性最高，其次是硫酸根和硝酸根自由基。对于甲基丙烯醛和甲基乙烯基酮，在298 K下测定了以下速率常数：k(OH+甲基丙烯醛) = (9.4 ± 0.7) × 10⁹ M⁻¹ s⁻¹，k(OH+甲基乙烯基酮) = (7.3 ± 0.5) × 10⁹ M⁻¹ s⁻¹，k(NO₃+甲基丙烯醛) = (4.0 ± 1.0) × 10⁷ M⁻¹ s⁻¹，k(NO₃+甲基乙烯基酮) = (9.7 ± 3.4) × 10⁶ M⁻¹ s⁻¹，k(SO₄⁻+甲基丙烯醛) = (9.9 ± 4.9) × 10⁷ M⁻¹ s⁻¹，k(SO₄⁻+甲基乙烯基酮) = (1.0 ± 0.2) × 10⁸ M⁻¹ s⁻¹。获得并讨论了OH、NO₃和SO₄⁻与甲基丙烯醛、甲基乙烯基酮、甲基丙烯酸和丙烯酸反应的温度和pH依赖性以及阿伦尼乌斯参数。对羟基自由基引发的甲基丙烯醛和甲基乙烯基酮氧化进行了产物研究。在甲基丙烯醛 + OH的反应中，甲基乙二醛和羟基丙酮被鉴定为初级氧化产物，产率分别为0.099和0.162。甲基乙二醛主要在甲基乙烯基酮的氧化中产生，产率为0.052。对于这两种前体化合物，首次观察到在甲基丙烯醛和甲基乙烯基酮的氧化中分别生成了产率为0.051和0.111的乙醇醛。此外，从这两种前体化合物的氧化中都检测到了高度官能化的C4化合物，但甲基乙烯基酮是首次检测到。基于已知的过氧自由基反应机理制定了反应方案。第一代异戊二烯氧化产物的水相转化可能对对流层中重要羰基和二羰基成分的水相收支有贡献，预计这有利于aqSOA的形成。
