Instituto de Investigaciones en Fisicoquímica de Córdoba (I.N.F.I.Q.C.), Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
J Phys Chem A. 2012 Jun 21;116(24):6127-33. doi: 10.1021/jp2113889. Epub 2012 Mar 2.
Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with methyl crotonate and ethyl crotonate have been determined at 298 K and atmospheric pressure. The decay of the organics was monitored using gas chromatography with flame ionization detection (GC-FID), and the rate constants were determined using the relative rate method with different reference compounds. Room temperature rate coeficcients were found to be (in cm(3) molecule(-1) s(-1)): k(1)(OH + CH(3)CH═CHC(O)OCH(3)) = (4.65 ± 0.65) × 10(-11), k(2)(Cl + CH(3)CH═CHC(O)OCH(3)) = (2.20 ± 0.55) × 10(-10), k(3)(OH + CH(3)CH═CHC(O)OCH(2)CH(3)) = (4.96 ± 0.61) × 10(-11), and k(4)(Cl + CH(3)CH═CHC(O)OCH(2)CH(3)) = (2.52 ± 0.62) × 10(-10) with uncertainties representing ±2σ. This is the first determination of k(1), k(3), and k(4) under atmospheric pressure. The rate coefficients are compared with previous determinations for other unsaturated and oxygenated VOCs and reactivity trends are presented. In addition, a comparison between the experimentally determined k(OH) with k(OH) predicted from k vs E(HOMO) relationships is presented. On the other hand, product identification under atmospheric conditions has been performed for the first time for these unsaturated esters by the GC-MS technique in NO(x)-free conditions. 2-Hydroxypropanal, acetaldehyde, formaldehyde, and formic acid were positively observed as degradation products in agreement with the addition of OH to C2 and C3 of the double bond, followed by decomposition of the 2,3- or 3,2-hydroxyalkoxy radicals formed. Atmospheric lifetimes, based on of the homogeneous sinks of the unsaturated esters studied, are estimated from the kinetic data obtained in the present work.
在 298 K 和大气压下，测定了羟基自由基和氯原子与甲基巴豆酸酯和乙基巴豆酸酯反应的速率系数。使用气相色谱-火焰电离检测（GC-FID）监测有机物的衰减，并用不同参比化合物的相对速率法确定速率常数。室温下的速率系数为（cm(3)分子(-1) s(-1)）：k(1)(OH + CH(3)CH═CHC(O)OCH(3)) = (4.65 ± 0.65) × 10(-11)，k(2)(Cl + CH(3)CH═CHC(O)OCH(3)) = (2.20 ± 0.55) × 10(-10)，k(3)(OH + CH(3)CH═CHC(O)OCH(2)CH(3)) = (4.96 ± 0.61) × 10(-11)，k(4)(Cl + CH(3)CH═CHC(O)OCH(2)CH(3)) = (2.52 ± 0.62) × 10(-10)，不确定度表示为 ±2σ。这是第一次在大气压下测定 k(1)、k(3)和 k(4)。将速率系数与其他不饱和和含氧挥发性有机化合物的先前测定值进行比较，并提出了反应性趋势。此外，还介绍了通过 k 与 HOMO 能量关系预测的 k(OH)与实验测定的 k(OH)之间的比较。另一方面，首次在无氮氧化物条件下通过 GC-MS 技术在大气条件下对这些不饱和酯进行了产物鉴定。在与双键的 C2 和 C3 加成一致的情况下，观察到 2-羟基丙醛、乙醛、甲醛和甲酸作为降解产物，随后分解形成的 2,3-或 3,2-羟基烷氧基自由基。基于所研究的不饱和酯的均相汇，根据本工作获得的动力学数据估算大气寿命。
