Aqueous reactions of organic triplet excited states with atmospheric alkenes
Aqueous reactions of organic triplet excited states with atmospheric alkenes
复制标题
DOI：
10.5194/acp-19-5021-2019
复制
发表时间：
2019-04-12
影响因子：
6.3
通讯作者：
Anastasio, Cort
中科院分区：
文献类型：
--
作者：
Kaur, Richie;Hudson, Brandi M.;Anastasio, Cort
有色有机物（即有机物）在激发态上形成三重态。例如，棕色碳）吸收光。虽然这些“三胞胎”可以是大气中的水滴和颗粒（例如，例如，在一个实施例中，它们迅速氧化酚类），但关于它们对大气中许多种类的有机化合物的反应性知之甚少。在这里，我们测量的双分子速率常数的三重激发态的二苯甲酮（（BP）-B-3*），一个模型物种，与17个水溶性的C-3-C-6烯烃，已被发现在大气中或合理的替代品确定的物种。测量的速率常数（k（ALK+3BP*））变化30倍，并且在（0.24-7.5）X 109 M-1 s-1的范围内。大气中发现的生物成因烯烃。例如，在一个实施例中，顺式-3-己烯-1-醇、乙酸顺式-3-己烯酯和茉莉酮酸甲酯快速反应，速率常数大于1 × 10（9）M-1 s（-1）。速率常数取决于烯烃的特性，例如双键的位置、立体化学和双键上的烷基取代。在k（ALK+3BP*）和计算的烯烃的单电子氧化电位（OP）（R-2 = 0：58）之间存在合理的相关性;相反，速率常数与键解离势、键解离自由能或计算的氢提取能垒不相关。使用OP关系，我们估计了一些不饱和异戊二烯和柠檬烯氧化产物的水相速率常数，3BP*：值在（0.080-1.7）x 10（9）M-1 s（-1）的范围内，通常柠檬烯产物的值更快。反应性较低的三重态的速率常数可能更与环境相关，可能慢大约25倍。使用我们预测的速率常数，沿着与其他文献中的反应值，我们得出结论，三重可能是轻微的氧化剂异戊二烯和柠檬烯相关的化合物在多云或多雾的气氛中，除了在三重是非常活跃的情况下。
Triplet excited states of organic matter are formed when colored organic matter (i. e., brown carbon) absorbs light. While these " triplets" can be important photooxidants in atmospheric drops and particles (e. g., they rapidly oxidize phenols), very little is known about their reactivity toward many classes of organic compounds in the atmosphere. Here we measure the bimolecular rate constants of the triplet excited state of benzophenone ((BP)-B-3*), a model species, with 17 water-soluble C-3-C-6 alkenes that have either been found in the atmosphere or are reasonable surrogates for identified species. Measured rate constants (k(ALK+3BP*)) vary by a factor of 30 and are in the range of (0.24-7.5) x 109M 1 s 1. Biogenic alkenes found in the atmosphere -e. g., cis-3hexen- 1-ol, cis-3-hexenyl acetate, and methyl jasmonate react rapidly, with rate constants above 1 x 10(9) M-1 s(-1). Rate constants depend on alkene characteristics such as the location of the double bond, stereochemistry, and alkyl substitution on the double bond. There is a reasonable correlation between k(ALK+3BP*) and the calculated one-electron oxidation potential (OP) of the alkenes (R-2 = 0: 58); in contrast, rate constants are not correlated with bond dissociation enthalpies, bond dissociation free energies, or computed energy barriers for hydrogen abstraction. Using the OP relationship, we estimate aqueous rate constants for a number of unsaturated isoprene and limonene oxidation products with 3BP* : values are in the range of (0.080-1.7) x 10(9) M-1 s(-1), with generally faster values for limonene products. Rate constants with less reactive triplets, which are probably more environmentally relevant, are likely roughly 25 times slower. Using our predicted rate constants, along with values for other reactions from the literature, we conclude that triplets are probably minor oxidants for isoprene-and limonene-related compounds in cloudy or foggy atmospheres, except in cases in which the triplets are very reactive.