Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy
Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy
复制标题
阴离子光电子能谱鉴定异戊二烯氧化反应产物
DOI：
10.1021/acs.jpca.1c08176
复制
发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Jarrold, Caroline Chick
中科院分区：
文献类型：
--
作者：
Dobulis, Marissa A.;Thompson, Michael C.;Jarrold, Caroline Chick
我们提出了在几种不同条件下异戊二烯氧化的研究，可以模拟大气和燃烧化学。阴离子是由异戊二烯/氧化剂气体混合物通过脉冲放电产生一系列物质形成的，通过质谱法分离，并通过阴离子光电子（PE）光谱计算进行表征。具体来说，对紫外线照射的异戊二烯/O2混合物和异戊二烯/O2/ h2混合物进行了采样，前者会产生O3，后者在通过放电时会产生•OH。在这两种条件下生成的离子的质谱显示，生成了完整的分子离子、离子-分子配合物（如O2 -、O4 -和O2 -·异戊二烯）和单一去质子化的物质（如去质子化的异戊二烯，C5H7 -）。此外，使用两种气体混合物都可以观察到较小的和氧化的碎片，尽管相对丰度不同。从紫外线照射的异戊二烯/ o2气体混合物中，观察到臭氧分解异戊二烯，甲基乙二醛和二甲基乙二醛引发的反应的其他完整分子产物。在两种气体混合物中观察到的异戊二烯的破碎和氧化包括m/z39、53、67、69和83，我们将其归因于一系列烷基和烯氧基阴离子。完整分子和复合物与碎片和反应产物的共存证明了该离子源作为一种简单有效的阴离子形成方法的多功能性，可用于研究可能与大气和燃烧化学相关的物质。
We present a study on the oxidation of isoprene under several different conditions that may model both atmospheric and combustion chemistry. Anions, formed by passing isoprene/oxidant gas mixtures through a pulsed discharge generating a range of species, are separated via mass spectrometry and characterized by anion photoelectron (PE) spectroscopy supported by computations. Specifically, a UV-irradiated isoprene/O2mixture, which additionally produces O3, and an isoprene/O2/H2mixture, which generates•OH when passed through the discharge, were sampled. The mass spectra of ions generated under both conditions show the production of intact molecular ions, ion–molecule complexes (e.g., O2–, O4–, and O2–·isoprene), and singly deprotonated species (e.g., deprotonated isoprene, C5H7–). In addition, both smaller and oxidized fragments are observed using both gas mixtures, though relative abundances differ. From the UV-irradiated isoprene/O2gas mixture, additional intact molecular products of reactions initiated by ozonolysis of isoprene, methylglyoxal, and dimethylglyoxal were observed. Fragmentation and oxidation of isoprene observed in both gas mixtures included species withm/z39, 53, 67, 69, and 83 that we attribute to a series of alkyl- and alkenoxide-based anions. The coexistence of intact molecules and complexes with fragments and reaction products demonstrates the versatility of this ion source as a simple and efficient anion formation method for studying species that may be relevant in atmospheric and combustion chemistry.