Measurements of Kinetics and Equilibria for the Condensed Phase Reactions of Hydroperoxides with Carbonyls to Form Peroxyhemiacetals
Measurements of Kinetics and Equilibria for the Condensed Phase Reactions of Hydroperoxides with Carbonyls to Form Peroxyhemiacetals
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DOI：
10.1021/acsearthspacechem.0c00008
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发表时间：
2020-03-19
影响因子：
3.4
通讯作者：
Ziemann, Paul J.
中科院分区：
文献类型：
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作者：
Bakker-Arkema, Julia G.;Ziemann, Paul J.
非均相/多相反应可以影响二次有机气溶胶（SOA）的形成，组成和化学物理性质，但描述其动力学和平衡的数据仍然很少。在这里，我们合成并利用探针分子来研究氢过氧化物与酮和醛的凝聚相反应，包括在环境室中臭氧分解a-蒎烯产生的SOA中的那些。探针分子，其中包含一个氢过氧化物基团和一个UV吸收硝酸根基团，与酮（3-癸酮）或醛（壬醛）混合，并监测超过24小时，使用液相色谱与紫外-可见检测，以确定每个反应的速率和平衡常数。探针分子不与酮反应，但与醛可逆反应形成过氧半缩醛，该过程也由羧酸催化。过氧半缩醛的可逆分解的速率常数也使用衰减全反射傅里叶变换红外光谱测定。未催化的（u）和催化的（c）过氧半缩醛形成的正向（f）和反向（r）速率常数为k（f，u）= 1.5 +/- 0.4 M-1 h（-1），k（r，u）= 0.16 +/- 0.001 h（-1），k（f，c）= 0.62 +/- 0.07 M-2 h（-1），和kr，c = 0.055 +/- 0.006 M-1 h-1;平衡常数为Keq = 9.1 +/- 2 M-1。未观察到过氧半缩醛的Baeyer-Villiger分解的证据。当与α-蒎烯/O-3 SOA混合时，探针分子在20分钟内达到反应平衡，表明过氧半缩醛形成的大气时间尺度可以很短。使用壬醛实验的结果和测定的SOA的羰基含量，我们估计，高达25%的羰基在此SOA是醛。
Heterogeneous/multiphase reactions can influence the formation, composition, and chemical-physical properties of secondary organic aerosol (SOA), but data describing their kinetics and equilibria remain sparse. Here, we synthesized and utilized a probe molecule to investigate the condensed phase reactions of hydroperoxides with ketones and aldehydes, including those in SOA generated from the ozonolysis of a-pinene in an environmental chamber. The probe molecule, which contained a hydroperoxide group and a UV-absorbing nitrate group, was mixed with a ketone (3-decanone) or aldehyde (nonanal) and monitored over 24 h using liquid chromatography with UV-vis detection to determine the rate and equilibrium constants for each reaction. The probe molecule did not react with the ketone but reacted reversibly with the aldehyde to form a peroxyhemiacetal, a process that was also catalyzed by carboxylic acid. The rate constant for the reversible decomposition of the peroxyhemiacetal was also measured using attenuated total reflectance Fourier transform infrared spectroscopy. The forward (f) and reverse (r) rate constants for uncatalyzed (u) and catalyzed (c) peroxyhemiacetal formation were k(f,u) = 1.5 +/- 0.4 M-1 h(-1), k(r, u) = 0.16 +/- 0.001 h(-1), k(f, c) = 0.62 +/- 0.07 M-2 h(-1), and kr, c = 0.055 +/- 0.006 M-1 h-1; and the equilibrium constant was Keq = 9.1 +/- 2 M-1. No evidence of Baeyer-Villiger decomposition of the peroxyhemiacetal was observed. When mixed with alpha-pinene/O-3 SOA, the probe molecule reached reaction equilibrium within 20 min, indicating that atmospheric timescales for peroxyhemiacetal formation can be short. Using the results of the nonanal experiments and measured carbonyl content of the SOA, we estimate that up to 25% of the carbonyls in this SOA was aldehydes.