Effect of Ammonium Salts on the Decarboxylation of Oxaloacetic Acid in Atmospheric Particles
Effect of Ammonium Salts on the Decarboxylation of Oxaloacetic Acid in Atmospheric Particles
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铵盐对大气颗粒物中草酰乙酸脱羧的影响
DOI：
10.1021/acsearthspacechem.1c00025
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发表时间：
2021
影响因子：
3.4
通讯作者：
Nizkorodov, Sergey A.
中科院分区：
文献类型：
--
作者：
Klodt, Alexandra L.;Zhang, Kimberly;Olsen, Michael W.;Fernandez, Jorge L.;Furche, Filipp;Nizkorodov, Sergey A.
草酰乙酸（OAA）是由琥珀酸氧化形成的3-氧羧酸。OAA和其他3-氧羧酸在水溶液中发生脱羧反应，可由铵和胺催化。尽管以前对大气中的OAA有兴趣，但这种催化作用尚未在大气相关条件下进行研究。为了解决这个问题，我们用不同浓度的硫酸铵、硫酸氢铵、氯化铵和硫酸钠制备了1mm的OAA溶液，以模拟不同的大气条件。采用紫外-可见吸收光谱法监测脱羧程度。OAA的非催化脱羧寿命约为5 h。在中等酸性条件下（pH = 3-4）， OAA的脱羧速率随铵浓度的增加而线性增加，达到2.7 M左右，之后再添加铵就没有影响了。在这些条件下，OAA的有效寿命降至约1小时。密度泛函理论计算支持所提出的催化机制，预测OAA与铵反应后脱羧的自由能垒高度约降低21 kcal/mol。在酸性较强的溶液（pH < 1）中，OAA的脱羧作用被抑制，即使在铵的存在下，其寿命也可达数十小时。脱羧速率与OH预期氧化速率的比较表明，脱羧将是气溶胶颗粒和云/雾滴中OAA（可能还有其他3-氧羧酸）的主要损失机制。这一结果解释了为什么OAA很难在现场测量中检测到，即使它是琥珀酸的已知氧化产物。
Oxaloacetic acid (OAA) is a 3-oxocarboxylic acid formed from the oxidation of succinic acid. OAA and other 3-oxocarboxylic acids experience a decarboxylation reaction in aqueous solutions, which can be catalyzed by ammonium and amines. This catalysis has not been studied under atmospherically relevant conditions despite previous interest in OAA in the atmosphere. To address this, 1 mM solutions of OAA were prepared with varying concentrations of ammonium sulfate, ammonium bisulfate, ammonium chloride, and sodium sulfate to simulate various atmospheric conditions. The extent of the decarboxylation was monitored using UV–visible absorption spectroscopy. OAA’s uncatalyzed decarboxylation lifetime was around 5 h. Under moderately acidic conditions representative of aerosol particles (pH = 3–4), the decarboxylation rate increased linearly with ammonium concentration up to about 2.7 M, after which additional ammonium had no effect. The effective lifetime of OAA reduced to approximately 1 h under these conditions. Density functional theory calculations support the proposed catalytic mechanism, predicting the free energy barrier height for decarboxylation to be approximately 21 kcal/mol lower after OAA has reacted with ammonium. In more acidic solutions (pH < 1), OAA’s decarboxylation was suppressed, with lifetimes of tens of hours, even in the presence of ammonium. A comparison of the decarboxylation rate with the expected rate of oxidation by OH suggests that decarboxylation will be the dominant loss mechanism for OAA, and presumably other 3-oxocarboxylic acids, in aerosol particles and cloud/fog droplets. This result explains why OAA is hard to detect in field measurements even though it is a known oxidation product of succinic acid.
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影响因子：
0.8
作者：
Chuan-gang Fan;Ming-zhi Song
通讯作者：
Chuan-gang Fan;Ming-zhi Song
影响因子：
--
作者：
M. Mochida;A. Kawabata;K. Kawamura;H. Hatsushika;K. Yamazaki
通讯作者：
M. Mochida;A. Kawabata;K. Kawamura;H. Hatsushika;K. Yamazaki
pH 值以及 NaCl 和 CaCl2 盐对水相中丙酮酸的形态和光化学的影响。
影响因子：
2.9
作者：
Man Luo;D. Shemesh;M. N. Sullivan;M. R. Alves;Meishi Song;R. Gerber;V. Grassian
通讯作者：
V. Grassian
用于估计水相中脂肪族有机化合物的 OH 氧化速率常数的构效关系：烷烃、醇、有机酸和碱
DOI：
--
发表时间：
2008
期刊：
影响因子：
--
作者：
A. Monod;J. Doussin
通讯作者：
J. Doussin
影响因子：
6.3
作者：
Kaur, Richie;Labins, Jacqueline R.;Anastasio, Cort
通讯作者：
Anastasio, Cort