Theoretical investigation of reaction mechanisms for carboxylic acid formation in the atmosphere
Theoretical investigation of reaction mechanisms for carboxylic acid formation in the atmosphere
复制标题
DOI：
10.1021/ja000731z
复制
发表时间：
2000-09-20
影响因子：
15
通讯作者：
Ruiz-López, MF
中科院分区：
文献类型：
--
作者：
Aplincourt, P;Ruiz-López, MF
已经进行了理论计算来研究几种化学反应的机制，这些化学反应可以解释大气中甲酸的形成。所有设想的过程都涉及所谓的 Criegee 中间体 H2COO，它是在臭氧分解反应过程中产生的。我们专注于通过与 H2CO、H2O、SO2 和 CO2 的双分子反应实现羰基氧化物的异构化。将结果与先前文献报道的单分子异构化机制获得的结果进行比较。在双分子过程中，总是会形成中间加合物，其稳定性按以下顺序增加：CO2 (-24.5 kcal/mol) < SO2 (-43.1 kcal/mol) < H2O (-45 kcal/mol) < H2CO (-49 kcal/mol)（在 CCSD(T) 水平上的值，在 B3LYP 水平上进行零点能量校正）。请注意，该加合物的形成之前可能会也可能不会形成稳定的复合物。然后，加合物根据一步（H2O、SO2、CO2）或逐步机制（H2CO）分解形成最终产物。在 CCSD(T) 水平上，整个 H2COO + M --> HCOOH + M 反应能为 -118.3 kcal/mol。活化能的计算结果表明，与H2O、H2CO和SO2的反应可能发生，而与CO2的反应则不利。由于大气条件下 H2O 浓度较高，因此与该分子的反应应发挥主要作用。
Theoretical calculations have been carried out to investigate the mechanism of several chemical reactions that may explain the formation of formic acid in the atmosphere. All the envisaged processes involve the so-called Criegee intermediate, H2COO, which is generated in the course of the ozonolysis reaction. We focus on isomerization of carbonyl oxide through bimolecular reactions with H2CO, H2O, SO2, and CO2. The results are compared with those obtained for unimolecular isomerization mechanisms previously reported in the literature. In the bimolecular processes, there is always formation of an intermediate adduct, the stability of which increases in the order CO2 (-24.5 kcal/mol) < SO2 (-43.1 kcal/mol) < H2O (-45 kcal/mol) < H2CO (-49 kcal/mol) (values at the CCSD(T) level with zero-point energy correction at the B3LYP level). Note that the formation of this adduct may or may not be preceded by the formation of a stable complex. Afterward, the adduct decomposes to form the final products according to a one-step (H2O, SO2, CO2) or a stepwise mechanisms (H2CO). The whole H2COO + M --> HCOOH + M reaction energy is -118.3 kcal/mol at the CCSD(T) level. The computed results for activation energies suggest that the reactions with H2O, H2CO, and SO2 are likely to occur, whereas that with CO2 is unfavorable. Because of the high concentration of H2O in atmospheric conditions, the reaction with this molecule should play a major role.