Elm Jonas, Myllys Nanna, Kurtén Theo
Department of Physics, University of Helsinki , FI-00014 Helsinki, Finland.
Department of Chemistry, University of Helsinki , FI-00014 Helsinki, Finland.
J Phys Chem A. 2017 Jun 15;121(23):4578-4587. doi: 10.1021/acs.jpca.7b03759. Epub 2017 Jun 6.
We have studied the specific requirements of a given neutral organic molecule to act as a stabilizer in sulfuric acid induced new particle formation. Based on an analysis of the reaction Gibbs free energies between simple functional groups and sulfuric acid, carboxylic acid groups are identified to show the strongest hydrogen bonding interaction with sulfuric acid. The free energy associated with the hydrogen bonding between sulfuric acid and 14 different carboxylic acids of atmospheric relevance reveal that the binding strength is very dependent on the ability of sulfuric acid to form an additional hydrogen bond via its vacant S-OH group to a γ-carbonyl group in the organic molecule. Extending the analysis to monoterpene oxidation products and further to large dimer esters, we identify the following necessary criteria for a given organic oxidation product to efficiently stabilize sulfuric acid clustering: (1) weak or no intramolecular hydrogen bonds in the isolated monomer; (2) more than two carboxylic acid groups. As a proof of concept we show that these requirements correspond to the docking of a sulfuric acid molecule between two non-interacting carboxylic acid groups in the organic molecule. These findings suggests that, for a given organic oxidation product to participate in the initial steps in new particle formation involving sulfuric acid, very distinct molecular features are required.
我们研究了特定中性有机分子在硫酸诱导的新颗粒形成过程中作为稳定剂的具体要求。基于对简单官能团与硫酸之间反应吉布斯自由能的分析，确定羧酸基团与硫酸表现出最强的氢键相互作用。与硫酸和14种具有大气相关性的不同羧酸之间的氢键相关的自由能表明，结合强度非常依赖于硫酸通过其空的S-OH基团与有机分子中的γ-羰基形成额外氢键的能力。将分析扩展到单萜氧化产物，再进一步扩展到大型二聚酯，我们确定了给定有机氧化产物有效稳定硫酸簇的以下必要标准：（1）孤立单体中弱或无分子内氢键；（2）两个以上羧酸基团。作为概念验证，我们表明这些要求对应于硫酸分子在有机分子中两个非相互作用的羧酸基团之间的对接。这些发现表明，对于给定的有机氧化产物要参与涉及硫酸的新颗粒形成的初始步骤，需要非常独特的分子特征。
