Molecular Interaction of Pinic Acid with Sulfuric Acid: Exploring the Thermodynamic Landscape of Cluster Growth

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• 作者：Jonas Elm ; Theo Kurt茅n ; Merete Bilde ; Kurt V. Mikkelsen
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：September 11, 2014
• 年：2014
• 卷：118
• 期：36
• 页码：7892-7900
• 全文大小：333K
• ISSN：1520-5215

文摘

We investigate the molecular interactions between the semivolatile 伪-pinene oxidation product pinic acid and sulfuric acid using computational methods. The stepwise Gibbs free energies of formation have been calculated utilizing the M06-2X functional, and the stability of the clusters is evaluated from the corresponding 螖G values. The first two additions of sulfuric acid to pinic acid are found to be favorable with 螖G values of 鈭?.06 and 鈭?0.41 kcal/mol. Addition of a third sulfuric acid molecule is less favorable and leads to a structural rearrangement forming a bridged sulfuric acid鈥損inic acid cluster. The involvement of more than one pinic acid molecule in a single cluster is observed to lead to the formation of favorable (pinic acid)₂(H₂SO₄) and (pinic acid)₂(H₂SO₄)₂ clusters. The identified most favorable growth paths starting from a single pinic acid molecule lead to closed structures without the further possibility for attachment of either sulfuric acid or pinic acid. This suggests that pinic acid cannot be a key species in the first steps in nucleation, but the favorable interactions between sulfuric acid and pinic acid imply that pinic acid can contribute to the subsequent growth of an existing nucleus by condensation.