Adsorption of 2-Chloroethyl Ethyl Sulfide on Silica: Binding Mechanism and Energy of a Bifunctional Hydrogen-Bond Acceptor at the Gas鈥揝urface Interface

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• 作者：Joshua Abelard ; Amanda R. Wilmsmeyer ; Angela C. Edwards ; Wesley O. Gordon ; Erin M. Durke ; Christopher J. Karwacki ; Diego Troya ; John R. Morris
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：January 8, 2015
• 年：2015
• 卷：119
• 期：1
• 页码：365-372
• 全文大小：344K
• ISSN：1932-7455

文摘

This work investigates the fundamental nature of sulfur mustard surface adsorption by characterizing interfacial hydrogen bonding and other intermolecular forces for the surrogate molecule (simulant) 2-chloroethyl ethyl sulfide (2-CEES). Adsorption at the surface of amorphous silica is the focus of this work because of silica鈥檚 low chemical reactivity, well-known properties, and abundance in the environment. 2-CEES has two polar functional groups, the chloro and thioether moieties, available to accept hydrogen bonds from free surface silanol groups. Diethyl sulfide and chlorobutane are also investigated to independently assess the role of the chloro and thioester functionalities in the overall adsorption mechanism and to explore the interplay between the charge transfer and electrostatic contributions to total hydrogen-bond strength. Our approach utilizes infrared spectroscopy to study specific surface鈥搈olecule interactions and temperature-programmed desorption to measure the activation energy for desorption of adsorbed molecules. Our results indicate that 2-CEES adsorbs to silica by hydrogen bonding through either the chloro or thioether moieties but is unable to form a more stable configuration in which both polar groups interact simultaneously with adjacent silanol groups. The activation energy for desorption of 2-CEES is nearly 43 kJ/mol, driven by both strong hydrogen bonding and other non-bonding interactions. A systematic study of chloroalkanes reveals that each methylene group contributes approximately 5鈥? kJ/mol to the overall desorption energy.