Dimethylsilanediol (DMSD) is a contaminant in the U.S. water processing assembly on the International Space Station (ISS). The DMSD is presumed to form when VMS compounds react with hydroxyl radicals in the gas phase. Multiple volatile methyl siloxanes (VMS) have been detected on the ISS, and according to a simple model based on reaction kinetics, trimethylsilanol (TMS), hexamethylcyclotrisiloxane (D3), and decamethylcyclopentasiloxane (D5) are the major contributors to the DMSD production. A proposed four-step mechanism for the reaction between TMS and a hydroxyl radical was investigated using electronic structure calculations. Molecular structure optimizations and vibrational frequency calculations were performed in NWChem using the M06-2x functional and 6-31+G** basis set. Calculated free energy values indicate that the formation of DMSD via the proposed mechanism is thermodynamically favorable.

Computational investigation of DMSD production in the ISS atmosphere

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.