Auto-Oxidation Mechanisms of Volatile Silicon Compounds in the Atmosphere

Abstract:

Volatile silicon compounds (VOSiCs) are air pollutants present in both indoor and outdoor environments. We have been using ab initio and RRKM theory / master equation kinetic modelling to study the atmospheric chemical mechanisms of VOSiC oxidation. Silanes and siloxanes are shown to underrgo auto-oxidation mechanisms, in which the intermediate alkoxyl radicals rearrange from Si-CH2O to Si-OCH2 with a very low reaction barrier, then react with a second O2. Addition of the second O2 is predicted to lead to the formation of esters, which are known oxidation products of VOSiCs. The production of highly oxygenated compounds following a single radical initiation reaction has implications for the ability of VOSiCs to contribute to ozone and particle formation in both outdoor and indoor environments.