Oxygen-for-Sulfur Exchange in the Gas Phase: Reactions of Al and Si Oxyanions with H2S

Abstract

Gas-phase Si and Al oxyanions were formed by particle bombardment, isolated by mass, and then reacted with H2S in an ion trap secondary ion mass spectrometer (IT-SIMS). The reactions proceeded by different reaction pathways depending on whether the oxyanions were even- or odd-electron species. The radical anion SiO2•- reacted with H2S by abstracting a •SH radical to form the even-electron SiO2SH-. Once formed, the even electron SiO2SH- reacted with a second H2S molecule by O-for-S exchange to form SiOS2H-. The radical anion SiO3•- abstracted an •H radical from H2S to form even-electron SiO3H-, which then underwent two consecutive O-for-S exchange reactions with H2S to form SiO2SH- and SiOS2H-. For the reactions of the even-electron anion AlO2-, the products of two consecutive O-for-S exchange reactions with H2S were AlOS- and AlS2-. The radical abstraction reactions and the O-for-S exchange reactions of SiO3H-, AlO2-, and AlOS- were efficient in the 30−50% range. The efficiency of the O-for-S exchange reaction of SiO2SH- (producing SiOS2H-) was substantially less efficient at 8%.