Quantum Chemistry Guide to PTRMS Studies of As-Yet Undetected Products of the Bromine-Atom Initiated Oxidation of Gaseous Elemental Mercury

A series of BrHgY compounds (Y = NO₂, ClO, BrO, HOO, etc.) are expected to be formed in the Br-initiated oxidation of Hg(0) to Hg­(II) in the atmosphere. These BrHgY compounds have not yet been reported in any experiment. This article investigates the potential to use proton-transfer reaction mass spectrometry (PTRMS) to detect these atmospherically important species. We show that reaction of the standard PTRMS reagent (H₃O⁺) with BrHgY leads to stable parent (M + 1) ions, BrHgYH⁺, for most of these radicals, Y. Rate constants for the proton transfer reaction H₃O⁺ + BrHgY are computed using average dipole orientation theory. Calculations are also carried out on the commercially available compounds HgCl₂, HgBr₂, and HgI₂ to enable tests of the present work