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.