Notes. The proton affinities are calculated as , where and are the enthalpies of formation of the protonated molecule MH⁺, the neutral molecule M, and the proton, outside any electric fields, respectively (see Appendix D). The last column is the reaction enthalpy for a dissociative reaction of a protonated molecule with a negative dust grain Z⁻ + MH⁺ → Z + M + H (see Appendix D). The dashed line marks the threshold for reactions being considered in the code. The heat of formation data are from Millar et al. (1997) and Linstrom & Mallard (2022).