Forward and backward thermal rate coefficients and associated error bars for the reactions (a) (Eq. (2), k_{2,- 2}); (b) (Eq. (3), k_{3,- 3}); (c) (Eq. (4), k_{4,- 4}); (d) (Eq. (5), k_{5,- 5}) at temperatures up to 600 K. Also shown are the QCT values obtained for the atom-exchange reactions (Eqs. (11) and (12)) and available results from the literature (Roueff et al. 2015; Colzi et al. 2020; Westley 1980); CT stands for capture theory (Georgievskii & Klippenstein 2005). Solid thick lines show the predicted QCT thermally averaged rates using the Arrhenius-Kooij formula of Eq. (13).