tokens: measured in the various environments described in the Section 1 (Garrod et al. 2008 ; Barone et al. 2015 ; Codella et al. 2017 ; Quénard et al. 2017 ). Those models rely on different formamide formation routes (the gas-phase reaction NH 2 + H 2 CO in Barone et al. ( 2015 ), Codella et al. ( 2017 ), and a combination of irradiated surface chemistry and gas-phase chemistry in Garrod et al. 2008 and Quénard et al. 2017 ). On the contrary, the destruction routes are common in all models and are dominated by ion–molecule reactions involving formamide and HCO + , H, H 3 O + , He + , and C + . Moreover, some reactions involving neutral radicals have been invoked, such as the one involving the OH radical (Belloche et al. 2017 ), but no experimental or theoretical data are available on the rate coefficients for those reactions, which are, anyway, expected to be very slow based on what is known on the reaction NH 2 CHO + H (Haupa, Tarczay Lee 2019 ). The proton transfer reactions with HCO + and H dominate the formamide destruction in ‘standard’ conditions, while that with H 3 O + is a dominant formamide sink in the water-rich gas. Instead, the reactions involving He + and C + ions, which provide in general a smaller contribution to the formamide destruction, proceed via charge transfer and lead to a significant fragmentation of the ionized formamide, especially in the case of He + collisions because of the large amount of energy released in the process (see for instance, the article by Ascenzi et al. 2019 for the case of similar molecules). In summary, even though proton transfer processes can lead to fragmentation, NH 2 CHOH + is expected to be also an important by-product in the main destruction route of formamide. As already mentioned in the Section 1 , the most probable fate of protonated formamide will be its recombination with interstellar free electrons. The global electron–ion recombination rate coefficient assumed in the KIDA data base, and used in all the models cited above, is given by k ( T ) = 7.5 × 10 −7 ( T /300) −0.5 cm 3 s −1 , and very nicely compares with the value calculated in this work, which is larger by only 10 per cent, contrarily to other similar cases such as the one of protonated methanimine (CH 2 NH) where the guessed values substantially differ (Yuen et al. 2019 ). Our recommendation is to update the data bases for astrochemical modelling with the present value of 8.33 × 10 −7 ( T /300) −0.5 cm 3 s −1 , which is the result of rigorous calculations rather than an assumed value. Concerning the branching ratios, our method is not yet able to determine the yield in the different exit channels and, therefore, an experimental determination, such as those achieved by using the heavy ion storage ring CRYRING (Geppert Larsson 2008 ), is required. We note, however, that it is highly improbable that all the channels mentioned in the KIDA data base have the same yield. It can be instructive to compare the case of protonated formamide
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