“…On top of that, the N-and C-cyanomethanimine isomers do not emerge as the unique exception to the MEP, since recent detections in the ISM of many other isomeric families have also raised serious doubts about its general applicability regarding structural isomers. Some of these findings have demonstrated that high-energy structural isomers can share similar abundances to their more stable counterparts, as is the case for the H 2 CN and H 2 NC isomers (Cabezas et al 2021;Agúndez et al 2023a;San Andrés et al 2023) and the two most stable isomers within the C 3 H 4 O family (trans-propenal, CH 2 CHCHO, and methyl ketene, CH 3 CHCO; Bermúdez et al 2018;Fuentetaja et al 2023), or even higher, as noted for the C 3 H 2 O, C 2 H 4 O 2 , and C 2 H 5 N 2 O isomeric families (see, e.g., Loomis et al 2015 andShingledecker et al 2019;Mininni et al 2020;Rivilla et al 2023, respectively). Therefore, it is clear that the MEP cannot be taken as a strict rule to argue about the actual detectability of high-energy structural isomers in the ISM.…”