and 5 (298-483 K). Lower temperatures are particularly relevant when considering processes occurring in environments such as Saturn's moon Titan. We address some effects of temperature on our conclusions in the Supporting information. The energy content per HCN in the studied structures varies between +7.5 and -16.1 kcal/mol (Fig. ). In other words, note that to arrive at a reaction energy, the values shown in Figure needs to be multiplied with the number of HCN in each structure. For example, for adenine, this multiplication factor is 5, whilst for a polymer it is n. Most investigated structures are clearly thermodynamically downhill from HCN in aqueous solution at 298 K. The overall thermodynamic favorability of HCN-self reactions is thus one part of the explanation for the commonly observed chemical complexity of reaction mixtures. The only materials predicted to be unstable relative to HCN are 3, 9, 12 and 14, effectively ruling these out as plausible reaction products under the studied conditions.