Hydrogen cyanide (HCN) is a widely available molecule in planetary and interplanetary environments. It has been observed that the polymerization of HCN can lead to the formation of nucleobases and proteins (Matthews & Minard 2006). Thus, HCN and its reactivity are considered to be very important for prebiotic chemistry. Our evaluation covers several molecules and oligomers, most of which have been discussed in the literature (Ruiz-Bermejo et al., 2021), and ranks them based on thermodynamic preference. In our study, we compute the relative energies of a series of HCN-derived materials relative to HCN in liquid water. We perform an automated search with semi-empirical methods to extract the lowest energy conformers for each compound. Our work relies on density functional theory (DFT) calculations with thermal corrections coupled to an implicit solvation model to better emulate the polymerization environments. These methodologies allow us to discuss the impact of our results at relevant environments such as that of Saturn’s Moon Titan or the early Earth conditions. The most stable HCN-derived material in our set is the nucleobase adenine, computed to lie ~26 kcal mol-1 below HCN in a water solution. Our enumeration of thermodynamically plausible reaction products and the reaction routes for the abiotic formation of organic macromolecules starting from simple units of HCN offers extensive insights into the chemical and the physical limitations of suspected key prebiotic processes (Sandström & Rahm 2021). 1. C. N. Matthews, R. D. Minard, Faraday Discuss. 2006, 133, 393. 2. M. Ruiz-Bermejo, J. L. de la Fuente, C. Pérez-Fernández, E. Mateo-Martí, Processes 2021, 9, 597. 3. H. Sandström, M. Rahm, ACS Earth Space Chem. 2021, 5, 2152–2159.