A Thermodynamic Landscape of Hydrogen Cyanide-Derived Molecules and Polymers

Hydrogen cyanide (HCN)-derived molecules and polymers are featured in several hypotheses on the origin of life. Over half a century of investigations into HCN self-reactions have led to many suggestions regarding the structural nature of the products and an even greater number of proposed polymerization pathways. A comprehensive overview of possible reactions and structures is missing. In this work, we use quantum chemical calculations to map the relative Gibbs free energy of most HCN-derived molecules and polymers that have been discussed in the literature. Our computed free energies indicate that several previously considered polymerization pathways are not spontaneous and should be discarded from future consideration. Among the most thermodynamically favored products are polyaminoimidazole and adenine.