Autocatalytic Reaction between HCN and Cysteamine Produces Hydrophobic, Catalytic, Liquid Compartments

Although HCN has been explored extensively as a precursor in the prebiotic synthesis of biological molecules, macroscopic system-level phenomena, originating from reactions of HCN, such as autocatalysis, oscillations, pattern formation, and phase separation have attracted less attention. Autocatalysis and phase separation are particularly interesting in the context of the origin of life because they are sources of self-replication and compartmentalization. In this work, we investigate the reaction between HCN and cysteamine in water, which exhibits both sigmoidal reaction kinetics and the formation of a distinct liquid phase. We studied the origin of the sigmoidal kinetics using NMR spectroscopy and other techniques, investigated the chemical composition of the products using single-crystal X-ray diffraction and mass spectrometry, and probed the absorption of inert additives into the second liquid phase. Our studies show that the sigmoidal kinetics arise from an autocatalytic feedback loop driven by both an increase in pH and the catalytic nature of the newly formed phase itself. Product analysis revealed co-oligomers with a backbone derived from HCN and branches from cysteamine. This composition suggests that co-oligomerization with thiols provides a route to tractable oligomers, mitigating the formation of insoluble HCN polymers. Furthermore, this second liquid phase effectively sequesters hydrophobic molecules like benzene, demonstrating its capacity to act as a primitive compartment. The phenomena that we observed may provide some insight into prebiotic chemical networks and early-stage chemical evolution.