Continuous reaction networks, which do not rely on purification or timely additions of reagents, serve as models for chemical evolution and have been demonstrated for compounds thought to have played important roles for the origins of life such as amino acids, hydroxy acids, and sugars. Step-by-step chemical protocols for ribonucleotide synthesis are known, but demonstrating their synthesis in the context of continuous reaction networks remains a major challenge. Herein, compounds proposed to be important for prebiotic RNA synthesis, including glycolaldehyde, cyanamide, 2-aminooxazole, and 2-aminoimidazole, are generated from a continuous reaction network, starting from an aqueous mixture of NaCl, NH4Cl, phosphate, and HCN as the only carbon source. No well-timed addition of any other reagents is required. The reaction network is driven by a combination of γ radiolysis and dry-down. γ Radiolysis results in a complex mixture of organics, including the glycolaldehyde-derived glyceronitrile and cyanamide. This mixture is then dried down, generating free glycolaldehyde that then reacts with cyanamide/NH3to furnish a combination of 2-aminooxazole and 2-aminoimidazole. This continuous reaction network models how precursors for generating RNA and other classes of compounds may arise spontaneously from a complex mixture that originates from simple reagents.

A prevailing strategy in origins of life studies is to explore how chemistry constrained by hypothetical prebiotic conditions could have led to molecules and system level processes proposed to be important for life’s beginnings. This strategy has yielded model prebiotic reaction networks that elucidate pathways by which relevant compounds can be generated, in some cases, autocatalytically. These prebiotic reaction networks provide a rich platform for further understanding and development of emergent “life-like” behaviours. In this review, recent advances in experimental and analytical procedures associated with classical prebiotic reaction networks, like formose and Miller-Urey, as well as more recent ones are highlighted. Instead of polymeric networks, i.e., those based on nucleic acids or peptides, the focus is on small molecules. The future of prebiotic chemistry lies in better understanding the genuine complexity that can result from reaction networks and the construction of a centralised database of reactions useful for predicting potential network evolution is emphasised.

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