Stability of Amines with Minerals and Metal Salts in Hydrothermal Fluids.

Amines are key intermediates in biogeochemical nitrogen cycling and are potential precursors to amino acids and other biomolecules in hydrothermal systems on Earth and ocean worlds. While their reactivity and chemistry under high-temperature conditions have been previously studied, far less is known about how inorganic components such as metal ions and minerals influence amine stability and transformation pathways. Here, we investigate the hydrothermal reactivity of three representative amines (benzylamine, cyclohexylamine, and cyclohexylmethylamine) at 250 °C in the presence of Al-, Fe-, Mg-, and Zn- bearing minerals and metal salts. The amines exhibited moderate conversion and formed products including alcohols, alkenes, aldehydes, and diamines. Minerals and dissolved metal salts produced only minor enhancements or suppressions in total amine conversion and did not substantially alter product distributions or reaction pathways. These results indicate that small aliphatic and aromatic amines are not strongly affected by metal- and mineral-rich hydrothermal fluids. The limited influence of inorganic materials suggests that amines could persist and accumulate in hydrothermal environments, supporting their role as chemical precursors in prebiotic synthesis.