Abstract
Hydrogen cyanide (HCN)-derived polymers have been recognized as sources of relevant organic molecules in prebiotic chemistry and material sciences. However, there are considerable gaps in the knowledge regarding the polymeric nature, the physicochemical properties, and the chemical pathways along polymer synthesis. HCN might have played an important role in prebiotic hydrothermal environments; however, only few experiments use cyanide species considering hydrothermal conditions. In this work, we synthesized an HCN-derived thermal polymer simulating an alkaline hydrothermal environment (i.e., HCN (l) 0.15 M, 50 h, 100 °C, pH approximately 10) and characterized its chemical structure, thermal behavior, and the hydrolysis effect. Elemental analysis and infrared spectroscopy suggest an important oxidation degree. The thermal behavior indicates that the polymer is more stable compared to other HCN-derived polymers. The mass spectrometric thermal analysis showed the gradual release of several volatile compounds along different thermal steps. The results suggest a complicate macrostructure formed by amide and hydroxyl groups, which are joined to the main reticular chain with conjugated bonds (C=O, N=O, –O–C=N). The hydrolysis treatment showed the pH conditions for the releasing of organics. The study of the synthesis of HCN-derived thermal polymers under feasible primitive hydrothermal conditions is relevant for considering hydrothermal vents as niches of chemical evolution on early Earth.
Highlights
Hydrogen cyanide, HCN, has been considered as a paramount raw material to reach high chemical complexity in the field of prebiotic chemistry and chemical evolution [1,2,3,4]
Elemental analysis shows that the synthesized polymer (HCN-DTP) is compositionally different from other HCN-derived polymers; it is highly oxidized
HCN is abundant throughout the universe, and it can be formed in hydrothermal chimneys
Summary
HCN, has been considered as a paramount raw material to reach high chemical complexity in the field of prebiotic chemistry and chemical evolution [1,2,3,4]. HCN could have been formed from different endogenic sources, on early Earth [3,5,6,7,8,9], or it could be formed exogenically and carried to Earth [4,10,11,12]. The concentration of HCN on primitive environments is still discussed. HCN patches with a >1 mol L−1 concentration. HCN could have been produced under hydrothermal conditions from CH4 , NH3 , and other dissolved species (i.e., N2 , CO). The main reactions are as follows: CH4 + NH3 → HCN + 3H
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