HNCO-based synthesis of formamide in planetary atmospheres^⋆

¹ J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 18223, Prague 8, Czech Republic
² Charles University in Prague Faculty of Science, Department of Physical and Macromolecular Chemistry, Albertov 2030, 12840, Prague 2, Czech Republic
³ Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221, Prague 8, Czech Republic
⁴ Institute of Biophysics of the Czech Academy of Sciences, Krˇalovopolskˇa 135, 61265, Brno, Czech Republic
e-mail: cassone@ibp.cz
⁵ CNRS, IPAG, Univ. Grenoble Alpes, 38000, Grenoble, France

Received: 12 March 2018
Accepted: 2 June 2018

Abstract

Time-resolved Fourier transform infrared emission spectroscopy, Fourier transform absorption infrared spectroscopy, and high-resolution UV–ViS emission spectroscopy have been used to characterize the chemistry of isocyanic acid (HNCO) under glow discharge conditions in planetary atmospheres. HNCO mixtures (i.e., composed of di-hydrogen or ammonia) have been investigated in order to unveil the possible reaction pathways leading to the synthesis of the key prebiotic molecule formamide (HCONH₂), upon planetary atmospheres containing isocyanic acid in presence of di-hydrogen and, separately, of ammonia. In addition, ab initio molecular dynamics simulations coupled with a modern metadynamics technique have been performed in order to identify the most likely chemical pathways connecting HNCO to formamide. It turned out that the direct hydrogenation of HNCO is thermodynamically favored. Incidentally, the experimental results – supplied by a simplified kinetic model – also proved the favorability of the reaction HNCO + H₂ → HCONH₂ which, moreover, spontaneously takes place in unbiased ab initio molecular dynamics simulations carried out under the effect of intense electric fields.