Crossroads at the Origin of Prebiotic Chemical Complexity: Hydrogen Cyanide Product Diversification

Products of hydrogencyanide (HCN) reactivity are suspected toplay important roles in astrochemistry and, possibly, the origin oflife. The composition, chemical structure, and mechanistic detailsfor formation of products from HCN's self-reactions have, however,proven elusive for decades. Here, we elucidate base-catalyzed reactionmechanisms for the formation of diaminomaleonitrile and polyiminein liquid HCN using ab initio molecular dynamics simulations. Bothmaterials are proposed as key intermediates for driving further chemicalevolution. The formation of these materials is predicted to proceedat similar rates, thereby offering an explanation of how HCN'sself-reactions can diversify quickly under kinetic control. Knowledgeof these reaction routes provides a basis for rationalizing subsequentreactivity in astrochemical environments such as on Saturn'smoon Titan, in the subsurface of comets, in exoplanet atmospheres,and on the early Earth.

Automated summary

We elucidate the mechanisms behind the formation of diaminomaleonitrile and polyimine in liquid HCN using molecular dynamics simulations. These materials are proposed as important intermediates for further chemical evolution. The similar formation rates of these materials provide an explanation of how HCN's self-reactions can quickly diversify under kinetic control. Understanding these reaction routes helps in rationalizing subsequent reactivity in astrochemical environments such as on Titan, comets, exoplanet atmospheres, and the early Earth.