Peptide Bonds in the Interstellar Medium: Facile Autocatalytic Formation from Nitriles on Water-Ice Grains

TL;DR

This study demonstrates that acetamide and related amides can form efficiently on water-ice grains in space via autocatalytic reactions involving nitriles and water, with quantum tunnelling significantly influencing reaction rates.

Contribution

It provides the first computational evidence of autocatalytic formation of amides from nitriles on water-ice clusters in the interstellar medium, highlighting a plausible pathway for prebiotic chemistry.

Findings

Reactions proceed auto-catalytically on water-ice clusters.

Quantum tunnelling significantly affects reaction rates.

Amides can form from nitriles and water in space environments.

Abstract

A recent suggestion that acetamide, \ce{CH3C(O)NH2}, could be readily formed on water-ice grains by the acid induced addition of water across the \ce{CN} bond is now shown to be valid. Computational modelling of the reaction between \ce{R-CN} (R = H, \ce{CH3}) and a cluster of 32 molecules of water and one \ce{H3O+} proceeds auto-catalytically to form firstly a hydroxy imine \ce{R-C(OH)=NH} and secondly an amide \ce{R-C(O)NH2}. Quantum mechanical tunnelling, computed from small-curvature estimates, plays a key role in the rates of these reactions. This work represents the first credible effort to show how amides can be formed from abundant substrates, namely nitriles and water, reacting on a water-ice cluster containing catalytic amounts of hydrons in the interstellar medium with consequential implications towards the origins of life.