How an organic molecule forms in space

Among the growing number of complex organic molecules detected in space, methyl isocyanate (CH₃NCO) is especially intriguing. In the lab, the molecule takes part in the synthesis of short amino-acid chains known as peptides. Conceivably, the same reactions could have occurred during the prebiotic evolution of the molecules of life. But for that pathway to work, CH₃NCO first has to form. Identifying the molecule’s formation mechanisms is the topic of a computational investigation by Liton Majumdar of the University of Bordeaux and his collaborators. Methyl isocyanate is an industrially important (and highly toxic) chemical used in the manufacture of pesticides. In the cold vacuum of interstellar space, chemical reactions most likely take place either in the gas phase or on the surface of dust grains. Majumdar and his colleagues computed chemical reaction rates for reactions involving CH₃NCO and included them in a network of thousands of reactions used for modeling the chemistry of interstellar gas and dust. The simulations demonstrated that CH₃NCO forms efficiently only on grain surfaces. What’s more, the range of favorable conditions that the researchers investigated included the surfaces of icy comets and the cool, dusty envelopes of protostars. Both are locations where CH₃NCO has been spotted. (L. Majumdar et al., Mon. Not. R. Astron. Soc. 473, L59, 2017, doi:10.1093/mnras/stx2325 .)