arXiv subjects

John M. Simmie

Publications and source records attributed to John M. Simmie.

3 recordsLinked to original sources

arXiv2026

Glycine in the interstellar medium revisited: Resolving conformational complexity kinetically

Numerous attempts to detect glycine, a simple amino acid and a key building block of proteins in all life on Earth, in the interstellar medium have so far been unsuccessful in spite of the fact that it is present in meteorites, comets and asteroids. Glycine is conformationally diverse, existing in eight different forms, and the aim is to show that interconversions, in the dark, are governed by quantum mechanical tunnelling at temperatures from 300 K down to 10 K and to compute the rate at which these changes occur resulting in recommendations to maximise a successful outcome.

astro-ph.GA↗

arXiv2026

Cis--Trans Rotational Isomerism of Seleno-, Thio-, and Formic Acids and Their Dimers: Chemical Kinetics under Interstellar Conditions

Tunnelling reactions of molecules embedded on cryogenic noble-gas matrices are being used in fundamental studies of how reactivity varies with the nature of the supposedly inert matrix as well as pointers to the chemistry occurring in the interstellar medium on ice-grains. To these ends we present chemical kinetic rate constants for the \textit{cis} to \textit{trans} isomerisation of seleno-, thio- and monomeric formic acids and that of their three dimeric species, based on multidimensional calculations in the gas-phase, from 10~K to 300~K as a guide to the matrix reactions.

astro-ph.GA↗

arXiv2022

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

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.

astro-ph.GA↗