Quantum Chemical Exploration of Nitriles in Prebiotic Chemistry and Astrobiology

Abstract: The Universe hosts countless different chemical environments, such as planets, moons, comets and the interstellar medium. The diverse pressures, temperatures and chemical compositions of these environments make a wide variety of processes possible. Knowledge about the chemical processes that occur in such remote locations is largely limited by what is observable by telescopes or site-specific missions. Gaining a deeper understanding of this chemistry is valuable when testing different hypotheses regarding the history and evolution of our Universe and can be important for informing the design of space missions. In this thesis we computationally evaluate the thermodynamic and kinetic stability of chemical structures that may be relevant to prebiotic chemistry, the chemistry that preceded life, and astrobiology. The thesis describes the use of steered molecular dynamics to study the formation of iminoacetonitrile, a hydrogen cyanide dimer and a proposed prebiotic intermediate. The mechanism of iminoacetonitrile formation is found to be consistent with an established hypothesis. However, the reaction is predicted to proceed over a timescale of several months near room temperature, two orders of magnitude slower than the rate of polymer appearance. Future studies into the reactivity of iminoacetonitrile are proposed to better delineate a comparison between theory and experiments. We investigate the plausibility for a different kind of membrane structure, the azotosome, to form in the frigid hydrocarbon lakes of Titan. Comparisons of the stability of azotosomes relative to the crystal structure of their building block acrylonitrile predict that self-assembly of such membranes is unlikely.