Nitrogen-containing heterocycles present an intriguing astrochemical mystery. 45 different varieties have been detected on meteorites with non-terrestrial isotopic abundances, but none have been detected in the interstellar medium, despite numerous search attempts. It is unclear if these species are more likely to form through low-temperature gas-phase chemistry, photoprocessing of icy grains, aqueous chemistry in a meteorite parent body, or a combination of processes. Additionally, the Cassini-Huygens mission revealed the likelihood of N-heterocycles in Titan’s atmosphere, however formation mechanisms in this environment are also unclear. Further exploration of these questions requires a broader catalog of potential N-heterocycle precursors and formation pathways, particularly for low temperature gas phase chemistry. Here, results of ab initio molecular dynamics simulations of radical neutral, gas phase N-heterocycle forming reactions will be discussed. These simulations were performed with an ab initio nanoreactor, a computational tool developed for chemical discovery. Multiple novel reactions have been revealed thus far, with a focus on pathways to pyrrole and pyridine. Many reactants are similar to molecules previously identified in cold molecular clouds or Titan's atmosphere, but have not been the subjects of astronomical searches due to a lack of the prerequisite laboratory spectroscopy. Therefore, the results of these simulations can be used to direct future experimental work both to measure the vibrational and rotational spectra of these reactants and experimentally determine rate coefficients for the pathways of interest.

Expanding the astrochemical catalog: Novel gas phase n-heterocycle formation pathways identified with an ab initio nanoreactor

ACS Spring Meeting 2021

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