CRAHCN-O: A Consistent Reduced Atmospheric Hybrid Chemical Network Oxygen Extension for Hydrogen Cyanide and Formaldehyde Chemistry in CO-, N-, HO-, CH-, and H-Dominated Atmospheres.

Hydrogen cyanide (HCN) and formaldehyde (HCO) are key precursors to biomolecules such as nucleobases and amino acids in planetary atmospheres. However, many reactions which produce and destroy these species in atmospheres containing CO and HO are still missing from the literature. We use a quantum chemistry approach to find these missing reactions and calculate their rate coefficients using canonical variational transition state theory and Rice-Ramsperger-Kassel-Marcus/master equation theory at the BHandHLYP/aug-cc-pVDZ level of theory. We calculate the rate coefficients for 126 total reactions and validate our calculations by comparing with experimental data in the 39% of available cases. Our calculated rate coefficients are most frequently within a factor of 2 of experimental values and generally always within an order of magnitude of these values. We discover 45 previously unknown reactions and identify 6 from this list that are most likely to dominate HCO and HCN production and destruction in planetary atmospheres. We highlight O + CH → HCO + H as a new key source and HCO + O → HCO + OH as a new key sink, for HCO in upper planetary atmospheres. In this effort, we develop an oxygen extension to our consistent reduced atmospheric hybrid chemical network (CRAHCN-O), building off our previously developed network for HCN production in N-, CH-, and H-dominated atmospheres (CRAHCN). This extension can be used to simulate both HCN and HCO production in atmospheres dominated by any of CO, N, HO, CH, and H.