2021MNRAS.506.1019A

Methyl formate, HCOOCH₃, and many of its isotopologues have been detected in astrophysical regions with considerable abundances. However, the recipe for the formation of this molecule and its isotopologues is not yet known. In this work, we attempt to investigate, theoretically, the successful recipe for the formation of interstellar HCOOCH₃ and its deuterated isotopologues. We used the gas-grain chemical model, UCLCHEM, to examine the possible routes of formation of methyl formate on grain surfaces and in the gas-phase in low-mass star-forming regions. Our models show that radical-radical association on grains are necessary to explain the observed abundance of DCOOCH₃ in the protostar IRAS 16293-2422. H-D substitution reactions on grains significantly enhance the abundances of HCOOCHD₂, DCOOCHD₂, and HCOOCD₃. The observed abundance of HCOOCHD₂ in IRAS 16293-2422 can only be reproduced if H-D substitution reactions are taken into account. However, HCOOCH₂D remain underestimated in all of our models. The deuteration of methyl formate appears to be more complex than initially thought. Additional studies, both experimentally and theoretically, are needed for a better understanding of the interstellar formation of these species.