New Insights into the Formation of CH₃OCH₃ and CH₃SCH₃ without and with the Assistance of Na⁺ Ions and Some Implications for Interstellar Chemistry: An In Silico Approach

Abstract

As new facets of reaction chemistry are getting unraveled frequently, obtaining new insights and understanding the possible formation of the simplest ethers CH3OCH3 (dimethyl ether: DME) and CH3SCH3 (dimethyl sulfide: DMS) in DMS/DME chemistry are not well-studied so far and so are the description of the molecular reaction mechanisms by the structural evolution and sequence of bond breaking and bond formation. In this context, in silico studies have been accomplished using the density functional theory (DFT) and meta-hybrid-DFT approaches, and benchmarking compound methods. Theoretical investigations have been carried out along with a collective implementation of the potential energy surface (PES) (i.e., energy profile), rendering the energetics of the reaction, followed by the intrinsic reaction coordinate (IRC) approach. The PES examination acquired from the formation pathways of both species gives the impression that the construction of the DMS molecule appears to be energetically more favorable than that of the DME species. The role of the metal cation (here, the Na cation is chosen) in the chemistry occurring in the proposed reactions is not well-researched so far; herein, it is found that incorporation of an alkali metal cation (Na+) lowers the energy barrier significantly for both organic species and facilitates the molecular reactions. Out of five proposed reactions (without and with the assistance of the Na+ ion), the formation of DMS species for two reactions appeared to be the most feasible among all. The NCI plot and a few selected and important topological parameters analyzed from the quantum theory of atoms in molecules (QTAIM) tool are capable of recognizing the evolution of types, nature, and strength of interactions (H-bonding, NCIs, etc.), recuperating the bonding patterns along with the proceeding of the whole chemical process. Interestingly, as DMS is yet to be detected (or not known experimentally) in the interstellar medium (ISM), understanding theoretically the formation of DMS via possible reaction paths under the suitable/putative conditions in the ISM will be an interesting workout in future work.