The formation of interstellar organic molecules: H2C3O a DFT and ELF theoretical study

Abstract

This quantum study at B3LYP/6-311 ++ G (d, p) with ELF analysis were performed in order to understand the formation of propynal and cyclopropenone, two molecules detected in the interstellar medium. The formation of these molecules is supposed to be through reactions between carbon monoxide (CO) and acetylene (C2H2) in the cold conditions of interstellar clouds. All the structures, reagents, products and transition states, have been optimized and the geometrical parameters are given as well as the dipole moments. The reaction paths are elaborated and discussed here using the IRC method implemented in the Gaussian program. The determined activation energies allow an estimation of the rate constants. The ELF analysis performed here seems to be a valuable tool for screening the evolution of the bonds during the formation processes. The two reactions probably occur in one step. The propadienone, another possible isomer, has been also studied. It is formed through a third reaction. A stable triplet ground state of this molecule, the thermodynamic consideration and a small dipole moment can explain the fact that it is not detected yet in the interstellar medium. M06-2X and WB97XD functional were also used for comparing results.