Computational studies of ion–neutral reactions of astrochemical relevance: Formation of hydrogen peroxide, acetamide, and amino acetonitrile

• DFT computations were carried out to study ion–neutral reactions.
• Reactions involve benzene and naphthalene.
• Water and amino acid precursors can be synthesized from reactions.
• Aromatic hydrocarbons participate in reactions as catalysts.
• These approaches can be used as models to study reactions on dust grain surfaces.

Aromatic hydrocarbons (AHs) and their derivatives have been suggested as the building blocks of interstellar dust grains and are responsible for the evolution of astrobiological molecules via surface reactions in space. Gas-phase studies of molecules and ions known to exist in space are crucial to understand relevant ion–molecule reactions and the generation of new species. Reactions catalyzed by large species such as AHs remain relatively unexplored. Our computational studies focus on the energetics and reaction mechanisms of the formation of representative molecules (i.e., hydrogen peroxide, acetamide, and amino acetonitrile) that are critical for the origin of water and amino acids in the universe. Calculations have been carried out using Gaussian 09 to obtain the structures, energetics, and reaction mechanisms to investigate the formation of hydrogen peroxide (H2O2), acetamide (CH3C(O)NH2), and amino acetonitrile (NH2CH2CN). Our results suggest that there are energetically accessible reaction pathways leading to the formation of these molecules through species which have been discovered in the interstellar medium (ISM). Ionized benzene and polycyclic aromatic hydrocarbons (PAHs) can act as catalysts to facilitate the formation of astromolecules. The theoretical studies can enhance our understanding of ion–molecule reactions that are relevant to the formation of important astromolecules in the gas phase, and provide a new way to investigate the formation of polyatomic molecules on surfaces of dust grains such as large PAHs.

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