The reaction of the benzene cation with acetylenes for the growth of PAHs in the interstellar medium

We investigated the formation of the naphthalene cation from the successive addition of two acetylenes on the benzene cation. A DFT approach was used for that purpose. The entry channel corresponding to the addition of the acetylenes is the energetically highest part of the entire reaction pathway. It was recalculated using the ab initio W1-F12 and G4 thermochemical protocols. At these levels, the energetically highest point in the entry channel is shown to be just below the energy of the free reactants. This Letter shows that the formation of the naphthalene cation from benzene and acetylenes should proceed in space.