Reaction pathways for growth of polycyclic aromatic hydrocarbons under combustion conditions, a DFT study

Models of soot formation include the growth of polycyclic aromatic hydrocarbons (PAHs) as an essential step. We investigate two reaction pathways for growth of PAHs, both initiated by radical formation. The first type, the so called HACA mechanism, is based on stepwise acetylene addition and we identify promising reactions not considered before. Examples are the synthesis of perylene and phenanthro[ 1,10,9,8 - opqra] perylene. The second type of reaction concerns direct condensation of phenyl, naphthyl or anthracenyl with another PAH. Pathways for these reactions require merely up to 100 kJ mol(-1) for the activation barrier, which makes them viable candidates for PAH growth.