Detailed kinetic study of the growth of small polycyclic aromatic hydrocarbons. 1. 1-naphthyl plus ethyne

A better understanding of the formation of polycyclic aromatic hydrocarbons (PAH) is of great practical interest because of their potential hazardous health effects and their role as intermediates in soot and fullerene format ion. The potential surfaces of the reactions C6H5 + C2H2 and 1-C10H7 + C2H2 were explored by density-functional theory using BLYP and B3LYP functional s. Vibrational analysis allowed the determination of thermodynamic data and deduction of high-pressure-limit rate constants via transition state theor y. The pressure and temperature dependences of these chemically activated r eactions were computed using the modified strong collision approximation. T he comparison of the predictions for the C6H5 + C2H2 system with experiment al data showed good agreement in particular at high temperatures relevant f or a combustion environment. The dominant product from acetylene addition t o I-naphthyl at low pressures is the five-membered ring species acenaphthyl ene, consistent with the more pronounced formation of fullerenes under such conditions. High pressure favors formation of stabilized initial adducts, i.e., phenylvinyl and 1-naphthylvinyl. Some products not considered previou sly, such as 1-acenaphthenyl, 1-naphthylacetylene, 2-vinylphenyl, and 1-vin yl-2-phenyl, are found to be important under some pressure and temperature conditions. All of our results are consistent with known free-radical chemi stry. Rate constants describing the formation of phenylacetylene, phenylvin yl, -vinyl-2-phenyl, 1-naphthylvinyl, 1-vinyl-8-naphthyl, 1-napthylacetylen e, acenaphthylene, and 1-acenaphthenyl are given at 20 and 40 Ton as well a s at 1 and 10 atm for the temperature range from 300 to 2100 K.