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 formation. The potential surfaces of the reactions C 6 H 5 + C 2 H 2 and 1-C 10 H 7 + C 2 H 2 were explored by densityfunctional theory using BLYP and B3LYP functionals. Vibrational analysis allowed the determination of thermodynamic data and deduction of high-pressure-limit rate constants via transition state theory. The pressure and temperature dependences of these chemically activated reactions were computed using the modified strong collision approximation. The comparison of the predictions for the C 6 H 5 + C 2 H 2 system with experimental data showed good agreement in particular at high temperatures relevant for a combustion environment. The dominant product from acetylene addition to 1-naphthyl at low pressures is the five-membered ring species acenaphthylene, 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 previously, such as 1-acenaphthenyl, 1-naphthylacetylene, 2-vinylphenyl, and 1-vinyl-2-phenyl, are found to be important under some pressure and temperature conditions. All of our results are consistent with known free-radical chemistry. Rate constants describing the formation of phenylacetylene, phenylvinyl, 1-vinyl-2-phenyl, 1-naphthylvinyl, 1-vinyl-8-naphthyl, 1-naphthylacetylene, acenaphthylene, and 1-acenaphthenyl are given at 20 and 40 Torr as well as at 1 and 10 atm for the temperature range from 300 to 2100 K.

No abstract

The dynamics of collisions of CO2 with a perfluorinated alkanethiol self-assembled monolayer (F-SAM) on gold were investigated by classical trajectory calculations using explicit atom (EA) and united atom (UA) models to represent the F-SAM surface. The CO2 molecule was directed perpendicularly to the surface at initial collision energies of 1.6, 4.7, 7.7, and 10.6 kcal/mol. Rotational distributions of the scattered CO2 molecules are in agreement with experimental distributions determined for collisions of CO2 with liquid surfaces of perfluoropolyether. The agreement is especially good for the EA model. The role of the mass in the efficiency of the energy transfer was investigated in separate simulations in which the mass of the F atoms was replaced by either that of hydrogen or chlorine, while keeping the potential energy function unchanged. The calculations predict the observed trend that less energy is transferred to the surface as the mass of the alkyl chains increases. Significant discrepancies were found between results obtained with the EA and UA models. The UA surface leads to an enhancement of the energy transfer efficiency in comparison with the EA surface. The reason for this is in the softer structure of the UA surface, which facilitates transfer from translation to interchain vibrational modes.