Fig. 5. Potential energy surfaces of the benzene + ethynyl radical + methylidyne radical reaction pathways to tropylacetylene radical. The B1 pathway (black) involves first a reaction with the ethynyl radical to form B1-2 phenylacetylene and is followed by a reaction with a methylidyne radical. In the B2 pathway (red) the order is reversed and this pathway occurs via the B2-2 tropyl radical. The energies include the zero point vibrational energy correction and are calculated with respect to the entrance energy.