Formation of isomeric terphenyls and triphenylene by pyrolysis of benzene

The pyrolysis of benzene has been investigated at 773, 923, and 1073 K and the mechanisms of formation of isomeric terphenyls and triphenylene have been studied, the results being compared with those obtained by pyrolysis of benzene solutions containing diphenyl and o=terphenyl. No differences in the mechanisms of the formation of terphenyls and triphenylene could be observed at the selected temperatures, even if ring fission and a higher degree of polymerization occurred at 1073 K. The addition of diphenyl and o-terphenyl showed that the reactions leading to the formation of isomeric terphenyls and triphenylene in the pyrolysis of pure benzene do not pass through stable intermediates.