Shock Tube Study of Thermal Rearrangement of 1,5-Hexadiyne over Wide Temperature and Pressure Regime

The pyrolysis of 1,5-hexadiyne has been studied in a high-pressure single pulse shock tube to investigate the mechanisms involved in the production of benzene from propargyl radicals. Analysis of the reaction products by gas chromatography and matrix isolation Fourier transform infrared spectroscopy has positively identified six linear C 6 H 6 species and two cyclic C 6 H 6 species. Of these species cis -1,3-hexadien-5-yne and trans -1,3-hexadiene-5-yne have been unambiguously identified for the first time and provide vital information concerning a low-temperature route to benzene that does not involve the formation of fulvene; however, the data also provide support for two high-temperature paths from propargyl radicals to benzene via fulvene. Thus experimental evidence has been gained that supports two different routes to benzene formation. The mechanisms and rate coefficients that have been obtained in this work are discussed.