Thermal isomerization of azulene. Single-pulse shock tube investigation

Article abstract of DOI:10.1002/ijch.199600036

The thermal isomerization of azulene was studied behind reflected shocks in a pressurized driver single-pulse shock tube. The temperature range covered was 1050-1400 K at overall densities of ～2.5 × 10^-5 mol/cm³. The main reaction of azulene under these conditions is a unimolecular isomerization to naphthalene, but it also isomerizes, although at a much lower rate, to another isomer. The suggested tetracyclic triene intermediate structure for the uzulene-naphthalene isomerization can lead also to transition states that can describe isomerizations to 1-methylene-1H-indene and 1,2,3-metheno-1H-indene,2,3-dihydro. Small quantities of C₂H₂, C₄H₂, C₆H₆, and C₆H₅-C≡CH were also found in the post-shock samples, particularly at high temperatures. The Arrhenius parameters of the two high pressure limit rate constants for the isomerization processes are: azulene ??? naphthalene, k₁ = 10^12.93 exp(-62.8 × 10³/RT) s^-1 azulene → second isomer, k₂ = 10^12.42 exp(-69.5 × 10³/RT) s^-1 A discussion of the mechanism for these isomerization processes is presented. * Author to whom correspondence should be addressed.