Abstract
The dissociation of 1, 2 and 4% 1,4-dioxane dilute in krypton was studied in a shock tube using laser schlieren densitometry, LS, for 1550-2100 K with 56 +/- 4 and 123 +/- 3 Torr. Products were identified by time-of-flight mass spectrometry, TOF-MS. 1,4-dioxane was found to initially dissociate via C-O bond fission followed by nearly equal contributions from pathways involving 2,6 H-atom transfers to either the O or C atom at the scission site. The 'linear' species thus formed (ethylene glycol vinyl ether and 2-ethoxyacetaldehyde) then dissociate by central fission at rates too fast to resolve. The radicals produced in this fission break down further to generate H, CH3 and OH, driving a chain decomposition and subsequent exothermic recombination. High-level ab initio calculations were used to develop a potential energy surface for the dissociation. These results were incorporated into an 83 reaction mechanism used to simulate the LS profiles with excellent agreement. Simulations of the TOF-MS experiments were also performed with good agreement for consumption of 1,4-dioxane. Rate coefficients for the overall initial dissociation yielded k(123Torr) = (1.58 +/- 0.50) x 10(59) x T-(13.63) x exp(-43970/T) s(-1) and k(58Torr) = (3.16 +/- 1.10) x 10(79) x T-19.13 x exp(-51326/T) s(-1) for 1600 < T < 2100 K.