The thermochemical kinetics of the retro-‘ene’ reactions of molecules with the general structure (allyl)XYH in the gas phase. Part X. Unimolecular thermal decomposition of diallyl ether

Abstract

The gas-phase thermal decomposition of diallyl ether (DAE) was investigated in the temperature range 545–627 K. The reaction yields acrolein and propene as the only products and appears to be a homogeneous, unimolecular process. First-order rate constants (determined using the internal standard technique) were insensitive to a 15-fold change in surface:volume ratio, the extent of conversion, and the addition of 5·8-fold excess of toluene or hex-1-ene. The rate constants were also invariant over a 13-fold variation in initial DAE pressure and were found to fit the Arrhenius relationship (i). Conversions obtained on the basis of the products agree with those using the internal log (K₁/s^–1)=(11·83 ± 0·13)–(40·90 ± 0·35 kcal mol^–1)/2·3RT(i) standard method. The thermal decomposition of DAE fits into the general context of retro-‘ene’ reactions involving a concerted [1,5] shift via a six-centre transition state as found for but-3-enols, but-3-enoic acids, and allylamines.