The thermochemical kinetics of the retro-‘ene’ reactions of molecules with the general structure (allyl)XYH in the gas phase. Part IX. Unimolecular thermal decompostion of allylmethylamine

Abstract

The gas-phase unimolecular thermal decomposition of N-allyl-N-methylamine (AMA) was investigated in the temperature range 602–694 K. The principal products are propene and methyleneamine. First-order rate constants, calculated using the internal standard method, fit the Arrhenius relationship (i). The reaction appears log (k₁/s^–1)=(11·37 ± 0·56)–(43·38 ± 1·62 kcal mol^–1)/2·3RT§(i) to be homogeneous as a 15-fold change in surface:volume ratio of the reaction vessel yields no significant change in the rate constants. The decomposition of AMA follows a retro-‘ene’ mechanism via a 6-centre transition state. The Arrhenius parameters for AMA decomposition are compared with those observed for other alkylallylamines. The significance of these observations in an evaluation of the extent of charge separation, i.e. non-synchronism, in the transition state is discussed.