Homogeneous gas-phase pyrolysis of acetamide

Abstract

The homogeneous gas-phase pyrolysis of acetamide was studied in a static system over the temperature range 425–545°C; the stoichiometry was 2CH₃CONH₂→CH₃COOH + NH₃+ CH₃CN up to 60% reaction. Beyond this point the reaction of ammonia with acetic acid to form water and acetamide and the decomposition of acetic acid became significant. Reaction occurred by a process second order in acetamide and by an auto-catalytic process, first order in acetamide and first order in acetic acid. The rate constants were represented by the equations k₂= 3.9 × 10⁸ exp (– 36,200/RT) 1. mole ^–1 sec^–1, k₂= 2.1 × 10⁸ exp (– 30,100/RT) 1. mole ^–1 sec^–1, for the uncatalyzed and catalyzed reactions respectively. Nitric oxide has no effect on the reaction, while propionic acid was about as effective as acetic acid in catalyzing the docomposition. Hydrogen chloride was about ten times as effective. The suggested mechanism involves the bimolecular conversion of acetamide into its less stable hydroxy-imide forms and the rapid reaction of this compound to yield the observed products.