EXPERIMENTAL AND THEORETICAL-STUDY OF THE ISOMERIZATION OF N-METHYLPYRROLE

The isomerisation of N-methylpyrrole to 2-methylpyrrole has been investigated experimentally by means of a single pulse shock tube over the temperature range 1000 to 1350 K and theoretically by ab initio calculations. Between 1000 and 1100 K the isomerization is found to occur via an intramolecular methyl shift. The experimental rate constant for this rearrangement was found to be k(iso) = 10(12.8(+/- 0.4)) exp[-56.2(+/- 2.0) kcal mol-1/RT] s-1. Ab initio calculations gave Arrhenius parameters for the methyl shift in good agreement with the experimental values. Methyl shifting produces the intermediate 2-methyl-2H-pyrrole which undergoes a hydrogen shift of low activation energy to form the product of isomerisation, 2-methylpyrrole. Above about 1240 K there is a competing free-radical process which produces methane, pyrrole and traces of higher molecular weight products.