Gas-phase thermal unimolecular isomerizations of acetylcyclopropane. Part I. The equilibrium between 2,3-dihydro-5-methylfuran and acetylcyclopropane

Abstract

Contrary to earlier literature reports, the isomerization of 2,3-dihydro-5-methyl furan to acetylcyclopropane has been found to be a reversible process. Equilibrium constants for the temperature range 673–731 K have been obtained from the kinetically complex acetylcyclopropane isomerization system and yield the van't Hoff relationship log K= 0·96 ± 0·25 –(9·6 ± 3·3 kJ mol^–1)/θ, where θ= 2·303 RT This is in good agreement with estimates based on thermodynamic group additivity concepts, and indicates that any interaction between the carbonyl group and the cyclopropane ring has little overall effect on the stability of acetylcyclopropane.