Isomerization of cyclobutenes. Part 9.—Thermal unimolecular isomerization of 1,2-dimethylcyclobutene in solution

Abstract

The thermal isomerization of 1,2-dimethylcyclobutene to 2,3-dimethylbuta-1,3-diene has been investigated in the liquid phase in the temperature range 155–199°C. The reactant isomerizes by a first-order process. Rate constants for the reaction were obtained in solutions of dimethylphthalate (DMP) 1-dodecene (D) and benzonitrile (B). These rate constants fitted the following Arrhenius equations; k_DMP= 10^13.635 exp (–35,190/RT) sec^–1, k_D= 10^13.287 exp (–34,620/RT) sec^–1, k_B= 10^13.233 exp (–34,380/RT) sec^–1. All the evidence suggests that the isomerization is a unimolecular process. The effects of the solvent on the energetics of the isomerization are considered.