Thermal isomerization of cyclobutenes. Part 10.—3,3-Dimethylcyclobutene and 1,3,3-trimethylcyclobutene

Abstract

The thermal isomerization of 3,3-dimethylcyclobutene and 1,3,3-trimethylcyclobutene have been investigated in the gas phase in the temperature ranges 150–200°C and 172–213°C respectively. These isomerizations were homogeneous first-order reactions with rate constants independent of pressure over a wide pressure range. The rate constant for the isomerization of 3,3-dimethylcyclobutene fitted the Arrhenius equation, k= 10^13·93 exp (–36,090/RT) sec^–1. Those for the 1,3,3-trimethylcyclobutene fitted the Arrhenius equation, k= 10^13·90 exp (–37,030/RT) sec^–1. The effect of alkyl substitutents on the free energy of activation for the isomerization of cyclobutenes is discussed.