Cope rearrangement of 3,3-dimethylhexa-1,5-diene

Abstract

The isomerization of 3,3-dimethylhexa-1,5-diene to 6-methylhepta-1,5-diene is reversible and an example of the Cope rearrangement. Rate constants have been determined from 217 to 282°C and equilibrium constants up to 400°C. From these data Arrhenius parameters have been evaluated for the forward and backward reactions and also the entropy and enthalpy differences between the two dienes. Vapour pressures of the 3,3-dimethylhexa-1,5-diene as a function of temperature are also reported. The A factors for the isomerizations are discussed in terms of the entropy loss associated with the formation of a six-membered ring transition complex.