A thermodynamic study of the dimerization of cyclopentadiene

Abstract

The heat of dimerization of cyclopentadiene to endo-dicyciopentadiene in the liquid phase at 25º was measured in an adiabatic calorimeter to be -9.22 ± 0.3 kcal/mole monomer. The rate of dimerization in the liquid phase at 25º was followed with a dilatometer and the initial second-order rate constant found to be 4.99 x 10^-5. mole^-l min^-l. The vapour pressure of endo-dicyclopentadiene, measured by a boiling point method in the range 77.5-149.6º, gave the relation (p in torr): RInp ? 11342/T -2.6505In T + 54.7855 The standard heats of formation of solid, 31.1 ± 0.5 kcal/mole, and gaseous, 42.2 ± 0. 6 kcal/mole, endo-dicyclopentadiene were derived, and the strain energy and dimerization equilibria discussed.