Thermally induced nucleation. I. A new way to obtain activation energies for unimolecular reactions

Thermal diffusion cloud chambers have been used to study a variety of physical chemical phenomena, particularly homogeneous nucleation. A new and potentially valuable application of the diffusion cloud chamber—the monitoring of thermally allowed reactions—is presented. It is shown that a low concentration of benzocylobutenol dissolved in nonane will induce temperature dependent nucleation. At constant temperature the rate of nucleation decays exponentially over time. Exponential decay constants obtained from rates of nucleation, when plotted in Arrhenius fashion, give an activation energy of 31 kcal/mol—the same value reported for the racemization of a chiral benzocyclobutenol derivative.