Intramolecular energy transfer in the isomerization of cyclobutanone

We report the use of the results of calculations of the rate constant for the unimolecular isomerization of cyclobutanone to test a modified version of the Zhao–Rice classical MRRKM theory. The modification consists of using, in place of the Zhao–Rice approximation for the rate of intramolecular energy transfer, the local Lyapunov function which describes the divergence of initially nearby trajectories started in the region of the cantorus. The rate of isomerization of cyclobutanone obtained from trajectory calculations is used as the standard for comparison of the two calculations of the rate of intramolecular energy transfer which are shown to yield very similar, although not identical, rate constants.