Abstract The general theory presented in part I is applied to a “large” molecule: the decomposition of chemically activated ethoxy-1,2-dioxctane into formaldehyde and ethyl formate. Microcanonical (specific-energy) rate constants for dioxetane decomposition are calculated at total energies of 2.5, 7.5 and 10.0 kcal/mole. It is found that the presence of selection rules increases the rate constant, but this effect decreases rapidly as the energy increases. The rate constant is shown to be proportional to the average effective total number of final states at a given energy, which is a form of a phase space theory result. Estimated value of the rate constant under experimental conditions is calculated to be in the range 10 9–10 11 s −1, which agrees reasonably well with the experiment estimate ⩾10 8 s −1.