Kinetics of the thermal isomerization of bicyclo[1.1.1]pentane and 1,3-dimethylbicyclo[1.1.1]pentane

The thermal decomposition of bicyclo[1.1.1]pentane (I) in the vapor phase in the temperature range from 553.0 to 582.0°K led to 1,4-pentadiene as the only detectable product. The kinetics of the decomposition obeyed the first-order rate equation up to 93% conversion. The rate of the reaction was unaffected by a 17-fold increase in the surface-to-volume ratio of the reaction vessel. The rate constant at 576.1°K was studied as a function of pressure. At 0.25 torr, the rate constant had fallen off to almost one-half of its value at 35 torr, the highest pressure that was used. The value at infinite pressure was estimated to be about 8% higher. From the temperature dependence of the reaction, the first-order rate constant, at about 5 torr, was observed to fit the equation: k = 1015.24e-49,000±500/RT sec-1. The thermal decomposition of 1,3-dimethylbicyclo[1.1.1]pentane (II) was studied at a pressure of about 3 torr in the temperature range from 568.2 to 594.3°K. The kinetics of the process fitted a first-order rate equation, the rate constant being given by 1016.20e-53,000±2000/RT sec-1. © 1968, American Chemical Society. All rights reserved.