The Slow Combustion of cyclopropane. I. General Kinetics
Proceedings of the Royal Society A
The kinetics of the reaction between oxygen and cyclopropane have been investigated by the static method in the range 380 to 430° C, and with partial pressures of the reactants between 40 and 400 mm. There is an initial period of negligible pressure change, the rate then acceler ating exponentially to a maximum. The effect of conditions on three rate characteristicsthe maximum rate the net branching factor (A') and the induction period (6)obtained from the pressure-time curves, has been
... s, has been studied. These characteristics are very sensitive to surface conditions. Addition of nitrogen has no effect, but addition of hydrogen reduces the rate, probably owing to removal of some reaction product from the vessel wall. With lower oxygen pressures pmax. is proportional to both the oxygen and cycZopropane pressures, while with higher oxygen pressures it varies as the square of the q/cZopropane pressure and is independent of the oxygen pressure. The variation of A' is similar to that of Pmax.-l/0> however, is proportional to the cyclopropane and probably to the oxygen pres sure. The overall activation energy for pmax. or A ' is about 35 kcal, and for l/d about 53 kcal. No detailed reaction scheme is proposed in this part. The results are discussed from the general point of view that the oxidation involves a chain mechanism with degenerate branching, and it is shown that the initiation step is probably heterogeneous.