The thermal decomposition of azomethane-d6

The thermal decomposition of azomethane-d₆ has been studied. There is a short chain reaction, and measurements have been made of the rate of production of N₂, CD₄, and C₂D₆. A mechanism is suggested which accounts for these results fairly well. A comparison is made with some similar results of Forst for azomethane. Measurements have also been made of the reaction inhibited by NO. It is believed that the N₂ production, extrapolated to zero NO pressure, measures the rate of the initial step CD₃N₂CD₃ → 2 CD₃ + N₂. This has an activation energy at high pressures of 50.7 kcal per mole and an Arrhenius A·factor of 10^15.49 sec^?1. This is to be compared to values of 55.5 and 10^17.3 found by Forst and Rice for CH₃N₂CH₃ → 2 CH₃ + N₂. The pressure fall-off behavior for CD₃N₂CD₃ → 2 CD₃ + N₂ has also been investigated and compared to the theoretical curves, which seem to fit satisfactorily except at the lowest pressure, where experimental errors may be large. Unexpectedly, the fall-off curve crosses that for CH₃N₂CH₃ → 2 CH₃ + N₂. It is suggested that the extrapolation to zero NO pressure may not be entirely correct in the CH₃N₂CH₃ case where the chain is longer than with CD₃N₂CD₃. It is believed that the decomposition of azomethane-d₆ is a better example for unimolecular-rate theory than is that of azomethane.