The thermal decomposition of azomethane‐d₆

Abstract

Abstract'Ihe 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 N, , CD, , and C,D, . .\ 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 N, production, extrapolated to zero N O pressure, measures the rate of the initial step CD,N,CD, + 2 CDzi + N, . This has an activation energy at high pressures of 50.7 kcal per mole and an Arrhenius A.factor of 101s,49 sec-l. This is to be compared to values of 55.5 and found by Forst and Rice for CH,N,CH, + 2 CH, + N, . The pressure fall-off behavior for CD,N,CD, + 2 CD, + hT2 has also been investigated and compared to the theoretical curses, which seem to fit satisfactorily except a t the lowest pressure, where experimental errots may be large. Unexpectedly, the fall-off curve crosses that for CH,N,CH, + 2 CH, + N,. I t is suggested that the extrapolation to zero N O pressure may not be entirely correct in the CH,K,CH, case where the chain is longer than with CD,N,CD, .It is believed that the decomposition of azomethane-d, is a better example for unimolecular-rate theory than is that of azomethane.

The thermal decomposition of azomethane. III. Kinetics of the noninhibited reaction

“…The absence of any effect on composition of products produced by the addition of CzF6 also shows that the added moderator has no effect on the excited di-R, which means that reactions (21) and (22) do not occur to any significant extent because most excited di-R* collide with an azomethane molecule before they have a chance to decompose. Note that di-R is a large radical, of the same size as compound I, and therefore should have a comparable lifetime.…”

“…Reaction (4), or some reaction similar to it, seems required to provide a second source of nitrogen and to propagate the chain [7,20,21]. I t is immaterial whether reaction (4) is a simple one-step process, as written, or a two step process, for the kinetic consequences would be indistinguishable.…”