Di-imide: Some Physical and Chemical Properties, and the Kinetics and Stoichiometry of the Gas-phase Decomposition

Abstract

Preparation of di-imide by passing hydrazine vapor through a microwave discharge yields mixtures with NH 3 containing typically about 15% N 2 H 2 , estimated from the gases evolved on decomposition. The behavior of the mixture (which melts at −65 °C) on warming from −196 to −30 °C suggests a strong interaction between the components. Measurements of magnetic susceptibility and e.p.r. experiments showed that N 2 H 2 is not strongly paramagnetic, which with other observations points to a singlet rather than a triplet ground-state.Di-imide can be vaporized efficiently, together with NH 3 , by rapid warming, and the vapor is surprisingly long-lived, with a typical half-life of several minutes at room temperature. The near-u.v. (3200–4400 Å) absorption spectrum of the vapor was photographed; it shows well-defined but diffuse bands, with ε max = 6(± 3) at 3450 Å.Di-imide decomposes at room temperature in two ways:[Formula: see text][Formula: see text]Formation of NH 3 was not observed but cannot be ruled out. The decomposition of the vapor is complicated by a sizeable and variable decomposition that occurs rapidly during the vaporization. The stoichiometry of this and the vapor-phase decomposition depends on total pressure and di-imide concentration. The kinetics of the decomposition of the vapor were studied from 22 to 200 °C by following the disappearance of N 2 H 2 by absorption of light at 3450 Å, or the formation of N 2 H 4 by absorption at 2400 Å, and by mass spectrometry. The kinetics are complex and can be either first- or second-order, or mixed, depending on surface conditions. The effect of olefin additives on the decomposition was studied, and is also complex.Mechanisms for the decomposition are discussed, including the possible role of trans-cis isomerization. The relatively long lifetime found for di-imide in the gas phase suggests that it may be an important intermediate in many reactions of hydronitrogen systems.