Kinetics of Decomposition of 1,1-Diamino-2,2-Dinitroethylene (Fox-7): 5. Vapor Pressure and Reaction in the Gas Phase

The pressure of 1,1-diamino-2,2-dinitroethylene (FOX-7) vapors in the temperature range 140–160°C is determined by the manometric method. The correlation dependence of log P_vap on 1/T is established, which makes it possible to estimate the value of P_vap with satisfactory accuracy in the temperature range of 100–200°C. The kinetics of the reaction in the gas phase are measured at temperatures of 200–230°C and m/V = 10^–3–10^–4 g/cm³. It is found that under these conditions, in parallel with the usual monomolecular isomerization reaction into the aci-form, a chain process of the direct oxidation of FOX-7 by NO₂ proceeds. The consequence of this reaction is a significant decrease in the activation energy observed and the appearance of a dependence of the rate on the experimental conditions. The scheme of the main stages of the chain reaction is presented and the conditions necessary for the manifestation of this reaction are determined.