Kinetics of the Thermal Dissociation of N2F4 in Shock Waves

The equilibrium dissociation of N2F4⇌2NF2 was studied in shock waves, yielding an equilibrium constant identical to those obtained previously in static measurements. The thermal dissociation rate for N2F4 diluted with argon, helium, and SF6 was studied between 350° and 450° at total pressures of 0.58–2.7 atm. The reaction M + N2F4⇌ lim kMM + 2NF2 was found to be first order in M and first order in N2F4, indicating a bimolecular mechanism. The rate constant for argon could be expressed either by kAr = 1.5 × 1012T0.5exp ( − 15 200 / RT) liter/mole·sec or kAr = 3.0 × 10.T0.5 (E0 / RT)4.0exp ( − E0 / RT) liter/mole·sec, where E0 is the dissociation energy of N2F4, here taken to be 18.4 kcal/mole. For the other gases, the activation energy was unchanged, the relative rate constants being given throughout the temperature range by kHe / kAr = 1.2 ± 0.1, kSF6 / kAr = 1.7 ± 0.2, and kN2F4 / kAr = 1.8 ± 0.2. The rate constants are discussed in terms of collision theory.