Thermodynamic properties of tetrafluorohydrazine and the difluoroamino radical

Abstract

The equilibrium dissociation of tetrafluorohydrazine via the reaction NZFd(g) * 2NFz(g) has been studied behind incident shock waves over the temperature range 375-1500 K. At temperatures above 500 K, the N2F4 is completely dissociated and absorption measurements in this region yielded the absorptivity of NF2 as a function of temperature. Absorption measurements in the temperature range 375-462 K yielded equilibrium constants for the above reaction. On the basis of second and third law analyses of the data, a value of 20.9 f 0.4 kcal mol-' for the heat of dissociation of NzF4 was obtained. In addition, previously reported measurements of the equilibrium constants for the reaction NF3(g) * NF2(g) + F(g) have been reanalyzed and a value of 57.2 f 1.0 kcal mol-' was obtained for the heat of dissociation of NF3. The above results were then used to obtain revised values for the heats of formation of N2F4 (AHfozg8[NZF4(g)] = -5.3 f 1.4 kcal mol-l) and NF2 (AHfozg8[NFZ(g)] = 7.8 f 1.0 kcal mol-').