Spectrophotometric Determination of the Rate of Dissociation of Tetrafluorohydrazine Behind a Shock Wave

The rate of dissociation of tetrafluorohydrazine in N₂ and Ar was determined at temperatures between 344° and 410°K and total pressures between 0.6 and 6.0 atm. The reaction was carried out by shock heating the gas mixtures in a shock tube. The progress of the reaction behind the incident shock wave was followed by a time‐resolved spectrophotometric technique. The absorption coefficient of NF₂ at λ2602 Å was determined experimentally between 350° and 571°K and found to be 537±10 liter/mole·cm. The kinetics data indicated that the dissociation in 99% N₂ was quasiunimolecular throughout the experimental pressure range, attaining its first‐order limit at a total pressure not far above 6 atm and its second‐order region below 0.6 atm. The observed pressure for the region of transition from first‐ to second‐order kinetics was reasonably consistent with the transition pressure obtained from classical theory on the basis of the estimated value (2×10¹⁵ sec⁻¹) of the pre‐exponential factor for the limiting high‐pressure first‐order specific rate. At approximately 2 atm the observed specific rate for the nitrogen mixture was given by $$k_2({\mathrm{N}}_2{\text{)=10}}^{\text{14.98±0.42}}\exp \text{[(−19.4±0.7}\mathrm{kcal/mole}\mathrm{)/RT]}{\sec }^{\text{−1}}$$ between 344° and 407°K. The indicated uncertainties are the standard deviations of the associated values.