Thermal Decomposition of Fluoroform in a Single-Pulse Shock Tube. I

The thermal decomposition of CF3H has been studied between 1200° and 1600°K behind reflected shock waves in a single-pulse shock tube. The principal reaction products are found to be tetrafluoroethylene and hydrogen fluoride. This fact, coupled with thermochemical considerations, suggests that the primary process in the pyrolysis of fluoroform is CF3H→CF2+HF. The observed activation energy, Eobs=63 kcal/mole, is lower than the heat of the reaction which is 75 kcal/mole if a ``reasonable'' value for the heat of formation of the CF2 biradical, ΔHf°(CF2)=−24 kcal/mole, is used. The reasons for this are discussed, and it is suggested that under present reaction conditions, the unimolecular decomposition may be in the falloff region.