Abstract: The reaction mechanism of C6F6-HNO2 aqueous solution was studied using laser flash photolysis-transient absorption spectrum technique under irradiation at 355 nm. The characteristic absorption peaks and the kinetic parameters of transient species were also investigated. The hydroxyl radical derived from the photolysis of HNO2 was added to hexafluorobenzene with a second-order rate constant of 1.8×109 L·mol-1·s-1 to form an adduct, C6F6…OH, which had absorption peaks at 250, 270, and 400 nm. The C6F6…OH adduct decayed by the elimination of HF to yield C6F5O· with an apparent first-order rate constant 6.1×105 s-1. In the presence of O2, C6F6…OH underwent a complex reaction with a rate constant of 2.8×106 L·mol-1·s-1 to form C6F6OHO2, which had the same absorption bands as C6F6…OH. The final products were identified using the GC-MS technique and the possible reaction pathways were also discussed.

Key words: Hexafluorobenzene(C6F6), Laser flash photolysis, Transient absorbance spectrum, Nitrous acid, Free radical