Very‐low‐pressure pyrolysis of nitroso‐ and pentafluoronitrosobenzene CNO bond dissociation energies

The high‐pressure absolute rate constants for the decomposition of nitrosobenzene and pentafluoronitrosobenzene were determined using the very‐low‐pressure pyrolysis (VLPP) technique. Bond dissociation energies of D H 0 (C 6 H 5 NO) = 51.5 ± 1 kcal/mole and D H 0 (C 6 F 5 NO) = 50.5 ± 1 kcal/mole could be deduced if the radical combination rate constant is set at log k r ( M −1 ·sec −1 ) = 10.0 ± 0.5 for both systems and the activation energy for combination is taken as 0 kcal/mole at 298°K. δ H f 0 (C 6 H 5 NO), δ H f 0 (C 6 F 5 NO), and δ H f 0 (C 6 F 5 ) could be estimated from our kinetic data and group additivity. The values are 48.1 ± 1, –160 ± 2, and – 130.9 ± 2 kcal/mole, respectively. C–X bond dissociation energies of several perfluorinated phenyl compounds, D H 0 (C 6 F 5 –X), were obtained from the reported values of δ H f 0 (C 6 F 5 X) and our estimated δ H f 0 (C 6 F 5 ) [X = H, CH 3 , NO, Cl, F, CF 3 , I, and OH].