Very‐low‐pressure pyrolysis of nitroso‐ and pentafluoronitrosobenzene CNO 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].