| Autor: |
Zhang X; Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark 07102, New Jersey, United States., Sangwan M; Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark 07102, New Jersey, United States., Yan C; Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark 07102, New Jersey, United States., Koshlyakov PV; Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia., Chesnokov EN; Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia., Bedjanian Y; Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), CNRS, Orléans 45071, Cedex 2, France., Krasnoperov LN; Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark 07102, New Jersey, United States. |
| Abstrakt: |
The rate constant of the disproportionation channel 1a of the self-reaction of hydroxyl radicals OH + OH → H 2 O + O (1a) was measured at ambient temperature as well as over an extended temperature range to resolve the discrepancy between the IUPAC recommended value ( k 1a = 1.48 × 10 -12 cm 3 molecule -1 s -1 , discharge flow system, Bedjanian et al. J. Phys. Chem. A 1999, 103, 7017) and a factor of ca. 1.8 higher value by pulsed laser photolysis (2.7 × 10 -12 cm 3 molecule -1 s -1 , Bahng et al. J. Phys. Chem. A 2007, 111, 3850, and 2.52 × 10 -12 cm 3 molecule -1 s -1 , Altinay et al. J. Phys. Chem. A 2014, 118, 38). To resolve this discrepancy, the rate constant of the title reaction was remeasured in three laboratories using two different experimental techniques, namely, laser-pulsed photolysis-transient UV absorption and fast discharge flow system coupled with mass spectrometry. Two different precursors were used to generate OH radicals in the laser-pulsed photolysis experiments. The experiments confirmed the low value of the rate constant at ambient temperature ( k 1a = (1.4 ± 0.2) × 10 -12 cm 3 molecule -1 s -1 at 295 K) as well as the V-shaped temperature dependence, negative at low temperatures and positive at high temperatures, with a turning point at 427 K: k 1a = 8.38 × 10 -14 × ( T /300) 1.99 × exp(855/ T ) cm 3 molecule -1 s -1 (220-950 K). Recommended expression over the 220-2384 K temperature range: k 1a = 2.68 × 10 -14 × ( T /300) 2.75 × exp(1165/ T ) cm 3 molecule -1 s -1 (220-2384 K). |
