Kinetics of the Gas-Phase Reaction of Hydroxyl Radicals with Dimethyl Methylphosphonate (DMMP) over an Extended Temperature Range (273–837 K) |
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| Authors: | Xiaokai Zhang Daria A Barkova Pavel V Koshlyakov Ilya E Gerasimov Evgeni N Chesnokov Lev N Krasnoperov |
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| Institution: | 1.Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ 07102, USA;2.Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (D.A.B.); (P.V.K.); (I.E.G.), (E.N.C.) |
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| Abstract: | The kinetics of the reaction of hydroxyl radical (OH) with dimethyl methylphosphonate (DMMP, (CH3O)2CH3PO) (reaction 1) OH + DMMP → products (1) was studied at the bath gas (He) pressure of 1 bar over the 295–837 K temperature range. Hydroxyl radicals were produced in the fast reaction of electronically excited oxygen atoms O(1D) with H2O. The time-resolved kinetic profiles of hydroxyl radicals were recorded via UV absorption at around 308 nm using a DC discharge H2O/Ar lamp. The reaction rate constant exhibits a pronounced V-shaped temperature dependence, negative in the low temperature range, 295–530 K (the rate constant decreases with temperature), and positive in the elevated temperature range, 530–837 K (the rate constant increases with temperature), with a turning point at 530 ± 10 K. The rate constant could not be adequately fitted with a standard 3-parameter modified Arrhenius expression. The data were fitted with a 5-parameter expression as: k1 = 2.19 × 10−14(T/298)2.43exp(15.02 kJ mol−1/RT) + 1.71 × 10−10exp(−26.51 kJ mol−1/RT) cm3molecule−1s−1 (295–837 K). In addition, a theoretically predicted pressure dependence for such reactions was experimentally observed for the first time. |
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| Keywords: | kinetics hydroxyl radical dimethyl methylphosphonate DMMP laser photolysis transient absorption V-shaped temperature dependence pressure dependence |
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