Low-Temperature Kinetics of Reactions of OH Radical with Ethane, Propene, and 1-Butene

Published

November 1, 2003

Author(s)

A B. Vakhtin, J E. Murphy, S R. Leone

Abstract

The kinetics of the reactions of the OH radical with ethane (k₁), propene (k₂), and 1-butene (k₃) are studied over a temperature range of T = 96-296 K. The low-temperature environment is provided by a pulsed Laval nozzle supersonic expansion of nitrogen with admixed radical precursor and reactant gases. The OH radicals are produced by pulsed photolysis of H₂O₂ at 248 nm. Laser-induced fluorescence of the OH radicalsexcited in the (1,0) band of the A²ς⁺-X² II_i transation is used to monitor the OH decay kinetics to obtain the bimolecular rate coefficients. At T=296 K, the rate constants k₁, k₂, and k₃ are also measured as a function of total pressure. The room-temperature fall-off parameters are used as the basis for extrapolation of the low-temperature kinetic data obtained over a limited range of gas number density, to predict the high-pressure limits of all three rate coefficients at low temperatures. The temperature dependece of the measured high-pressure rate constants for T=96-296 K can beexpressed as follows: K₁, difference} = (8.2 1.3)x10^-12(T/300) ^{(-0.88 0.20) cm}u3^ molecule ^-1 S^-1,K₂difference] = (2.95 0.10)x10^-11(T/300) ^{(-1.06 0.13) cm}u3^ molecule ^-1S^-1, k₃difference}= (3.01 0.15) x10^{-11(1.44 0.01)} cm³molecule^-1S^-1. All three high-pressure rate constants show a slight negative temperature dependence, which is generally in agreement with both low-temperature and high temperature kinetic data available in the literature. Incorporating the new experimental data on K₁ in photochemical models of Saturn's atmosphere may significantly increase the calculated fate photochemical conversion of H₂O into C-O containing molecules.

Citation

Journal of Physical Chemistry A

Volume

107

Issue

No. 47

Pub Type

Journals

Keywords

alkenes, hydroxyl radical, laser induced fluorescence, laval novvle supersonic expangion, low temperature reaction kinetics

Citation

Vakhtin, A. , Murphy, J. and Leone, S. (2003), Low-Temperature Kinetics of Reactions of OH Radical with Ethane, Propene, and 1-Butene, Journal of Physical Chemistry A (Accessed April 24, 2024)