Temperature Dependence of the Reaction of Chlorine Atoms with CH_3OH and CH_3CHO

Abstract

Rate constants of the reactions Cl + CH_3OH → CH_2OH + HCl (k_1) and Cl + CH_3CHO → CH_3C(O) + HCl (k_3) were measured at 100 Torr over the temperature range 230.3 - 297.1 K. Radical chemistry was initiated by pulsed laser photolysis of Cl_2 in mixtures of CH_3OH and CH_3CHO in a flow reactor. Heterodyne near-IR (NIR) wavelength modulation spectroscopy was used to directly detect HO_2 produced from the subsequent reaction of CH_2OH with O_2 in real-time to determine the rate of reaction of Cl with CH_3OH. The rate of Cl + CH_3CHO was measured relative to that of the Cl + CH_3OH reaction. Secondary chemistry, including that of the adducts HO_2·CH_3OH and HO_2·CH_3CHO, were taken into account. The Arrhenius expressions were found to be k_1(T) = 5.02^(+1.8)_(-1.5)×10^(-11)exp[(20±88)/T] cm^3 molecule^(-1) s^(-1) and k_3(T) =6.38^(+2.4)_(-2.0)×10^(-11)exp[(56±90)/T] cm^3 molecule^(-1) s^(-1) (2σ uncertainties). The average values of the rate constants over this temperature range were k_1 = (5.45±0.37)×10^(-11) cm^3 molecule^(-1) s^(-1) and k_3 = (8.00±1.27)×10^(-11)cm^3 molecule^(-1) s^(-1) (2σ uncertainties), consistent with current literature values.

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