Relative and absolute kinetic studies of 2-butanol and related alcohols with tropospheric Cl atoms

Abstract

A newly constructed chamber/Fourier transform infrared system was used to determine the relative rate coefficient, k_i, for the gas-phase reaction of Cl atoms with 2-butanol (k₁), 2-methyl-2-butanol (k₂), 3-methyl-2-butanol (k₃), 2,3-dimethyl-2-butanol (k₄) and 2-pentanol (k₅). Experiments were performed at (298 ± 2) K, in 740 Torr total pressure of synthetic air, and the measured rate coefficients were, in cm³ molecule⁻¹ s⁻¹ units (±2σ): k₁ = (1.32 ± 0.14) × 10⁻¹⁰, k₂ = (7.0 ± 2.2) × 10⁻¹¹, k₃ = (1.17 ± 0.14) × 10⁻¹⁰, k₄ = (1.03 ± 0.17) × 10⁻¹⁰ and k₅ = (2.18 ± 0.36) × 10⁻¹⁰, respectively. Also, all the above rate coefficients (except for 2-pentanol) were investigated as a function of temperature (267–384 K) by pulsed laser photolysis–resonance fluorescence (PLP-RF). The obtained kinetic data were used to derive the Arrhenius expressions: k₁(T) = (6.16 ± 0.58) × 10⁻¹¹exp[(174 ± 58)/T], k₂(T) = (2.48 ± 0.17) × 10⁻¹¹exp[(328 ± 42)/T], k₃(T) = (6.29 ± 0.57) × 10⁻¹¹exp[(192 ± 56)/T], and k₄(T) = (4.80 ± 0.43) × 10⁻¹¹exp[(221 ± 56)/T] (in units of cm³ molecule⁻¹ s⁻¹ and ±σ). Results and mechanism are discussed and compared with the reported reactivity with OH radicals. Some atmospheric implications derived from this study are also reported.