H-Abstraction by OH from Large Branched Alkanes: Overall Rate Measurements and Site-Specific Tertiary Rate Calculations

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• 作者：Dapeng Liu ; Fethi Khaled ; Binod R. Giri ; Emmanuel Assaf ; Christa Fittschen ; Aamir Farooq
• 刊名：Journal of Physical Chemistry A
• 出版年：2017
• 出版时间：February 9, 2017
• 年：2017
• 卷：121
• 期：5
• 页码：927-937
• 全文大小：666K
• ISSN：1520-5215

文摘

Reaction rate coefficients for the reaction of hydroxyl (OH) radicals with nine large branched alkanes (i.e., 2-methyl-3-ethyl-pentane, 2,3-dimethyl-pentane, 2,2,3-trimethylbutane, 2,2,3-trimethyl-pentane, 2,3,4-trimethyl-pentane, 3-ethyl-pentane, 2,2,3,4-tetramethyl-pentane, 2,2-dimethyl-3-ethyl-pentane, and 2,4-dimethyl-3-ethyl-pentane) are measured at high temperatures (900–1300 K) using a shock tube and narrow-line-width OH absorption diagnostic in the UV region. In addition, room-temperature measurements of six out of these nine rate coefficients are performed in a photolysis cell using high repetition laser-induced fluorescence of OH radicals. Our experimental results are combined with previous literature measurements to obtain three-parameter Arrhenius expressions valid over a wide temperature range (300–1300 K). The rate coefficients are analyzed using the next-nearest-neighbor (N–N–N) methodology to derive nine tertiary (T₀₀₃, T₀₁₂, T₀₁₃, T₀₂₂, T₀₂₃, T₁₁₁, T₁₁₂, T₁₁₃, and T₁₂₂) site-specific rate coefficients for the abstraction of H atoms by OH radicals from branched alkanes. Derived Arrhenius expressions, valid over 950–1300 K, are given as (the subscripts denote the number of carbon atoms connected to the next-nearest-neighbor carbon): T₀₀₃ = 1.80 × 10^–10 exp(−2971 K/T) cm³ molecule^–1 s^–1; T₀₁₂ = 9.36 × 10^–11 exp(−3024 K/T) cm³ molecule^–1 s^–1; T₀₁₃ = 4.40 × 10^–10 exp(−4162 K/T) cm³ molecule^–1 s^–1; T₀₂₂ = 1.47 × 10^–10 exp(−3587 K/T) cm³ molecule^–1 s^–1; T₀₂₃ = 6.06 × 10^–11 exp(−3010 K/T) cm³ molecule^–1 s^–1; T₁₁₁ = 3.98 × 10^–11 exp(−1617 K/T) cm³ molecule^–1 s^–1; T₁₁₂ = 9.08 × 10^–12 exp(−3661 K/T) cm³ molecule^–1 s^–1; T₁₁₃ = 6.74 × 10^–9 exp(−7547 K/T) cm³ molecule^–1 s^–1; T₁₂₂ = 3.47 × 10^–11 exp(−1802 K/T) cm³ molecule^–1 s^–1.