2017

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

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

D. Liu, F. Khaled, B. R. Giri, E. Assaf, C. Fittschen, A. Farooq

The Journal of Physical Chemistry A 121 (5), 927-937, 2017
D. Liu, F. Khaled, B. R. Giri, E. Assaf, C. Fittschen, A. Farooq
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2017


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 (T003T012T013T022T023T111T112T113, 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) cm3molecule–1 s–1T012 = 9.36 × 10–11 exp(−3024 K/T) cm3 molecule–1 s–1T013 = 4.40 × 10–10exp(−4162 K/T) cm3 molecule–1 s–1T022 = 1.47 × 10–10 exp(−3587 K/T) cm3 molecule–1 s–1T023 = 6.06 × 10–11 exp(−3010 K/T) cm3 molecule–1 s–1T111 = 3.98 × 10–11 exp(−1617 K/T) cm3molecule–1 s–1T112 = 9.08 × 10–12 exp(−3661 K/T) cm3 molecule–1 s–1T113 = 6.74 × 10–9exp(−7547 K/T) cm3 molecule–1 s–1T122 = 3.47 × 10–11 exp(−1802 K/T) cm3 molecule–1 s–1.
DOI: 10.1021/acs.jpca.6b10576