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
Large branched alkanes, Rate calculations
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 (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 × 10–10exp(−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 × 10–9exp(−7547 K/T) cm3 molecule–1 s–1; T122 = 3.47 × 10–11 exp(−1802 K/T) cm3 molecule–1 s–1.

 
DOI: 10.1021/acs.jpca.6b10576