Abstract
Reaction rate coefficients-for the reaction of hydroxyl (OH) radicals with nine large branched alkalies (i.e., 2-inethyl-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-dirnethyl-3-ethyl-pentaney and 2,4-diniethy1-3-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 (T-003, T-0/2, T-013, T-022, T-023, T-111, T1-12, T-313, and T-122)-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): T-003 = 1.80 X 10(-10) exp(-2971 K/T) cm(3) molecule(-1) s(-1); T-012 = 9.36 X 10(-11) exp(-3024 K/T) cm(3) molecule (-1) s(-1); T-013 = 4;40 X 10(-10) exp(-4162 K/T) cm(3) molecule(-1) s(-1) T-022 = 1.47 X 10(-10) exp(-3587 K/T) cm(3) molecule(-1) s(-1) ; molecule(-1) s(-1); T-112 = 9.08 X 10(-12) exp(-3661 K/T) cm(3) molecule(-1) s(-1); T-113 =6.74 x 10(-9) exp(-7547 K/T) cm(3) molecule(-1) s(-1); T-023 = 6.06 X 10(-11)-exp(-3010 KIT) cm(3) molecule(-1) s(-1); T-11, = 3.98 X 10(-11) exp(-1617 K/T) cm(3) T-122 = 3.47 X 10(-11) exp(-1802 KIT) cin(3) molecule(-1) s(-1).