Abstract
Site-specific rate constants for hydrogen (H) and deuterium (D) abstraction by hydroxyl (OH) radicals were determined experimentally by monitoring the reaction of OH with two normal and six deuterated alkanes. The studied alkanes include propane (C3H8), propane 2,2 D2 (CH3CD2CH3), propane 1,1,1-3,3,3 D6 (CD3CH2CD3), propane D8 (C3D8), n-butane (n-C4H10), butane 2,2-3,3 D4 (CH3CD2CD2CH3), butane 1,1,1-4,4,4 D6 (CD3CH2 CH2CD3), and butane D10 (C4D10). Rate constant measurements were carried out over 840-1470 K and 1.2-2.1 atm using a shock tube and OH laser absorption. Previous low-temperature data were combined with the current high-temperature measurements to generate three-parameter fits which were then used to determine the site-specific rate constants. Two primary (P-1,P-H and P-1,P-D) and four secondary (S-00,S-H, S-00,S-D, S-01,S-H, and S-01,S-D) H- and D-abstraction rate constants, in which the subscripts refer to the number of C atoms connected to the next-nearest-neighbor C atom, are obtained. The modified Arrhenius expressions for the six site-specific abstractions by OH radicals are P-1,P-H = 1.90 x 10(-18)T(2.00) exp(-340.87 K/T) cm(3) molecule(-1) s(-1) (210-1294 K); P-1,P-D = 2.72 x 10(-17) T-1.60 exp(-895.57 K/T) cm(3) molecule(-1) s(-1) (295-1317 K); S-00,S-H = 4.40 x 10(-18) T-1.93 exp(121.50 K/T) cm(3) molecule(-1) s(-1) (210-1294 K); S-00,S-D = 1.45 x 10(-20) T-2.69 exp(282.36 K/T) cm(3) molecule(-1) s(-1) (295-1341 K); S-01,S-H = 4.65 x 10(-17) T-1.60 exp(-236.98 K/T) cm(3) molecule(-1) s(-1) (235-1407 K); S-01,S-D = 1.26 x 10(-18) T-2.07 exp(-77.00 K/T) cm(3) molecule(-1) s(-1) (294-1412 K).