Experimentally determined site-specific reactivity of the gas-phase OH and Cl + i-butanol reactions between 251 and 340 K

Product branching ratios for the gas-phase reactions of i-butanol, (CH3)2CHCH2OH, with OH radicals (251, 294, and 340 K) and Cl atoms (294 K) were quantified in an environmental chamber study and used to interpret i-butanol site-specific reactivity. i-Butyraldehyde, acetone, acetaldehyde, and formaldehyde were observed as major stable end products in both reaction systems with carbon mass balance indistinguishable from unity.

Product branching ratios for OH oxidation were found to be temperature-dependent with the α, β, and γ channels changing from 34 ± 6 to 47 ± 1%, from 58 ± 6 to 37 ± 9%, and from 8 ± 1 to 16 ± 4%, respectively, between 251 and 340 K. Recommended temperature-dependent site-specific modified Arrhenius expressions for the OH reaction rate coefficient are (cm3 molecule-1 s-1): kα(T) = 8.64 × 10-18 × T1.91exp(666/T); kβ(T) = 5.15 × 10-19 × T2.04exp(1304/T); kγ(T) = 3.20 × 10-17 × T1.78exp(107/T); kOH(T) = 2.10 × 10-18 × T2exp(−23/T), where kTotal(T) = kα(T) + kβ(T) + kγ(T) + kOH(T).