High-Temperature Measurements and a Theoretical Study of the Reaction of OH with 1,3-Butadiene

The reaction of hydroxyl (OH) radicals with 1,3-butadiene (C(4)H(6)) was studied behind reflected shock waves over the temperature range 1011-1406 K and at pressures near 2.2 atm. OH radicals were produced by shock-heating tert-butyl hydroperoxide, (CH(3))(3)-CO-OH, and were monitored by narrow line width ring dye laser absorption of the well-characterized R(1)(5) line of the OH A-X (0,0) band near 306.7 nm. OH time histories were modeled using a comprehensive 1,3-butadiene oxidation mechanism, and rate constants for the reaction of OH with 1,3-butadiene were extracted by matching modeled and measured OH concentration time histories. Detailed error analyses yielded an uncertainty estimate of +/-13% at 1200 K for the rate coefficient of the target reaction. The current data extends the temperature range of the only previous high-temperature study for this reaction. The rate coefficient and the branching fractions for the H-abstraction channels of the target reaction were also calculated over the temperature range 250-2500 K using variational transition-state theory based on QCISD(T)/cc-pVinfinityZ//B3LYP/6-311++G(d,p) quantum chemistry. The calculations are in good agreement with the experimental results above 1200 K.