Low-Temperature Combustion Chemistry of n-Butanol: Principal Oxidation Pathways of Hydroxybutyl Radicals

• DOI: 10.1021/jp403792t
• Publication Date: 2013-06-28T16:52:23Z
• Authors: Oliver Welz; Judit Zádor; John D. Savee; Leonid Sheps; David L. Osborn; Craig A. Taatjes
• Keywords: Isotopologue

Reactions of hydroxybutyl radicals with O2 were investigated by a combination quantum-chemical calculations and experimental measurements product formation. In pulsed-photolytic Cl-initiated oxidation n-butanol, the time-resolved isomer-specific concentrations probed using multiplexed tunable synchrotron photoionization mass spectrometry (MPIMS). The interpretation data is underpinned potential energy surfaces for reactions four isomers (1-hydroxybut-1-yl, 1-hydroxybut-2-yl, 4-hydroxybut-2-yl, 4-hydroxybut-1-yl) calculated at CBS-QB3 RQCISD(T)/cc-pV∞Z//B3LYP/6-311++G(d,p) levels theory. observed yields display substantial temperature dependence, arising from competition among three fundamental pathways: (1) stabilization hydroxybutylperoxy radicals, (2) bimolecular formation in + reactions, (3) decomposition radicals. 1-hydroxybut-1-yl reaction dominated direct HO2 elimination corresponding peroxy radical forming butanal as stable coproduct. chemistry other mainly proceeds via alcohol-specific internal H-atom abstractions involving H atom either -OH group or carbon attached to group. We observe evidence recently reported water pathway (Welz et al. J. Phys. Chem. Lett. 2013, 4 (3), 350-354) 4-hydroxybut-2-yl reaction, supporting its importance γ-hydroxyalkyl reactions. Experiments 1,1-d2 4,4,4-d3 isotopologues n-butanol suggest presence yet unexplored pathways acetaldehyde.