Experimental and theoretical studies of rate coefficients for the reaction O( ³P) + C ₂H ₅OH at high temperatures

Rate coefficients of the reaction O( ³P) + C ₂H ₅OH in the temperature range 782-1410 K were determined using a diaphragmless shock tube. O atoms were generated by photolysis of SO ₂ at 193 nm with an ArF excimer laser; their concentrations were monitored via atomic resonance absorption. Our data in the range 886-1410 K are new. Combined with previous measurements at low temperature, rate coefficients determined for the temperature range 297-1410 K are represented by the following equation: k(T) = (2.89 ± 0.09) × 10 ^-16T ^1.62 exp[-(1210 ± 90)/T] cm ³ molecule ^-1 s ^-1; listed errors represent one standard deviation in fitting. Theoretical calculations at the CCSD(T)/6-311+G(3df, 2p)//B3LYP/6-311+G(3df) level predict potential energies of various reaction paths. Rate coefficients are predicted with the canonical variational transition state (CVT) theory with the small curvature tunneling correction (SCT) method. Reaction paths associated with trans and gauche conformations are both identified. Predicted total rate coefficients, 1.60 × 10 ^-22T ^3.50 exp(16/T) cm ³ molecule ^-1 s ^-1 for the range 300-3000 K, agree satisfactorily with experimental observations. The branching ratios of three accessible reaction channels forming CH ₃CHOH + OH (1a), CH ₂CH ₂OH + OH (1b), and CH ₃CH ₂O + OH (1c) are predicted to vary distinctively with temperature. Below 500 K, reaction la is the predominant path; the branching ratios of reactions 1b,c become ∼40% and ∼11%, respectively, at 2000 K.