Mechanism of the 1-C4H9+O reaction and the kinetics of the intermediate 1-C4H9O radical

Abstract

The 1-C4H9 + O reaction has been investigated in two quasi-static reactors with different detection systems. From a time-resolved measurement of OH formation by laser induced fluorescence (T = 295 K, p = 21 mbar, bath gas: He) an inverted vibrational state distribution for OH X (2)Pi (v = 0, 1, 2) was observed. By using Fourier transform infrared spectroscopy, relative product yields of 0.55 +/- 0.08 for 1-C4H8, 0.397 +/- 0.05 for HCHO and 0.053 +/- 0.02 for C3H7CHO were determined (T = 298 K, p = 2 mbar, bath gas: He). The results are explained in terms of the formation and subsequent decomposition of an intermediate chemically activated 1-C4H9O radical and a competing abstraction channel leading directly to OH + 1-C4H8. A modeling by statistical rate theory based on ab initio results for the stationary points of the potential energy surface of C4H9O allows the quantitative description of the product branching ratios. From this modeling, threshold energies of E-06 = 55 +/- 6 and E-07 = 88 +/- 6 kJ mol(-1) for the beta -C-C and the beta -C-H bond dissociation, respectively, in 1-C4H9O are obtained. For the 1,5 H atom shift, a most probable value of E-05 = 40 +/- 5 kJ mol(-1) follows from a comparison of our quantum chemical results with data from the literature.