Rate constants for the decomposition of 2-butoxy radicals and their reaction with NO and O2

The reactivity of 2-butoxy radicals has been investigated using the laser photolysis/laser induced fluorescence technique. Three reactions have been studied: (i) The rate constants for the reaction with NO have been measured by the same technique at total pressures between 0.03 < p < 0.4 bar of helium and at five temperatures between 295 - 348 K. No pressure dependence has been found within the experimental error, and a small negative temperature dependence has been found, in agreement with earlier studies: k(1) = (4.4 +/- 0.6) x 10(-12) exp((4.9 +/- 0.3) kJ mol(-1)/RT) cm(3) s(-1). (ii) The rate constant with O-2 has been measured at room temperature and 0.131 bar of helium: k(2) = (9 +/- 2) x 10(-15) cm(3) s(-1). Significant quenching of 2-butoxy fluorescence by O2 prevented experiments in a larger temperature range: k(q),(O2) = (4 +/- 1) x 10(-11) cm(3) s(-1). (iii) The temperature and pressure dependence of the unimolecular decomposition at total pressures between 0.01 < p < 0.8 bar of helium and at four temperatures between 291 - 348 K. The low and the high pressure limiting rate constants as well as the broadening factor F-cent have been extracted from a falloff analysis of the experimental results: k(3,0,He) = 3.2 x 10(-8) exp(-35.9 kJ mol(-1)/RT) cm(3) s(-1), k(3,infinity) = 1.1 x 10(14) exp(-53.6 kJ mol(-1)/RT) s(-1), and F-3,F-c = 0.87 - T/870 K. We anticipate an uncertainty of +/-30% for these rate constants. These results are in excellent agreement with earlier predictions (C. Fittschen, H. Hippler and B. Viskolcz, Phys. Chem. Chem. Phys., 2000, 2, 1677 - 1683 (ref. 1); R. Mereau, M.- T. Rayez, F. Caralp and J.-C. Rayez, Phys. Chem. Chem. Phys., 2000, 2, 3765 ( ref. 2)).