Kinetic Study of Reactions of C2H5O and C2H5O2 with NO at 298 K and 0.55 - 2 torr

Article abstract of DOI:10.1002/kin.550271109

The kinetics of C2H5O and C2H5O2 radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis.The temporal profiles of C2H5O were monitored by LIF.The rate constant for C2H5O + NO -> Products (2), measured in the presence of helium, has been found to be pressure dependent: k₂ = (1.25 +/- 0.04) x 10^-11, (1.66 +/- 0.06) x 10^-11, (1.81 +/- 0.06) x 10^-11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm³ molecule^-1 s^-1).The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C2H5O + NO + M -> C2H5ONO + M (2a), C2H5O + NO -> CH3CHO + HNO (2b).The following calculated average values were obtained for the low and high pressure limits of k_2a and for k_2b : k⁰_2a = (2.6 +/- 1.0) x 10^-28 cm⁶ molecule^-2 s^-1, k^infinite_2a = (3.1 +/- 0.8) x 10^-11 cm³ molecule^-1 s^-1 and k_2b ca. 8 x 10^-12 cm³ molecule^-1 s^-1.The present value of k⁰_2a, obtained with He as the third body, is significantly lower than the value (2.0 +/- 1.0) x 10^-27 cm⁶ molecule^-2 s^-1 recommended in air.The rate constant for the reaction C2H5O2 + NO -> C2H5O + NO2 (3) has been measured at 1 torr of He from the simulation of experimental C2H5O profiles.The value obtained for k₃ = (8.2 +/- 1.6) x 10^-12 cm³ molecule^-1 s^-1 is in good agreement with previous studies using complementary methods.