Kinetic study of reactions of C 2 H 5 O 2 with NO at 298 K and 0.55 – 2 torr

The kinetics of C 2 H 5 O 2 and C 2 H 5 O 2 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 C 2 H 5 O were monitored by LIF. The rate constant for C 2 H 5 O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k 2 = (1.25±0.04) × 10 −11 , (1.66±0.06) × 10 −11 , (1.81±0.06) × 10 −11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm 3 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: C 2 H 5 O + NO + M → C 2 H 5 ONO + M (2a), C 2 H 5 O + NO → CH 3 CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k 2a and for k 2b : k   2a 0= (2.6±1.0) × 10 −28 cm 6 molecule −2 s −1 , k   2a x= (3.1±0.8) × 10 −11 cm 3 molecule −1 s −1 and k 2b ca. 8 × 10 −12 cm 3 molecule −1 s −1 . The present value of k   2a 0 , obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10 −27 cm 6 molecule −2 s −1 recommended in air. The rate constant for the reaction C 2 H 5 O 2 + NO → C 2 H 5 O + NO 2 (3) has been measured at 1 torr of He from the simulation of experimental C 2 H 5 O profiles. The value obtained for k 3 = (8.2±1.6) × 10 −12 cm 3 molecule −1 s −1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc.