Kinetics of the R + NO2 Reactions (R = i-C3H7, n-C3H7, s-C4H9 and t-C4H9) in the Temperature Range 201-489 Kt

The bimolecular rate coefficients of four alkyl radical reactions with NO2 have been measured in direct time-resolved experiments. Reactions were studied under pseudo-first-order conditions in a temperature-controlled tubular flow reactor coupled to a laser photolysis/photoionization mass spectrometer (LP-PIMS). The measured reaction rate coefficients are independent of helium bath gas pressure within the experimental ranges covered and exhibit negative temperature dependence. For i-C3H7 + NO2 and t-C4H9 + NO2 reactions, the dependence of ordinate (logarithm of reaction rate coefficients) on abscissa (1/7 or log(T) was nonlinear. The obtained results (in cm(3)s(-1)) can be expressed by the following equations: k(n-C3H7 + NO2) = ((4.34 +/- 0.08) x 10(-11)) (T/300 K)(-0.14 +/- 0.08) (203-473 K, 1-7 Torr), k(i-C3H7 + NO2) = ((3.66 +/- 2.54) x 10(-12)) exp(656 +/- 201 KM(T/300 K)(1.26 +/- 0.68) (220-489 K, 1-11 Torr), k(s-C4H9 + NO2) = ((4.99 +/- 0.16) x 10(-11))(T/300 K)(-1.74 +/- 0.12) (241-485 K, 2 - 12 Torr) and k(t-C4H9 + NO2) = ((8.64 +/- 4.61) x 10(-12)) exp(413 +/- 154 K/T)(T/300 K)(0.51 +/- 0.55) (201-480 K, 2-11 Torr), where the uncertainties shown refer only to the 1 standard deviations obtained from the fitting procedure. The estimated overall uncertainty in the determined bimolecular rate coefficients is about 20%.