Kinetics studies of the reactions of methyldioxy with nitric oxide, nitrogen dioxide, and methyldioxy at 298 K

Abstract

The flash photolysis/ultraviolet absorption technique was used to measure the rate constants for the reactions CH/sub 3/O/sub 2/ + NO ..-->.. CH/sub 3/O + NO/sub 2/ (1), CH/sub 3/O/sub 2/ + NO/sub 2/ + M ..-->.. CH/sub 3/O/sub 2/NO/sub 2/ + M (2), and CH/sub 3/O/sub 2/ + CH/sub 3/O/sub 2/ ..-->.. products (3) at 298 K over the pressure range 50 to 700 torr. Values for k/sub 1/ and k/sub 3/ were determined to be (7.1 +- 1.4) x 10/sup -12/ cm/sup 3/ molecule/sup -1/s/sup -1/ and (3.6 +- 0.7) x 10/sup -13/ cm/sup 3/ molecule/sup -1/s/sup -1/, respectively, where k/sub 3/ is defined by the relation -d(CH/sub 3/O/sub 2/)/dt = 2k/sub 3/(CH/sub 3/O/sub 2/)/sup 2/; k/sub 2/ was found to vary strongly with pressure, indicating that the reaction occurs primarily by addition and is in the falloff region between second- and third-order kinetics. Experimentally determined parameters describing the shape of the falloff curve for k/sub 2/ were in reasonable agreement with those obtained by using theoretical methods developed by Troe and co-workers. An upper limit of 7 x 10/sup -18/ cm/sup 3/ molecule/sup -1/s/sup -1/ was determined for the rate constant for the reaction CH/sub 3/O/sub 2/ +more » CO ..-->.. products.« less