Kinetic study of the reactions of NO3 with 3-chloropropene, 3-bromopropene and 3-iodopropene using LIF detection

Abstract

The kinetics of the reactions of the nitrate radical, NO₃, with 3-chloropropene and 3-bromopropene have been studied in the temperature range 296–428 K, using the discharge-flow technique coupled to detection of NO₃ by laser-induced fluorescence. The results obtained for the room-temperature rate constants are (0.49 ± 0.02)× 10^–14 and (0.38 ± 0.02)× 10^–14 cm³ molecule^–1 s^–1, respectively, and the proposed Arrhenius expressions are k=(1.92 ± 0.79)× 10^–11 exp[(– 2480 ± 143/T)] and k=(1.27 ± 0.37)× 10^–12 exp[(– 1737 ± 104)/T] cm³ molecule^–1 s^–1, respectively (errors quoted as σ).

The study of the reaction between the NO₃ radical and 3-iodopropene has also been attempted using the same conditions. The decomposition of 3-iodopropene with increasing temperature and the occurrence of some radical–radical reactions makes it difficult to establish the Arrhenius parameters. A room-temperature rate constant of k⩽ 3.91 ± 0.02 × 10^–14 cm³ molecule^–1 s^–1 has been estimated.

An estimate of the corresponding rate coefficients for the reactions of these halopropenes with the OH radical has been made. Tropospheric half-lives are calculated at night and during the day for typical NO₃ and OH concentrations, and show that both radicals provide an effective tropospheric sink for these compounds.