Temperature dependence of the reactions of the nitrate radical with dichloroalkenes followed by LIF detection

Abstract

Absolute rate coefficients for the reaction of NO₃ with 1,1-dichloropropene, 2,3-dichloropropene and (E)-1,3-dichloropropene have been measured using the discharge-flow technique coupled to an LIF detection system for a range of temperatures from 296 to 430 K. The measured room-temperature rate constants are (1.52 ± 0.76)× 10^–14, (1.39 ± 0.30)× 10^–14 and (0.95 ± 0.14)× 10^–14 cm³ molecule^–1 s^–1, respectively. The Arrhenius expressions k=(2.85 ± 1.21)× 10^–11 exp[–(2274 ± 313)/T], k=(0.16 ± 0.02)× 10^–11 exp[–(1420 ± 82)/T], k=(5.86 ± 1.60)× 10^–11 exp[(–2575 ± 192)/T] cm³ molecule^–1 s^–1, are proposed for the three reactions.

The reactivity of alkenes containing vinylic halogen atoms is discussed and compared with that of simple alkenes. A dependence of room-temperature rate constants and energy of activation on haloalkene ionization potential, corrected for the strength of the mesomeric interaction between the chlorine atom and the carbon–carbon π bond, is found.

Tropospheric half lives of these compounds have been estimated at night and during the day for typical NO₃ and OH tropospheric concentrations, in order to assess the lifetime of these compounds in the atmosphere.