TEMPERATURE-DEPENDENCE OF THE REACTIONS OF THE NITRATE RADICAL WITH DICHLOROALKENES FOLLOWED BY LIF DETECTION

Absolute rate coefficients for the reaction of NO3 with 1,1-dichloropr opene, 2,3-dichloropropene and (E)-1,3-dichloropropene have been measu red using the discharge-flow technique coupled to an LIF detection sys tem for a range of temperatures from 296 to 430 K. The measured room-t emperature rate constants are (1.52 +/- 0.76) x 10(-14), (1.39 +/- 0.3 0) x 10(-14) and (0.95 +/- 0.14) x 10(-14) cm(3) molecule(-1) s(-1), r espectively. The Arrhenius expressions k = (2.85 +/- 1.21) x 10(-11) e xp[-(2274 +/- 313)/T], k = (0.16 +/- 0.02) x 10(-11) exp[-(1420 +/- 82 )/T], k = (5.86 +/- 1.60) x 10(-11) exp[(-2575 +/- 192)/T] cm(3) molec ule(-1) s(-1), are proposed for the three reactions. The reactivity of alkenes containing vinylic halogen atoms is discussed and compared wi th that of simple alkenes. A dependence of room-temperature rate const ants and energy of activation on haloalkene ionization potential, corr ected for the strength of the mesomeric interaction between the chlori ne atom and the carbon-carbon pi bond, is found. Tropospheric half liv es 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.