Temperature-dependent ozonolysis kinetics of selected alkenes in the gas phase: an experimental and structure-activity relationship (SAR) study.
The kinetics of the reactions of ozone with several alkenes have been measured at atmospheric pressure between 217 and 301 K using EXTRA (EXTreme RAnge chamber). This work represents the first kinetic determinations of the system and focuses on the temperature-dependence of alkene ozonolysis, which is an important tropospheric process impacting upon climate and human health, yet few studies have investigated these reactions as a function of temperature. Temperature-dependent rate coefficients have been established for 3,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene and 4-methyl-1-pentene at 217-301 K and atmospheric pressure. The derived Arrhenius expressions are as follows: k = (2.68+2.23-1.23) x 10-15 exp[-(16.29 +/- 1.20/RT)], k = (7.31+9.39-4.05) x 10-15 exp[-(15.33 +/- 1.84/RT)] and k = (5.21+2.85-1.85) x 10-15 exp[-(15.66 +/- 0.87/RT)] cm3 molecule-1 s-1 for 3,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene and 4-methyl-1-pentene, respectively.A strong linear correlation has been observed between a simple structure-activity relationship (SAR) and the activation energy, Ea, possessing an R2 value of 0.90. However, no significant correlation was observed for the A-factor. Notwithstanding, with accurate predictions of the SAR for Ea and log k298, values for the A-factor can be retrieved, and hence the prediction of k at any temperature. The newly acquired data agree well with the original SAR and suggest that the factors controlling the rate of ozonolysis reaction are captured accurately by the SAR index.
Leather
Kimberley E
KE
The Centre for Atmospheric Science, The School of Earth, Atmospheric and Environmental Science, The University of Manchester, Simon Building, Brunswick Street, Manchester, UKM13 9PL.
McGillen
Max R
MR
Percival
Carl J
CJ