Simulation chamber investigation of the reactions of ozone with short‐chained alkenes

Abstract

Reaction rate coefficients and product yields in the gas phase reaction of O3 with the short‐chained alkenes ethene, propene, 1‐butene, isobutene, (E)‐butene, and (Z)‐butene were determined by Simulation of Atmospheric Photochemistry in a Large Reaction Chamber (SAPHIR). In a first set of experiments, reaction rate coefficients were acquired in an absolute reaction rate study from the measured concentration time profiles of ozone and the alkenes with side reactions being suppressed by adding a radical scavenger. The rate coefficients obtained agree well with literature data; for all but one alkene, the deviation was less than 10%. In a second set of experiments, OH yields were derived from the additional alkene turnover in the absence of a radical scavenger. In contrast to other studies, the OH yields determined in the dry chamber (propene, 0.10 ± 0.07; 1‐butene, 0.00 ± 0.08, isobutene, 0.30 ± 0.14; (Z)‐butene, 0.18 ± 0.09; and (E)‐butene, 0.70 ± 0.12) differed from the yields obtained under humid conditions (propene, 0.30 ± 0.08; 1‐butene, 0.30 ± 0.09; isobutene, 0.80 ± 0.10; (Z)‐butene, 0.40 ± 0.05; and (E)‐butene, 0.60 ± 0.12). The only exception was ethene ozonolysis, where no OH production was observed. HO2 yields (propene, 1.50 ± 0.75; 1‐butene, 1.60 ± 0.80; and isobutene, 2.00 ± 1.00) estimated from the additional ozone turnover compared to the experiments where radicals were not scavenged are reported here for the first time. Furthermore, the yields of the stable ozonolysis products CO, acetaldehyde, and formaldehyde were acquired by monitoring the concentration time profile of the respective compound.