, for the reaction of ozone with ethene and tetramethylethene, perspectively, in Figure . The experimentally determined value of k exp O 3 for ethene is shown as a red vertical line, . The value of the theoretical k QC O 3 for reactions R1 and R2 of Figure , however, are three and two orders of magnitude different (brown and purple lines in Figure ). The mismatch in the absolute value of the rate constants is also observed in the exponential decay of ozone, as it reacts slower than in experiments (Figure ). The mismatch between experimental and theoretical data is even more pronounced for tetramethylethene. Because this reaction is too fast to be determined experimentally, the lower limit of k exp O 3 is shown as a dashed red vertical line in Figure .