“…Rate coefficients, in cm 3 molecule -1 s -1 , at 296 ± 2 K and 1 atm, for the reactions of OH radicals with alkenes are: k OH,propene = 3.0 × 10 -11 , 14 k OH,ethylene = 8.5 × 10 -12 , k OH,1-butene = 3.1 × 10 -11 , k OH,cis-2-butene = 5.6 × 10 -11 , k OH,1-pentene = 3.1 × 10 -11 , k OH,2-methyl-2-butene = 8.7 × 10 -11 , k OH,2,3-dimethyl-2-butene = 1.1 × 10 . 21 The Cl and OH reactions with alkenes and the corresponding rate coefficients are collected in two different groups. In the first group, hydrogen atoms connected to carbon atoms at the double bound are replaced by methyl groups (ethylene, propene, cis-2-butene, 2-methyl-2-butene and 2,3-dimethyl-2-butene) and an increase on the rate coefficients, from k OH,ethylene to k OH,2,3-dimethyl-2-butene (or from k Cl,propene to k Cl,2-methyl-2-butene ), is observed, as evidenced in Figure 3.…”