Formation of β-hydroxycarbonyls from the OH radical-initiated reactions of selected alkenes

beta-Hydroxycarbonyls can be formed from the gas-phase reactions of alkenes with the OH radical, both in the presence and in the absence of NO. To date, because of analytical difficulties, few data have been reported for the formation of this class of compound from the reactions of the OH radical with alkenes. We have determined that beta-hydroxyketones can be readily analyzed by gas chromatography, and in this work we have shown that in 1 atm of air the beta-hydroxyalkoxy radicals formed in the reactions of the OH radical with trans-2-butene, trans-3-hexene, 1-butene, and alpha-pinene in the presence of NO primarily decompose rather-than react with O-2. Rate constant ratios k(d)/k(o2) (or lower limits thereof), where k(d) and k(o2) are respectively the: rate constants for the decomposition and the reaction with O-2 of the intermediate beta-hydroxyalkoxy radicals, have been obtained for the reactions of the CH3CH(O)CH(OH)CH3, CH3CH2CH(O)CH2OH, and CH3CH2CH(O)CH(OH)CH2CH3 radicals at 296 +/- 2 K and atmospheric pressure. Using the O-3 reactions with the alkenes to generate OH radicals, the reactions of the OH radical with trans-2-butene, trans-3-hexene, and alpha-pinene in the absence of NO lead to the formation of the expected beta-hydroxycarbonyls and (at least for trans-2-hutene) the alpha,beta-diol.