Gas-phase Ozone Reactions with Z-3-Hexenal and Z-3-Hexen-1-ol: Formation Yields of OH Radical, Propanal, and Ethane

Abstract

The formation yields of OH radical, propanal, and ethane from the reactions of ozone with Z-3-hexenal (3HA) and Z-3-hexen-1-ol (3HO) were measured under atmospheric conditions. These OH yields were determined to be 0.32 « 0.07 for 3HA and 0.28 « 0.06 for 3HO. The relative formation yield of the C 2 H 5 CHOO intermediate was estimated based upon the formation yields of propanal and ethane, which consistently suggested that C 2 H 5 CHOO is formed more efficiently from the O 3 + 3HA reaction than from the 3HO reaction.The green leaf volatiles (GLVs), Z-3-hexenal (3HA) and Z-3-hexen-1-ol (3HO) are emitted when plants are wounded. 1,2In lawn mowing activity, emission of 3HA and 3HO has been observed not only immediately following lawn mowing, but also from drying lawn clippings. Emissions from drying lawn clippings last for several hours, which suggests the emission of 3HA and 3HO into the atmosphere would typically continue into late afternoon.3,4 3HA and 3HO contain a C=C double bond and hence reactions with O 3 are an important atmospheric fate of these GLVs. Using the reported rate constants, 5,6 the lifetimes of 3HA and 3HO due to reactions with O 3 can be estimated to be 8 and 4 h ([O 3 ] = 40 ppb), respectively, which are comparable to the lifetimes with respect to OH reactions (a few hours). Recently, it has been recognized that the release of GLVs would have an impact on atmospheric chemistry, for example through secondary organic aerosol formation following their O 3 and OH reactions. 7,8The gas-phase reactions of O 3 with alkenes can initiate the atmospheric oxidation of alkenes. Furthermore, the ozone reactions are known to produce OH radicals, the most important atmospheric oxidant. OH formation from O 3 + alkene reactions is thought to be a potential source of OH not only during the nighttime but also in the daytime. 9 The initial step of O 3 + alkene reactions is believed to be the formation of an energized primary ozonide, followed by its rapid decomposition into a carbonyl oxide (Criegee intermediate, CI) and a carbonyl compound. The CI contains excess energy and can either be stabilized or decompose into other products, including OH radicals. The expected initial stage of the reaction of O 3 with 3HA/3HO is schematically shown in Figure 1.In this study, we measured the yields of OH radical formation from the reactions of O 3 with 3HA and 3HO. Furthermore, the formation yields of propanal and ethane were also measured in order to estimate the branching ratio of decomposition of the primary ozonide (º a and º b in Figure 1).All experiments were conducted using a 6 m 3 evacuable chamber at 1 atm and 298 « 2 K. Details of this chamber have been reported elsewhere. 5 The concentrations of gaseous species were monitored using a Fourier transform infrared (FTIR) spectrometer equipped with multireflection mirror optics (optical path length: 221.5 m). The initial concentrations of O 3 and substituted Z-3-hexenes (3HX, which are 3HA or 3HO) were 15 and 0.21 ppm, respectively.The OH formation yields from O 3 +...

Gas-phase ozonolysis of trans-2-hexenal: Kinetics, products, mechanism and SOA formation

“…Further, studies carried out on the ozonolysis of oxygenated alkenes indicate that the decomposition of the primary ozonide displays a preference for the pathway yielding an oxygenated carbonyl [46][47][48] . Hence, the formation of the alkyl-substituted bi-radical and the formation of glyoxal could be favored.…”

Mechanism and Product Distribution of the O3-Initiated Degradation of (E)-2-Heptenal, (E)-2-Octenal, and (E)-2-Nonenal

“…This observation has consequences for the interpretation of the preferred fragmentation channel of the primary ozonide and is discussed further below. Additionally, Uchida et al 27 in their study of the ozonolysis of (Z)-3-hexenal proposed that the alkyl chain biradical can decompose through two pathways. Based on their work, the alkyl substituted biradical of the ozonolysis reaction under study CH 3 (CH 2 ) n C • HOO • (n = 3, 4 or 5) can undergo the following decomposition pathway: However, as stated above, we did not observe variations in the CO or CO 2 concentrations in our experimental conditions.…”

“…Paulson et al 40 have determined an OH yield of 16% for the ozonolysis of methyl vinyl ketone (CH 2 CHC(O)CH 3 ), and Uchida et al 27 have reported an OH formation yield of 32% for the ozonolysis of (Z)-3-hexenal (CH 3 CH 2 CH CHCH 2 C(O)H). Since in our ozonolysis systems it would appear, based on the discussion above, that only the CH 3 (CH 2 ) n C • HOO • (n = 3, 4, or 5) Criegee biradicals will be producing OH, based on the work of Uchida et al 27 we estimate that OH radical production is probably of the order of 15% or less.…”

“…In the experiments cyclohexane was added to scavenge any OH radicals formed. Uchida et al 27 have studied the product formation from the ozonolysis of the C6 3-alkenal (Z)-3-hexenal in a chamber at 298 K and 1 atm using in situ long-path Fourier transform infrared (FTIR) spectroscopy for the analysis. The authors report a yield of (35 ± 1) % for the primary product propanal obtained using 1,3,5-trimethylbenzene and CO as OH radical scavengers.…”

“…Grosjean et al have studied the products resulting from the ozonolysis of the C3 2-alkenal acrolein (CH 2 CHC­(O)­H) at temperatures between 12 and 17 °C, Grosjean and Grosjean have investigated the products from the ozonolysis of the C4 2-alkenal crotonaldehyde (CH 3 CHCHC­(O)­H) at room temperature, and Grosjean et al the products resulting from the reaction of O 3 with the C6 2-alkenal trans -2-hexenal at ambient temperature. More recently, Uchida et al have studied the products produced in the ozonolysis of the C6 3-alkenal ( Z )-3-hexenal under atmospheric conditions. To our knowledge, there are no previous product studies for the reactions of OH radicals with the C7–C9 2-alkenals under study in this work; however, Kerdouci et al have reported product analyses for the reactions of NO 3 radicals with ( E )-2-hexenal, ( E )-2-heptenal, and ( E )-2-octenal where they observed that unsaturated peroxynitrate type compounds were the main products formed via H atom abstraction by NO 3 from the aldehyde entity and subsequent consecutive additions of O 2 and NO 2 to the resulting CH 3 (CH 2 ) n CHCHC­(O) radicals ( n = 2, 3, or 4).…”