Effect of the Keto Group on Yields and ... - ACS Publications

Subscriber access provided by Northern Illinois University

Article

Effect of the Keto Group on Yields and Composition of Organic Aerosol Formed from OH Radical-Initiated Reactions of Ketones in the Presence of NO

x

Lucas B. Algrim, and Paul Jeffrey Ziemann J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b05839 • Publication Date (Web): 10 Aug 2016 Downloaded from http://pubs.acs.org on August 16, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry A is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Effect of the Keto Group on Yields and Composition of Organic Aerosol Formed from OH Radical-Initiated Reactions of Ketones in the Presence of NOx

Lucas B. Algrim†,|| and Paul J. Ziemann†,||,*

Submitted to Journal of Physical Chemistry A

†

Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO

80309 ||

Cooperative Institute for Research in Environmental Sciences (CIRES), University of

Colorado, Boulder, CO 80309 *

Author to whom correspondence should be addressed.

Telephone: 303-492-9654 Fax: 303-492-1149 Email: [email protected]

1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT: Yields of secondary organic aerosol (SOA) were measured for OH radicalinitiated reactions of the 2- through 6-dodecanone positional isomers and also n-dodecane and n-tetradecane in the presence of NOx. Yields decreased in the order n-tetradecane > dodecanone isomer average > n-dodecane, and the dodecanone isomer yields decreased as the keto group moved toward the center of the molecule, with 6-dodecanone being an exception. Trends in the yields can be explained by the effect of carbon number and keto group presence and position on product vapor pressures, and by the isomer-specific effects of the keto group on branching ratios for keto alkoxy radical isomerization, decomposition, and reaction with O2. Most importantly, results indicate that isomerization of keto alkoxy radicals via 1,5- and 1,6-H shifts are significantly hindered by the presence of a keto group whereas decomposition is enhanced. Analysis of particle composition indicates that the SOA products are similar for all isomers, and that compared to those formed from the corresponding reactions of alkanes the presence of a pre-existing keto group opens up additional heterogeneous/multiphase reaction pathways that can lead to the formation of new products. The results demonstrate that the presence of a keto group alters gas and particle phase chemistry, and provide new insights into the potential effects of molecular structure on the products of the atmospheric oxidation of volatile organic compounds and subsequent formation of SOA.

2


Page 2 of 44

Page 3 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


INTRODUCTION Global anthropogenic emissions of non-methane hydrocarbons total ~100 Tg annually.1 An important atmospheric sink for these volatile organic compounds (VOCs) is reaction with OH radicals, NO3 radicals, or O3, which occur by mechanisms that result in products containing carbonyl, hydroxyl, carboxyl, ester, peroxide, and nitrate functional groups.2 Addition of functional groups, without fragmentation of the carbon backbone, forms products of lower volatility that are more likely to partition to the particle phase and so contribute to secondary organic aerosol (SOA) formation.3,4 SOA is a major component of fine particulate matter5 and can have significant effects on the atmospheric chemistry and fate of organic compounds,6 regional and global climate, visibility, and human health.7 Previous studies have investigated the effects of factors such as the VOC, oxidant, NOx, humidity, and particle acidity on SOA formation.8 Studies of the effect of VOC structure have focused primarily on alkanes, alkenes, and aromatics, the major hydrocarbon emissions to the atmosphere, for which differences in carbon number, chain branching, rings, and C=C double bonds can influence SOA composition and yields.9-13 Much less attention has been given to the effects of oxygenated functional groups that are present on reaction products (and some VOC emissions) and are known to have significant effects on mechanisms of oxidation and therefore atmospheric aging.3,4 Chacon-Madrid and Donahue14,15 investigated the effects of functional groups on SOA formation by comparing the yields of SOA formed from oxidation of series of alkanes and oxygenated compounds with similar vapor pressures. Consistent with expectations, the presence of aldehyde, keto, and carboxyl groups tended to reduce SOA yields,

3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

apparently due to enhanced fragmentation of the carbon backbone during oxidation that led to the formation of more volatile products. Results indicated, however, that reactant vapor pressures and oxidation states were not sufficient to explain SOA yields, and additional details of reaction mechanisms and the molecular structures of reaction products must be considered. In this study we systematically investigated the effect of keto groups on SOA products and yields formed from OH radical-initiated reactions of a series of five C12 ketone isomers, 2- through 6-dodecanone, in the presence of NOx. We chose ketones because they are formed through a variety of reaction mechanisms and their chemistry is similar to that of n-alkanes, which is reasonably well understood.16,17 The results provide new insights into the effects of molecular structure on VOC chemistry and SOA formation that will be useful for evaluating and improving reaction mechanisms developed to predict these processes in the atmosphere.

METHODS Chemicals. The 2-, 3-, 4-, 5-, and 6-dodecanone isomers (≥ 95% purity) were obtained from ChemSampCo, dodecane (>99% purity) and heptanal (95& purity) were obtained from Sigma-Aldrich, NO (CP Grade, 99% purity) was obtained from Matheson, and methyl nitrite was synthesized18 and stored in a lecture bottle at room temperature. The purity determined by infrared spectroscopy was 99%. Environmental Chamber Experiments. Experiments were conducted in an 8.0 m3 Teflon chamber at ambient temperature (~25 °C) and pressure (~630 torr). Chamber air ( average dodecanone isomers (37%) > n-dodecane (31%) is then consistent with the increasing order in compound vapor pressures: ntetradecane (1.4 Pa) < average dodecanone isomers (3.6 Pa) < n-dodecane (15 Pa). Furthermore, for the 2- through 5-dodecanone isomers the decrease in yield as the keto group is moved towards the middle of the molecule: 2- (57%) > 3- (41%) > 4- (24%) > 5-

15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(20%) is consistent with the increase in isomer vapor pressure: 2- (2.6 Pa) > 3- (3.4 Pa) > 4- (3.8 Pa) > 5- (4.0 Pa). A number of observations indicate that the differences in SOA yields are not only due to differences in the vapor pressures of parent compounds, however. For example, although the SOA yields and vapor pressures for n-tetradecane (64% and 1.4 Pa) and 2-dodecanone (57% and 2.6 Pa) are similar, the SOA yield for ndodecane (31%) is greater than that for 5-dodecanone (20%) even though their respective vapor pressures are 15 Pa and 4.0 Pa. Also, whereas the vapor pressures of the dodecanone isomers increase monotonically from 2- to 6-dodecanone, there is a sharp increase in the SOA yield from 5- (20%) to 6-dodecanone (45%). It appears, therefore, that the differences in SOA yields are due not only to differences in vapor pressures of the parent ketone but also to the effects of molecular structure on reaction mechanisms and products. SOA Modeling. In light of the interesting trends observed in SOA yields, a kinetic model was developed to attempt to better understand the effect of ketone isomer structure on these values. For simplicity, we focused on formation of first generation products, which were classified into four categories according to the reaction mechanism shown in Scheme 1: (1) K-N [1], and products formed from keto alkoxy radicals by (2) reaction with O2 (K-C [2]), (3) decomposition (R + C [3]), and (4) isomerization (K-HN [4], K-HC [5], CHA-N [6], K-CHA [7], UCE-N [8], K-DHF [9]). Rates of H-atom abstraction from each dodecanone carbon by reaction with an OH radical were calculated using the structure activity relationships of Kwok and Atkinson.37 Reactions of keto peroxy radicals with NO were assumed to form the K-N [1] and keto alkoxy radical with branching ratios of 0.285 and 0.715, the same as those measured for reactions of

16


Page 16 of 44

Page 17 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


alkylperoxy radicals.26 Keto alkoxy radicals were assumed to react with O2 to form K-C [2] with a rate constant of 3.9 × 104 s-1 (adjusted from 4.7 × 104 s-1 for 760 torr30 to 630 torr ambient pressure), and rates of decomposition and isomerization to form R + C [3] and keto hydroxyalkyl radicals were calculated using the methods of Vereecken and Peeters.28,29 Keto hydroxyperoxy radicals formed by reaction of keto hydroxyalkyl radicals with O2 were assumed to react with NO to form the K-HN [4] + CHA-N [6] and keto hydroxyalkoxy radicals with branching ratios of 0.125 and 0.875, the same as those measured for reactions of hydroxyperoxy radicals.41 Keto hydroxyalkoxy radicals were then assumed to react with O2 with a rate constant of 3.9 × 104 s-1 and rates of decomposition and isomerization were calculated using to the methods of Vereecken and Peeters,31,32 which account for effects of keto groups. There was no need to include effects of hydroxyl or nitrooxy groups in these calculations since the model only treated formation of first generation products. These values were then used in a kinetics model with the experimental conditions to predict the yields of the four product classes. We note that the model does not account for partitioning of products to the particles to form SOA, loss of gas phase products to the wall, or the effects of secondary reaction products on SOA yields. These omissions will be discussed below. Molar yields of the four product classes calculated for reaction of each isomer are shown in Figure 6. The K-N [1] yield is the same for all isomers, whereas the yields of products formed by keto alkoxy radical isomerization, decomposition, and reaction with O2 depend on isomer structure because of the activating or deactivating effect of the keto group on the reaction pathways. Most importantly, when a keto alkoxy radical is formed following H-atom abstraction at a carbon adjacent to the keto group (an α-carbon), either

17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

by reaction with an OH radical or by keto alkoxy radical isomerization, this α-keto alkoxy radical subsequently reacts solely by decomposition because of strong activation of that pathway. The yield of R + C [3] decomposition products is thus determined primarily by the number of competitive reaction pathways that can lead to formation of α-keto alkoxy radicals. Another factor that can significantly affect the branching ratios for reactions of keto alkoxy radicals (other than α-keto alkoxy radicals), however, is that the rates of isomerization are predicted to be slower when the keto group is present in the 6- or 7-member ring transition state, as occurs when isomerization involves an alkoxy group and H-atom located on opposite sides of the keto group (Scheme 3). In this case reaction with O2 becomes competitive, leading to the formation of K-C [2]. And lastly, it is important to note that relative to the rates of abstraction of H atoms from CH2 groups, abstraction at α-carbons is slightly deactivated, whereas abstraction at β-carbons is highly activated. These effects of structure on reaction pathways provide a basis for the trends observed in Figure 6. For 2-dodecanone, the presence of a long alkyl chain allows isomerization to outcompete reaction with O2 for all keto alkoxy radical isomers, and in most cases the same is true with regards to decomposition. Only for α-keto alkoxy radicals formed by abstraction of an H atom from the 3-carbon, either by an OH radical or isomerization when the alkoxy group is located on the 6-carbon, is decomposition competitive. Thus, for this isomer almost all keto alkoxy radical products are formed by isomerization. A sizeable shift in the product distribution occurs with 4-dodecanone, primarily because isomerization of the keto alkoxy radical formed by H-atom abstraction at the β-carbon in the 2-position (predicted to account for 22% of the keto alkoxy radicals formed by

18


Page 18 of 44

Page 19 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


reaction with OH radicals) is restricted by the presence of the keto group, thus allowing reaction with O2 to dominate. The pronounced difference in the product distribution between the 5- and 6-dodecanone isomers is due to a similar effect. In this case, enhanced H-atom abstraction occurs at the two highly activated β-carbons (each are predicted to account for 25% of the keto alkoxy radicals formed by reaction with OH radicals), and because isomerization of the keto alkoxy radical formed by reaction at the 3-carbon of 5dodecanone is restricted by the presence of the keto group, reaction with O2 dominates at that site. In the case of 6-dodecanone, however, the keto alkoxy radical formed by Hatom abstraction from the β-carbon in the 4-position (predicted to account for 26% of the keto alkoxy radicals formed by reaction with OH radicals) is able to isomerize by abstraction of a primary H-atom from the terminal CH3 group (Scheme 3). Although this isomerization pathway is about an order of magnitude slower than those involving secondary H atoms, in this case it is still about an order of magnitude faster than either decomposition or reaction with O2. Moreover, because this pathway leads to the formation of primary functional groups, which reduce vapor pressure more than secondary functional groups, it will further increase the SOA yield. According to this model then, reactions of the 5- and 6-dodecanone isomers are uniquely sensitive to the effect of keto group location on keto alkoxy radical reaction pathways, which leads to a significant increase in isomerization products for the 6-isomer. It is quite interesting, however, that this sensitivity is eliminated when 1,6-H shifts (Scheme 3), which are predicted to be about an order of magnitude slower than 1,5-H shifts,32 are incorporated into the model. These shifts allow isomerization to occur across the keto group, so that

19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

the model instead predicts a relatively linear decrease in the yield of isomerization products. The mass yields of isomerization products (calculated from the molar yields in Figure 6 by assuming a mean molecular weight of 250) predicted with and without the inclusion of 1,6-H atom shift reactions are shown in Figure 7, where they are compared with the measured SOA mass yields. The results show that the monotonic decrease in SOA yields from 2- to 5-dodecanone is also observed in the yields of isomerization products predicted by both models, but that only when the model does not include 1,6-H shifts do the predictions reproduce the increase in SOA yield observed from 5- to 6dodecanone. The comparison thus indicates that 1,5-H shifts are the only significant isomerization pathway in these reactions, and that the effect of keto group position on the branching ratios for keto alkoxy radical reaction with O2, decomposition, and isomerization contributes to the decrease in SOA yield from 2- to 5-dodecanone (along with the effect of parent ketone vapor pressure) and is primarily responsible for the increase in SOA yield from 5- to 6-dodecanone. The predicted yield of isomerization products is expected to be higher than the SOA yield measured for each isomer (as is observed), because the model does not account for gas-particle or gas-wall partitioning. Not all isomerization products are expected to partition entirely to the particles (Table S2 in Supporting Information), especially first generation products such as K-HC [5], KCHA [7], UCE-N [8] and K-DHF [9], and when products are present in the gas phase they can partition to the chamber walls, thus reducing SOA yields.25,27,42-45 Such effects should be similar for all isomers, however, and thus not responsible for the observed trends in SOA yields.

20


Page 20 of 44

Page 21 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The good agreement between the trends in the model predictions and measured SOA yields supports the model assumption that most of the products that contribute to SOA are formed primarily through reaction pathways that include isomerization, which is consistent with the results of SOA product analyses. As shown in Figure 1 and Table 1, most of the SOA products elute in regions A and B of the chromatograms, and all of these can be assigned to isomerization products. Only K-N [1] and K-N-N [10], which elute in region C, are formed through pathways that do not include isomerization. And as shown in Figure 6 for K-N [1] (and thus likewise for K-N-N [10]), the yields of these products should be independent of isomer structure and so not responsible for the observed trends in SOA yields. It is also important to note that the comparison of model predicted yields of first generation isomerization products with measured yields of SOA that includes both first and second generation products is justified for a number of reasons. For example, Figure 5A shows time profiles of SOA mass concentrations measured for the five dodecanone isomers, which are equivalent to profiles of SOA yields since the amount of dodecanone reacted at any time was nearly the same in all experiments. These profiles show that the order of SOA yields measured at any time in the experiments was the same as those measured at the end of the experiments (Figure 5B): 2- > 6- > 3- > 4- > 5-. This result indicates that in the early stages of reaction, when SOA was composed almost entirely of first generation products, the SOA yields followed the same order as yields measured at the end, when both first and second generation products contributed to SOA. Thus, the model-measurement comparison made above should have yielded the same conclusions if SOA yields were measured after only a few minutes of reaction instead of after 60 min of reaction. This was not done here because of

21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

the difficulty of accurately measuring small relative changes in dodecanone concentrations. It is important to mention here that the formation of high mass concentrations (1– 3 mg m–3) of SOA in these experiments probably helped to maximize the effects of reaction pathways on measured SOA yields, since under these conditions isomerization products should be mostly in the particle phase, whereas products formed by other pathways should be predominantly in the gas phase (Table S2). The measured SOA yields are therefore likely to be more sensitive to branching between these pathways than if they were conducted at ~10 µg m–3 concentrations that are more typical of the polluted atmosphere.5 The measured SOA yields are also probably higher than they would be for experiments conducted at ambient SOA mass concentrations, due to enhanced gas-toparticle partitioning and shorter timescales for reaching gas-particle partitioning equilibrium. The enhanced partitioning directly increases SOA yield, whereas the shorter timescales (which here would be ~1 s for an accommodation coefficient of 1, compared to a timescale of ~10 min for reaching gas-wall partitioning equilibrium) increase SOA yields by reducing the loss of gaseous reaction products to the chamber walls.42-45 Finally, we note that partitioning of gas phase products to either the particles or the walls, which is enhanced by high and low SOA mass concentrations, respectively, reduces their accessibility to OH radicals and thus the formation of multigeneration products. In this study no attempt was made to correct the measured SOA yields for any of these effects, but because of the similarity in the products of the reactions investigated it is likely that the observed trends in yields are not significantly affected. One should, however, be cautious about directly applying these (or other reported) SOA yields to the atmosphere.

22


Page 22 of 44

Page 23 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CONCLUSIONS The atmospheric fate of an organic compound is determined in large part by its molecular structure, which influences the rates and pathways by which it can react with various oxidants, and the products that are formed. In general, oxidation adds functional groups to the parent compound, thereby reducing its volatility, although concurrent cleavage of C–C bonds can lead to smaller, more volatile products. Whereas the less volatile products are more likely to condense to form SOA, the more volatile ones can undergo more extensive oxidation through continued gas phase reactions. The branching between these so-called functionalization and fragmentation pathways15,46 thus plays a key role in both SOA formation and VOC degradation. Because functional groups that are added during oxidation not only reduce volatility, but also activate reaction pathways that lead to C–C bond cleavage, the oxidative aging process can promote either the formation or destruction of SOA. In the study presented here the competing effects of a keto group on VOC reaction pathways and product volatility are clearly demonstrated through a systematic investigation of the chemical composition and yields of SOA formed from reactions of a series of ketone isomers and alkanes. Results show that SOA yields are strongly dependent on the structure of the isomer, because of the effect of the keto group on product vapor pressure as well as the branching between functionalization and fragmentation pathways. In particular, it is shown through a combination of measurements and modeling that the presence and position of the keto group on the carbon chain influences product formation through its effect on a number of elementary reaction processes, including H-atom abstraction, the branching of keto alkoxy radical

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

reactions between isomerization, decomposition, and reaction with O2, and acid catalyzed cyclization/dehydration reactions that occur in particles to form a variety of new products. The ability of the model to explain the trends observed in measured SOA yields reflects well on current knowledge of VOC reaction mechanisms and SOA formation, although future studies should attempt more quantitative comparisons of measured yields of SOA and individual products with predictions of models that also include processes such as gas-particle and gas-wall partitioning and heterogeneous/multiphase chemistry. Such studies will challenge experimentalists and modelers, but should accelerate the development of measurement and modeling capabilities well beyond what is currently possible.

ACKNOWLEDGMENTS This material is based on work supported by the National Science Foundation under Grants AGS-1219508 and AGS-1420007. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation (NSF).

SUPPORTING INFORMATION Table S1: Summary of experimental information used for calculating SOA yields Table S2: Estimated compound vapor pressures and the fraction of compound in particles

24


Page 24 of 44

Page 25 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


REFERENCES 1. Scientific Assessment of Ozone Depletion: World Meterolological Organization Global Ozone Research and Monitoring Project; Report No. 37; Geneva, Switzerland, 1994; February 1995. 2. Atkinson, R.; Arey, J. Atmospheric Degradation of Volatile Organic Compounds Chem. Rev. 2003, 103, 4605−4638. 3. Kroll, J. H.; Seinfeld, J. H. Chemistry of Secondary Organic Aerosol: Formation and Evolution of Low-Volatility Organics in the Atmosphere. Atmos. Environ. 2008, 42, 3593–3624. 4. Ziemann, P. J.; Atkinson, R. Kinetics, Products, and Mechanisms of Secondary Organic Aerosol Formation. Chem. Soc. Rev. 2012, 41, 6582−6605. 5. Zhang, Q.; Jimenez, J. L.; Canagaratna, M. R.; Allan, J. D.; Coe, H.; Ulbrich, I. M.; Alfarra, M. R.; Takami, A.; Middlebrook, A. M; Sun, Y. L.; et al. Ubiquity and Dominance of Oxygenated Species in Organic Aerosols in Anthropogenically-Influenced Northern Hemisphere Midlatitudes. Geophys. Res. Lett. 2007, 34, L13801. 6. Ravishankara, A. R. Heterogeneous and Multiphase Chemistry in the Troposphere. Science. 1997, 276, 1058−1065. 7. Pöschl , U. Atmospheric Aerosols: Composition, Transformation, Climate and Health Effects. Angew. Chem., Int. Ed. 2005, 44, 7520− 7540. 8. Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; et al. The Formation, Properties and Impact of Secondary Organic Aerosol: Current and Emerging Issues. Atmos. Chem. Phys. 2009, 9, 5155.

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

9. Lim, Y. B.; Ziemann, P. J. Effects of Molecular Structure on Aerosol Yields from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NOx. Environ. Sci. Technol. 2009, 43, 2328−2334. 10. Matsunaga, A.; Docherty, K. S.; Lim, Y. B.; Ziemann, P. J. Composition and Yields of Secondary Aerosol Formed from OH Radical-Initiated Reactions of Linear Alkenes in the Presence of NOx: Modeling and Measurements. Atmos. Environ. 2009, 43, 1349−1357. 11. Tkacik, D. S., Presto, A. A., Donahue, N. M., and Robinson, A. L.: Secondary Organic Aerosol Formation from Intermediate-Volatility Organic Compounds: Cyclic, Linear, and Branched Alkanes, Environ. Sci. Technol. 2012, 46, 8773–8781. 12. Yee, L. D., Craven, J. S., Loza, C. L., Schilling, K. A., Ng, N. L., Canagaratna, M. R., Ziemann, P. J., Flagan, R. C., and Seinfeld, J. H.: Effect of Chemical Structure on Secondary Organic Aerosol Formation from C12 Alkanes, Atmos. Chem. Phys. 2013, 13, 11121–11140. 13. Hunter, J. F.; Carrasquillo, A. J.; Daumit, K. E.; Kroll. J. H. Secondary Organic Aerosol Formation from Acyclic, Monocyclic, and Polycyclic Alkanes. Environ. Sci. Technol. 2014, 48, 10227-10234. 14. Chacon-Madrid, H. J.; Presto, A. A.; Donahue, N. M. Functionalization vs. Fragmentation: n-Aldehyde Oxidation Mechanisms and Secondary Organic Aerosol Formation. Phys. Chem. Chem. Phys. 2010, 12, 13975−13982. 15. Chacon-Madrid, H. J.; Donahue, N. M. Fragmentation vs. Functionalization: Chemical Aging and Organic Aerosol Formation. Atmos. Chem. Phys. 2011, 11, 10553−10563.

26


Page 26 of 44

Page 27 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


16. Atkinson, R.; Arey, J.; Aschmann, S. M. Atmospheric Chemistry of Alkanes: Review and Recent Developments. Atmos. Environ. 2008, 42, 5859−5871. 17. Ziemann, P. J. Effects of Molecular Structure on the Chemistry of Aerosol Formation from the OH-Radical-Initiated Oxidation of Alkanes and Alkenes. Int. Rev. Phys. Chem. 2011, 30, 161–195. 18. Taylor, W. D.; Allston, T. D.; Moscato, M. J.; Fazekas, G. B.; Kozlowski, R.; Takacs, G. A. Atmospheric Photodissociation Lifetimes for Nitromethane, Methyl Nitrite, and Methyl Nitrate. Int. J. Chem. Kinet. 1980, 12, 231–240. 19. Atkinson, R.; Carter, W. P. L.; Winer, A. M.; Pitts, J. N. An Experimental Protocol for the Determination of OH Radical Rate Constants with Organics using Methyl Nitrite Photolysis as an OH Radical Source. J. Air Pollut. Control Assoc. 1981, 31, 1090–1092. 20. de Gouw, J.; Warneke, C. Measurements of Volatile Organic Compounds in the Earth’s Atmosphere using Proton-Transfer-Reaction Mass Spectrometry. Mass Spectrom. Rev. 2007, 26, 223–257. 21. Tobias, H. J.; Kooiman, P. M.; Docherty, K. S.; Ziemann, P. J. Real-Time Chemical Analysis of Organic Aerosols Using a Thermal Desorption Particle Beam Mass Spectrometer. Aerosol Sci. Technol. 2000, 33, 170−190. 22. Docherty, K.; Ziemann, P. Effects of Stabilized Criegee Intermediate and OH Radical Scavengers on Aerosol Formation from Reactions of β-Pinene with O3. Aerosol Sci. Technol. 2003, 37, 877-891. 23. Aimanant, S.; Ziemann, P. J. Development of Spectrophotometric Methods for the Analysis of Functional Groups in Oxidized Organic Aerosol. Aerosol Sci. Technol. 2013, 47, 979−990.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

24. Odum, J. R.; Hoffmann, T.; Bowman, F.; Collins, D.; Flagan, R. C.; Seinfeld, J. H. Gas/Particle Partitioning and Secondary Organic Aerosol Yields. Environ. Sci. Technol. 1996, 30, 2580−2585. 25. Yeh, G. K.; Ziemann, P. J. Gas-Wall Partitioning of Oxygenated Organic Compounds: Measurements, Structure-Activity Relationships, and Correlation with Gas Chromatographic Retention Factor. Aerosol Sci. Technol. 2015, 49, 726−737. 26. Yeh, G. K.; Ziemann, P. J. Alkyl Nitrate Formation from the Reactions of C8−C14 nAlkanes with OH Radicals in the Presence of NOx. J. Phys. Chem. A 2014, 118, 8147– 8157. 27. La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B. Impact of Chamber Wall Loss of Gaseous Organic Compounds on Secondary Organic Aerosol Formation: Explicit Modeling of SOA Formation from Alkane and Alkene Oxidation. Atmos. Chem. Phys. 2016, 16, 1417–1431. 28. Orlando, J. J.; Tyndall, G. S. Laboratory Studies of Organic Peroxy Radical Chemistry: An Overview with Emphasis on Recent Issues of Atmospheric Significance. Chem. Soc. Rev. 2012, 41, 6294–6317. 29. Crounse, J. D.; Nielsen, L. B.; Jørgensen, S.; Kjaergaard, H. G.; Wennberg, P. O. Autoxidation of Organic Compounds in the Atmosphere. J. Phys. Chem. Lett. 2013, 4, 3513–3520. 30. Atkinson, R. Rate Constants for the Atmospheric Reactions of Alkoxy Radicals: An Updated Estimation Method. Atmos. Environ. 2007, 41, 8468−8485. 31. Vereecken, L.; Peeters, J. Decomposition of Substituted Alkoxy Radicals-Part I: A

28


Page 28 of 44

Page 29 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Generalized Structure-Activity Relationship for Reaction Barrier Heights. Phys. Chem. Chem. Phys. 2009, 11, 9062−9074. 32. Vereecken, L.; Peeters, J. A Structure-Activity Relationship for the Rate Coefficient of H-Migration in Substituted Alkoxy Radicals. Phys. Chem. Chem. Phys. 2010, 12, 12608−12620. 33. Harrison, A.; Kallury, R. K. M. R. Chemical Ionization Mass Spectra of Mononitroarenes. Org. Mass Spectrom. 1980, 15, 284–288. 34. Gong, H.; Matsunaga, A.; Ziemann, P. J. Products and Mechanism of Secondary Aerosol Formation from the Reactions of Linear Alkenes with NO3 Radicals. J. Phys. Chem. A 2005, 109, 4312− 4324. 35. Lim, Y. B.; Ziemann, P. J. Chemistry of Secondary Organic Aerosol Formation from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NOx . Aerosol Sci. Technol. 2009, 43, 604–619. 36. Aimanant, S.; Ziemann, P. J. Chemical Mechanisms of Aging of Aerosol Formed from the Reaction of n-Pentadecane with OH Radicals in the Presence of NOx. Aerosol Sci. Technol. 2013, 47, 979−990. 37. Kwok, E. S. C.; Atkinson, R. Estimation of Hydroxyl Radical Reaction Rate Constants for Gas Phase Organic Compounds using a Structure-Reactivity Relationship: An Update. Atmos. Environ. 1995, 29, 1685–1695. 38. Atkinson, R. A Structure-Activity Relationship for the Estimation of Rate Constants for the Gas-Phase Reactions of OH Radicals with Organic Compounds. Int. J. Chem. Kinet. 1987, 19, 799-828. 39. Stein, S. E. N. M. S. D. C. ‘Mass Spectra’. NIST Chem. WebBook, NIST Stand. Ref.

29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Database Number 69; Linstrom, P. J., Mallard, W. G., Eds.; Natl. Inst. Stand. Technol.: Gaithersburg, MD, 2011. 40. Hilal, S. H.; Karickhoff, S.W.; and Carreira, L. A. Prediction of the Vapor Pressure Boiling Point, Heat of Vaporization and Diffusion Coefficient of Organic Compounds, Qsar Comb. Sci., 2003, 22, 565–574. 41. Yeh, G. K.; Ziemann, P. J. Identification and Product Yields of 1,4-Hydroxynitrates in Particles Formed from the Reactions of C8−C16 n-Alkanes with OH Radicals in the Presence of NOx. J. Phys. Chem. A 2014, 118, 8797−8806. 42. Matsunaga, A.; Ziemann, P. J. Gas-Wall Partitioning of Organic Compounds in a Teflon Film Chamber and Potential Effects on Reaction Product and Aerosol Yield Measurements. Aerosol Sci. Technol. 2010, 44, 881–892. 43. Zhang, X.; Cappa, C. D.; Jathar, S. H.; McVay, R. C.; Ensberg, J. J.; Kleeman, M. J.; Seinfeld, J. H. Influence of Vapor Wall Loss in Laboratory Chambers on Yields of Secondary Organic Aerosol. Proc. Natl. Acad. Sci. U. S. A. 2014, 111, 5802−5807. 44. McVay, R. C.; Cappa, C. D.; Seinfeld, J. H. Vapor-Wall Deposition in Chambers: Theoretical Considerations. Environ. Sci. Technol. 2014, 48, 10251–10258. 45. Krechmer, J. E.; Pagonis, D.; Ziemann, P. J.; Jimenez, J. L. Quantification of GasWall Partitioning in Teflon Environmental Chambers Using Rapid Bursts of LowVolatility Oxidized Species Generated in Situ. Environ. Sci. Technol. 2016, 50, 5757– 5765. 46. Lambe, A. T.; Onasch, T. B.; Croasdale, D. R.; Wright, J. P.; Martin, A. T.; Franklin, J. P.; Massoli, P.; Kroll, J. H.; Canagaratna, M. R.; Brune, W. H.; et al. Transitions from Functionalization to Fragmentation Reactions of Laboratory Secondary Organic Aerosol

30


Page 30 of 44

Page 31 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(SOA) Generated from the OH Oxidation of Alkane Precursors. Environ. Sci. Technol. 2012, 46, 5430–5437.

31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 1. Mechanism of reaction of dodecanone with OH radicals in the presence of NOx to form first and second generation products. The original keto group and products formed when this group participates in cyclization reactions are highlighted in red, and αketo alkoxy decomposition products are highlighted in blue. Compound acronyms beginning with K contain the unreacted keto group, and R1, R2, and R3 are alkyl groups.

32


Page 32 of 44

Page 33 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 2. Reaction for derivatizing carbonyl groups in SOA products.

33



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 3. Isomerization reactions of keto alkoxy radicals with estimated rate constants.

34


Page 34 of 44

Page 35 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. HPLC-UV chromatograms measured for carbonyl derivatized SOA collected from 1 and 60 min reactions of 2-dodecanone with OH radicals in the presence of NOx, and CI-ITMS mass spectra of SOA fractions collected for regions A, B, and C in each chromatogram.

35



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 2. TDPBMS mass spectra of SOA formed from 60 min reactions of 2- through 6dodecanone isomers with OH radicals in the presence of NOx. Spectra are averages for the 60 min period when the lights were turned on. Contributions from DOS seed particles have been removed, the signal in each spectrum is normalized to m/z 197, and signal ≥ m/z 290 has been multiplied by 10.

36


Page 36 of 44

Page 37 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. TDPBMS time profiles of ions that are characteristic of major first (m/z 197), first + second (m/z 244), and second (m/z 258 and 305) generation SOA products formed from the 60 min reaction of 2-dodecanone with OH radicals in the presence of NOx. Lights were turned on at time zero.

37



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4. PTR-MS time profiles of characteristic ions of possible aldehyde products formed in the 60 min reaction of 5-dodecanone with OH radicals in the presence of NOx, and a time profile of heptanal calculated using a kinetics model. Lights were turned on at time zero.

38


Page 38 of 44

Page 39 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. (A) SOA yields and (B) time profiles of SOA mass concentrations measured for 60 min reactions of 2- through 6-dodecanone isomers with OH radicals in the presence of NOx.

39



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 6. Model predicted molar yields of major first generation products of 60 min reactions of 2- through 6-dodecanone isomers with OH radicals in the presence of NOx. Products include keto nitrates and products formed from keto alkoxy radicals by isomerization, decomposition, or reaction with O2. Values designated by filled symbols were calculated using a model that included only isomerization via 1,5-H atom shifts whereas the model used to calculate values designated by open symbols included both 1,5- and 1,6-H atom shifts.

40


Page 40 of 44

Page 41 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. Measured mass yields of SOA and model predicted mass yields of first generation isomerization products formed from 60 min reactions of 2- through 6dodecanone isomers with OH radicals in the presence of NOx. Values designated by filled symbols were calculated using a model that included only keto alkoxy radical isomerization via 1,5-H atom shifts whereas the model used to calculate values designated by open symbols included both 1,5- and 1,6-H atom shifts. For purposes of comparison the right-hand axis was adjusted so that for 2-dodecanone the symbols for SOA yield and yield of isomerization products coincide.

41



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 44

Table 1. Assignment of SOA products of 1 and 60 min reactions of 2-dodecanone with OH radicals in the presence of NOx, based on HPLC-UV and CI-ITMS analysis of carbonyl derivatized products. Product

1

First Generation K-HN [4] + CHA-N [6]

2

HPLC Region

Mp

1 Min

60 Min

A1

A60, B60

3

Md

261

441

Ion Formation 6 Pathway CI

B1

B60

214

394

MdH – 63 + MdH – (63 + 18) + Mp – 17 + Mp – (46 + 18)

377 317

MdH – 18 + MdH – (18 + 60) + Mp – 17 + Mp – 18

426 379 363 319 303

MdH + MdH – 47 + MdH – 63 + MdH – (47 + 60) + MdH – (63 + 60) + Mp – 62

440

MdH – 63

393 377 375

MdH – (63 + 47) + MdH – (63 + 63) + MdH – (63 + 47 + 18) + Mp – 17 + Mp – (46 + 18)

375

MdH – (198 + 63)

197 196 C1

C60

245

425

183 Second Generation K-N-HN [12] + N-CHA-N [14] + CHA-N-N [16]

B60

322

502

N-CHA-N [14] + CHA-N-N [16] K-N-HN [12]

305 258

K-N-HC [11] + K-N-CHA [13] + K-CHA-N [19] K-N-CHA [13] + K-CHA-N [19] K-N-HC [11]

B60

CEs-N [17]

B60

275

635

455

322

393

322

UD 260

K-CE-HN [18]

275

455

C60

306

486

244

42


+

+

+

+

MdH – 63 + Mp – 62 +

MpH – 63 + MpH – 62 +

393 375

MdH – 63 + MdH – (63 + 18) + MpH – 62

424 377 361 359

MdH – 63 + MdH – (63 + 47) + MdH – (63 + 63) + MdH – (63 + 47 + 18) + Mp – 62

213 K-N-N [10]

+

Mp – 17 + Mp – (46 + 18)

213 CE-HN-N [15]

+

+

258 211 275

+

379 361 244 197

K-CHA [7] K-HC [5] K-N [1]

m/z EI

CHA-N [6] K-HN [4] K-HC [5] + K-CHA [7]

5

4

+

Page 43 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Products are designated according to the acronyms and numbers used in Scheme 1. Regions A, B, and C are shown in chromatograms Figure 1 with subscripts for 1 and 60 min reactions. 3 Mp is the molecular weight of underivatized product. 4 Md is the molecular weight of derivatized product, and UD refers to underivatized products. 5 m/z values correspond to characteristic peaks observed in TDPBMS EI and ITMS CI mass spectra. 6 Masses of neutral fragments correspond to the followiing molecules or radicals: 17 (OH), 18 (H2O), 46 (NO2), 47 (HNO2), 62 (NO3), 63 (HNO3), 198 (dinitrophenyl hydrazine). Loss of 60 is due to reduction of the two NO2 (46) groups on the aromatic ring to NH2 (16) groups in the ion source. 2

43



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC Graphic

44


Page 44 of 44

Effect of the Keto Group on Yields and ... - ACS Publications

Recommend Documents