UV absorption probing of the conformer-dependent reactivity of a Criegee intermediate CH<sub>3</sub>CHOO

Sheps, Leonid; Scully, Ashley M.; Au, Kendrew

doi:10.1039/c4cp04408h

Cited by 160 publications

(318 citation statements)

References 33 publications

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“…Thus, their steady-state concentrations would be too low to have a significant impact in SO 2 oxidation under typical atmospheric conditions, as shown in modeling results (15,16). On the other hand, previous experimental data for syn-CH 3 CHOO (3,24) are not precise enough to determine its main decay pathways in the atmosphere.…”

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confidence: 76%

“…Experimental results (Table 1) show that CH 2 OO and anti-CH 3 CHOO react with water vapor very quickly (3,(22)(23)(24). Thus, their steady-state concentrations would be too low to have a significant impact in SO 2 oxidation under typical atmospheric conditions, as shown in modeling results (15,16).…”

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confidence: 95%

“…Whereas studies (17)(18)(19)(20) (24) have reported that the antiform of methyl-substituted CI (CH 3 CHOO, R 1 = H in Fig. 1) reacts with water vapor much faster than the syn-form (R 1 = CH 3 in Fig.…”

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confidence: 99%

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Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Huang

Chao

Lin

2015

Proc. Natl. Acad. Sci. U.S.A.

228

276

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Criegee intermediates are thought to play a role in atmospheric chemistry, in particular, the oxidation of SO 2 , which produces SO 3 and subsequently H 2 SO 4 , an important constituent of aerosols and acid rain. However, the impact of such oxidation reactions is affected by the reactions of Criegee intermediates with water vapor, because of high water concentrations in the troposphere. In this work, the kinetics of the reactions of dimethyl substituted Criegee intermediate (CH 3 ) 2 COO with water vapor and with SO 2 were directly measured via UV absorption of (CH 3 ) 2 COO under near-atmospheric conditions. The results indicate that (i) the water reaction with (CH 3 ) 2 COO is not fast enough (k H2O < 1.5 × 10 −16 cm 3 s −1 ) to consume atmospheric (CH 3 ) 2 COO significantly and (ii) (CH 3 ) 2 COO reacts with SO 2 at a near-gas-kinetic-limit rate (k SO2 = 1.3 × 10 −10 cm 3 s −1 ). These observations imply a significant fraction of atmospheric (CH 3 ) 2 COO may survive under humid conditions and react with SO 2 , very different from the case of the simplest Criegee intermediate CH 2 OO, in which the reaction with water dimer predominates in the CH 2 OO decay under typical tropospheric conditions. In addition, a significant pressure dependence was observed for the reaction of (CH 3 ) 2 COO with SO 2 , suggesting the use of low pressure rate may underestimate the impact of this reaction. This work demonstrates that the reactivity of a Criegee intermediate toward water vapor strongly depends on its structure, which will influence the main decay pathways and steady-state concentrations for various Criegee intermediates in the atmosphere. Ozonolysis of unsaturated hydrocarbons produces highly reactive Criegee intermediates (CIs) (1), which may (i) decompose to radical species like OH radicals or (ii) react with a number of atmospheric species, for example, with SO 2 to form SO 3 and with NO 2 to form NO 3 (2, 3). The SO 2 oxidation by CIs has gained special attentions because the SO 3 product would be converted into H 2 SO 4 , an important constituent of aerosols and acid rain (4-8). For example, Mauldin et al. (4) (2) demonstrated an efficient method to prepare a CI in a laboratory by the reaction of iodoalkyl radical with O 2 (for example, CH 2 I + O 2 → CH 2 OO + I). This method can produce a CI of high enough concentration that allows direct detection. With photoionization mass spectrometry (PIMS) detection, Welz et al. (2) measured the rate coefficients of the simplest CI (CH 2 OO) reactions with SO 2 and NO 2 . Notably, these new rate coefficients, confirmed by a few later investigations (9-11), are orders of magnitude larger than those previously used (12, 13) in atmospheric models (e.g., MCM v3.3, available at mcm.leeds. ac.uk/MCM/browse.htt?species=CH2OO), suggesting a greater role of CIs in atmospheric chemistry. This result also indicates previous ozonolysis analyses may be affected by complicated and partly unknown side reactions and may contain errors in some of the reported rate coefficients.Typical...

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confidence: 76%

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confidence: 95%

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Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Huang

Chao

Lin

2015

Proc. Natl. Acad. Sci. U.S.A.

228

276

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“…7 Because SCIs are readily consumed, they have very low steady-state concentrations, 8 and consequently their fate in the atmosphere is not well established. 1 To provide a relatively clean source of SCIs for spectroscopic, 9-21 dynamics, [22][23][24][25][26] and kinetics studies, [27][28][29][30][31][32][33][34][35][36] SCIs are almost exclusively made from photo-oxidation reactions of (R 1 R 2 )CI 2 in the presence of O 2 (where R 1 /R 2 represent hydrogen atoms or alkyl radicals To provide accurate rate constants and to aid experimental measurements, unimolecular decomposition rate constants of syn-CH 3 CHOO under atmospheric conditions are computed here from first principles using Miller's semiclassical transition state theory (SCTST) [41][42][43][44][45] in combination with a two-dimensional master equation (2DME) approach. 7,46 This chemical kinetics analysis is performed using a high accuracy potential energy surface that is constructed with a modification of the HEAT protocol.…”

Section: Introductionmentioning

confidence: 99%

Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study

Nguyen

McCaslin

McCarthy

et al. 2016

The Journal of Chemical Physics

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The thermal decomposition of syn-ethanal-oxide (syn-CH 3 CHOO) through vinyl hydrogen peroxide (VHP) leading to hydroxyl radical is characterized using a modification of the HEAT thermochemical protocol. The isomerization step of syn-CH 3 CHOO to VHP via a 1,4 H-shift, which involves a moderate barrier of 72 kJ/mol, is found to be rate determining. A two-dimensional master equation approach, in combination with semi-classical transition state theory, is employed to calculate the time evolution of various species as well as to obtain phenomenological rate coefficients. This work suggests that, under boundary layer conditions in the atmosphere, thermal unimolecular decomposition is the most important sink of syn-CH 3 CHOO. Thus, the title reaction should be included into atmospheric modeling. The fate of cold VHP, the intermediate stabilized by collisions with a third body, has also been investigated. Published by AIP Publishing. [http://dx

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“…[25,26] (CH3)2COO is likely to survive longer in humid environments than CH2OO and play a greater role in H2SO4 production, as it is comparatively unreactive to H2O and (H2O)2, but more reactive to SO2. [24] Alternatively, reactions with trace species may be locally important if they are sufficiently fast.…”

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Reactions between Criegee Intermediates and the Inorganic Acids HCl and HNO₃: Kinetics and Atmospheric Implications

2016

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Criegee intermediates (CIs) are a class of reactive radicals that are thought to play a key role in atmospheric chemistry through reactions with trace species that can lead to aerosol particle formation. Recent work has suggested that water vapor is likely to be the dominant sink for some CIs, although reactions with trace species that are sufficiently rapid can be locally competitive. Herein, we use broadband transient absorption spectroscopy to measure rate constants for the reactions of the simplest CI, CH2OO, with two inorganic acids, HCl and HNO3, both of which are present in polluted urban atmospheres. Both reactions are fast; at 295 K, the reactions of CH2OO with HCl and HNO3 have rate constants of 4.6×10−11 cm3 s−1 and 5.4×10−10 cm3 s−1, respectively. Complementary quantum‐chemical calculations show that these reactions form substituted hydroperoxides with no energy barrier. The results suggest that reactions of CIs with HNO3 in particular are likely to be competitive with those with water vapor in polluted urban areas under conditions of modest relative humidity.

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UV absorption probing of the conformer-dependent reactivity of a Criegee intermediate CH₃CHOO

Cited by 160 publications

References 33 publications

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study

Reactions between Criegee Intermediates and the Inorganic Acids HCl and HNO₃: Kinetics and Atmospheric Implications

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UV absorption probing of the conformer-dependent reactivity of a Criegee intermediate CH3CHOO

Cited by 160 publications

References 33 publications

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO 2

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO 2

Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study

Reactions between Criegee Intermediates and the Inorganic Acids HCl and HNO3: Kinetics and Atmospheric Implications

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UV absorption probing of the conformer-dependent reactivity of a Criegee intermediate CH₃CHOO

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Reactions between Criegee Intermediates and the Inorganic Acids HCl and HNO₃: Kinetics and Atmospheric Implications