Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie; MacLeod, Matthew

doi:10.1002/kin.20919

Cited by 24 publications

(43 citation statements)

References 41 publications

(71 reference statements)

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“…The measured mean values of •OH reaction constants were compared with the literature values (Table 1 and Supplemental Data, Figure S1). For the cyclic VMS of D3, D4, and D5, the measured values from the present study were close to those measured by Atkinson [6] and those predicted by AOPWIN [13], whereas they were apparently smaller than those of Safron et al [20] and Xiao et al [21]. For D6, the measured values from the present study were statistically similar to those of Safron et al [21] but apparently greater than those of the AOPWIN [13] prediction.…”

Section: The Measured •Oh Reaction Constants For Vms and Comparison Wsupporting

confidence: 84%

“…For the cyclic VMS of D3, D4, and D5, the measured values from the present study were close to those measured by Atkinson [6] and those predicted by AOPWIN [13], whereas they were apparently smaller than those of Safron et al [20] and Xiao et al [21]. For D6, the measured values from the present study were statistically similar to those of Safron et al [21] but apparently greater than those of the AOPWIN [13] prediction. For L2, the measured values from the present study were similar to those measured by Atkinson [6] and Sommerlade et al [22], whereas they were apparently greater than those measured by Markgraf and Wells [23] or predicted by AOPWIN [13].…”

Section: The Measured •Oh Reaction Constants For Vms and Comparison Wsupporting

confidence: 84%

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Quantitative structure‐reactivity relationships of hydroxyl radical rate constants for linear and cyclic volatile methylsiloxanes

Kim

2017

Enviro Toxic and Chemistry

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An accurate understanding of the fate of volatile methylsiloxanes (VMS) in air is crucial for determining their persistence and concentrations in the environment. Although oxidation by atmospheric hydroxyl radicals (•OH) is considered as a major degradation mechanism for airborne VMS, the existing bimolecular rate constants with •OH measured and modeled for any given VMS compound varied greatly, depending on the approaches used to generate the data. The objectives of the present study were to measure •OH reaction rate constants for 4 cyclic and 4 linear VMS based on a relative rate method using a newly designed atmospheric chamber and to establish structure-reactivity relationships for the kinetics. In the past, the reaction rate constants for VMS were generally recognized to increase with the number of the methyl groups per molecule, the only differential factor in the existing models. However, the new measurements indicated that molecular structure should also be considered in the prediction of the reaction rates. Better empirical models were developed by simple and multiple linear regressions of the measured values from the present study and the literature. A high correlation existed for the reaction rates with the number of the methyl group attached at 2 distinct siloxane structures (i.e., linear and cyclic VMS). Even better correlations were obtained with one or 2 molecular descriptors that are directly related to the size of VMS, which, in turn, not only depend on the number of methyl groups, but the linear/cyclic structures as well for permethylsiloxanes. Environ Toxicol Chem 2017;36:3240-3245. © 2017 SETAC.

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Section: The Measured •Oh Reaction Constants For Vms and Comparison Wsupporting

confidence: 84%

Section: The Measured •Oh Reaction Constants For Vms and Comparison Wsupporting

confidence: 84%

Quantitative structure‐reactivity relationships of hydroxyl radical rate constants for linear and cyclic volatile methylsiloxanes

Kim

2017

Enviro Toxic and Chemistry

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“…Two conditions guide us in using MS, the boiling point and thermal stability of the silanes and their species in the reaction medium. If they are thermally stable and volatile, one should use GC/MS, which gives good separation and a rich MS spectrum [36,93]. However, GC/MS is not a common technique due to the use of water as a reactant.…”

Section: Identification Techniquesmentioning

confidence: 99%

Kinetics of Alkoxysilanes and Organoalkoxysilanes Polymerization: A Review

2019

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Scientists from various different fields use organo-trialkoxysilanes and tetraalkoxysilanes in a number of applications. The silica-based materials are sometimes synthesized without a good understanding of the underlying reaction kinetics. This literature review attempts to be a comprehensive and more technical article in which the kinetics of alkoxysilanes polymerization are discussed. The kinetics of polymerization are controlled by primary factors, such as catalysts, water/silane ratio, pH, and organo-functional groups, while secondary factors, such as temperature, solvent, ionic strength, leaving group, and silane concentration, also have an influence on the reaction rates. Experiments to find correlations between these factors and reaction rates are restricted to certain conditions and most of them disregard the properties of the solvent. In this review, polymerization kinetics are discussed in the first two sections, with the first section covering early stage reactions when the reaction medium is homogenous, and the second section covering when phase separation occurs and the reaction medium becomes heterogeneous. Nuclear magnetic resonance (NMR) spectroscopy and other techniques are discussed in the third section. The last section summarizes the study of reaction mechanisms by using ab initio and Density Functional Theory (DFT) methods alone, and in combination with molecular dynamics (MD) or Monte Carlo (MC) methods.

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“…For chamber experiments that employed H 2 O 2 , the OH concentration was calculated by fitting the gas-phase D5 concentration to a first-order exponential, fixing the initial point of the fit as the initial D5 concentration (fits had R 2 > 0.75), and using the value for the reaction rate of OH with D5, k = 2.1 ± 0.1 × 10 −12 cm 3 molec −1 s −1 , which was measured using the relative rate method at 297 ± 3 K (Alton and Browne, 2020). Note that other experimental evaluations of the reaction rate of OH with D5 that use the relative rates method vary by less than a factor of 2 (the reasons for this difference are not known), which would not affect the order of magnitude of the OH concentration estimate (Kim and Xu, 2017;Safron et al, 2015;Xiao et al, 2015).…”

mentioning

confidence: 99%

Secondary Organic Aerosol Formation from the Oxidation of Decamethylcyclopentasiloxane at Atmospherically Relevant OH Concentrations

Charan

Huang

Buenconsejo

et al. 2021

Preprint

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Abstract. Decamethylcyclopentasiloxane (D5, C10H30O5Si5) is measured at ppt levels outdoors and ppb levels indoors. Primarily used in personal care products, its outdoor concentration is correlated to population density. Since understanding the aerosol formation potential of volatile chemical products is critical to understanding particulate matter in urban areas, the secondary organic aerosol yield of D5 was studied under a range of OH concentrations, OH exposures, NOx concentrations, and temperatures. The secondary organic aerosol (SOA) yield from the oxidation of D5 is extremely dependent on the OH concentration, and differing measurements of the SOA yield from the literature are resolved in this study. Here, we compare experimental results from environmental chambers and flow tube reactors. Generally, there are high SOA yields (> 68 %) at OH mixing ratios of 5 × 109 molec cm−3. At atmospherically relevant OH concentrations, the SOA yield is largely < 5 % and usually ~1 %. This is significantly lower than SOA yields used in emission and particulate matter inventories and demonstrates the necessity of OH concentrations similar to the ambient environment when extrapolating SOA yield data to the outdoor atmosphere.

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Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Cited by 24 publications

References 41 publications

Quantitative structure‐reactivity relationships of hydroxyl radical rate constants for linear and cyclic volatile methylsiloxanes

Quantitative structure‐reactivity relationships of hydroxyl radical rate constants for linear and cyclic volatile methylsiloxanes

Kinetics of Alkoxysilanes and Organoalkoxysilanes Polymerization: A Review

Secondary Organic Aerosol Formation from the Oxidation of Decamethylcyclopentasiloxane at Atmospherically Relevant OH Concentrations

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