Kinetics and products of the gas-phase reactions of (CH3)4Si, (CH3)3SiCH2OH, (CH3)3SiOSi(CH3)3 and (CD3)3SiOSi(CD3)3 with Cl atoms and OH radicals

Atkinson, Roger; Tuazon, Ernesto C.; Kwok, Eric S. C.; Arey, Janet; Aschmann, Sara M.; Bridier, Isabelle

doi:10.1039/ft9959103033

Cited by 40 publications

(84 citation statements)

References 16 publications

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“…Scheme 2 shows possible formation pathways for several of these products. Formation of the OH substitution product is similar to the reaction sequence proposed by Atkinson [25]. Note that formation of a multiply substituted product does not necessarily require multiple OH abstractions, since an auto-oxidation process based on internal hydrogen rearrangements [26] could lead to several substitutions.…”

Section: Resultsmentioning

confidence: 67%

Molecular Characterization of Secondary Aerosol from Oxidation of Cyclic Methylsiloxanes

Johnston

2016

J. Am. Soc. Mass Spectrom.

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Cyclic volatile methylsiloxanes (cVMS) have been identified as important gas-phase atmospheric contaminants, but knowledge of the molecular composition of secondary aerosol derived from cVMS oxidation is incomplete. Here, the chemical composition of secondary aerosol produced from the OH-initiated oxidation of decamethylcyclopentasiloxane (D5, C10H30O5Si5) is characterized by high performance mass spectrometry. ESI-MS reveals a large number of monomeric (300 < m/z < 470) and dimeric (700 < m/z < 870) oxidation products. With the aid of high resolution and MS/MS, it is shown that oxidation leads mainly to the substitution of a CH3 group by OH or CH2OH, and that a single molecule can undergo many CH3 group substitutions. Dimers also exhibit OH and CH2OH substitutions and can be linked by O, CH2 and CH2CH2 groups. GC-MS confirms the ESI-MS results. Oxidation of D4 (C8H24O4Si4) exhibits similar substitutions and oligomerizations to D5, though the degree of oxidation is greater under the same conditions and there is direct evidence for the formation of peroxy groups (CH2OOH) in addition to OH and CH2OH.

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Section: Resultsmentioning

confidence: 67%

Molecular Characterization of Secondary Aerosol from Oxidation of Cyclic Methylsiloxanes

Johnston

2016

J. Am. Soc. Mass Spectrom.

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“…The observed products of the OH ϩ siloxane reactions have been used to propose the atmospheric mechanisms of MM, MDM, and MD 2 M. For MM the major product observed is pentamethyldisiloxanol (MDOH, HO -Si(CH 3 ) 2 -O -Si(CH 3 ) 3 ), but experiments done by Atkinson et al [6] conclude that MDOH is a "second generation" product of water reacting with a siloxane ester product. Even though it may not be a direct product, due to the water in the atmosphere MDOH is most likely an important component in determining the atmospheric assessment of MM.…”

Section: Resultsmentioning

confidence: 97%

“…The plots in Figure 3 show a distinct gap in the rise of the siloxanol relative to MDM loss. This gap may be an indication that these siloxanols are indeed secondary products resulting from the ester, OCHO -Si -R 1 R 2 [6], reacting with water. No siloxane ester was observed using the experimental system described.…”

Section: Octamethyltrisiloxane (Mdm)mentioning

confidence: 92%

“…MDOH has been observed as an MM/OH reaction product by Carter et al [2]. Atkinson et al [6] have recently reported that MDOH is most likely a "secondary" product with the primary ester ((CH 3 ) 3 Si -O -(CH 3 ) 2 Si -OCHO) reacting with water to form MDOH. Because of the humidity of the air surrounding our experimental chambers, this could explain the observation of the silanol formation.…”

Section: Hexamethyldisiloxane (Mm)mentioning

confidence: 98%

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The hydroxyl radical reaction rate constants and atmospheric reaction products of three siloxanes

Markgraf

Wells²

1997

Int. J. Chem. Kinet.

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The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH 3 molecule Ϫ1 s Ϫ1 , respectively. Investigation of the OH ϩ siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry.

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“…Diethylamine is a large-volume chemical used as a solvent, a corrosion inhibitor, and as an intermediate in the manufacture of other chemicals [3] and is also emitted from animal husbandry operations [4]. 2-Methoxy-6-(trifluoromethyl)pyridine has been considered as a crop protection agent, and 1,1,3,3,3-pentamethyldisiloxan-1-ol is formed during the atmospheric degradation of hexamethyldisiloxane [5], a volatile methylsiloxane which is used in health care products and as an intermediate in the manufacture of polydimethylsiloxanes [6]. The reactions of gaseous nitric acid with MTFMP and of O 3 with (CH 3 ) 3 SiOSi(CH 3 ) 2 OH were also investigated.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the reactions of OH radicals with 2‐methoxy‐6‐(trifluoromethyl)pyridine, diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol at 298 ± 2 K

Tuazon

Martín

Aschmann

et al. 2011

Int J of Chemical Kinetics

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Rate constants for the reactions of 2-methoxy-6-(trifluoromethyl)pyridine, diethylamine, and 1,1,3,3,3-pentamethyldisiloxan-1-ol with OH radicals have been measured at 298 ± 2 K using a relative rate method. The measured rate constants (cm 3 molecule −1 s −1 ) are (1.54 ± 0.21) × 10 −12 for 2-methoxy-6-(trifluoromethyl)pyridine, (1.19 ± 0.25) × 10 −10 for diethylamine, and (1.76 ± 0.38) × 10 −12 for 1,1,3,3,3-pentamethyldisiloxan-1-ol, where the indicated errors are the estimated overall uncertainties including those in the rate constants for the reference compounds. No reaction of 2-methoxy-6-(trifluoromethyl)pyridine with gaseous nitric acid was observed, and an upper limit to the rate constant for the reaction of 1,1,3,3,3-pentamethyldisiloxan-1-ol with O 3 of <7 × 10 −20 cm 3 molecule −1 s −1 was determined. Using a 12-h average daytime OH radical concentration of 2 × 10 6 molecule cm −3 , the lifetimes of the volatile organic compounds studied here with respect to reaction with OH radicals are 7.5 days for 2-methoxy-6-(trifluoromethyl)pyridine, 1.2 h for diethylamine, and 6.6 days for 1,1,3,3,3-pentamethyldisiloxan-1-ol. Likely reaction mechanisms are discussed. C 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 631

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Kinetics and products of the gas-phase reactions of (CH3)4Si, (CH3)3SiCH2OH, (CH3)3SiOSi(CH3)3 and (CD3)3SiOSi(CD3)3 with Cl atoms and OH radicals

Abstract: Kinetics and Products of theGas-phase Reactions of (CH,),Si, (CH , ) ,S i CH .OH, (CH , ) ,S i 0 s i (CH , ) , and (C D , ) ,S i 0 s i (C D , ) , with

Cited by 40 publications

References 16 publications

Molecular Characterization of Secondary Aerosol from Oxidation of Cyclic Methylsiloxanes

Molecular Characterization of Secondary Aerosol from Oxidation of Cyclic Methylsiloxanes

The hydroxyl radical reaction rate constants and atmospheric reaction products of three siloxanes

Kinetics of the reactions of OH radicals with 2‐methoxy‐6‐(trifluoromethyl)pyridine, diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol at 298 ± 2 K

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