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Direct measurements of unimolecular and bimolecular reaction kinetics of the Criegee intermediate (CH3)2COO

Direct measurements of unimolecular and bimolecular reaction kinetics of the Criegee intermediate (CH3)2COO
Direct measurements of unimolecular and bimolecular reaction kinetics of the Criegee intermediate (CH3)2COO
The Criegee intermediate acetone oxide, (CH3)2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O2 and characterized by synchrotron photoionization mass spectrometry and by cavity ring-down ultraviolet absorption spectroscopy. The rate coefficient of the reaction of the Criegee intermediate with SO2 was measured using photoionization mass spectrometry and pseudo-first-order methods to be (7.3 ± 0.5) × 10–11 cm3 s–1 at 298 K and 4 Torr and (1.5 ± 0.5) × 10–10 cm3 s–1 at 298 K and 10 Torr (He buffer). These values are similar to directly measured rate coefficients of anti-CH3CHOO with SO2, and in good agreement with recent UV absorption measurements. The measurement of this reaction at 293 K and slightly higher pressures (between 10 and 100 Torr) in N2 from cavity ring-down decay of the ultraviolet absorption of (CH3)2COO yielded even larger rate coefficients, in the range (1.84 ± 0.12) × 10–10 to (2.29 ± 0.08) × 10–10 cm3 s–1. Photoionization mass spectrometry measurements with deuterated acetone oxide at 4 Torr show an inverse deuterium kinetic isotope effect, kH/kD = (0.53 ± 0.06), for reactions with SO2, which may be consistent with recent suggestions that the formation of an association complex affects the rate coefficient. The reaction of (CD3)2COO with NO2 has a rate coefficient at 298 K and 4 Torr of (2.1 ± 0.5) × 10–12 cm3 s–1 (measured with photoionization mass spectrometry), again similar to rate for the reaction of anti-CH3CHOO with NO2. Cavity ring-down measurements of the acetone oxide removal without added reagents display a combination of first- and second-order decay kinetics, which can be deconvolved to derive values for both the self-reaction of (CH3)2COO and its unimolecular thermal decay. The inferred unimolecular decay rate coefficient at 293 K, (305 ± 70) s–1, is similar to determinations from ozonolysis. The present measurements confirm the large rate coefficient for reaction of (CH3)2COO with SO2 and the small rate coefficient for its reaction with water. Product measurements of the reactions of (CH3)2COO with NO2 and with SO2 suggest that these reactions may facilitate isomerization to 2-hydroperoxypropene, possibly by subsequent reactions of association products.
1089-5639
4-15
Chhantal-Pun, Rabi
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Welz, Oliver
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Savee, John D.
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Eskola, Arkke J.
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Lee, Edmond P.F.
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Blacker, Lucy
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Hill, Henry R.
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Ashcroft, Matilda
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Khan, M. Anwar H.
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Lloyd-Jones, Guy C.
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Evans, Louise
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Rotavera, Brandon
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Huang, Haifeng
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Osborn, David L.
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Mok, Daniel K.W.
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Dyke, John M.
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Shallcross, Dudley E.
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Percival, Carl J.
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Orr-Ewing, Andrew J.
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Taatjes, Craig A.
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Chhantal-Pun, Rabi
39e57185-32e2-4fab-ba67-9cdcbb499555
Welz, Oliver
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Savee, John D.
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Eskola, Arkke J.
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Lee, Edmond P.F.
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Blacker, Lucy
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Hill, Henry R.
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Ashcroft, Matilda
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Khan, M. Anwar H.
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Lloyd-Jones, Guy C.
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Evans, Louise
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Rotavera, Brandon
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Huang, Haifeng
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Osborn, David L.
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Mok, Daniel K.W.
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Dyke, John M.
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Shallcross, Dudley E.
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Percival, Carl J.
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Orr-Ewing, Andrew J.
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Taatjes, Craig A.
381610dc-019b-4dd3-bbf0-3cccb63b13dd

Chhantal-Pun, Rabi, Welz, Oliver, Savee, John D., Eskola, Arkke J., Lee, Edmond P.F., Blacker, Lucy, Hill, Henry R., Ashcroft, Matilda, Khan, M. Anwar H., Lloyd-Jones, Guy C., Evans, Louise, Rotavera, Brandon, Huang, Haifeng, Osborn, David L., Mok, Daniel K.W., Dyke, John M., Shallcross, Dudley E., Percival, Carl J., Orr-Ewing, Andrew J. and Taatjes, Craig A. (2017) Direct measurements of unimolecular and bimolecular reaction kinetics of the Criegee intermediate (CH3)2COO. Journal of Physical Chemistry A, 121 (1), 4-15. (doi:10.1021/acs.jpca.6b07810).

Record type: Article

Abstract

The Criegee intermediate acetone oxide, (CH3)2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O2 and characterized by synchrotron photoionization mass spectrometry and by cavity ring-down ultraviolet absorption spectroscopy. The rate coefficient of the reaction of the Criegee intermediate with SO2 was measured using photoionization mass spectrometry and pseudo-first-order methods to be (7.3 ± 0.5) × 10–11 cm3 s–1 at 298 K and 4 Torr and (1.5 ± 0.5) × 10–10 cm3 s–1 at 298 K and 10 Torr (He buffer). These values are similar to directly measured rate coefficients of anti-CH3CHOO with SO2, and in good agreement with recent UV absorption measurements. The measurement of this reaction at 293 K and slightly higher pressures (between 10 and 100 Torr) in N2 from cavity ring-down decay of the ultraviolet absorption of (CH3)2COO yielded even larger rate coefficients, in the range (1.84 ± 0.12) × 10–10 to (2.29 ± 0.08) × 10–10 cm3 s–1. Photoionization mass spectrometry measurements with deuterated acetone oxide at 4 Torr show an inverse deuterium kinetic isotope effect, kH/kD = (0.53 ± 0.06), for reactions with SO2, which may be consistent with recent suggestions that the formation of an association complex affects the rate coefficient. The reaction of (CD3)2COO with NO2 has a rate coefficient at 298 K and 4 Torr of (2.1 ± 0.5) × 10–12 cm3 s–1 (measured with photoionization mass spectrometry), again similar to rate for the reaction of anti-CH3CHOO with NO2. Cavity ring-down measurements of the acetone oxide removal without added reagents display a combination of first- and second-order decay kinetics, which can be deconvolved to derive values for both the self-reaction of (CH3)2COO and its unimolecular thermal decay. The inferred unimolecular decay rate coefficient at 293 K, (305 ± 70) s–1, is similar to determinations from ozonolysis. The present measurements confirm the large rate coefficient for reaction of (CH3)2COO with SO2 and the small rate coefficient for its reaction with water. Product measurements of the reactions of (CH3)2COO with NO2 and with SO2 suggest that these reactions may facilitate isomerization to 2-hydroperoxypropene, possibly by subsequent reactions of association products.

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Accepted/In Press date: 13 October 2016
e-pub ahead of print date: 18 October 2016
Published date: 12 January 2017
Organisations: Chemistry

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Local EPrints ID: 404640
URI: https://eprints.soton.ac.uk/id/eprint/404640
ISSN: 1089-5639
PURE UUID: 8580b2d3-88a3-4166-85e2-cef2b106b36b
ORCID for John M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

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Date deposited: 13 Jan 2017 16:25
Last modified: 06 Jun 2018 13:17

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Contributors

Author: Rabi Chhantal-Pun
Author: Oliver Welz
Author: John D. Savee
Author: Arkke J. Eskola
Author: Edmond P.F. Lee
Author: Lucy Blacker
Author: Henry R. Hill
Author: Matilda Ashcroft
Author: M. Anwar H. Khan
Author: Guy C. Lloyd-Jones
Author: Louise Evans
Author: Brandon Rotavera
Author: Haifeng Huang
Author: David L. Osborn
Author: Daniel K.W. Mok
Author: John M. Dyke ORCID iD
Author: Dudley E. Shallcross
Author: Carl J. Percival
Author: Andrew J. Orr-Ewing
Author: Craig A. Taatjes

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