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Title: Direct measurements of unimolecular and bimolecular reaction kinetics of the Criegee intermediate (CH 3) 2COO

Here, the Criegee intermediate acetone oxide, (CH 3) 2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O 2 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 SO 2 was measured using photoionization mass spectrometry and pseudo-first-order methods to be (7.3 ± 0.5) × 10 –11 cm 3 s –1 at 298 K and 4 Torr and (1.5 ± 0.5) × 10 –10 cm 3 s –1 at 298 K and 10 Torr (He buffer). These values are similar to directly measured rate coefficients of anti-CH 3CHOO with SO 2, 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 N 2 from cavity ring-down decay of the ultraviolet absorption of (CH 3) 2COO yielded even larger rate coefficients, in the range (1.84 ± 0.12) × 10 –10 to (2.29 ± 0.08) × 10 –10 cm 3 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), formore » reactions with SO 2, 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 cm 3 s –1 (measured with photoionization mass spectrometry), again similar to rate for the reaction of anti-CH 3CHOO with NO 2. 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 (CH 3) 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 (CH 3) 2COO with SO 2 and the small rate coefficient for its reaction with water. Product measurements of the reactions of (CH 3) 2COO with NO 2 and with SO 2 suggest that these reactions may facilitate isomerization to 2-hydroperoxypropene, possibly by subsequent reactions of association products.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [1] ;  [1] ;  [1] ;  [1] ;  [5] ;  [1] ;  [2] ;  [2] ;  [2] ;  [6] ;  [7] ;  [1] ;  [6] ;  [1] ;  [2]
  1. The Univ. of Bristol (United Kingdom)
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  3. Sandia National Lab. (SNL-CA), Livermore, CA (United States); Univ. of Helsinki, Helsinki (Finland)
  4. Univ. of Southampton, Southampton (United Kingdom); The Hong Kong Polytechnic Univ., Hung Hom (Hong Kong)
  5. The Univ. of Bristol (United Kingdom); Univ. of Edinburgh (United Kingdom)
  6. The Univ. of Manchester, Manchester (United Kingdom)
  7. The Hong Kong Polytechnic Univ., Hung Hom (Hong Kong)
Publication Date:
Report Number(s):
SAND-2017-0648J
Journal ID: ISSN 1089-5639; 650604
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 121; Journal Issue: 1; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1340693