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Temperature-dependence of the rates of reaction of trifluoroacetic acid with criegee intermediates

Chhantyal-Pun, Rabi, McGillen, Max R., Beames, Joseph, Khan, M. Anwar H., Percival, Carl J., Shallcross, Dudley E. and Orr-Ewing, Andrew J. 2017. Temperature-dependence of the rates of reaction of trifluoroacetic acid with criegee intermediates. Angewandte Chemie - International Edition 56 (31) , pp. 9044-9047. 10.1002/anie.201703700

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Abstract

The rate coefficients for gas-phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240–340 K. The rate coefficients k(CH2OO + CF3COOH)=(3.4±0.3)×10−10 cm3 s−1 and k((CH3)2COO + CF3COOH)=(6.1±0.2)×10−10 cm3 s−1 at 294 K exceed estimates for collision-limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre-reactive complex. Fits to a model incorporating this complex formation give k [cm3 s−1]=(3.8±2.6)×10−18 T2 exp((1620±180)/T) + 2.5×10−10 and k [cm3 s−1]=(4.9±4.1)×10−18 T2 exp((1620±230)/T) + 5.2×10−10 for the CH2OO + CF3COOH and (CH3)2COO + CF3COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Uncontrolled Keywords: atmospheric chemistry; Criegee biradical; kinetics; reactive intermediates; trifluoroacetic acid; zwitterions
Publisher: Wiley-Blackwell
ISSN: 1433-7851
Funders: Natural Environment Research Council and Marie Sk�odowska-Curie Individual Fellowships
Date of First Compliant Deposit: 30 June 2017
Date of Acceptance: 14 June 2017
Last Modified: 20 Dec 2017 13:31
URI: http://orca.cf.ac.uk/id/eprint/101960

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