Temperature dependence of the rates of reaction of trifluoroacetic acid with Criegee intermediates

Rabi Chhantyal Pun, Max McGillen, JM Beames, Anwar Khan, Carl J Percival, Dudley Shallcross, Andrew Orr-Ewing

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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) x 10-10 cm3 s-1 and k((CH3)2COO + CF3COOH) = (6.1 +/- 0.2) x 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) x 10-18 T2 exp((1620 +/- 180)/T) + 2.5 x 10-10 and k [cm3 s-1] = (4.9 +/- 4.1) x 10-18 T2 exp((1620 +/- 230)/T) + 5.2 x 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.
Original languageEnglish
Pages (from-to)9172-9175
Number of pages4
JournalAngewandte Chemie - International Edition
Volume129
Issue number31
Early online date29 Jun 2017
DOIs
Publication statusPublished - 24 Jul 2017

Keywords

  • KINETICS
  • Reactive Intermediates
  • Atmospheric Chemistry;
  • Criegee Biradical
  • Zwitterion
  • TFA

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