OH- INITIATED OXIDATION OF A SERIES OF FLUORINATED DIKETONES: ROLE OF KETO-ENOL TAUTOMERIZATION ON REACTIVITY

PEDRO LUGO; VIANNI STRACCIA; CYNTHIA B. RIVELA; MARIA BELEN BLANCO

Simposio; 26th International Symposium on Gas Kinetics and Related Phenomena; 2022

Introduction: Diketones are characterized by the presence of two carbonyl groups (C=O) separated by a carbon atom and present a keto-enol equilibrium. If the hydrogen bond acceptors are close, it changes the equilibrium to its enol form1. Due to their properties, diketones have been used in the chemical industry2, for example: CF3C(O)CH2C(O)CH3 (1,1,1-Trifluoro-2,4-pentanedione) is used as a chelating ligand3 and for the preparation of trifluoromethyl pyrimidines by reaction with guanidines. However, to our knowledge, the effects of these compounds on the chemistry of the atmosphere have not yet been evaluated. Objectives: To determine the rate coefficients of the following reactions at 298 ± 3 K: CF3C(O)CH2C(O)CH3 (TFP) + OH Products, k1CF3C(O)CH2C(O)CH2CH3 (TFH) + OH Products, k2CF3C(O)CH2C(O)CH(CH3)2 (TFMH) + OH Products, k3 Materials and methods: Kinetic experiments were carried out in two atmospheric simulation chambers, one located at the University of Wuppertal-Germany coupled to in situ Fourier Transform Infrared Spectroscopy (FTIR) and the other chamber located at the National University of Córdoba (LUQCA) coupled with Gas Chromatography with Flame Detector (GC-FID) at (990 ± 10) mbar of air and a temperature of (298 ± 3) K.Results: The following rate coefficients (in cm3 molecule−1s−1) have been determined with FTIR analysis: k1(TFP+OH) = (1.30 ± 0.22) ×10-11, k2(TFH+OH) = (2.25 ± 0.45) ×10-11 and k3(TFMH+OH) = (3.19 ± 0.38) ×10-11. On the other hand, the rate coefficients obtained by GC-FID (in cm3molecule−1s−1) were the following: k1(TFP+OH) = (1.27 ± 0.30) ×10-11, k2(TFH+OH) = (2.07 ± 0.48) ×10-11 and k3(TFMH+OH) = (3.47 ± 0.84) ×10-11.Conclusions: This work represents the first kinetic study for the three reactions studied under atmospheric conditions. The rate coefficients show an increase of the rate coefficients of the reactions studied with the number of CH3 substituents. In addition, reactivity trends were developed and the tropospheric lifetimes of these fluorinated diketones were estimated to assess their atmospheric impact.