Kinetics study of the gas-phase reactions of CHF2CF2OCHF2 and CF3CHFCF2OCH2CF2CF3 with OH radicals at 253–328K

Understanding the insight into the mechanisms and dynamics of the OH-initiated oxidation of CHF2CF2OCHF2 and the subsequent reactions in the presence of NO and O2

The mechanism and dynamics of CHF₂CF₂OCHF₂ initiated by OH radical evaluated through the density functional theory and variflex code. The solvation pattern of PCM was utilized to analyze the influence of water on the CHF₂CF₂OCHF₂ + OH reaction. The most feasible reaction channel is resulting in the product CF₂CF₂OCHF₂ with H₂O by hydrogen abstraction. The computed rate coefficient is consistent with the experimental data. The results turned out that aqueous water act as a disincentive to the title reaction. In the atmosphere, the computation results testified that OH, H₂O, NH₃ and HCOOH could not accelerate the degradation of the CHF₂CF₂OCHF₂ through OH-initiated in view of the Gibbs free barriers. The research of the follow-up oxidation procedure of the products CHF₂CF₂OCF₂ and CF₂CF₂OCHF₂ with O₂/NO reactions indicated that CF₂O and CHF₂ were the most feasible products. The atmospheric lifetimes of CHF₂CF₂OCHF₂ were in the scope of 71.10-4.74 years in altitude of 0-12 km and at 200-300 K. This research supplies discernment into the conversion of CHF₂CF₂OCHF₂ in a complex environment.

Kinetics of CF3CH2OCH3 (HFE-263fb2), CHF2CF2CH2OCH3 (HFE-374pcf), and CF3CF2CH2OCH3 (HFE-365mcf3) with OH radicals, IR absorption cross sections, and global warming potentials

Hydrofluoroethers (HFEs), like CF3CH2OCH3 (HFE-263fb2), CHF2CF2CH2OCH3 (HFE-374pcf), and CF3CF2CH2OCH3 (HFE-365mcf3), have been proposed in the last decades as the third-generation replacements of perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) because of their...

CHF2CF2OCHF2: conformational analysis and direct dynamics study of its reaction with Cl atoms and atmospheric fate

Conformers of CHF₂CF₂OCHF₂ are identified, and the kinetics of its reaction with Cl atoms and final atmospheric degradation products are studied to assess atmospheric impact.

A theoretical investigation on the conformation and the interaction of CHF₂OCF₂CHF₂ (desflurane II) with one water molecule

The conformation and the interaction of CHF₂OCF₂CHF₂ (desflurane II) with one water molecule is investigated theoretically using the ab initio MP2/aug-cc-pvdz and DFT-based M062X/6-311++G(d,p) methods. The calculations include the optimized geometries, the harmonic frequencies of relevant vibrational modes along with a natural bond orbital (NBO) analysis including the NBO charges, the hybridization of the C atom and the intra- and intermolecular hyperconjugation energies. In the two most stable conformers, the CH bond of the F2HCO- group occupies the gauche position. The hyperconjugation energies are about the same for both conformers and the conformational preference depends on the interaction between the non-bonded F and H atoms. The deprotonation enthalpies of the CH bonds are about the same for both conformers, the proton affinity of the less stable conformer being 3 kcal mol−1 higher. Both conformers of desflurane II interact with water forming cyclic complexes characterized by CH…O and OH…F hydrogen bonds. The binding energies are moderate, ranging from −2.4 to −3.2 kcal mol−1 at the MP2 level. The origin of the blue shifts of the ν(CH) vibrations is analyzed. In three of the complexes, the water molecule acts as an electron donor. Interestingly, in these cases a charge transfer is also directed to the non bonded OH group of the water molecule. This effect seems to be a property of polyfluorinated ethers.

Rate Constants for the Reactions of Hydroxyl Radical with Several Fluoroethers by the Relative Rate Method

Relative rate experiments were used to measure ratios of chemical kinetics rate constants as a function of temperature for the reactions of OH with eight fluoroethers, including CF3OCF2CHF2, CF3OCF2CHFCF3, CHF2CF2OCHF2, CF3CHFCF2OCH2CF3, (CF3)2CHOCHF2, CF2HCF2OCH2CF3, CHF2CF2OCHFCF3, and CF3CH2OCH2CF3. The temperature ranges were about 270-400 K. Each compound was measured against at least two references. Results are compared with previous data where available. An approach using model compounds for the approximate estimation of rate constants for the fluoroethers is discussed. Observed temperature dependences for fluoroethers from the present work and some literature work are shown to be accurately predictable, based on a previously determined correlation of k298K with the pre-exponential factor, A, in the Arrhenius equation k = Ae(-E/RT).