Theoretical Study on the Reactions of (CF3)2CFOCH3 + OH/Cl and Reaction of (CF3)2CFOCHO with Cl Atom

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.

Computational exploration of regioselectivity and atmospheric lifetime in NO3-initiated reactions of CH3OCH3 and CH3OCH2CH3

The NO₃-initiated reactions of CH₃OCH₃ and CH₃OCH₂CH₃ have been investigated by the BHandHLYP method in conjunction with the 6-311G(d,p) basis set. Thermodynamic and kinetic data are further refined using the comparatively accurate CCSD(T) method. According to the values of reaction enthalpies (ΔH_r,298^θ) and reaction Gibbs free energies (ΔG_r,298^θ) from CH₃OCH₂CH₃ with NO₃ system, we find that H-abstraction pathway from the α-CH₂ group is more exothermic. It is further confirmed by the calculated CH bond dissociation energy of CH₃OCH₂CH₃ molecule. All the rate constants, computed through means of canonical variational transition state with small-curvature tunneling correction, are fitted to the three-parameter expressions k₁=1.54×10^-23T^3.34exp(-1035.53/T) and k₂=3.55×10^-26T^4.31exp(-281.24/T)cm³molecule^-1s^-1 and branching ratios are computed over the temperature range 200-600K. The branching ratios are also discussed. The atmospheric lifetimes of CH₃OCH₃ and CH₃OCH₂CH₃ determined by the NO₃ radical are about 270 and 29days, respectively.

Theoretical insight into OH- and Cl-initiated oxidation of CF3OCH(CF3)2 and CF3OCF2CF2H &fate of CF3OC(X•)(CF3)2 and CF3OCF2CF2X• radicals (X=O, O2)

In this study, the mechanistic and kinetic analysis for reactions of CF₃OCH(CF₃)₂ and CF₃OCF₂CF₂H with OH radicals and Cl atoms have been performed at the CCSD(T)//B3LYP/6-311++G(d,p) level. Kinetic isotope effects for reactions CF₃OCH(CF₃)₂/CF₃OCD(CF₃)₂ and CF₃OCF₂CF₂H/CF₃OCF₂CF₂D with OH and Cl were estimated so as to provide the theoretical estimation for future laboratory investigation. All rate constants, computed by canonical variational transition state theory (CVT) with the small-curvature tunneling correction (SCT), are in reasonable agreement with the limited experimental data. Standard enthalpies of formation for the species were also calculated. Atmospheric lifetime and global warming potentials (GWPs) of the reaction species were estimated, the large lifetimes and GWPs show that the environmental impact of them cannot be ignored. The organic nitrates can be produced by the further oxidation of CF₃OC(•)(CF₃)₂ and CF₃OCF₂CF₂• in the presence of O₂ and NO. The subsequent decomposition pathways of CF₃OC(O•)(CF₃)₂ and CF₃OCF₂CF₂O• radicals were studied in detail. The derived Arrhenius expressions for the rate coefficients over 230–350 K are: k_T(1)= 5.00 × 10⁻²⁴T^3.57 exp(−849.73/T), k_T(2)= 1.79 × 10⁻²⁴T^4.84 exp(−4262.65/T), k_T(3)= 1.94 × 10⁻²⁴T^4.18 exp(−884.26/T), and k_T(4) = 9.44 × 10⁻²⁸T^5.25 exp(−913.45/T) cm³ molecule⁻¹ s⁻¹.

Variational transition state theory: theoretical framework and recent developments

This article reviews the fundamentals of variational transition state theory (VTST), its recent theoretical development, and some modern applications.

Atmospheric chemistry of ethers, esters, and alcohols on the lifetimes, temperature dependence, and kinetic isotope effect: an example of CF3CX2CX2CX2OX with OX reactions (X = H, D)

Mechanisms and kinetics of the reaction of CF₃CX₂CX₂CX₂OX with OX (X= H, D) radical are investigated on a sound theoretical basis.

Atmospheric chemistry of CF3(CX2)2CH2OH: rate coefficients and temperature dependence of reactions with chlorine atoms and the subsequent pathways of alkyl and alkoxy radicals (X = H, F)

The atmospheric and kinetic properties of CF₃(CX₂)₂CH₂OH (X = H, F) with chlorine atoms were studied by density functional and canonical variational transition state theories in conjunction with the small-curvature tunneling correction.

Atmospheric chemistry of alkyl iodides: theoretical studies on the mechanisms and kinetics of CH3I/C2H5I + NO3 reactions

Mechanisms and kinetics of the reactions of the NO₃ radical with CH₃I and C₂H₅I have been investigated from a sound theoretical basis.