Ab initio configuration interaction study of the structure and magnetic properties of radicals and radical ions derived from group 13–15 trihydrides

The structures, characteristic vibrations and magnetic properties of two isoelectronic series of radicals and radical ions derived from group 13–15 trihydrides have been investigated by post-Hartree-Fock theoretical techniques. Møller-Plesset perturbation theory based on an unrestricted Hartree-Fock determinant has been employed to determine the structures and vibrational frequencies in the 9-electron series, BH⁻₃, CH₃, and NH⁺₃. These species are found to be planar. Spin density distributions and ionization energetics have been estimated using a variational configuration interaction procedure. A positive electron affinity for BH₃ has not been demonstrated. The effect of out-of-plane vibrations on the hyperfine coupling constants is determined at a similar level of theory. In the 17-electron series AlH⁻₃, SiH₃, and PH⁺₃, pyramidal structures are found by using and extended split-valence basis at the SCF level. The computed harmonic force field suggests that a tentative assignment of a matrix isolated infrared spectrum to SiH₃ is incorrect. This conclusion is reinforced by calculation of the vibrational intensity patterns. Hyperfine interaction tensors computed at the optimized geometries from the UHF wavefunction with a more complete polarized double-zeta basis set are in accord with experiment. Vibrational effects are estimated by averaging the UHF spin density over an energy surface determined by second-order perturbation theory. Corrections due to vibrations are smaller than in the carbon series and single-point configuration interaction calculations confirm the reliability of the UHF spin densities.     

Ab initio study of reactions of hydroxyl radicals with chloro‐ and fluoro‐substituted methanes

Ab initio calculations at the unrestricted Hartree–Fock (UHF) level have been performed to investigate the hydrogen abstraction reactions of ^? OH radicals with methane and nine halogen‐substituted methanes (F, Cl). Geometry optimization and vibrational frequency calculations have been performed on all reactants, adducts, products, and transition states at the UHF/6‐31G* level. Single‐point energy calculations at the MP2/6‐31++G* level using the UHF/6‐31G* optimized geometries have also been carried out on all species. Pre‐ and postreaction adducts have been detected on the UHF/6‐31G* potential energy surfaces of the studied reactions. Energy barriers, ΔE^?, reaction energies, ΔE_r, reaction enthalpies, ΔH_r, and activation energies, E_a, have been determined for all reactions and corrected for zero‐point energy effects. Both E_a and ΔH_r come into reasonable agreement with the experiment when correlation energy is taken into account and when more polarized and diffuse basis sets are used. The E_a values, estimated at the PMP2/6‐31++G* level, are found to be in good agreement with the experimental ones and correctly reproduce the experimentally observed trends in fluorine and chlorine substitution effects. A linear correlation between E_a and ΔH_r is obtained, suggesting the presence of an Evans–Polanyi type of relationship. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 426–440, 2001     

Theoretical study of the CCl3 radical

Employing the STO-3G and 4–31 G basis sets within the unrestricted Hartree-Fock method the equilibrium structure of the CCl₃ radical was calculated. The calculations predict the radical to be non-planar with both basis sets used. Using the UHF optimized geometries the SWX_α calculations have been performed to calculate energy levels, ionization potentials and electron affinities of CCl₃.     

Photoelectrochemical pK Scale for weak CH-acids

The method of laser photoelectron emission from metals in electrolyte solutions has been used to measure the rate constants w₃ for the electrochemical reduction of simple organic radicals R to carbanions R^–. The following empirical rule has been established: the changes in the standard redox potential E° for R^–/R in series of organic radicals are equal to the changes in the potential corresponding to individual values of w₃. On the basis of this rule and the value of E° for CH₃ ^–/CH₃ E° values were obtained for C₂H₅, n-C₃H₇, n-C₄H₉, CH₂OH, CH₃CHOH, (CH₃)₂COH, CH₂Cl, CHF₂, CHFCl, CHCl₂, CF₂Cl, CFCl₂, CF₃, CCl₃, C₆H₅, C₆Cl₅, and a scale of pK for the CH acids conjugate to R^–. Consideration is given to the nature of the changes in E° and p^K on passing from aqueous solutions to solutions in water-dioxane mixtures and in acetonitrile.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1508–1514, July, 1990.     

Uniform quality gaussian basis sets for molecular calculations,I. C1 hydrocarbons

The optimality of MO basis sets of Gaussian functions, when constructed from AO basis sets optimized for the neutral atom or for atom ions, is investigated. A formal charge parameter Q is defined and used to adjust the AO basis sets to the molecular environment, by virtue of a simple quadratic expression. Calculations on a series of C₁ hydrocarbons (CH₂, CH₃, CH₃⁺, CH₃^?, CH₄) using 3G basis sets indicate considerable variations in the optimum Q value with the molecular species. The proposed method offers a simple alternative technique to a full molecular basis set optimization.     

Theoretical study on the chemical fate of adducts formed through free radical addition reactions to carotenoids

It is well known that free radicals are responsible for oxidative stress and cause numerous health disorders. As a result, the study of molecules that can scavenge free radicals is significant. One of the most important classes of free radical scavengers are carotenoids (CAR). In this work, the effectiveness of the CAR in terms of the radical adduct formation (RAF) reaction is studied using density functional theory calculations (in polar and non-polar environments). The reactions between four CAR [β-carotene (BC), zeaxanthin (ZEA), canthaxanthin (CANTA) and astaxanthin (ASTA)] with eight different radicals (^?OH, ^?OOH, ^?CH₃, ^?O–CH₃, ^?OO–CH₃, ^?SH, ^?O–CH₂–CH=CH₂, and ^?OO–CH₂–CH=CH₂), as well as substantial further reactions involved in the radical chain propagation, are analyzed. According to our results, the RAF reactions are controlled to a larger extent by the nature of the free radical than by the particular CAR they are reacting with. Thermochemistry calculations predict that each CAR molecule is able to scavenge at least two free radicals, which would lead to the termination of the radical chain process. Epoxy and diepoxy CAR species can be formed, being epoxy molecules as good free radical scavengers as their parent CAR. ASTA and CANTA are predicted to be less reactive, when reacting through RAF mechanism, than BC and ZEA.     

The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressures

The Cl‐atom‐initiated oxidation of two esters, ethyl formate [HC(O)OCH₂CH₃] and ethyl acetate [CH₃C(O)OCH₂CH₃], has been studied at pressures close to 1 atm as a function of temperature (249–325 K) and O₂ partial pressure (50–700 Torr), using an environmental chamber technique. In both cases, Cl‐atom attack at the CH₂ group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O^?)CH₃ [R = H, CH₃]. The atmospheric fate of these radicals involves competition between reaction with O₂ to produce an anhydride compound, RC(O)OC(O)CH₃, and the so‐called α‐ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH₃C(O). For both species studied, the α‐ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH₃C(O)OCH(O^?)CH₃ and HC(O)OCH(O^?)CH₃, respectively, leading to increased occurrence of the O₂ reaction at reduced temperature. The data are combined with those obtained from similar studies of other simple esters to provide a correlation between the rate of occurrence of the α‐ester rearrangement and the structure of the reacting radical. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 397–413, 2010     

The evaluation of molecular electron affinities

The performance of a variety of levels of theory in evaluating molecular electron affinities (EAs) has been systematically examined. Calculations have been carried out for six different basis sets and for nine theoretical procedures including unrestricted (UHF) and restricted (RHF) Hartree-Fock theory, Møler-Plesset perturbation theory (UMP2, UMP3, UMP4), configuration interaction (UCISD, RCISD, RCISD(Q)) and equations-of-motion (EOM) approaches. Electron affinities were evaluated for CH₃, NH₂, OH, F, C₂H, CN, BO, N₃, OCN, and NO₂. Very poor results are generally obtained unless diffuse functions are included in the basis set and electron correlation is incorporated. Even with the largest basis set used in the present study (6-311 + + G(2d, 2p)), there are still residual errors greater than 0.2 eV (UMP4) or 0.6 eV (CISD) in the absolute EAs. However, better results are obtained under certain circumstances for relative EAs. The results appear to be significantly affected by spin contamination in the UHF wave-functions. For those systems for which spin contamination is small, best absolute values of the EAs generally come from the EOM and UMP2 calculations, whereas the most constant errors (thereby allowing systematic correction) are found at the UMP4, CISD, and RCISD(Q) levels. For the systems for which spin contamination is larger, best results are obtained with the CI-based procedures (CISD and RCISD(Q)). The errors in calculated EAs for the molecules with differing electronic characteristics can vary quite widely. Caution must therefore be exercised before applying schemes which rely on a constancy of errors to estimate electron affinities. The UMP procedures appear particularly suspect in this regard if spin contamination is significant. The RCISD(Q) approach is recommended under such circumstances.     

Ab initio chemical kinetics for reactions of H atoms with SiHx (x = 1–3) radicals and related unimolecular decomposition processes

Hydrogen atoms and SiH_x (x = 1–3) radicals coexist during the chemical vapor deposition (CVD) of hydrogenated amorphous silicon (a‐Si:H) thin films for Si‐solar cell fabrication, a technology necessitated recently by the need for energy and material conservation. The kinetics and mechanisms for H‐atom reactions with SiH_x radicals and the thermal decomposition of their intermediates have been investigated by using a high high‐level ab initio molecular‐orbital CCSD (Coupled Cluster with Single and Double)(T)/CBS (complete basis set extrapolation) method. These reactions occurring primarily by association producing excited intermediates, ¹SiH₂, ³SiH₂, SiH₃, and SiH₄, with no intrinsic barriers were computed to have 75.6, 55.0, 68.5, and 90.2 kcal/mol association energies for x = 1–3, respectively, based on the computed heats of formation of these radicals. The excited intermediates can further fragment by H₂ elimination with 62.5, 44.3, 47.5, and 56.7 kcal/mol barriers giving ¹Si, ³Si, SiH, and ¹SiH₂ from the above respective intermediates. The predicted heats of reaction and enthalpies of formation of the radicals at 0 K, including the latter evaluated by the isodesmic reactions, SiH_x + CH₄ = SiH₄ + CH_x, are in good agreement with available experimental data within reported errors. Furthermore, the rate constants for the forward and unimolecular reactions have been predicted with tunneling corrections using transition state theory (for direct abstraction) and variational Rice–Ramsperger–Kassel–Marcus theory (for association/decomposition) by solving the master equation covering the P,T‐conditions commonly employed used in industrial CVD processes. The predicted results compare well experimental and/or computational data available in the literature. © 2013 Wiley Periodicals, Inc.     

Ab initio calculations on the barrier height for the hydrogen addition to ethylene and formaldehyde. The importance of spin projection

Heats of reaction and barrier heights have been computed for H + CH₂CH₂ → C₂H₅, H + CH₂O → CH₃O, and H + CH₂O → CH₂OH using unrestricted Hartree-Fock and Møller–Plesset perturbation theory up to fourth order (with and without spin annihilation), using single-reference configuration interaction, and using multiconfiguration self-consistent field methods with 3-21G, 6-31G(d), 6-31G(d,p), and 6-311G(d,p) basis sets. The barrier height in all three reactions appears to be relatively insensitive to the basis sets, but the heats of reaction are affected by p-type polarization functions on hydrogen. Computation of the harmonic vibrational frequencies and infrared intensities with two sets of polarization functions on heavy atoms [6-31G(2d)] improves the agreement with experiment. The experimental barrier height for H + C₂H₄ (2.04 ± 0.08 kcal/mol) is overestimated by 7?9 kcal/mol at the MP2, MP3, and MP4 levels. MCSCF and CISD calculations lower the barrier height by approximately 4 kcal/mol relative to the MP4 calculations but are still almost 4 kcal/mol too high compared to experiment. Annihilation of the largest spin contaminant lowers the MP4SDTQ computed barrier height by 8?9 kcal/mol. For the hydrogen addition to formaldehyde, the same trends are observed. The overestimation of the barrier height with Møller-Plesset perdicted barrier heights for H + C₂H₄ → C₂H₅, H + CH₂O → CH₃O, and H + CH₂O → CH₂OH at the MP4SDTQ /6-31G(d) after spin annihilation are respectively 1.8, 4.6, and 10.5 kcal/mol.     

Kinetics of reactions between methoxycarbonyl,methyl, and methoxy radicals formed in flash photolysis of dimethyl oxalate in gas phase

Flash photolysis of dimethyl oxalate produced the radicals CH₃, CH₃O, and COOCH₃. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40-torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO₂, CH₄, C₂H₄, C₂H₆, CH₂O, CH₃OH, CH₃OCH₃, HCOOCH₃, CH₃COOCH₃, CH₃OCOOCH₃, CH₃C₆H₁₁, and CH₃OC₆H₁₁. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals, k₁ = 2.7 × 10¹⁰ dm³ mol^?1 s^?1, measured with the same equipment. The rate coefficients for reactions (5)–(8) are:      

Reactions of CH3O2 radicals on solid surface

The reaction probability of CH₃O₂ radicals with NO₂, CH₄, C₃H₆, and CH₃CHO on the solid surface of KCl in flow at low pressure and temperature range of 297–353 K has been studied. The chosen conditions allowed excluding homogeneous interaction of radicals. The heterogeneous radical decay of peracetic acid served as a source of CH₃O₂ radicals. On the basis of ESR measurements of CH₃O₂ radicals with the above‐mentioned compounds, a heterogeneous reaction mechanism has been identified. The reactivity of NO₂ was greatest for the compounds studied. The effective activation energy was evaluated to be 10.4 ± 0.8 kJ/mol for the reaction of RO₂ radicals with NO₂ and ?21.3 ± 2.8 kJ/mol for methane. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 591–595, 2004     

Structures,Vibrational Spectra,and Relative Energetics of CH3COIO3 Isomers

The structures, vibrational spectra, relative energetics, and enthalpies of formation of CH₃COIO₃ isomers have been investigated with B3LYP, B3P86 and B3PW91 methods in conjugation with the 6‐31+G(d), 6‐311+G(d,p) and 6‐311++G(3df,3pd) basis sets. The CH₃COOIO₂ structure was found to be the most stable form among the isomers with an estimated enthalpy of formation of ?314.6 kJ·mol^?1. The enthalpies of formation for CH₃COOOOI, CH₃COOOIO and CH₃COIO₃ are ?180.7, ?184.9 and ?50.6 kJ·mol^?1, respectively. The implication of the formation of CH₃COIO₃ isomers from the atmospheric cross‐reactions of the acetylperoxy (CH₃COO₂) and iodine monoxide (IO) radicals was examined and the possible dissociation products of the most likely CH₃COIO₃ isomers were determined.     

Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane

The reaction mechanisms for oxidation of CH₃CCl₂ and CCl₃CH₂ radicals, formed in the atmospheric degradation of CH₃CCl₃ have been elucidated. The primary oxidation products from these radicals are CH₃CClO and CCl₃CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH₃CCl₃ have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving ??(OH + CH₃CCl₃) = (5.4 ± 3) 10^?12 exp(?3570 ± 890/RT) cm³ molecule^?1 s^?1. A value of this rate constant of 1.3 × 10^?14 cm³ molecule^?1 s^?1 at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH₃ CCl₃ reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants at 298 K are: ??(OH + CH₃CCl₃) = (1.09 ± 0.35) × 10^?14, ??(OH + CH₃CClO) = (0.91 ± 0.32) × 10^?14, ??(OH + CCl₃CHO) = (178 ± 31) × 10^?14, ??(OH + CCl₂O) < 0.1 × 10^?14; all in units of cm³ molecule^?1 s^?1. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.     

A spectrokinetic study of CH2I and CH2IO2 radicals

The UV absorption spectrum and kinetics of CH₂I and CH₂IO₂ radicals have been studied in the gasphase at 295 K using a pulse radiolysis UV absorption spectroscopic technique. UV absorption spectra of CH₂I and CH₂IO₂ radicals were quantified in the range 220–400 nm. The spectrum of CH₂I has absorption maxima at 280 nm and 337.5 nm. The absorption cross-section for the CH₂I radicals at 337.5 nm was (4.1 ± 0.9) × 10^?18 cm² molecule^?1. The UV spectrum of CH₂IO₂ radicals is broad. The absorption cross-section at 370 nm was (2.1 ± 0.5) × 10^?18 cm² molecule^?1. The rate constant for the self reaction of CH₂I radicals, k = 4 × 10^?11 cm³ molecule^?1 s^?1 at 1000 mbar total pressure of SF₆, was derived by kinetic modelling of experimental absorbance transients. The observed self-reaction rate constant for CH₂IO₂ radicals was estimated also by modelling to k = 9 × 10^?11 cm³ molecule^?1 s^?1. As part of this work a rate constant of (2.0 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1 was measured for the reaction of F atoms with CH₃I. The branching ratios of this reaction for abstraction of an I atom and a H atom were determined to (64 ± 6)% and (36 ± 6)%, respectively. © 1994 John Wiley & Sons, Inc.     

FT‐IR kinetic and product study of the Br‐initiated oxidation of dimethyl sulfide

An FT‐IR kinetic and product study of the Br‐atom‐initiated oxidation of dimethyl sulfide (DMS) has been performed in a large‐volume reaction chamber at 298 K and 1000‐mbar total pressure as a function of the bath gas composition (N₂ + O₂). In the kinetic investigations using the relative kinetic method, considerable scatter was observed between individual determinations of the rate coefficient, suggesting the possibility of interference from secondary chemistry in the reaction system involving dimethyl sulfoxide (DMSO) formation. Despite the experimental difficulties, an overall bimolecular rate coefficient for the reaction of Br atoms with DMS under atmospheric conditions at 298 K of ≤1 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ can be deduced. The major sulfur products observed included SO₂, CH₃SBr, and DMSO. The kinetic observations in combination with the product studies under the conditions employed are consistent with rapid addition of Br atoms to DMS forming an adduct that mainly re‐forms reactants but can also decompose unimolecularly to form CH₃SBr and CH₃ radicals. The observed formation of DMSO is attributed to reactions of BrO radicals with DMS rather than reaction of the Br–DMS adduct with O₂ as has been previously speculated and is thought to be responsible for the variability of the measured rate coefficient. The reaction CH₃O₂ + Br → BrO + CH₃O is postulated as the source of BrO radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 883–893, 1999     

Thermochemical properties from G3MP2B3 calculations,Set‐2: Free radicals with special consideration of CH2CH?C•CH2, cyclo−•C5H5, •CH2OOH,HO?•CO,and HC(O)O•

After a set of 32 free radicals was presented (Int J Chem Kin 34, 550–560, 2002), an additional 60 free radicals (Set‐2) were studied and characterized by energy minimum structures, harmonic vibrational wave numbers ω_e, moments of inertia I_A, I_B, and I_C, heat capacities C^o_p(T), standard entropies S^o(T), thermal energy contents H^o(T) ? H^o(0), and standard enthalpies of formation Δ_fH^o(T) at the G3MP2B3 level of theory. Thermodynamic functions at T = 298.15 K are presented and compared with recent experimental values where these are available. The mean absolute deviation between calculated and experimental Δ_fH^o(298.15) values by the previous set of 32 radicals is 3.91 kJ mol^?1. For the sake of comparison, only 49 species out of the 60 radicals of Set‐2 are characterized by experimental enthalpies of formation, and the corresponding mean absolute deviation between calculated and experimental Δ_fH^o(298.15) values is 8.96 kJ mol^?1. This situation is cause for demand of more and also more accurate experimental values. In addition to the above properties, parent molecules of a large set of the respective radicals are calculated to obtain bond dissociation energies D^o(298.15). Radical stabilization owing to resonance is discussed using the complete sets of total atomic spin densities ρ as a support. In particular, a short review about recent developments of the first‐order Jahn–Teller radical c‐C₅H₅^? is presented. In addition, radicals with negative bond energies are described, such as ^?CH₂OOH where the reaction path to CH₂O + HO^? has been calculated, as well as radicals which have two different parent molecules, for example C?N? O^?. For the reaction HO^? + CO → H^? + CO₂, two reaction paths are characterized by a total of 14 stationary points where the intermediate radicals HO? ^?CO and HC(O)O^? are involved. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 661–686, 2004     

Ab initio MO calculations of hyperfine coupling constants. A basis set study for 19F, 35Cl, 19F,and 35Cl

Hyperfine coupling constants (HFCC ) of the ¹⁹F and ³⁵Cl atoms and the ¹⁹F and ³⁵Cl radical anions have been calculated by the unrestricted Hartree–Fock (UHF ) method using polarization and diffuse functions with contracted double-zeta as well as uncontracted basis sets. The A_dip values are fairly insensitive to changes in the basis set and show good accordance with experimental and other theoretical studies. The isotropic HFCCS a_N of ¹⁹F, ¹⁹F, and ³⁵Cl show strong dependence on d functions and the state of contraction of the s, p set. Spin-projected UHF wave functions lead to better agreement with experiment.     

Computational NMR coupling constants: Shifting and scaling factors for evaluating 1JCH

Optimized shifting and/or scaling factors for calculating one‐bond carbon–hydrogen spin–spin coupling constants have been determined for 35 combinations of representative functionals (PBE, B3LYP, B3P86, B97‐2 and M06‐L) and basis sets (TZVP, HIII‐su3, EPR‐III, aug‐cc‐pVTZ‐J, ccJ‐pVDZ, ccJ‐pVTZ, ccJ‐pVQZ, pcJ‐2 and pcJ‐3) using 68 organic molecular systems with 88 ¹J_CH couplings including different types of hybridized carbon atoms. Density functional theory assessment for the determination of ¹J_CH coupling constants is examined, comparing the computed and experimental values. The use of shifting constants for obtaining the calculated coupling improves substantially the results, and most models become qualitatively similar. Thus, for the whole set of couplings and for all approaches excluding those using the M06 functional, the root‐mean‐square deviations lie between 4.7 and 16.4 Hz and are reduced to 4–6.5 Hz when shifting constants are considered. Alternatively, when a specific rovibrational contribution of 5 Hz is subtracted from the experimental values, good results are obtained with PBE, B3P86 and B97‐2 functionals in combination with HIII‐su3, aug‐cc‐pVTZ‐J and pcJ‐2 basis sets. Copyright © 2013 John Wiley & Sons, Ltd.     

Kinetics and mechanism of atmospheric reactions of partially fluorinated alcohols

Gas-phase reactions typical of the Earth’s atmosphere have been studied for a number of partially fluorinated alcohols (PFAs). The rate constants of the reactions of CF₃CH₂OH, CH₂FCH₂OH, and CHF₂CH₂OH with fluorine atoms have been determined by the relative measurement method. The rate constant for CF₃CH₂OH has been measured in the temperature range 258–358 K (k = (3.4 ± 2.0) × 10¹³exp(?E/RT) cm³ mol^?1 s^?1, where E = ?(1.5 ± 1.3) kJ/mol). The rate constants for CH₂FCH₂OH and CHF₂CH₂OH have been determined at room temperature to be (8.3 ± 2.9) × 10¹³ (T = 295 K) and (6.4 ± 0.6) × 10¹³ (T = 296 K) cm³ mol^?1 s^?1, respectively. The rate constants of the reactions between dioxygen and primary radicals resulting from PFA + F reactions have been determined by the relative measurement method. The reaction between O₂ and the radicals of the general formula C₂H₂F₃O (CF₃CH₂? and CF₃?HOH) have been investigated in the temperature range 258–358 K to obtain k = (3.8 ± 2.0) × 10⁸exp(?E/RT) cm³ mol^?1 s^?1, where E = ?(10.2 ± 1.5) kJ/mol. For the reaction between O₂ and the radicals of the general formula C₂H₄FO (? HFCH₂O, CH₂F?HOH, and CH₂FCH₂?) at T = 258–358 K, k = (1.3 ± 0.6) × 10¹¹exp(?E/RT) cm³ mol^?1 s^?1, where E = ?(5.3 ± 1.4) kJ/mol. The rate constant of the reaction between O₂ and the radicals with the general formula C₂H₃F₂O (?F₂CH₂O, CHF₂?HOH, and CHF₂CH₂?) at T = 300 K is k = 1.32 × 10¹¹ cm³ mol^?1 s^?1. For the reaction between NO and the primary radicals with the general formula C₂H₂F₃O (CF₃CH₂? and CF₃?HOH), which result from the reaction CF₃CH₂OH + F, the rate constant at 298 K is k = 9.7 × 10⁹ cm³ mol^?1 s^?1. The experiments were carried out in a flow reactor, and the reaction mixture was analyzed mass-spectrometrically. A mechanism based on the results of our studies and on the literature data has been suggested for the atmospheric degradation of PFAs.