Rate constants for the gas‐phase reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals at 250–430 K

The rate constants k₁ for the reaction of CF₃CF₂CF₂CF₂CF₂CHF₂ with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm³ reaction chamber with either CHF₂Cl or CH₂FCF₃ as a reference compound. OH radicals were produced by UV photolysis of an O₃–H₂O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k₁ (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10^?15 cm³ molecule^?1 s^?1 (FP‐LIF method) and (1.72 ± 0.07) × 10^?15 cm³ molecule^?1 s^?1 (LP‐LIF method), whereas the K₁ (298 K) values determined by the relative method were (1.87 ± 0.11) × 10^?15 cm³ molecule^?1 s^?1 (CHF₂Cl reference) and (2.12 ± 0.11) × 10^?15 cm³ molecule^?1 s^?1 (CH₂FCF₃ reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K₁ = (4.71 ± 0.94) × 10^?13 exp[?(1630 ± 80)/T] cm³ molecule^?1 s^?1. Using kinetic data for the reaction of tropospheric CH₃CCl₃ with OH radicals [k₁ (272 K) = 6.0 × 10^?15 cm³ molecule^?1 s^?1, tropospheric lifetime of CH₃CCl₃ = 6.0 years], we estimated the tropospheric lifetime of CF₃CF₂CF₂CF₂CF₂CHF₂ through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004     

含CF3CF2CF2C(CF3)2基团支链型氟表面活性剂的合成及性能研究

全氟辛酸/全氟辛基磺酸(PFOA/PFOS)类氟表面活性剂因不易被生物降解且对环境有毒害作用, 被列为持久性有机污染物. 采用引入氟碳支链的策略作为PFOA/PFOS替代物的研发取向, 以六氟丙烯二聚体为原料合成了新型阳离子型、两性型、双子型和非离子型氟表面活性剂, 并对它们的表面活性和急性毒性性能进行了测试. 结果表明, 所合成的支链型表面活性剂表面活性高且毒性低. 因此, 基于六氟丙烯二聚体(HFPD)合成PFOS/PFOA替代物是一种简单、经济且环保的方法.     

Design and synthesis of the novel branched fluorinated surfactant intermediates with CF3CF2CF2C(CF3)2 group

Here we reported a novel and efficient method for the synthesis of the critical intermediates of branched fluorinated surfactants with CF₃CF₂CF₂C (CF₃)₂- group using HFPD as starting material. The reaction conditions were mild and easy to handle, which was promisingly applied to the industrial production.     

Kinetic and thermochemical parameters of chlorine atom transfer reactions from CF3Cl,CF3CF2Cl,CF2ClCF2Cl,and CF2ClCFCl2 in gas phase

The following reactions: (1) were studied over the temperature ranges 533–687 K, 563–663 K, and 503–613 K for the forward reactions respectively and over 683–763 K, for the back reaction. Arrhenius parameters for chlorine atom transfer were determined relative to the combination of the attacking radicals. The ΔH_r°(1) = ?3.95 ± 0.45 kcal mol^?1 was calculated and from this value the ΔH∮(C₂F₅Cl) = ?2.66.3 ± 2.5 kcal mol^?1 and D(C₂F₅-Cl) = 82.0 ± 1.2 kcal mol^?1 were obtained. Besides, the ΔH_r°(2) was estimated leading to D(CF₂ClCF₂Cl) = 79.2 ± 5 Kcal mol^?1. The bond dissociation energies and the heat of formation are compared with those of the literature. The effect of the halogen substitutents as well as the importance of the polar effects for halogen transfer processes are discussed.     

Kinetic study of the reactions of Cl atoms with CF3CH2CH2OH, CF3CF2CH2OH, CHF2CF2CH2OH, and CF3CHFCF2CH2OH

The reaction kinetics of chlorine atoms with a series of partially fluorinated straight-chain alcohols, CF(3)CH(2)CH(2)OH (1), CF(3)CF(2)CH(2)OH (2), CHF(2)CF(2)CH(2)OH (3), and CF(3)CHFCF(2)CH(2)OH (4), were studied in the gas phase over the temperature range of 273-363 K by using very low-pressure reactor mass spectrometry. The absolute rate coefficients were given by the expressions (in cm(3) molecule(-1) s(-1)): k(1) = (4.42 +/- 0.48) x 10(-11) exp(-255 +/- 20/T); k(1)(303) = (1.90 +/- 0.17) x 10(-11), k(2) = (2.23 +/- 0.31) x 10(-11) exp(-1065 +/- 106/ T); k(2)(303) = (6.78 +/- 0.63) x 10(-13), k(3) = (8.51 +/- 0.62) x 10(-12) exp(-681 +/- 72/T); k(3)(303) = (9.00 +/- 0.82) x 10(-13) and k(4) = (6.18 +/- 0.84) x 10(-12) exp(-736 +/- 42/T); k(4)(303) = (5.36 +/- 0.51) x 10(-13). The quoted 2sigma uncertainties include the systematic errors. All title reactions proceed via a hydrogen atom metathesis mechanism leading to HCl. Moreover, the oxidation of the primarily produced radicals was investigated, and the end products were the corresponding aldehydes (R(F)-CHO; R(F) = -CH(2)CF(3), -CF(2)CF(3), -CF(2)CHF(2), and -CF(2)CHFCF(3)), providing a strong experimental indication that the primary reactions proceed mainly via the abstraction of a methylenic hydrogen adjacent to a hydroxyl group. Finally, the bond strengths and ionization potentials for the title compounds were determined by density functional theory calculations, which also suggest that the alpha-methylenic hydrogen is mainly under abstraction by Cl atoms. The correlation of room-temperature rate coefficients with ionization potentials for a set of 27 molecules, comprising fluorinated C2-C5 ethers and C2-C4 alcohols, is good with an average deviation of a factor of 2, and is given by the expression log(k) (in cm(3) molecule(-1) s(-1)) = (5.8 +/- 1.4) - (1.56 +/- 0.13) x (ionization potential (in eV)).     

The CO_2 laser-induced radical-chain reactions between CH_3CF_2H and chlorine-atom donors CF_2ClCFCl_2, CF_3CCl_3 CFCl_3 or CF_2Cl_2

The CO_2 laser induced room temperature reactions of CH_3CF_2H or another protium-donorCH_3CHClCH_3 with chlorine-atom donors (Z--Cl) CFCl_2CF_2Cl, CF_3CCl_3, CFCl_3 or CF_2Cl_2, havebeen investigated. Some of these reactions can yield two important monomers (CF_2=CH_2 andCF_2=CFCl) for fluoropolymers simultaneously. The yield dependence of these two alkenes on experi-mental conditions has been studied. A laser-initiated chain process is supported by identifica-tion of Z--H intermediates in these reactions.     

(CF3)2PAsH2 und (CF3)2AsAsH2

(CF₃)₂PAsH₂ and (CF₃)₂AsAsH₂ (CF₃)₂PAsH₂ is obtained in yields between 30 and 60% according to eq. (1) (CF₃)₂AsAsH₂ is formed by the analogous reaction with (CF₃)₂AsI, but is not sufficiently stable to be isolated. Both compounds are decomposed according to eq. (2) (CF₃)₂PAsH₂ can be studied in solution below ?40°C; it is characterized by molar mass determination and by its n.m.r. spectra (¹H, ¹⁹F, ³¹P). Reactions with polar [HBr, (CH₃)₂AsH, (CH₃)₂PN(CH₃)₂] and nonpolar [Br₂, As₂(CH₃)₄] reagents proceed by cleavage of the P? As bond.     

Kinetics for the gas‐phase reactions of OH radicals with the hydrofluoroethers CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2 at 268–308 K

Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH₂FCF₂OCHF₂(k₁), CHF₂CF₂OCH₂CF₃ (k₂), CF₃CHFCF₂OCH₂CF₃(k₃), and CF₃CHFCF₂OCH₂CF₂CHF₂(k₄) by using a relative rate method. OH radicals were prepared by photolysis of ozone at UV wavelengths (>260 nm) in 100 Torr of a HFE–reference–H₂O–O₃–O₂–He gas mixture in a 1‐m³ temperature‐controlled chamber. By using CH₄, CH₃CCl₃, CHF₂Cl, and CF₃CF₂CF₂OCH₃ as the reference compounds, reaction rate constants of OH radicals of k₁ = (1.68) × 10^?12 exp[(?1710 ± 140)/T], k₂ = (1.36) × 10^?12 exp[(?1470 ± 90)/T], k₃ = (1.67) × 10^?12 exp[(?1560 ± 140)/T], and k₄ = (2.39) × 10^?12 exp[(?1560 ± 110)/T] cm³ molecule^?1 s^?1 were obtained at 268–308 K. The errors reported are ± 2 SD, and represent precision only. We estimate that the potential systematic errors associated with uncertainties in the reference rate constants add a further 10% uncertainty to the values of k₁–k₄. The results are discussed in relation to the predictions of Atkinson's structure–activity relationship model. The dominant tropospheric loss process for the HFEs studied here is considered to be by the reaction with the OH radicals, with atmospheric lifetimes of 11.5, 5.9, 6.7, and 4.7 years calculated for CH₂FCF₂OCHF₂, CHF₂CF₂OCH₂CF₃, CF₃CHFCF₂OCH₂CF₃, and CF₃CHFCF₂OCH₂CF₂CHF₂, respectively, by scaling from the lifetime of CH₃CCl₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 239–245, 2003     

Substituent effects on the disproportionation‐combination rate constant ratios for gas‐phase halocarbon radicals. IV. Reactions of ·CF3 + CF3CH2CF2· and CF3CH2CF2· + CF3CH2CF2·

Rate constant ratios, k_d/k_c, for the disproportionation/combination reaction at a temperature of 295 ± 2 K, have been measured as 0.034 ± 0.009 for the collision between CF₃CH₂CF₂ + CF₃ radicals and as 0.075 ± 0.019 for CF₃CH₂CF₂ + CF₃CH₂CF₂ radicals. The effect of the two fluorine substituents on the rate constant ratio is compared to previous k_d/k_cs with CF₃CH₂CH₂, CF₃CH₂CHCl, and CF₃CH₂CHCF₃ radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet: 31: 237–243, 1999     

Thermal decomposition of CF3 and the reaction of CF2 + OH --> CF2O + H

The reflected shock tube technique with multipass absorption spectrometric detection (at a total path length of approximately 1.75 m) of OH-radicals at 308 nm has been used to study the dissociation of CF3-radicals [CF3 + Kr --> CF2 + F + Kr (a)] between 1,803 and 2,204 K at three pressures between approximately 230 and 680 Torr. The OH-radical concentration buildup resulted from the fast reaction F + H2O --> OH + HF (b). Hence, OH is a marker for F-atoms. To extract rate constants for reaction (a), the [OH] profiles were modeled with a chemical mechanism. The initial rise in [OH] was mostly sensitive to reactions (a) and (b), but the long time values were additionally affected by CF2 + OH --> CF2O + H (c). Over the experimental temperature range, rate constants for (a) and (c) were determined from the mechanistic fits to be kCF3+Kr = 4.61 x 10-9 exp(-30,020 K/T) and kCF2+OH = (1.6 +/- 0.6) x 10-10, both in units of cm3 molecule-1 s-1. Reaction (a), its reverse recombination reaction reaction (-a), and reaction (c) are also studied theoretically. Reactions (c) and (-a) are studied with direct CASPT2 variable reaction coordinate transition state theory. A master equation analysis for reaction (a) incorporating the ab initio determined reactive flux for reaction (-a) suggests that this reaction is close to but not quite in the low-pressure limit for the pressures studied experimentally. In contrast, reaction (c) is predicted to be in the high-pressure limit due to the high exothermicity of the products. A comparison with past and present experimental results demonstrates good agreement between the theoretical predictions and the present data for both (a) and (c).     

Preparation and synthetic applications of aryl tetraflates (ArOSO2CF2CF2H)

We have recently developed an improved synthetic route to 1,1,2,2-tetrafluoroethanesulfonic acid (HCF2CF2SO3H, TFESA) and explored the applications of this newly available superacid in catalysis. Low volatility, ease of handling, and a convenient 1H NMR handle make this acid an attractive alternative to triflic acid. TFESA can also be converted to several of its derivatives: anhydride, sulfonyl chloride, and sulfonyl fluoride, which provide a good entry point for the synthesis of aryl sulfonates. We prepared several aryl esters of 1,1,2,2-tetrafluoroethanesulfonic acid (aryl tetraflates) and showed that they can be used in a number of palladium-catalyzed coupling reactions (Suzuki, Heck, and Buchwald-Hartwig couplings). While the reactivity of tetraflates lies between that of triflates and chlorides, tetraflates appear to be more thermally stable. Additionally, the presence of a hydrogen atom in the tetraflate group facilitates monitoring of reactions and characterization of derivatives.     

Die Gasphasenstrukturen von CF3NBr2 und (CF3)2NBr

The Gas Phase Structures of CF₃NBr₂ and (CF₃)₂NBr The gas phase structures of the trifluoromethyl bromoamines CF₃NBr₂ and (CF₃)₂NBr were determined by electron diffraction. CF₃NBr₂: N? Br = 188.0(3), N? C = 148.1(13) pm, BrNBr = 111.1(6)° and BrNC = 107.3(8)°; (CF₃)₂NBr: N? Br = 186.9(4), N? C = 144.9(7) pm, BrNC = 114.9(9)° and CNC = 118.6(24)°. The results for these bromoamines are compared to those for the analogous fluoro and chloroamines.     

Die NMR-Spektren von CF3I,CF3IF2 und CF3IF4

The NMR Spectra of CF₃I, CF₃IF₂, and CF₃IF₄ The ¹⁹F-NMR and ¹³C-NMR spectra of CF₃I, CF₃IF₂ and CF₃IF₄ were recorded in acetonitrile solution. The chemical shifts of the CF₃-groups are strongly dependent on the oxidation state of the iodine atom. With increasing oxidation state the resonances of the CF₃-groups in the ¹⁹F-NMR spectra are characteristically shifted to high field, whereas in the ¹³C-NMR spectra a characteristic shift to low field is measured. The absolute value of the coupling constants ¹J(¹⁹F? ¹³C) increases with increasing oxidation state from 344 Hz (CF₃I) via 354 Hz (CF₃IF₂) to 359 Hz (CF₃IF₄).     

Kinetics and products of chlorine atom initiated oxidation of HCF2OCF2OCF2CF2OCF2H and HCF2O(CF2O)n‐(CF2CF2O)mCF2H

Smog chamber/FTIR techniques were used to measure k(Cl + HCF₂OCF₂OCF₂‐CF₂OCF₂H) = k(Cl + HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H) = (5.0 ± 1.4) × 10^?17 cm³ molecule^?1 s^?1 in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The Cl‐initiated atmospheric oxidation of HCF₂OCF₂OCF₂CF₂OCF₂H and the sample of HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H used in this work gave COF₂ in molar yields of (476 ± 36)% and (859 ± 63)%, respectively, with no other observable carbon containing products (i.e., essentially complete conversion of both hydrofluoropolyethers into COF₂). The results are discussed with respect to the atmospheric chemistry and environmental impact of hydrofluoropolyethers of the general formula HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 819–825, 2008     

Perfluoralkyltellur-Verbindungen: Oxidation von (CF3)2Te Darstellungen und Eigenschaften von (CF3)2TeCl2, (CF3)2TeBr2, (CF3)2Te(ONO2)2 und (CF3)2TeO [1]

Perfluorosalkyl Tellurium Compounds: Oxidation of (CF₃)₂Te; Preparations and Properties of (CF₃)₂TeCl₂, (CF₃)₂TeBr₂, (CF₃)₂Te(ONO₂)₂, and (CF₃)₂TeO From the oxidation of (CF₃)₂Te with Cl₂, Br₂, O₂, and ClONO₂ the new trifluoromethyl tellurium compounds (CF₃)₂TeCl₂, (CF₃)₂TeBr₂, (CF₃)₂TeO, and (CF₃)₂Te(ONO₂)₂ are prepared. The ¹⁹F, ¹³C and ¹²⁵Te n.m.r. spectra, the vibrational and mass spectra as well as the chemical properties of these compounds are described. By variation of the reaction conditions CF₃TeCl₃ and CF₃TeBr₃ are also formed. It has not been possible to isolate (CF₃)₂TeI₂, but there is some evidence that it is formed as an intermediate. (CF₃)₂Te reacts with ozone to a very unstable compound, which decomposes at low temperature.     

Rate constants for the reactions of OH radicals with CH3OCF2CF3, CH3OCF2CF2CF3, and CH3OCF(CF3)2

The rate constants for the reactions of OH radicals with CH₃OCF₂CF₃, CH₃OCF₂CF₂CF₃, and CH₃OCF(CF₃)₂ have been measured over the temperature range 250–430 K. Kinetic measurements have been carried out using the flash photolysis, laser photolysis, and discharge flow methods combined respectively with the laser induced fluorescence technique. The influence of impurities in the samples was investigated by using gas‐chromatography. The following Arrhenius expressions were determined: k(CH₃OCF₂CF₃) = (1.90) × 10⁻¹² exp[−(1510 ± 120)/T], k(CH₃OCF₂CF₂CF₃) = (2.06) × 10⁻¹² exp[−(1540 ± 80)/T], and k(CH₃OCF(CF₃)₂) = (1.94) × 10⁻¹² exp[−(1450 ± 70)/T] cm³ molecule⁻¹ s⁻¹. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 846–853, 1999