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.     

Recent advances on synthesis of potentially non-bioaccumulable fluorinated surfactants

Fluorinated surfactants are exceptional compounds that have found many applications in everyday life. This review focuses on severe issues on the toxicity, persistency and bioaccumulation of these halogenated products, especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), the half-lives of which are several years in human serum. After an introduction on their productions, uses and hazards, this minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants that may be potentially non-bioaccumulable. These routes have been devoted on: (i) the preparation of CF₃-X-(CH₂)_n-SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the use of fluorinated polyethers (achieved either by oligomerization of hexafluoropropylene oxide (HFPO) or by ring opening cationic oligomerization of fluorinated oxetanes; (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodoperfluoralkanes to produce C_nF_2n + 1-(VDF)₂-CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide to prepare (CF₃)₂CF(TFP)_x-R_H, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of either (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above pathways led to various highly fluorinated (but yet not perfluorinated) telomers or cooligomers, the chemical changes of which enabled to obtain original surfactants as novel alternatives to PFOA, ammonium perfluorooctanoate (APFO), or PFOS regarded as the PCBs of the XXIst century.     

Original fluorinated surfactants potentially non-bioaccumulable

This minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants potentially non-bioaccumulable. Various strategies have been focused on (i) the preparation of CF₃–X–(CH₂)_n–SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the oligomerization of hexafluoropropylene oxide (HFPO) to further synthesize oligo(HFPO)–CF(CF₃)CO–R_H (where R_H stands for an hydrophilic chain); (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodopentafluoroethane or 1-iodononafluorobutane to produce C_nF_2n+1–(VDF)₂–CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide or diethyl hydrogenophosphonate to prepare (CF₃)₂CF(TFP)_x–R_H or CF₃–CH₂–CH₂–(TFP)_y–P(O)(OH)₂, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above strategies led to various highly fluorinated (but yet not perfluorinated) telomers whose chemical changes enabled to obtain original surfactants as novel alternatives to perfluorooctanoic acid (PFOA), ammonium perfluorooctanoate (APFO), or perfluorooctylsulfonic acid (PFOS) regarded as bioaccumulable, persistent, and toxic.     

Hydrogen abstraction from CF3CF2CFH2 and CF3CFHCF2H by OH radicals and Cl atoms: theoretical enthalpies and rate constants

The hydrogen abstraction reactions of CF₃CF₂CFH₂ and CF₃CFHCF₂H with OH radicals and Cl atoms have been studied theoretically by a dual-level direct dynamics method. Two stable conformers of CF₃CF₂CFH₂ with C _s and C ₁ symmetries and all possible abstraction channels for each reaction are all taken into consideration. Optimized geometries and frequencies of all the stationary points and extra points along minimum-energy path (MEP) have been computed at the BB1K/6-31+G(d, p) level of theory. To refine the energy profile of each reaction channel, single point energy calculations have been performed by the BMC-CCSD method. The rate constants are evaluated by canonical variational transition state theory (CVT) with the small-curvature tunneling correction method (SCT) over a wide temperature range of 200–1,000 K. The detailed branching ratios of four reactions are discussed. The good agreement found between our theoretical rate constants and the available experimental data suggests that the present approach could provide a reliable prediction for the CF₃CFHCF₂H + Cl reaction about which there is little experimental information. The kinetic calculations show that the SCT effect plays an important role in all channels. In addition, in order to further reveal the thermodynamic properties, the enthalpies of formation of the reactants (CF₃CF₂CFH₂ and CF₃CFHCF₂H) and the product radicals (CF₃CF₂CFH, CF₃CFCF₂H, and CF₃CFHCF₂) are evaluated by applying isodesmic reactions at both BMC-CCSD//BB1K/6-31+G(d, p) and MC-QCISD//BB1K/6-31+G(d, p) levels of theory.     

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).     

UV absorption spectrum of CF3CFClO2 and kinetics of the self reaction of CF3CFCl and CF3CFClO2 and the reactions of CF3CFClO2 with NO and NO2

The ultraviolet absorption spectrum of CF₃CFClO₂ and the kinetics of the self reactions of CF₃CFCl and CF₃CFClO₂ radicals and the reactions of CF₃CFClO₂ with NO and NO₂ have been studied in the gas phase at 295 K by pulse radiolysis/transient UV absorption spectroscopy. The UV absorption cross section of CF₃CFCl radicals was measured to be (1.78 ± 0.22) × 10^?18 cm² molecule^?1 at 220 nm. The UV spectrum of CF₃CFClO₂ radicals was quantified from 220 nm to 290 nm. The absorption cross section at 250 nm was determined to be (1.67 ± 0.21) × 10^?18 cm² molecule^?1. The rate constants for the self reactions of CF₃CFCl and CF₃CFClO₂ radicals were (2.6 ± 0.4) × 10^?12 cm³ molecule^?1 s^?1 and (2.6 ± 0.5) × 10^?12 cm³ molecule^?1 s^?1, respectively. The reactivity of CF₃CFClO₂ radicals towards NO and NO₂ was determined to (1.5 ± 0.6) × 10^?11 cm³ molecule^?1 s^?1 and (5.9 ± 0.5) × 10^?12 cm³ molecule^?1 s^?1, respectively. Finally, the rate constant for the reaction of F atoms with CF₃CFClH was determined to (8 ± 2) × 10^?13 cm³ molecule^?1 s^?1. Results are discussed in the context of the atmospheric chemistry of HCFC-124, CF₃CFClH. © 1994 John Wiley & Sons, Inc.     

Long path-FTIR studies of some atmospheric reactions involving CF3OO and CF3O radicals

In attempts to obtain kinetic and mechanistic data required for an assessment of atmospheric fate of alternative halocarbons containing a CF₃ group, reactions of the key free radical intermediates CF₃OO and CF₃O with several atmospheric compounds (i.e., NO, NO₂, alkanes and alkenes) have been studied at 297 ± 2 K in 700 torr of air. Experiments employed the long path-FTIR spectroscopic method for product analysis and the visible (400 nm) photolysis of CF₃NO → CF₃ + NO as a source for the precursor radical CF₃. Numerous labile and stable F-containing molecular products have been characterized based on kinetic and spectroscopic data obtained at sufficiently short photolysis time (≤1 min) to minimize heterogeneous decay on the reactor walls. Major new findings have been made for the reactions involving CF₃O radicals. The behavior of CF₃O radicals has been shown to be markedly different from that of CH₃O radicals, i.e., (1) O₂-reaction: no evidence for the F-atom transfer reaction CF₃O + O₂ → CF₂ O + FOO; (2) NO-reaction: addition reaction CH₃O + NO (+M) → CH₃ONO (+M), but F-transfer reaction CF₃O + NO → CF₂O + FNO; (3) NO₂-reaction: addition reaction for both radicals, but F-transfer reaction CF₃ + NO₂ → CF₂O + FNO₂ to a minor extent; (4) alkane-reaction: much faster H-abstraction by CF₃O, comparable to HO; (5) alkene-reaction: much faster addition reaction of CF₃O, comparable to HO. These results are summarized in this paper.     

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.     

A kinetic study of the reaction of fluorine atoms with CH3F,CH3Cl,CH3Br,CF2H2, CO,CF3H,CF3CHCl2, CF3CH2F,CHF2CHF2, CF2ClCH3, CHF2CH3, and CF3CF2H at 295 ± 2 K

A variety of relative and absolute techniques have been used to measure the reactivity of fluorine atoms with a series of halogenated organic compounds and CO. The following rate constants were derived, in units of cm³ molecule^?1 s^?1: CH₃F, (3.7 ± 0.8) × 10^?11, CH₃Cl, (3.3 ± 0.7) × 10^?11; CH₃Br, (3.0 ± 0.7) × 10^?11; CF₂H₂, (4.3 ± 0.9) × 10^?12; CO, (5.5 ± 1.0) × 10^?13 (in 700 torr total pressure of N₂ diluent); CF₃H, (1.4 ± 0.4) × 10^?13; CF₃CCl₂H (HCFC-123), (1.2 ± 0.4) × 10^?12; CF₃CFH₂ (HFC-134a), (1.3 ± 0.3) × 10^?12, CHF₂CHF₂ (HFC-134), (1.0 ± 0.3) × 10^?12; CF₂ClCH₃ (HCFC-42b), (3.9 ± 0.9) × 10^?12, CF₂HCH₃ (HFC-152a), (1.7 ± 0.4) × 10^?11; and CF₃CF₂H (HFC-125), (3.5 ± 0.8) × 10^?13. Quoted errors are statistical uncertainties (2σ). For rate constants derived using relative rate techniques, an additional uncertainty has been added to account for potential systematic errors in the reference rate constants used. Experiments were performed at 295 ± 2 K. Results are discussed with respect to the previous literature data and to the interpretation of laboratory studies of the atmospheric chemistry of HCFCs and HFCs. © 1993 John Wiley & Sons, Inc.     

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     

Trifluormethylnitrat,CF3ONO2

Trifluoromethyl Nitrate, CF₃ONO₂ From different routes to CF₃ONO₂, the reaction of CF₃OF with NO₂ at room temperature under high pressure is the most favorable to synthesize CF₃ONO₂ in preparative scale. The pure product is isolated for the first time after repeated trap‐to‐trap condensation in vacuo. CF₃ONO₂ is a colourless gas with a boiling point of –18 ± 3 °C (extrapol.) and a melting point of –163 °C. Trifluoromethyl nitrate decays slowly into CF₂O and FNO₂ at room temperature in the gas phase as well as in the liquid state at lower temperatures. Furthermore, CF₃ONO₂ is characterized spectroscopically by NMR, IR, Raman, and UV, and structurally by gas electron diffraction and quantum chemical calculations (B3LYP, MP2). The CF₃–O bond is in the plane of the NO₃ moiety, the central CF₃O–NO₂ bond of 1.493(6) Å is very long. The B3LYP/6‐31G* calculation reproduces best the experimental data.     

(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.     

Substituent effects on the disproportionation-combination rate constant ratios for gas-phase halocarbon radicals. Part III: Reactions of CF3 + CF3CH2 CHCF3 and CF3 CH2CHCF3 + CF3CH2 CHCF3

Disproportionation/combination rate constant ratios, k_d/k_c, for the reactive collision between CF₃CH₂CHX + CF₃ radicals and between CF₃CH₂CHX + CF₃CH₂CHX radicals have been measured for X = CF₃. The k_d/k_c = 0.066 ± 0.013 when H is transferred to the CF₃ radical and 0.125 ± 0.025 for H transfer to the CF₃CH₂CHCF₃ radical. Comparison of these results with previous work shows that X = CF₃ increases the k_c/k_c' s relative to X = Cl or H. The effect of the CF₃ substituent on the disproportionation rate is discussed. © 1996 John Wiley & Sons, Inc.     

Zur Kenntnis der Sulfensäurefluoride CF3SF und CF2ClSF sowie deren Dimeren

The Sulfenic Fluorides CF₃SF and CF₂CISF and their Dimers The reactions of R_fSCl (R_f = CF₃, CF₂Cl) with HgF₂ and AgF give R_fSF and the dimer product R_fSF₂SR_f in high yield and various ratios, in contrast, activated KF leads only to R_fSF in low yield. A complex of transition metal and sulfenic halide as an intermediate step is discussed for the dimerisation. As liquid CF₃SF₂SCF₃ disproportionates into CF₃SF₃ and CF₃SSCF₃ and the hydrolysis of CF₃SF₂SCF₃ gives the stable compound CF₃S(O)SCF₃ · PF₃ reacts with R_fSF as well as with R_fSF₂SR_f to R_fSPF₄. The products of the spontaneous decomposition of CF₂ClSF were investigated. I.r., n.m.r., and mass spectra are reported and discussed. It was possible to carry out vapour pressure measurements of CF₂ClSF.     

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     

Reaktion von Chlornitrat mit CF3I: Isolierung von Trifluormethylchloriodnitrat CF3I(Cl)ONO2 und Kristallstruktur von Trifluormethylioddinitrat CF3I(ONO2)2

Reaction of Chlorine Nitrate with CF₃I: Isolation of Trifluormethylchloroiodinenitrate CF₃I(Cl)ONO₂ and the Crystal Structure of Trifluormethyliodinedinitrate CF₃I(ONO₂)₂ CF₃I reacts with ClONO₂ to Iodine(III)-compounds. After an addition CF₃I(Cl)ONO₂ is isolated and characterized by vibrational spectra. With surplus ClONO₂ it is formed CF₃I(ONO₂)₂. CF₃I(ONO₂)₂ crystallizes monoclinic in the space group P2₁/c with the cell parameters a = 1 024.3(6) pm, b = 873.5(6) pm, c = 873.4(6) pm and Z = 4. We measered following bonding distances: I? O: 207.3(3) and 220.8(2) pm, I? C: 221.1(4) pm and N? O: from 119.1(4) to 141.5(3) pm. Through an intermolecular I ··· O-contact the central iodine becomes a distorted plane geometry.     

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     

Dissociation and IVR pathways for the CF3H(H2O)3 cluster

Classical trajectory simulations are used to study the intramolecular dynamics of isolated CF₃H and the CF₃H(H₂O)₃ cluster, by either exciting the CH stretch local mode to then=6 level or by adding an equivalent amount of energy to an OH stretch normal mode. Energy transfer from the CH local mode is statistically the same for CF₃H(H₂O)₃ as for isolated CF₃H, and agrees with previous experimental studies. Clusters excited with 6 quanta in the CH local mode are remarkably stable. Though the CF₃H-(H₂O)₃ intermolecular potential is only 1.5 kcal/mol, only 1 of 26 clusters excited with 6 quanta in the CH local mode dissociate within 10 ps. The absorption linewidth for the CH local mode in CF₃H(H₂O)₃ is related to IVR within CF₃H and not to the unimolecular lifetime of the cluster. When an OH stretch normal mode of the cluster is excited, energy transfer to CF₃H is negligible and nearly one half of the clusters dissociate within 10 ps.