Perfluoralkyljod-verbindungen: das trifluormethyljod-bis-trifluoracetat CF3J(OCOCF3)2

CF₃I(OCOCF₃)₂ is formed from the reactions of CF₃IF₂ or CF₃IO with trifluoroacetic anhydride at low temperature. During the reaction of CF₃IF₂ with (CF₃CO)₂O CF₃IF(OCOCF₃) is formed as an intermediate product. The preparation, the ¹⁹F-nmr spectra and the thermal decomposition are described.     

Synthesis,crystal structure and thermal properties of Na2Ti(CF3COO)6(CF3COOH)2

The compound Na₂Ti(CF₃COO)₆(CF₃COOH)₂ was synthesized as colorless crystals, extremely unstable in air, by the reaction of TiCl₄ with trifluoroacetic acid and sodium trifluoroacetate. Crystallographic studies have shown that this sodium trifluoroacetatotitanate is the first example of a tetravalent titanium carboxylate [Ti(RCOO)₆]²– containing titanium in an octahedral environment of oxygen atoms of carboxylate groups. Thermal decomposition of Na₂Ti(CF₃COO)₆(CF₃COOH)₂ in an argon atmosphere results in the complex fluoride Na₂TiF₆.     

1,2,4-Trimethyl-1,2,4-triazolidine-3-thiones and 3,4-dimethyl-2-methylimino-1,3,4-thiadiazolidines

The reaction of aldehydes and ketones with 1,2,4-trimethylthiosemicarbazide in chloroform in the presence of CF₃COOH gives the corresponding 1,2,4-triazolidine-3-thiones, which in an excess of trifluoroacetic acid irreversibly and quantitatively recyclize to 2-imino-1,3,4-thiadiazolidine derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 403–407, March, 1992.     

Gas phase structure and conformational properties of trifluoroacetic anhydride, CF3C(O)OC(O)CF3

The geometric structure of trifluoroacetic anhydride, CF₃C(O)OC(O)CF₃, has been studied by gas electron diffraction (GED) and quantum chemical calculations (MP2 and B3LYP with 6-31G^* basis sets). The GED analysis results in a single conformer with synperiplanar orientation of the two CO bonds. This analysis, however, cannot discriminate between a planar equilibrium structure (C_2v symmetry) with large amplitude torsional motions around the OC bonds and a nonplanar equilibrium structure (C₂ symmetry) with a low barrier at the planar arrangement. An effective dihedral angle φ(COCO=18(4)° is obtained. Both quantum chemical methods predict a nonplanar equilibrium structure of C₂ symmetry and φ(COCO)=16.5° and 13.9°, respectively.     

A NEW EFFICIENT SYNTHESIS OF TRIFLUOROACETYL HALIDES AND MIXED ANHYDRIDES OF PHOSPHORUS AND TRIFLUOROACETIC ACIDS

Abstract

Reaction of trifluoroacetic anhydride with chloroanhydrides of phosphorus acids R₂P(O)CI results in formation of mixed anhydrides R₂P(O) OCOCF₃ and trifluoroacetic acid halides CF₃COX (X=Cl, Br, I) in quantitative yield.     

Synthesis and Crystal Structure of Copper(II) Trifluoroacetates,Cu2(CF3COO)4 · 2 CH3CN and Cu(CF3COO)2(H2O)4

Cu₂(CF₃COO)₄ · 2 CH₃CN ( I ) and Cu(CF₃COO)₂(H₂O)₄ ( II ) have been prepared by concentrating of acetonitrile and aqueous solutions respectively. According to X-ray data, the complex I consists of binuclear molecules with Cu–O 1.969 Å, Cu–N 2.114 Å. The Cu…Cu distance was found to be 2.766 Å, one of the longest for dimeric structures, apparently, due to the high acidity of trifluoroacetic acid. The coordination environment of Cu atom in II can be described as 4 + 2: 2 Cu–O (H₂O) 1.937 Å, 2 Cu–O (CF₃COO) 1.985 Å, 2 Cu–O (H₂O) 2.447 Å. The mononuclear structure is stabilized by formation of two intra- and six intermolecular hydrogen bonds.     

A convenient and simple procedure for the preparation of nitrate esters from alcohols employing LiNO3/(CF3CO)2O

Alcohols in small peptides, monosaccharides and steroids (12 examples) are conveniently transformed to their corresponding nitrate esters upon treatment with an acetonitrile solution of LiNO₃ and trifluoroacetic anhydride. The in situ formed mixed anhydride (CF₃COONO₂) is proposed to be the reactive nitration reagent.     

Activation of molecular oxygen in trifluoroacetic acid

The interaction of molecular oxygen with aqueous trifluoroacetic acid (TFA) led to an increase in pH. This effect was explained by a decrease in the concentration of the protonated CF₃CO₂H₂⁺ and H₃O⁺ species after oxygen was fed in the reactor. Quantum-chemical calculations show that a radical pair can be formed in an activation-free exothermal reaction involving the radical residue of the acid, the CF₃CO₂H₂⁺...³O₂...CF₃CO₂⁻ peroxide radical, and the acid molecule in the CF₃C₂^·...HOO^· collision complex. It was assumed that the activation of molecular oxygen in aqueous TFA solutions, providing the activity of the system in oxidations of various organic and inorganic substrates, is related to the formation of peroxide radicals in them.     

Preparation of CF3COCl: investigation of operating parameters

The preparation of CF₃COCl through reaction between CF₃CCl₃ and SO₃ was investigated with particular reference to the following operating parameters: catalyst type and concentration, molar ratio C₂Cl₃F₃/SO₃ and composition of the isomeric mixture CF₃CCl₃/CClF₂CCl₂F.Such preparation was first investigated either batchwise or semi-continuously, in order to define at best the above parameters. It was then effected continuously on proper equipment, which allowed to separate the CF₃COCl at a degree of purity adequate to its direct use in the preparation of trifluoroacetic compounds.     

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     

Synthesis of the first difunctional N-fluoro perfluoroalkylsulfonylimides, CF3SO2NFSO2(CF2)nSO2NFSO2CF3

Synthesis of difunctional N,N′-difluoro perfluoroalkylsulfonamides, CF₃SO₂NFSO₂(CF₂)_nSO₂NFSO₂CF₃, where n=4, 6 is reported. A related compound with an oxygen linkage CF₃SO₂NFSO₂(CF₂)₂O(CF₂)₂SO₂NFSO₂CF₃ has also been prepared. These reagents showed good activity for electrophilic fluorination.     

Kinetics and mechanism of the reaction of CF3 radicals with NO2

The reaction of CF₃ with NO₂ was studied at 296 ± 2K using two different absolute techniques. Absolute rate constants of (1.6 ± 0.3) × 10⁻¹¹ and (2.1 _−0.3⁺⁰⁷) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ were derived by IR fluorescence and UV absorption spectroscopy, respectively. The reaction proceeds via two reaction channels: CF₃ + NO₂ → CF₂O + FNO, (70 ± 12)% and CF₃ + NO₂ → CF₃O + NO, (30 ± 12)%. An upper limit of 11% for formation of other reaction products was determined. The overall rate constant was within the uncertainty independent of total pressure between 0.4 to 760 torr. © 1996 John Wiley & Sons, Inc.     

Radiation chemistry of CF2 Cl2 in the gas and liquid phases: Effect of doses rate

The dose rate dependence of CF₂ Cl₂ decomposition was studied in both, gas and liquid phase, for the range of 2.95·10^{1 7}–1.9·10^{1 9} eV·g^–1·h^–1. The major products were found to be CF₃Cl, CFCl₃, CF₂Cl–CF₂Cl and CF₂Cl–CFCl₂. The decomposition of CF₂Cl₂ was found to decrease with decreasing dose rate for the liquid phase, while an opposite trend was found for gas phase radiolysis. A new mechanism which explains these contrasting findings was suggested. The contribution of radical and of ionic (or molecular) processes to the yields of the various products was estimated.     

Absolute rate constants for the self reactions of HO2, CF3CFHO2, and CF3O2 radicals and the cross reactions of HO2 with FO2, HO2 with CF3CFHO2, and HO2 with CF3O2 at 295 K

The kinetics of the self-reactions of HO₂, CF₃CFHO₂, and CF₃O₂ radicals and the cross reactions of HO₂ with FO₂, HO₂ with CF₃CFHO₂, and HO₂ with CF₃O₂ radicals, were studied by pulse radiolysis combined with time resolved UV absorption spectroscopy at 295 K. The rate constants for these reactions were obtained by computer simulation of absorption transients monitored at 220, 230, and 240 nm. The following rate constants were obtained at 295 K and 1000 mbar total pressure of SF₆ (unit: 10⁻¹² cm³ molecule⁻¹ s⁻¹): k(HO₂+HO₂)=3.5±1.0, k(CF₃CFHO₂+CF₃CFHO₂)=3.5±0.8, k(CF₃O₂+CF₃O₂)=2.25±0.30, k(HO₂+FO₂)=9±4, k(CF₃CFHO₂+HO₂)=5.0±1.5, and k(CF₃O₂+HO₂)=4.0±2.0. In addition, the decomposition rate of CF₃CFHO radicals was estimated to be (0.2–2)×10³ s⁻¹ in 1000 mbar of SF₆. Results are discussed in the context of the atmospheric chemistry of hydrofluorocarbons. © 1997 John Wiley & Sons, Inc.     

Binuclear ruthenium complexes of fluorous phosphine ligands: Synthesis, properties, and biphasic catalytic activity. Crystal structure of [Ru(μ-O2CMe)(CO)2P(CH2CH2(CF2)5CF3)3]2

The fluorocarbon soluble, binuclear ruthenium(I) complexes [Ru(μ-O₂CMe)(CO)₂L^F]₂, where L^F is the perfluoroalkyl substituted tertiary phosphine, P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃, or P(CH₂CH₂(CF₂)₅CF₃)₃, were synthesized and partition coefficients for the complexes in fluorocarbon/hydrocarbon biphases were determined. Catalytic hydrogenation of acetophenone to 1-phenylethanol in benzotrifluoride at 105 °C occured in the presence of either [Ru(μ-O₂CMe)(CO)₂P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃]₂ (1) or [Ru(μ-O₂CMe)(CO)₂P(CH₂CH₂(CF₂)₅CF₃)₃]₂ (2). The X-ray crystal structure of [Ru(μ-O₂CMe)(CO)₂P(CH₂CH₂(CF₂)₅CF₃)₃]₂ was determined. The compound exhibited discrete regions of fluorous and non-fluorous packing.     

The preparation of some trifluoroacetato complexes of zirconium

The preparation of a trifluoroacetato complex of zirconium from trifluoroacetic acid and zirconium oxide dichloride is described - Zr₂(CF₃COO)₅(OH)₃(H₂O)₃. From spectroscopic, and thermal gravimetric analysis, a dimeric structure is proposed. A monomeric zirconium trifluoroacetato complex containing 1,10-phenanthroline is also described - Zr(CF₃COO)₂(C₁₂H₈N₂)(OH)₂.     

The addition of (CF3SO2)2CHBr to vinylidene fluoride

It has been found that a mixture of (CF₃SO₂)₂CH₂ and (CF₃SO₂)₂CBr₂ can be used instead of (CF₃SO₂)₂CHBr in the radical addition to H₂CCF₂; the 1:1 and 1:2 adducts have been isolated and characterized. An improved synthesis of (CF₃SO₂)₂CBr₂ is also reported.     

An in-depth in situ IR study of the thermal decomposition of yttrium trifluoroacetate hydrate

The pyrolysis of Y(CF₃COO)₃·nH₂O at temperatures up to 1,000 °C, under flowing pure Ar, O₂ and O₂ saturated with water vapour, was extensively analysed. The formation of HF is observed directly and the existence of a :CF₂ diradical is inferred during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic one-stage decomposition of the anhydrate salt occurs at 267 °C, forming YF₃. Fourier transform infrared spectroscopy identified (CF₃CO)₂O, CF₃COF, COF₂, CO₂ and CO as the principal volatile species; and revealed the influence of water on the reactions liberating gaseous CF₃COOH, CHF₃, HF, and SiF₄ (from reactions with glass or quartz components). NO₂ and N₂O evolution suggested that traces of CH₃NO₂ were present in the starting material. Thermogravimetry and X-ray diffractometry indicated that the slow hydrolysis of the fluoride occurs between 630 and 655 °C, forming a mixture of Y₂O₃, YOF, Y₇O₆F₉, and YF₃. The decomposition and hydrolysis temperatures are significantly lower than previously reported, which has implications for sol–gel processing.     

Direct dynamics studies for the reactions of CF3CHFCF3 and CF3CF2CHF2 with H atoms

The rate constants of the hydrogen abstraction reactions of CF₃CHFCF₃ + H (R1) and CF₃CF₂CHF₂ + H (R2) have been calculated by means of the dual-level direct dynamics method. Optimized geometries and frequencies of stationary points and extra points along the minimum-energy path (MEP) are obtained at the MPW1K/6-311+G(d,p) level, and the classical energetic information is further corrected with the interpolated single-point energy (ISPE) approach by the G3(MP2) level of theory. Using the canonical variational transition state theory (CVT) with small-curvature tunneling corrections (SCT), the rate constants are evaluated over a wide temperature range of 200-2000 K. The calculated CVT/SCT rate constants are in good agreement with available experimental values. It is found that the variational effect is very small and almost negligible over the whole temperature region. However, the small-curvature tunneling correction plays an important role in the lower temperature range. Furthermore, the heats of formation of species CF₃CF₂CHF₂ (SC₁ or SC₂) and CF₃CF₂CF₂ are studied using isodesmic reactions to further elucidate the thermodynamic properties.