Fluoride-catalyzed hydroalkoxylation of hexafluoropropene with 2,2,2-trifluoroethanol

Trifluoroethoxylation of hexafluoropropene with 2,2,2-trifluoroethanol (TFE) were conducted using an alkali metal fluoride catalyst to produce CF₃CHFCF₂OCH₂CF₃. KF exhibited the highest yield and selectivity of CF₃CHFCF₂OCH₂CF₃, whereas LiF and NaF were inactive for the trifluoroethoxylation reaction. The same reaction also proceeded well in the presence of RbF or CsF, but yielded large amounts of olefinic and high molecular weight side products, implying that the size of alkali metal cation or the degree of MF dissociation plays an important role in determining the activity and the product composition. FT-IR and NMR experiments revealed that CsF interacts with TFE more strongly than KF through a hydrogen bonding. The experimental and spectroscopic results suggest that the degree of MF dissociation should be in the medium range for the selective production of CF₃CHFCF₂OCH₂CF₃ in high yield and selectivity.     

Vibrational spectra and normal coordinate analysis of 2,2,2-trichloroethanol and 2,2,2-trifluoroethanol

The vibrational spectra of 2,2,2-trichloroethanol and 2,2,2-trichloroethanol and their OD deuterated analogues have been studied in argon, nitrogen and mixed argon—nitrogen matrices. The matrix spectra of the CD₂ deuterated and totally deuterated trifluoroethanol and the Raman and i.r. spectra of the liquid alcohols have also been recorded. A vibrational assignment, supported by normal coordinate analysis, is proposed for both alcohols.     

The photochemical addition of 2,2,2-trifluoroethanol to methoxy-substituted stilbenes

The excited-state lifetime of the trans-stilbene chromophore in acetonitrile is prolonged by methoxy substituents in the meta positions. The long-lived singlet excited state of trans-3,5-dimethoxystilbene (trans-2d) is quenched upon the addition of 2,2,2-trifluoroethanol (TFE), and the Markovnikov ether is observed as the major product from steady-state irradiations. The results indicate that the reaction pathway proceeds through a carbocation intermediate.     

Catalyst-free one-pot synthesis of 1,4,5-trisubstituted pyrazoles in 2,2,2-trifluoroethanol

A simple, efficient and three component one-pot synthesis of 1,4,5-trisubstituted pyrazoles by condensation of β-dicarbonyls, N,N-dimethylformamide dimethyl acetal (DMFDMA) and hydrazine derivatives in 2,2,2-trifluoroethanol without using any catalyst and activation, is described.     

Intramolecular and liquid structure of 2,2,2-trifluoroethanol by X-ray diffraction

Intramolecular and liquid structure of 2,2,2-trifluoroethanol (TFE) have been investigated by x-ray diffraction at 25°C. The structural parameters for the skeleton of the molecules in the liquid phase are similar to those in the gas phase. The conformers of TFE molecules in the liquid phase are discussed. The O...O distance at about 284 pm and additional F...O one at about 302 pm were found to be characteristic for the first neighbor interactions. Various models (dimers and trimers) have been examined for analyzing the first neighbor structure. The liquid structure was explained in terms of small clusters consisting of two to three molecules rather than of a more extended polymeric network.Central Research Institute for Chemistry of the Hungarian Academy of Sciences, Budapest, P. O. Box 17, H-1525, Hungary.     

Use of the hexane-2,2,2-trifluoroethanol system in partition chromatography

The use of the hexane-2,2,2-trifluoroethanol heterophase system of solvents in partition chromatography is characterized. Gas-chromatographic retention indices and partition coefficients are used for the identification of organic compounds in this technique. The partition coefficients of compounds from 12 homologous series were measured in this heterophase system, and parameters for their group identification were calculated. The examples of the use of this system for solving different analytical problems are considered.     

Phototransposition reactions of arylboronate esters in acetonitrile and 2,2,2-trifluoroethanol

The phototransposition (para, meta, ortho) reactions of the arylboronate esters 4-, 3-, and 2-(4',4',5',5'-tetramethyl-1',3',2'-dioxaborolanyl)toluenes (1, 2, and 3, respectively) in both acetonitrile and 2,2,2-trifluoroethanol (TFE) using 254 nm irradiation have been examined. The irradiations resulted in steady-state compositions of para (5%), meta (19%), and ortho (76%) isomers in acetonitrile starting from the ortho isomer and para (12%), meta (54%), and ortho (35%) isomers in TFE starting from the para isomer. Analysis of the (13)C NMR spectrum of the product mixture obtained from the photochemistry of the para isomer selectively deuterated at C3 and C5 (1d(2)()) revealed that the boron-substituted carbon is the active one in the phototransposition reactions in both acetonitrile and TFE. Similar results were observed for irradiations of 1 in cyclohexane. Fluorescence spectra, singlet-state lifetimes, and Stern-Volmer quenching of fluorescence with 2,3-dimethyl-1,3-butadiene indicated that the excited singlet states of these three isomers were spectroscopic minima and that the excited singlet state was the reactive one for 3 in acetonitrile.     

A peptide co-solvent under scrutiny: self-aggregation of 2,2,2-trifluoroethanol

Trifluoroethanol (TFE) and its aggregates are studied via supersonic jet FTIR and Raman spectroscopy as well as by quantum chemistry and simple force field approaches. A multi-slit nozzle is introduced to study collisionally excited clusters. Efforts are made to extract harmonic frequencies from experiment for better comparison to theory. Based on deuteration, the OH stretching anharmonicity changes weakly upon dimerization, but increases for trimers. Among the possible dimer conformations, only an all-gauche, homoconfigurational, compact, OH-F connected structure is observed in an extreme case of chiral discrimination. Quantum tunneling assisted pathways for this surprising helicity synchronization are postulated. The oscillator coupling in hydrogen-bonded trimers is analyzed. Trans conformations of TFE start to become important for trimers and probably persist in the liquid state. Simple force fields can be refined to capture some molecular recognition features of TFE dimer, but their limitations are emphasized.     

Chromato-mass-spectrometric identification using partition coefficients in the system of hexane-2,2,2-trifluoroethanol

An additional characteristic of organic compounds, the partition coefficients in the heterophase solvent system n-hexane-2,2,2-trifluoroethanol, is shown to be useful for refining the results of chromatographic and gas chromatography-mass spectrometric identification. This opportunity is the most important for compounds that were not yet characterized by either mass spectra or chromatographic retention indices.     

Thermodynamic analysis of partially folded states of myoglobin in presence of 2,2,2-trifluoroethanol

The thermal denaturation of myoglobin was studied in the presence of 2,2,2-trifluoroethanol (TFE) at various pH values using differential scanning calorimetry and UV–visible spectroscopy. The most obvious effect of TFE was lowering the transition temperature up to 1.5 mol · kg⁻¹, beyond which no thermal transitions were observed. The protein conformation was analysed by fluorescence and circular dichroism measurements. Quantitative binding of ANS to the TFE induced molten globule state of myoglobin was studied by using isothermal titration calorimetry. The results enable quantitative estimation of the binding strength of ANS with the molten globule state of myoglobin along with the enthalpic and entropic contributions to the binding process. The results suggest occurrence of common structural features of the molten globule states of proteins offering two types of binding sites to ANS molecules which are a widely used fluorescence probe to characterise partially folded states of proteins.     

Conformation of 2,2,2-trifluoroethanol and the solvation structure of its 2-fluoropyridine clusters

The conformation of 2,2,2-trifluoroethanol (TFE) in the 2-fluoropyridine-(TFE)(m)-(H(2)O)(n) clusters in a supersonic jet has been investigated with fluorescence-detected infrared spectroscopy and quantum chemical calculations. It is common to the observed clusters that they form chain structures containing the weak interaction of the pyridyl CH with the fluorine or oxygen atom in the terminal TFE. The detectable conformation of TFE is gauche only even in the case of the existence of the strong base such as 2-fluoropyridine. This result is explained by the change in hyperconjugation among several dominant orbitals. The preference of the terminal TFE in the mixed clusters with TFE and water solvents is observed, which is ascribed to the stronger cooperative effect of TFE than water.     

NMR spectra of oriented 2,2,2-trifluoroethanol (CF3CH2OH)

Photolysis of hydrogen sulphide in argon, nitrogen and carbon monoxide matrices at 20 K produces HS radicals and S atoms. On warming the matrix, H₂S₂ and S₂ molecules are formed as a result of recombination reactions. The latter are identified by a blue-purple emission observed during warm-up of the matrix.     

Regio- and stereoselective ring-opening reactions of epoxides with indoles and pyrroles in 2,2,2-trifluoroethanol

Aliphatic and aromatic epoxides react regio- and stereoselectively with indoles and pyrroles in 2,2,2-trifluoroethanol without the use of a catalyst or any other additive. While aromatic epoxides are selectively attacked at the benzylic position, aliphatic epoxides react at the less-substituted position. Chiral epoxides react with >99 % ee (ee=enantiomeric excess).     

Effect of hydrogen bond strength on resorufin non-photochemical hole burning in ethanol-2,2,2-trifluoroethanol glasses

Relative hole burning efficiencies of resorufin in ethanol-2,2,2-trifluoroethanol (TFE) and TFE-hydroxyl deuterated ethanol (EtOD) mixed glasses as a function of the mole fraction of TFE are reported. The hole burning efficiency is found to increase in both mixed glass systems, with a greater increase occurring in EtOD/TFE glasses. In all cases the hole width was found to be independent of the glass composition. The relationship between the hole burning efficiency and hydrogen bond strengths is discussed.