Trifluoromethane Research Articles

Studies on potential moderator materials for very cold neutron sources

The increasing demand for long wavelength neutrons is being motivated by the need to study larger objects and slower motions characterizing the new materials related to the requirements of nowadays science and technology. However, not much work has been done so far towards the identification of materials and conditions able to produce a copious flux of very cold neutrons (VCN) at either stationary or pulsed sources. This work presents the results of a preliminary study aimed at exploring materials that look promising as potential moderators for VCN sources. For this purpose, a search is done for the existence of very low energy excitations in the generalized density of states of some molecular systems, which can be efficient to slow down already cold neutrons by exchanging energy with them. Besides reviewing and improving the available information on methane (II) and methane clathrate, it is found that such objective can be realized by the quantum dynamics corresponding to the librations of the methyl groups in the methyl fluoride and the p-xylene molecules encapsulated in two different molecular hosts at low temperatures.

Experimental and Theoretical Assessment of Inverter-Operated Split Air Conditioner with Low GWP Alternative Refrigerants

This article presents experimental evaluation and comparative analysis of low GWP alternative refrigerants, namely HC-290 (propane), HC-1270 (propylene), HC/HC-1270 blend, and HFC-32 (difluoro methane) as drop-in replacements for HCFC-22 (Chloro difluoro methane) in a typical 1.5 TR capacity inverter operated split type air conditioner (SAC). The experimental setup consisted of retrofitting an original HCFC-22 test unit following the soft optimization of the SAC system for each alternative refrigerant, followed by testing under controlled operating conditions as per the IS 1391, Part-1 standard at the half capacity and the rated capacity of inverter SAC. The results obtained were compared against the baseline HCFC-22 test unit. The optimized SAC gave EERIS (Indian Seasonal Energy Efficiency Ratio) of 4.63 for HC-290, 4.71 for HC-1270 and 4.87 for HC-290/HC-1270 blend, respectively increased by 8.94 %, 10.82 % and 14.58 % compared to HCFC-22. HFC-32 delivered the maximum cooling capacity of 6.78 kW, 3.67 % higher than baseline unit at the rated capacity. HC-290/HC-1270 blend exhibited the lowest power consumption and discharge temperature amongst all the refrigerants considered. The charge of flammable refrigerants has been optimized below LFL satisfying EN378 standard for the safety of inverter SAC in domestic applications.

A Comparative Study on Electrochemical Performance of Single versus Dual Networks in Lithium Metal/Polysulfide-Polyoxide Co-Network/Lithium Titanium Oxide Cathode

The present article introduces a strategy for controlling oxidation and reduction reactions within polymer electrolyte membrane (PEM) networks as a means of enhancing storage capacity through the complexation of dissociated lithium cations with multifunctional groups of the polymer network. Specifically, co-polymer networks based on polysulfide (PS) and polyoxide (PO) precursors, photo-cured in the presence of succinonitrile (SCN) and lithium bis(trifluoro methane sulfonyl imide) (LiTFSI) salt, exhibited ionic conductivity on the order of mid 10−4 S/cm at ambient temperature in the 30/35/35 (weight %) composition. Lithium titanate (LTO, Li4Ti5O12) electrode was chosen as an anode (i.e., a potential source of Li ions) against lithium iron phosphate (LFP, LiFePO4) cathode in conjunction with polysulfide-co-polyoxide dual polyelectrolyte networks to control viscosity for 3D printability on conformal surfaces of drone and aeronautic vehicles. It was found that the PS-co-PO dual network-based polymer electrolyte containing SCN plasticizer and LiTFSI salt exhibited extra storage capacity (i.e., specific capacity of 44 mAh/g) with the overall specific capacity of 170 mAh/g (i.e., for the combined LTO electrode and PEM) initially that stabilized at 153 mAh/g after 50th cycles with a reasonable capacity retention of over 90% and Coulombic efficiency of over 99%. Of particular interest is the observation of the improved electrochemical performance of the polysulfide-co-polyoxide electrolyte dual-network relative to that of the polyoxide electrolyte single-network.

Physiochemical study of 1-methyl imidazole trifluoro methane sulfonate ionic liquid in aqueous and aqueous amino acid solutions at different temperatures

The experimental density and speed of sound of 1-methyl imidazole trifluoro methane sulfonate ionic liquid in aqueous binary ([MIm][OTf]+H2O) solution and aqueous ternary ([MIm][OTf] + 0.05 mol.kg−1 aqueous glycine) solution are reported in the dilute concentration range (0.06 to 0.16 mol.kg−1) at the temperature between 288.15 and 318.15 K with 5K interval and at atmospheric pressure. These density (ρ) and speed of sound (u) data are utilized to derive various significant thermophysical parameters namely apparent molar volume of solute (Vϕ), isentropic compressibility of solution (κs) and apparent molar isentropic compressibility of solute (KS,ϕ). The limiting apparent molar volume (Vϕ0) and limiting apparent molar isentropic compressibility (KS,ϕ0) of [MIm][OTf] are estimated by extrapolation methods. By using Vϕ0and KS,ϕ0data of the studied binary and ternary systems, the values of transfer volumes i.e. volume changes due to transfer (ΔtrVϕ0)and transfer compressibility i.e. compressibility changes due to transfer(ΔtrKsϕ0) from aqueous to aqueous amino acid solution are estimated. The observed ΔtrVϕ0and ΔtrKsϕ0values are temperature dependent. The outcomes of this investigation are framed within the context of solute-solute and solute-solvent interactions.

Infrared Laser Stark Spectroscopy of Methyl Fluoride in 4He Nanodroplets.

We measured the rotationally resolved infrared spectra of helium solvated methyl fluoride at 3 μm and 10 μm, wherein lies C-H and C-F stretching bands, respectively. The linewidths (FWHM) were found to increase with increasing vibrational energy and range from 0.002 cm-1 in the v3 band (C-F stretch) at ~1047 cm-1, to 0.65 cm-1 in the v4 band (asymmetric C-H stretch) at ~2997 cm-1. In between these two bands we observed the lower and upper components of the Fermi triad bands (ν1/2ν2/2ν5) at ~2859 and ~2961 cm-1. We carried out Stark spectroscopy on the lower band on account of its narrower linewidths (0.04 vs. 0.14 cm-1, respectively). The objective of performing Stark spectroscopy was to see if there is any evidence for a rotational linewidth dependence on the external field strength, due to a reduced difference in between methyl fluorides rotational energy gap and the roton-gap of superfluid helium. We did not find any evidence for such an effect, which we largely attribute to the rotational energy gap not increasing significantly enough by the external field. We point to another molecule (formaldehyde) whose energy levels are predicted to show a more promising response to application of an external field.

Fractionation of stable carbon isotopes during formate consumption in anoxic rice paddy soils and lake sediments

Abstract. Formate is energetically equivalent to hydrogen and thus is an important intermediate during the breakdown of organic matter in anoxic rice paddy soils and lake sediments. Formate is a common substrate for methanogenesis, homoacetogenesis and sulfate reduction. However, how much these processes contribute to formate degradation and fractionate carbon stable isotopes is largely unknown. Therefore, we measured the conversion of formate to acetate, CH4 and CO2 and the δ13C of these compounds in samples of paddy soils from Vercelli, Italy, and the International Rice Research Institute (IRRI) in the Philippines and of sediments from the NE and SW basins of Lake Fuchskuhle, Germany. The samples were suspended in a phosphate buffer (pH 7.0) in both the absence and presence of sulfate (gypsum) and of methyl fluoride (CH3F), an inhibitor of aceticlastic methanogenesis. In the paddy soils, formate was mainly converted to acetate under both methanogenic and sulfidogenic conditions. Methane was only a minor product and was mainly formed from the acetate. In the lake sediments, the product spectrum was similar but only under methanogenic conditions. In the presence of sulfate, however, acetate and CH4 were only minor products. The isotopic enrichment factors (εform) of formate consumption, determined by Mariotti plots, were in the low range of −8 ‰ to −2.5 ‰ when sulfate was absent, and formate was mainly converted to acetate and CH4. However, no enrichment factor was detectable when formate was degraded with sulfate to mainly CO2. The δ13C of acetate was by about 25 ‰–50 ‰ more negative than that of formate, indicating acetate production by chemolithotrophic homoacetogenesis. Hence, formate seems to be an excellent substrate for homoacetogenesis in anoxic soils and sediments, so that this process is competing well with methanogenesis and sulfate reduction.

Protective behavior of phosphonate-functionalized imidazolium ionic liquid and its impact on the Li-ion battery performance

The commercial lithium-ion batteries (LIBs) rely on lithium hexafluorophosphate (LiPF6), which is extremely sensitive to moisture and liable to thermal decomposition. Lithium bis (trifluoro methane sulfonyl) imide (LiTFSI), as a promising electrolyte salt, possesses high thermal stability and excellent moisture tolerance. However, LiTFSI is closely related to severe corrosion of the aluminum (Al) current collector at high voltage. Herein, phosphonate-functionalized imidazolium ionic liquid (PFIL) is developed and utilized as an electrolyte co-solvent to inhibit the oxidative dissolution of the Al current collector. PFIL can suppress Al corrosion by participating in the interface reaction and forming a stable and reliable protective film on the surface of Al foils, as confirmed by X-ray photoelectron spectroscopy. Thanks to the corrosion suppression of the Al current collector, the Li||LiNi0.8Mn0.1Co0.1O2 (NCM811) cells with PFIL-containing electrolytes exhibit better cycling performance and improved capacity retention. This work proposes an effective strategy for the advancement of high-voltage LIBs and contributes to promoting the widespread use of the sulfone imide-based lithium salts.

Phytotoxic responses of wheat to an imidazolium based ionic liquid in absence and presence of biochar

Research on ionic liquids (ILs) and biochars (BCs) is a novel site of scientific interest. An experiment was designed to assess the effect of 1-propanenitrile imidazolium trifluoro methane sulfonate ([C2NIM][CF3SO3]) ionic liquid (IL) and IL-BC combination on the wheat plant. Three working standards of the IL; 50, 250, 500 and 1000 mg/L, prepared in deionized water, were tested in the absence and presence of BC on wheat seedling. Results indicated significant decrease ‏in seed germination (%), length, fresh weight, chlorophyll a, b and carotenoid contents of wheat ‏seedlings at 250, 500 and ‏1000 mg/L of the ‏IL. An admirable increase in phenolic and 2,2-diphenyl-1-picrylhydrazyl (DPPH) contents of wheat seedlings was noted at 250, 500 and ‏1000 mg/L of the IL. The application of BC significantly ‏ameliorated the negative effects of IL on the selected parameters of ‏wheat. It is inferred that the undesirable effects of the IL on wheat growth can be positively restored by addition of BC.

An ab initio study of the structural, vibrational and electronic properties of some tetrel-bonded complexes of methane and tetrafluoromethane

The binary complexes of ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride, as electron donors, with methane and tetrafluoromethane, as electron acceptors, have been studied by means of ab initio molecular orbital theory. The properties of interest are the molecular structures, interaction energies and vibrational spectra of the complexes, and the interactions of the molecular orbitals which result in the formation of the complexes. The adducts were found to fall into a number of structural types, including tetrel-bonded, hydrogen-bonded, halogen-bonded, pnicogen-bonded and chalcogen-bonded, depending on the particular combination of electron donor and acceptor. The complexes, irrespective of the type of interaction, were found to be uniformly very weakly bound. The results have been rationalized in terms of the properties of the donors and, together with the conclusions of previous studies involving methyl fluoride, difluoromethane and fluoroform, with the extent of fluorine substitution in the parent molecule, methane.

Highly conductive Poly(ε-caprolactone) and chitosan based polymer electrolyte for lithium metal battery

Poly (ε-caprolactone) (PCL) is an attractive polymer electrolyte material due to its ultralow glass transition temperature, high dielectric constant as well as excellent electrochemical stability, but its practical application has been greatly hindered due to the low ionic conductivity induced by the semi-crystalline structure. Herein, we elaborately modify PCL with chitosan (CS) to obtain an amorphous PCL-CS composite membrane, and develop a fast Li+ conducting quasi-solid polymer electrolyte (QPE) with lithium bis(trifluoro methane sulphonyl)imide (LiTFSI) and merely 10 wt% plasticizer. The optimized QPE with 50 wt% LiTFSI exhibits an ionic conductivity of 7.7 × 10−4 S cm−1, which is the highest among PCL-based polymer electrolyte. Fourier Transform Infrared spectroscopy and Raman spectra reveal that Li+ conducting via the solvation of partial plasticizer as well as contacted ionic clusters. In addition, its excellent stability and compatibility are validated by the integrated symmetric Li//Li cell that exhibits an ultra-long cycling for over 1850 h with no Li dendrite formation.

Structural, vibrational and electronic properties of some tetrel-bonded complexes of the fluorinated methanes methyl fluoride, difluoromethane and fluoroform: an ab initio study.

A search has been conducted, by means of ab initio molecular orbital theory, for potential tetrel-bonded complexes formed between the fluorinated methanes methyl fluoride, difluoromethane and fluoroform, and the related hydrides ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride. Eleven such complexes have been identified, six containing CH3F and five CH2F2. The complexes are typically less strongly bound than their hydrogen-bonded counterparts, and the interaction energies vary in a consistent way with the periodic trend of the electron donors. The intermolecular separations and changes of the relevant intramolecular bond lengths, the wavenumber shifts of the critical vibrational modes and the extents of charge transfer correlate, by and large, with the strengths of interaction.

Tuning the Selectivity of the Hydrogenation/Hydrogenolysis of 5-Hydroxymethylfurfural under Batch Multiphase and Continuous-Flow Conditions.

The hydrogenation/hydrogenolysis of 5‐hydroxymethylfurfural (HMF) has been carried out either under single (aqueous) phase or batch multiphase (MP) conditions using mutually immiscible aqueous/hydrocarbon phases, 5 % Ru/C as a catalyst, and both with and without the use of trioctylmethyl phosphonium bis‐(trifluoro methane) sulfonimide ([P8881][NTf2]) as an ionic liquid (IL). Alternatively, the hydrogenation of HMF was explored in the continuous‐flow (CF) mode with the same catalyst. By changing reaction parameters, experiments were optimized towards the formation of three products: 2,5‐bis(hydroxy methyl)furan (BHMF), 2,5‐bis(hydroxymethyl)tetrahydrofuran (BHMTHF), and 1‐hydroxyhexane‐2,5‐dione (HHD), which were obtained in up to 92, 90, and 99 % selectivity, respectively, at quantitative conversion. In particular, the single (aqueous) phase reaction of HMF (0.2 m) carried out for 18 h at 60 °C under 30 bar of H2, allowed the exclusive synthesis of BHMF from the partial (carbonyl) hydrogenation of HMF, while the MP reaction run at a higher T and p (100 °C and 50 bar) proved excellent to achieve only HHD derived from a sequence of hydrogenation/hydrogenolysis. It is worth noting that under MP conditions, the catalyst was perfectly segregated in the IL, where it could be recycled without any leaching in the aqueous/hydrocarbon phases. Finally, the hydrogenation of HMF was explored in a H‐Cube® flow reactor in the presence of different solvents, such as ethyl acetate, tetrahydrofuran, and ethanol. At 100 °C, 50 bar H2, and a flow rate of 0.1 mL min−1, the process was optimized towards the formation of the full hydrogenation product BHMTHF. Ethyl acetate proved the best solvent.

Line-by-line intensity measurements of methyl fluoride in the ν2 and ν5 bands

Systematic measurements of line intensities in the ν2 and ν5 bands of CH3F were performed for the first time for 2040 transitions using a mono-spectrum fitting technique utilizing a Voigt and Rautian profiles. The spectra are recorded at room temperature for eight pressures of CH3F from 0.1247 to 2.5080 Torr using the Bruker IFS125HR Fourier Transform spectrometer located at the LISA facility in Créteil. Strong intensity perturbations were observed and analyzed accounting for the strong Coriolis coupling ν2 and ν5 bands and l-type interactions in the ν5 band. The transition dipole moments squared were determined for each line, allowing determination of the vibrational transition moment and the Herman–Wallis coefficients of each band using the Aliev and Watson models. Comparison with data available in the literature permits to test the validity of these models applied to the ν2/ν5 dyad system strongly affected by resonances.

Frequency tunable laser closes in on terahertz gap

Using methyl fluoride as a new gain medium, the quantum cascade laser-pumped molecular laser covers 120 lines from 0.25 to 1.3 terahertz.

A quantum cascade laser-pumped molecular laser tunable over 1 THz

Despite decades of research, no frequency tunable sources span the terahertz gap between 0.3 and 3 THz. By introducing methyl fluoride (CH3F) as a new gain medium for a quantum cascade laser-pumped molecular laser (QPML), we demonstrate continuous-wave lasing from more than 120 discrete transitions, spanning the range from 0.25 to 1.3 THz. Thanks to its large permanent dipole moment and large rotational constants, methyl fluoride (CH3F) as a QPML gain medium combines a lower threshold, a larger power efficiency, and a wider tuning range than other molecules. These key features of the CH3F QPML, operated in a compact cavity at room temperature, pave the way to a versatile THz source to bridge the THz gap.

Fractionation of stable carbon isotopes during acetate consumption by methanogenic and sulfidogenic microbial communities in rice paddy soils and lake sediments

Abstract. Acetate is an important intermediate during the degradation of organic matter in anoxic flooded soils and sediments. Acetate is disproportionated to CH4 and CO2 by methanogenic or is oxidized to CO2 by sulfate-reducing microorganisms. These reactions result in carbon isotope fractionation, depending on the microbial species and their particular carbon metabolism. To learn more about the magnitude of the isotopic enrichment factors (ε) involved, acetate conversion to CH4 and CO2 was measured in anoxic paddy soils from Vercelli (Italy) and the International Rice Research Institute (IRRI, the Philippines) and in anoxic lake sediments from the northeastern and the southwestern basins of Lake Fuchskuhle (Germany). Acetate consumption was measured using samples of paddy soil or lake sediment suspended in water or in phosphate buffer (pH 7.0), both in the absence and presence of sulfate (gypsum), and of methyl fluoride (CH3F), an inhibitor of aceticlastic methanogenesis. Under methanogenic conditions, values of εac for acetate consumption were always in a range of −21 ‰ to −17 ‰ but higher in the lake sediment from the southwestern basin (−11 ‰). Under sulfidogenic conditions εac values tended to be slightly lower (−26 ‰ to −19 ‰), especially when aceticlastic methanogenesis was inhibited. Again, εac in the lake sediment of the southwestern basin was higher (−18 ‰ to −14 ‰). Determination of εCH4 from the accumulation of 13C in CH4 resulted in much lower values (−37 ‰ to −27 ‰) than from the depletion of 13C in acetate (−21 ‰ to −17 ‰ ), especially when acetate degradation was measured in buffer suspensions. The microbial communities were characterized by sequencing the bacterial 16S rRNA (ribosomal ribonucleic acid) genes as well as the methanogenic mcrA and sulfidogenic dsrB genes. The microbial communities were quite different between lake sediments and paddy soils but were similar in the sediments of the two lake basins and in the soils from Vercelli and the IRRI, and they were similar after preincubation without and with addition of sulfate (gypsum). The different microbial compositions could hardly serve for the prediction of the magnitude of enrichment factors.

Confinement effects on C–H and C–F stretching vibrational frequencies of difluoromethane in cold inert gas matrixes: a combined infrared spectroscopy and electronic structure theory study

Mid-infrared spectra of difluoromethane (DFM) have been recorded by confining the molecule in the matrix cages of pure argon, nitrogen and in the mixed matrixes of argon and nitrogen obtained by mixing the two gases in definite proportions. The measured spectra depict distinct confinement effects in terms of the infrared spectral shifts of the C–H and C–F stretching vibrational fundamentals as compared to the free molecules in the gas-phase, and also some remarkable changes in band appearances and relative intensities. The signs of the spectral shifts are observed to be different for the $$\upnu _{\text {C--H}}$$ and $$\upnu _{\text {C--F}}$$ transitions. Pronounced blue shifts are observed for the two $$\upnu _{\text {C--H}}$$ modes in pure nitrogen matrix, which progressively reduce in magnitude in the mixed matrixes, and is least in the pure argon matrix. On the other hand, distinct red shifts of the $$\upnu _{\text {C--F}}$$ vibrations are evident in pure nitrogen matrix, which are reduced in magnitude in the mixed matrixes, and become even less pronounced in pure argon matrix. The effect of Fermi resonances in the $$\upnu _{\text {C--H}}$$ region, that has motivated several previous investigations of DFM including high resolution gas phase studies, becomes explicit upon comparison of the matrix isolation spectrum with the gas phase spectrum. Electronic structure calculations using several DFT and DFT-D methods, in conjunction with NBO analysis, have been carried out for various sizes of $$\hbox {DFM-N}_{2}$$ and DFM-Ar complexes in order to understand the underlying interactions responsible for the observed shifts. The calculations are found to satisfactorily reproduce the observed variations in magnitude and direction of the shifts of both the $$\upnu _{\text {C--H}}$$ and $$\upnu _{\text {C--F}}$$ transitions for the change of the medium. It is inferred that the inert gas matrix environment exerts an electronic re-organization within the DFM molecule, and the consequent rehybridization of the carbon-centric hybrid orbital of the C–H and C–F bonds is responsible for the observed spectral shifts.

Volatile Organic Compound from Trichoderma asperelloides TSU1: Impact on Plant Pathogenic Fungi.

Soil microorganisms are well studied for their beneficial effects on plant growth and their impact on biocontrol agents. The production of volatile antifungal compounds emitted from soil fungi is considered to be an effective ability that can be applied in biofumigants in the control of plant diseases. A soil fungus, Trichoderma asperelloides TSU1, was isolated from flamingo flower cultivated soil and identified on the basis of the morphology and molecular analysis of the internal transcribed spacer (ITS), rpb2, and tef1-α genes. To test T. asperelloides TSU1-produced volatile organic compounds (VOCs) with antifungal activity, the sealed plate method was used. The VOCs of T. asperelloides TSU1 inhibited the mycelial growth of fungal pathogens that were recently reported as emerging diseases in Thailand, namely, Corynespora cassiicola, Fusarium incarnatum, Neopestalotiopsis clavispora, N. cubana, and Sclerotium rolfsii, with a percentage inhibition range of 38.88–68.33%. Solid-phase microextraction (SPME) was applied to trap VOCs from T. asperelloides TSU1 and tentatively identify them through gas chromatography–mass spectrometry (GC/MS). A total of 17 compounds were detected in the VOCs of T. asperelloides TSU1, and the dominant compounds were identified as fluoro(trinitro)methane (18.192% peak area) and 2-phenylethanol (9.803% peak area). Interestingly, the commercial 2-phenyethanol showed antifungal activity against fungal pathogens that were similar to the VOCs of T. asperelloides TSU1 by bioassay. On the basis of our study’s results, T. asperelloides TSU1 isolated from soil displayed antifungal abilities via the production of VOCs responsible for restricting pathogen growth.

Mechanochemical synthesis of adsorbents based on silicon oxycarbide composites

In the work, an attempt was made to mechanochemically synthesize silicon oxycarbide composites from activated carbon and silica. Structure of the composites was studied using powder X-ray diffraction and IR spectroscopy. Formation of silicon oxycarbides was confirmed by presence of Si-O-C bond. Influence of the raw materials ratio on structural and chemical properties of resulting composites was revealed. With an increase of silica share in the initial mixture, a decrease in specific surface area and pore volume was noted, as well as an increase of the concentration of surface functional groups. Samples of the composites were tested in processes of sorption of methyl orange and fluoride ions. It was established that adsorption capacity for methyl orange decreased, while that for fluoride ions significantly increased comparing to activated carbon.

Mechanistic study of nucleophilic fluorination for the synthesis of fluorine-18 labeled fluoroform with high molar activity from N-difluoromethyltriazolium triflate.

The synthesis of fluorine-18 labeled fluoroform with high molar activity has grown in importance for the development of fluorine-18 labeled aryl-CF3 radiopharmaceuticals that are useful as diagnostic radiotracers for the powerful technique of positron emission tomography (PET). We designed a strategy of synthesizing fluorine-18 labeled fluoroform from N1-difluoromethyl-N3-methyltriazolium triflate (1) via SN2 fluorination without stable fluorine isotope scrambling. Fluoroform was generated at rt in 10 min by fluorination of the triazolium precursor with TBAF (6 equiv.). We propose three routes (a), (b), and (c) for this fluorination. Quantum chemical calculations have been carried out to elucidate the mechanism of experimentally observed nucleophilic attack of fluoride at difluoromethyl group via route (a), not N3-methyl via route (b). 1H and 19F NMR studies using deuterium source have been performed to examine the competition between SN2 fluorination (route (a)) and the formation of difluorocarbene (route (c)). The observed superiority of SN2 pathway to formation of difluorocarbene in the reaction of the precursor using CsF in (CD3CN/(CD3)3COD (17.8 : 1)) gives the possibility of preparing the fluorine-18 labeled fluoroform in high molar activity.