Comparative study of degradation of <Emphasis Type="Italic">trans</Emphasis>-1,3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene,perfluoro-3-methylbutanone-2, and sulfur hexafluoride in dielectric-barrier discharge

Degradation of gaseous dielectrics after aging in barrier discharge has been experimentally studied and comparative analysis of their properties has been performed. The gases used as gaseous dielectrics have been trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), 2,3,3,3-tetrafluoropropene (HFO-1234yf), perfluoro-3-methylbutanone-2 CF₃C(O)CF(CF₃)₂, and sulfur hexafluoride SF₆. The product composition of gas degradation before and after 5-h aging in the barrier discharge has been determined by gas chromatography–mass spectrometry and gas chromatography. According to the measurement data, 2,3,3,3-tetrafluoropropene is less prone to degradation and has the highest dielectric strength among the test carbon-containing gases.     

HFO-1234yf as a CF3 Building Block: Synthesis of Trifluoromethyl Quinoline and Chromene Derivatives from Trifluoromethyl-ynones

Trifluoromethyl ynones derived from the refrigerant gas HFO-1234yf (2,3,3,3-tetrafluoropropene) react with nucleophiles via a Michael-type addition process and the allenolate intermediate formed reacts intramolecularly with a carbonyl group to form heterocyclic derivatives. Thus, reaction of 2-amino and 2-hydroxyl benzaldehyde or ketone substrates with trifluoromethyl ynone derivatives gives trifluoromethyl quinoline and chromene products by a one-pot tandem ring closing sequence, forming pharmaceutically relevant structures from an inexpensive starting material without the need for transition metals or column chromatography. The 2-trifluoromethylquinoline products also show unusual fluxional behaviour, which was explored through 2-D NMR and X-ray crystallographic studies.     

Pd/AlF3 Catalysts for Catalytic Dehydrofluorination of 1,1,1,3,3-Pentafluoropropane

A series of Pd/AlF₃ catalysts was prepared by an impregnation method and tested for vapor-phase dehydrofluorination of 1,1,1,3,3-pentafluoropropane(HFC-245fa) to synthesize 1,3,3,3-tetrafluoropropene(HFO-1234ze). The highest activity was obtained over Pd/AlF₃ catalyst containing 1.0%(mass fraction) of Pd, with an HFC-245fa conversion of 79.5% and an HFO-1234ze selectivity of 99.4% after the reaction at 300 ℃ for 100 h. The reactivity was related to the surface acidity, as AlF₃ provided active sites for the reaction. With the addition of Pd, the catalyst stability could be significantly improved. Raman spectroscopic and thermal-gravimetric analysis results reveal that there was less carbon deposit on spent Pd/AlF₃ catalyst surface because Pd could effectively pyrolyse it. Thus, Pd/AlF₃ catalysts were bi-functional for dehydrofluorination of HFC-245fa.     

Spherical resonator for vapor-phase speed of sound and measurements of 1,1,1,2,2,3,3-heptafluoro-3-methoxypropane (RE347mcc) and trans-1,3,3,3-tetrafluoropropene [R1234ze(E)]

We describe an apparatus to measure the speed of sound of gas samples at temperatures from (265 to 500) K with pressures up to 10 MPa. The speed of sound was determined from the frequency of the three lowest-order radial resonance modes for the gas in a spherical cavity machined from type 321 stainless steel for corrosion resistance. The spherical resonator was contained in an isothermal copper block that was maintained at the temperature of interest by a multilayer thermostat with vacuum insulation. The dimensions of the spherical cavity were characterized as a function of temperature and pressure though calibration measurements with high-purity argon. The performance of the apparatus was demonstrated with measurements of high-purity methane and ethane. Measurements of the sound speed of 1,1,1,2,2,3,3-heptafluoro-3-methoxypropane (RE347mcc) are reported at temperatures from (325 to 500) K with pressures up to 1.6 MPa. Measurements on trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) are reported at temperatures from (280 to 420) K with pressures up to 2.8 MPa. The average relative combined expanded uncertainties of the measured sound speed for RE347mcc and R1234ze(E) are (0.029 and 0.041)%, respectively.     

2,3,3,3-四氟丙烯的合成研究

本文综述了目前2,3,3,3-四氟丙烯（HFO-1234yf）的合成路线,包括氟-氯交换、脱卤化氢、脱卤、脱卤醇、脱次氯酸乙酰酯、脱水、加氢脱卤、脱氢、高温热解、SF₄参与的氟化反应、脱羧等。其中,以2-氯-3,3,3-三氟丙烯（HCFO-1233xf）为原料的氟-氯交换路线、以1,1,1,2,3-五氟丙烷（HFC-245eb）为原料的脱氟化氢路线和2-氯-1,1,1,2-四氟丙烷（HCFC-244bb）为原料的脱氯化氢路线均具有原料容易合成得到、容易实现气相连续化大规模生产的优势,具有工业化价值。另外,分析对这些路线拥有独立知识产权的氟化工企业现状,提出今后HFO-1234yf领域的研究重点。     

(Vapour + liquid) equilibrium data for the binary system of {trifluoroiodomethane (R13I1) + trans-1, 3, 3, 3-tetrafluoropropene (R1234ze (E))} at various temperatures from (258.150 to 298.150) K

(Vapour + liquid) equilibrium (VLE) data for the binary system of {trifluoroiodomethane (R13I1) + trans-1, 3, 3, 3-tetrafluoropropene (R1234ze (E))} were measured by a static-analytic method within the temperature range of (258.150 to 298.150) K. The experimental data were correlated using the Peng–Robinson equation of state (PR EoS) with the Huron–Vidal (HV) mixing rule involving the NRTL activity coefficient model. The results show good agreement with experimental values for the binary system at each temperature point. The maximum average absolute relative deviation of pressure is 0.28%, while the maximum average absolute deviation of vapour phase mole fraction is 0.0025. Obviously azeotropic behaviour can be found for the measured temperature range here.     

Experimental performance of moderately high temperature heat pump with working fluid R1234ze(Z)

Journal of Thermal Analysis and Calorimetry - Low global warming potential working fluid R1234ze(Z) is anticipated to be the working fluid of the choice for the moderately high temperature heat...     

Defluoroalkylation of sp3 C−F Bonds of Industrially Relevant Hydrofluoroolefins

A simple, one-pot procedure is reported for the selective defluoroalkylation of trifluoromethyl alkene derivatives with aldehydes and ketones. The reaction sequence allows construction of a new C−C bond in a highly selective manner from a single sp³ C−F bond of a CF₃ group in the presence of sp² C−F bonds. The scope incorporates industrially relevant fluorocarbons including HFO-1234yf and HFO-1234ze. No catalyst, additives or transition metals are required, rather the methodology relies on a recently developed boron reagent. Remarkably, the boron site of this reagent plays a dual role in the reaction sequence, being nucleophilic at boron in the C−F cleavage step (S_N2’) but electrophilic at boron en route to the carbon–carbon bond-forming step (S_E2’). The duplicitous behaviour is underpinned by a hydrogen atom migration from boron to the carbon atom of a carbene ligand.     

Potentialities of using liquefied gases as alternative solvents to substitute hexane for the extraction of aromas from fresh and dry natural products

The potential of liquefied gases, n-butane, dimethyl ether, and HFO-1234ze as effective and green alternative solvents to substitute hexane has been evaluated for the extraction of aromatic compounds from dry lavender flowers (Lavandula angustifolia Mill.) and fresh orange peels (Citrus sinensis (L.) Osbeck). The performance of these liquefied gases as solvents has been evaluated in terms of yield, olfactory perception, and composition of the extract and also in terms of energy used, green and economic impacts, and regulatory issues. First, a predictive evaluation of the solvation performance of each solvent was carried out using simulations with the conductor-like screening model for real solvent. Then solid–liquid extractions were performed using liquefied gases at a laboratory scale to determine the extraction yield, the chemical composition, and the olfactory perception of each extract. Finally, the applicability of liquefied gas extractions in an industrial process was assessed, taking into account the potential impact on process, quality, safety, regulation, and environment.     

Liquid viscosity of low-GWP refrigerant mixtures (R32 + R1234yf) and (R125 + R1234yf)

In this work, the viscosity of R1234yf, (R32 + R1234yf), and (R125 + R1234yf) in one-phase liquid was measured. The combined expanded uncertainty of viscosity measurement apparatus of confidence of 0.95 (k = 2) is about 2.0%. The measurements of mixtures containing (30.0, 50.0, and 70.0) wt% R32 or R125 were carried out between T = (283.0 and 323.0) K (at intervals of T = 5 K) and P = (1.58 and 2.74) MPa, with a moving piston viscometer (VISCOpro 1600, accuracy ±1.0%) and a Coriolis flowmeter (Ultramass MKII, accuracy ±0.001 g/ml). The measured data were correlated with a hard-sphere (RSH) method and the Grunberg and Nissan method. The average absolute deviations are (2.2 and 3.3)% for the (R32 + R1234yf) and (R125 + R1234yf) mixtures by RSH method, (2.8 and 1.3)% for the (R32 + R1234yf) and (R125 + R1234yf) mixtures by Grunberg and Nissan method, while (3.5 and 2.4)% for the (R32 + R1234yf) and (R125 + R1234yf) mixtures by RefProp V9.1, respectively.     

Effect of thermostatic expansion valve tuning on the performance enhancement and environmental impact of a mobile air conditioning system

Journal of Thermal Analysis and Calorimetry - In this work, the performance enhancement of a HFO-1234yf mobile air conditioning (MAC) system with a suction/liquid line heat exchanger (SLHX) was...     

Theoretical and experimental studies on the thermal decomposition and fire-extinguishing performance of cis-1,1,1,4,4,4-hexafluoro-2-butene

Due to the environmental problems caused by the existing Halon substitutes, it is essential to explore new extinguishants with better environmental friendliness. In this study, in order to evaluate the practicability of cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(Z)) as a potential Halon substitution product, the thermal decomposition mechanism and fire-extinguishing performance of HFO-1336mzz(Z) were studied by using density functional theory calculation and experimental analysis. The computational results show that thermal decomposition of HFO-1336mzz(Z) would result in some products that can further react with active OH˙ and H˙ radicals, which are indispensable reactants in the flame and combustion. Moreover, during the interaction between HFO-1336mzz(Z) and flame, the fire-extinguishing radical CF₃˙ would be produced, indicating the chemical-extinguishing mechanism and the pronounced fire-extinguishing performance of HFO-1336mzz(Z). To explore its actual fire-extinguishing effect, the fire-extinguishing concentration (FEC) of HFO-1336mzz(Z) on methane-air flame was measured in cup-burner. The FEC value of HFO-1336mzz(Z) is 6.84% in volume, which is lower than those of HFC-125 and HFC-116, and is slightly higher than that of HFC-236fa. Both the experimental and theoretical results suggest that HFO-1336mzz(Z) can be a promising candidate for Halon substitute.     

Nickel-Catalyzed Selective C(sp2)−F Bond Alkylation of Industrially Relevant Hydrofluoroolefin HFO-1234yf

The selective transition-metal catalyzed C−F bond functionalization of inexpensive industrial fluorochemicals represents one of the most attractive approaches to valuable fluorinated compounds. However, the selective C(sp²)−F bond carbofunctionalization of refrigerant hydrofluoroolefins (HFOs) remains challenging. Here, we report a nickel-catalyzed selective C(sp²)−F bond alkylation of HFO-1234yf with alkylzinc reagents. The resulting 2-trifluoromethylalkenes can serve as a versatile synthon for diversified transformations, including the anti-Markovnikov type hydroalkylation and the synthesis of bioactive molecule analogues. Mechanistic studies reveal that lithium salt is essential to promote the oxidative addition of Ni⁰(L_n) to the C−F bond; the less electron-rich N-based ligands, such as bipyridine and pyridine-oxazoline, feature comparable or even higher oxidative addition rates than the electron-rich phosphine ligands; the strong σ-donating phosphine ligands, such as PMe₃, are detrimental to transmetallation, but the less electron-rich and bulky N-based ligands, such as pyridine-oxazoline, facilitate transmetallation and reductive elimination to form the final product.     

Consecutive Transformations of Tetrafluoropropenes: Hydrogermylation and Catalytic C−F Activation Steps at a Lewis Acidic Aluminum Fluoride

Functionalization reactions of the refrigerants HFO‐1234yf (2,3,3,3‐tetrafluoropropene) and HFO‐1234ze (1,3,3,3‐tetrafluoropropene) were developed. The selectivity and reactivity towards CF₃ groups of C−F activation reactions can be controlled by employing either a germane or a silane as the hydrogen source. Unique transformations were designed to accomplish consecutive hydrogermylation and C−F activation steps. This allowed for an unprecedented transformation of an olefinic C−F bond into a C−H bond by heterogeneous catalysis. These reactions are catalyzed by nanoscopic aluminum chlorofluoride (ACF) under very mild conditions.     

C−H and C−F Bond Activation Reactions of Fluorinated Propenes at Rhodium: Distinctive Reactivity of the Refrigerant HFO‐1234yf

The reaction of [Rh(H)(PEt₃)₃] ( 1 ) with the refrigerant HFO‐1234yf (2,3,3,3‐tetrafluoropropene) affords an efficient route to obtain [Rh(F)(PEt₃)₃] ( 3 ) by C?F bond activation. Catalytic hydrodefluorinations were achieved in the presence of the silane HSiPh₃. In the presence of a fluorosilane, 3 provides a C?H bond activation followed by a 1,2‐fluorine shift to produce [Rh{(E)‐C(CF₃)=CHF}(PEt₃)₃] ( 4 ). Similar rearrangements of HFO‐1234yf were observed at [Rh(E)(PEt₃)₃] [E=Bpin ( 6 ), C₇D₇ ( 8 ), Me ( 9 )]. The ability to favor C?H bond activation using 3 and fluorosilane is also demonstrated with 3,3,3‐trifluoropropene. Studies are supported by DFT calculations.     

Defluorosilylation of Industrially Relevant Fluoroolefins Using Nucleophilic Silicon Reagents

A number of new magnesium and lithium silyl reagents were prepared and shown to be outstanding nucleophiles in reactions with industrially relevant fluoroolefins. These reactions result in a net transformation of either sp² or sp³ C?F bonds into C?Si bonds by two modes of nucleophilic attack (S_NV or S_N2′). The methods are mild, proceeding with high chemo‐ and regioselectivity. Mechanistic pathways are described that lead to new substitution patterns from HFO‐1234yf, HFO‐1234ze, and HFO‐1336mzz, previously inaccessible by transition metal catalyzed difluorosilylation routes.     

Electron density distribution in potassium bis -(carbonato)cuprate(II)

The electron density distribution in potassiumbis-(carbonato)cuprate(II) has been analyzed using x-ray diffraction data from an earlier structure determination. While the copper-ligand geometry is close to square planar the deformation density near the metal is strongly asymmetric. There are local maxima near the copper atom along the line of the Cu-K vectors. These resemble features found in corresponding regions in normal length metal-metal bonds. The observation is consistent with the long range nature of the Coulomb potential associated with the potassium ion.     

Modified thermal balance method for estimating minimum inerting concentraion of flammable refrigerant mixtures

R1234yf is considered as a better alternative for R134a (the conventional refrigerant) due to its low global warming potential value, while its usage is limited because of its flammability. The flammability of any flammable refrigerant can be reduced by adding dilutants that are inert. Two methods (group contribution method and thermal balance method) were used to estimate the minimum inerting concentration (which decides the flammability zone) of the binary mixtures (refrigerant?+?dilutant). It was observed that the group contribution method and the thermal balance method predicted minimum inerting concentration of the refrigerant mixture (refrigerant?+?dilutant) with an absolute error of more than 50% and 8%, respectively. Therefore, a modified thermal balance method is proposed in this study to estimate the minimum inerting concentration and found that the proposed method predicts the values with reasonable accuracy when compared with the available experimental data. Further, the minimum inerting concentration for the dilutants R125 and R245fa (that are not experimentally known) with R1234yf is estimated. The results indicated that R227ea has better inert effect with R1234yf when compared to other dilutants (R125, R134a and R245fa) considered in this study. It was also found that the critical inerting concentration for R1234yf is 36.5%.

     

Complexation ofp-xylene withp-isopropylcalix[4]arene: Crystal structures and thermal analysis of the empty form and the (1 : 1) and (2 : 1) complexes

This paper concerns inclusion complexes of thep-isopropylcalix[4]arene host withp-xylene as guest. It is shown that from a saturated solution inp-xylene, the macrocycle gives a 1 : 1 complex; on heating, the 1 : 1 complex is transformed into a 2: 1 complex, and then into the empty macrocycle. The compounds are studied by differential scanning calorimetry, thermogravimetry and X-ray powder diffraction; the three crystal structures are reported showing the arrangements of the macrocycles with and without their guests.Supplementary data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82143 (59 pages).     

Structural and quantum chemical analysis on 4,4′-di(2-hydroxybenzylamino)diphenylmethane

The title compound is analyzed by X-ray diffraction. ONIOM(B3LYP/6-31G(d,p):PM3) is used to investigate the optimized calculation and the frequency analysis of the molecule, in which the PM3 method was used for carbon and hydrogen atoms of the benzene ring and the B3LYP/6-31G(d,p) method was used for the other parts. Energy changes in the molecule are numerically investigated by the flexible scan at PM3 level. The nature of intramolecular interactions that stabilize the structure in vacuo and solid is studied. The results reveal that the molecule is flexible and molecular conformations can easily be mutually transformed through very small potential barriers.