Studies on sulfinatodehalogenation XIII. A new sulfinatodehalogenation reagent system: NaHSO3/K3[Fe(CN)6]

The reaction of perfluoroalkyl iodide or perfluoroalkyl bromide with sulfite radical anion (SO₂) generated from sodium bisulfite / potassium ferricyanide in water/ DMF at 70—75°C gave the corresponding perfluoroalkanesulfinate in good yield. Furthermore, it was shown that the reagent system can also initiate the addition of perfluoroalkyl iodide to olefins or alkynes at 50—65°C.     

SO2− and sodium perfluoroalkanesulfinate initiated addition of perfluoroalkyl iodide to olefin

The sulfinatodeiodination reagent Ce⁴⁺ ?NaHSO₃ was shown to be able to initiate the addition of perfluoroalkyl iodides to olefins at 50—70°C to give the corresponding adducts in good yield. Similarly, SO₂^? generated from Fe³⁺?NaHSO₃ system can also initiate the same addition although the reagent is not able to cause sulfinatodeiodination. Furthermore it was shown that sodium perfluoroalkanesulfinate is able to initiate the same addition and there is no exchange between the perfluoroalkyl groups of R'_FSO₂Na and R_FI.     

Reactions of [2-iodo-3-(perfluoroalkyl)propyl]glycidyl ethers with alcohols under basic conditions

On treatment with sodium alkoxides in the corresponding alcohols, [2-iodo-3-(perfluoroalkyl)propyl]glycidyl ethers are converted into 3-alkoxy-1-[3-(perfluoroalkyl)prop-2-enyloxy]-propan-2-ols in 56–78% yields, while its reaction with 2,2,2-trifluoroethanol and phenol under phase transfer conditions (NaOH, CH₂Cl₂-H₂O, Bu₄N⁺I⁻, 35–40 °C) gives 3-alkoxy1-[2-iodo-3-(perfluoroalkyl)propoxy]propan-2-ols (yields 45–72%).     

Syntheses and degradations of fluorinated heterocyclics

Tris (perluoro-n-heptyl)-s-triazine, the perfluoroether substituted-s-triazine [C₃F₇OCF(CF₃)CF₂OCF(CF₃]₃C₃N₃, 1,4-bis[(5-perfluoro-n-heptyl)-1, 2,4-oxadiazolyl]benzene, its perfluoroalky ether substituted analogue, and 3,5-bis(perfluoro-n-heptyl)-1,2,4-oxadiazole were synthesized and characterized. Each of these compounds was subjected to thermal and oxidative degradation at 235 and 325°C and to hydrolytic degradation at 235°C. Two benzene derivatives decomposed completely during heating in nitrogen or air at 325°C, tris(perfluoro-n-heptyl)-s-triazine was quantitatively hydrolyzed at 235°C. The perfluoroalkyl ether substituted triazine and 3,5-bis(perfluoro-n-heptyl)-1,2,4- oxadiazole were found to be stable under all conditions employed as evidenced by practically quantitative recovery of the test samples.     

Etude RMN du 13C de composes fluoroaliphatiques et de tensioactifs non ioniques perfluoroalkyles

Carbon-13 chemical shifts, spin-lattice relaxation times and nuclear Overhauser enhancement factors at 28°C are reported for a series of polyfluoroaliphatic compounds :

, and perfluoroalkyl nonionic surfactants C_mF_2m+1CH₂(OC₂H₄)_nOH with m = 6, 7 and n = 3, 4, 5, 6 and C₆F₁₃CH₂CH₂CONH(C₂H₄O)_nH with n = 3, 4. The influence of the perfluoroalkyl group on the ¹³C chemtcal shifts of the neighbouring hydrogenated carbons is discussed in terms of hyperconjugative type interactions between lone electron pairs on fluorine and the neighbouring CC or CO bond. Relaxation data show similar flexibilities of the fluorinated chains in the different molecules investigated. Nonionic surfactants exhibit segmental motions in both the hydrophobic perfluoroalkyl and the hydrophilic polyoxyethylene chains ; these motions appear to be similar to those of the analogous hydrogenated surfactants.     

Synthesis of Aryl-Manganese(III) Fluoride Complexes via α-Fluorine Elimination from CF3 and Difluorocarbene Generation

We report the synthesis of cyclometalated monoaryl Mn^III fluoro complexes using bis(trifluoromethyl)zinc reagent, Zn(CF₃)₂(DMPU)₂, under mild conditions via a reaction pathway that involves initial transmetalation followed by α-fluorine elimination. The formation of difluorocarbene in these reactions was detected by trapping experiments. Such facile difluorocarbene generation from Mn^III results in moderate enhancement of difluoropropanation and difluoropropenation of alkenes and alkynes using Zn(CF₃)₂(DMPU)₂ at lower temperature (20–60 °C) and short reaction time, suggesting potential application of manganese(III) perfluoroalkyl complexes as reactive species for carbene transfer reactivity.     

Studies on sulfinatodehalogenation: XVII. The sulfinatodehalogenation of primary perfluoroalkyl iodides and bromides by Rongalite

Using acetonitrile or DMF as cosolvent, both perfluoroalkyl iodides such as Cl(CF₂)_nI (n = 4,6,8, la—lc ), CF₃ (CF₂)_n I (n = 5,6,7, ld—lf ), I (CF₂)_n O (CF₂) SO₃ Na(n = 2,4,6, lg—li ) and perfluoroalkyl bromides such as Cl (CF₂)_n Br (n = 4,6, 3a—3b ) and C₇F₁₅ Br (3e) reacted with Rongalite in aqueous solution to give the corresponding sulfinates Cl (CF₂)_n SO₂ Na (n = 4,6,8, 2a—2c ), CF₃-(CF₂)_nSO₂Na (n = 5,6,7, 2d—2f ) and NaO₂S(CF₂)_nO(CF₂)₂SO₃Na (n = 2,4,6, 2g—2i ) in moderate yields. 1 H-perfluoroalkanes were formed as the main products when other solvents such as ethanol. iso-propanol, 1,4-dioxane and morpholine were used.     

Studies on sulfinatodehalogenation XXIV. Further study on sodium dithionite-initiated perfluoroalkylation of electron-rich aromatics

The application of the sulfinatodehalogenation reaction system for the perfluoroalkylation of electron-rich aromatics is further studied. It was shown that perfluoroalkyl iodides reacted with polyhydric phenols, N,N?dialkylanilines, 2,5-dimethylpyrrole, N?methylpyrrole initiated by Na₂S₂O₄?NaHCO₃ gave the corresponding perfluoroalkylated products in moderate to good yields.     

Influence of annealing temperature on the electrochemical and surface properties of the 5-V spinel cathode material LiCr0.2Ni0.4Mn1.4O4 synthesized by a sol–gel technique

LiCr_0.2Ni_0.4Mn_1.4O₄ was synthesized by a sol–gel technique in which tartaric acid was used as oxide precursor. The synthesized powder was annealed at five different temperatures from 600 to 1,000 °C and tested as a 5-V cathode material in Li-ion batteries. The study shows that annealing at higher temperatures resulted in improved electrochemical performance, increased particle size, and a differentiated surface composition. Spinel powders synthesized at 900 °C had initial discharge capacities close to 130 mAh g^?1 at C and C/2 discharge rates. Powders synthesized at 1,000 °C showed capacity retention values higher than 85 % at C/2, C, and 2C rates at 25 °C after 50 cycles. Annealing at 600–800 °C resulted in formation of spinel particles smaller than 200 nm, while almost micron-sized particles were obtained at 900–1,000 °C. Chromium deficiency was detected at the surface of the active materials annealed at low temperatures. The XPS results indicate presence of Cr⁶⁺ impurity when the annealing temperature was not high enough. The study revealed that increased annealing temperature is beneficial for both improved electrochemical performance of LiCr_0.2Ni_0.4Mn_1.4O₄ and for avoiding formation of Cr⁶⁺ impurity on its surface.     

Synthesis and Characterization of Novel Poly(Arylene Ether)s from 4,4′‐Thiodiphenol

Four novel perfluoroalkylated poly(arylene ether)s have been synthesized successfully using four perfluoroalkyl‐activated bisfluoro monomers. These polymers are synthesized through nucleophilic displacement of the fluorine atoms on the benzene ring with 4,4′‐thiodiphenol and are named as 1a, 1b, 1c and 1d, respectively. The polymers obtained by displacement of the fluorine atoms exhibit weight‐average molar masses up to 3.9×10⁴ g · mol^?1 in Gel permeation chromatography. These poly(arylene ether)s showed very high thermal stability up to 548°C for 10% weight loss in TGA under nitrogen and high glass transition temperature (T_g) up to 178°C in DSC depending on the repeat unit structures. The glass transition temperatures taken as peak in tan δ in DMA measurements are in good agreement with the DSC T_g values. All the polymers synthesized are soluble in a wide range of organic solvent such as CHCl₃, CHCl₂, THF, NMP, DMF and toluene. Transparent thin films of these polymers cast from THF exhibited tensile strengths up to 72 MPa, modulus up to 1.69 GPa with low elongation at break depending on their exact repeating unit structures. Rheological properties showed ease of processability of these polymers with no change in melt viscosity with temperature.     

Effect of temperature on O⊘ reactions and equilibria: A pulse radiolysis study

The pK_a of the hydroxyl radical was measured over the 20–80°C temperature range. At 20°C, the pK_a was 11.84 and fell to 10.81 at 80°C. The dissociation constant for the ozonide anion (O⊘₃⇌O₂+O⊘) was found to be 5.5 × 10^-7 mol dm^-3 at 20°C and 46.2 × 10^-7 mol dm^-3 at 70°C. The rate constants and activation energies for the reaction of O⊘ and OH with 2-propanol, methanol and 3-hexene-1,6-dicarboxylate ions have also been measured.     

Fluorination of polyhydrofluoroethylenes. II. Formation of perfluoroalkyl carboxylic acids on the surface region of poly(vinylidene fluoride) film by oxyfluorination,fluorination, and hydrolysis

Oxyfluorination and postfluorination behaviors of poly(vinylidene fluoride) films, as well as hydrolysis of the films treated so far, have been studied by infrared (IR) spectrometry. By exposing the polymer film to a mixture of oxygen and fluorine at about 90°C acyl fluoride groups attendant on the scission of the polymer chains were formed. The oxyfluorinated molecules could be further perfluorinated with fluorine alone at about 90°C, leaving many of the acyl fluoride groups. When the properly oxyfluorinated and postfluorinated film was further treated with a hot 6M sodium hydroxide solution the opaque layer of perfluoroalkyl sodium carboxylate of high molecular weight was formed on the surface of the film, to about 3 μm in thickness, which behaved as a cation exchanger. This new type of cation exchanger of perfluoroalkyl carboxylic acid was significantly more acidic than the usual methacrylic acid exchanger. It was able to adsorb the sodium ions from a neutral sodium chloride solution up to about 70% of the exchange capacity and to keep the ions stable while washing them with water, though it could be regenerated to the hydrogen form with a dilute acetic acid solution. The nature of the new ion exchanger has been examined in some detail by IR spectrometry with Li⁺, Na⁺, and Cs⁺ ions.     

Mercury forms and their transformation in pyrite under weathering

Pyrite is considered to be the major carrier of mercury in coal. Here, the chemical characteristics of two natural pyrite samples of different weathering degrees were characterized by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Thermal stability of Hg was also analyzed via temperature programmed desorption experiment (TPD). Characteristic ions such as S⁻, Fe⁺, FeS⁻, and FeS₂⁻ were detected on the surface of fresh pyrite. The release temperature of Hg ranged between 180°C and 300°C, and the characteristic peak of black HgS was recorded. In addition, abundant Fe₂O₃⁻, FeSO⁻, SO₄⁻, and HSO₄⁻ were detected on the surface of weathered pyrite, and the release temperature of Hg therein was mainly distributed at 260°C to 380°C and 520°C to 600°C, corresponding to the characteristic peaks of red HgS and HgSO₄, respectively. The results show that pyrite is acidified during weathering and that Hg forms in pyrite are transformed from the original state (HgS) to HgSO₄.     

Effect of molten salt synthesis temperature on TiO<Subscript>2</Subscript> and Li cycling properties

In this project, we synthesized TiO₂ compounds through the molten salt method (MSM) using Ti(IV) oxysulfate, as the Ti source. Molten salts in the ratio of 0.375 M LiNO₃:0.180 M NaNO₃:0.445 M KNO₃ were added and heated at temperatures of 145, 280, 380, and 480 °C for 2 h in air, respectively. A part of the sample prepared at 145 °C was further reheated to 850 °C for 2 h in air. X-ray diffraction studies showed that the amorphous phase was obtained when the sample was prepared at 145 °C, and polycrystalline to crystalline anatase phase was formed when heated from 280 to 850 °C, which is complementary to the results of selected area electron diffraction studies. Electrochemical properties were studied using galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy at a current density of 33 mA g^?1 (0.1 C rate) and a scan rate of 0.058 mV s^?1, in the voltage range 1.0–2.8 V vs. Li. Electrochemical cycling profiles for the amorphous TiO₂ samples prepared at 145 °C showed single-phase reaction with a low reversible capacity of 65 mAh g^?1, whereas compounds prepared at 280 °C and above showed a two-phase reaction of Li-poor and Li-rich regions with a reversible capacity of 200 mAh g^?1. TiO₂ produced at 280 °C showed the lowest capacity fading and the lowest impedance value among the investigated samples.     

Study of temperature effect on uni-univalent and uni-bivalent ion exchange reaction

Ion exchange equilibrium constant (K) for Cl⁻/Br⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 30 to 45°C. For both uni-univalent and uni-bivalent exchange systems, the value of K increases with rise in temperature i.e., from 1.16 at 30°C to 2.95 at 45°C for Cl⁻/Br⁻ system and 19.5 at 30°C to 30.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution. The article is published in the original.     

Supramolecular synthons in fluorinated and nitrogen-rich <Emphasis Type="Italic">ortho</Emphasis>-diaminotriazoles

5-Substituted 3,4-diamino-1,2,4-triazoles can be obtained in moderate to good yields in a one-pot reaction starting from a carboxylic acid and dimethylaminoguanidine monohydrochloride in polyphosphoric acid (PPA) at 120 °C. Several triazoles and bistriazoles have been prepared in this way, with substituents ranging from alkyl to aryl, including perfluoroaryl or perfluoroalkyl substituents. The crystal structure analysis of three perfluorinated diaminotriazoles has evidenced a most stable R₂² (8) R_{2}^{2} (8) H bonding synthon, involving the amino CNH₂ donor and the adjacent nitrogen ring acceptor; additionally, two new synthons consisting of chains of rings have been identified. The relevance of the short F⋯F intermolecular contacts found in the structures is also discussed.     

Influence of the Conditions for Preparing LaPO<Subscript>4</Subscript>-Based Materials with Inclusions of the LaP<Subscript>3</Subscript>O<Subscript>9</Subscript> Phase on Their Thermal and Mechanical Properties

A material based on lanthanum orthophosphate LaPO₄ with inclusion of particles of lanthanum metaphosphate LaP³O₉ was synthesized. The influence of the process parameters of the synthesis on the structure and properties of the material was determined. Heat treatment of the coprecipitated lanthanum phosphates at 700°C leads to the formation of a nanopowder with the LaPO₄crystallite size of approximately 17 nm. Heat treatment of the nanopowder at temperatures from 1100 to 1500°C yields compact materials based on the LaPO₄–LaP₃O₉ system. The heat treatment of the nanopowder at 1100°C leads to a sharp decrease in the porosity of the material (to ~5%) at insignificant grain growth (200–400 nm); under these conditions, the thermal conductivity [λ(25°C) = 3.2 W m–1 K^–1], microhardness [Hv(25°C) = 4.6 ± 0.4 GPa], Young’s modulus [E(25°C) = 132 ± 9 GPa], and cracking resistance [K_1c(25°C) = 1.6 ± 0.1 MPa m^1/2] pass through maxima. The thermal expansion coefficient of the material depends on the heat treatment conditions only slightly and amounts to (8.2 ± 0.2) × 10^–6 K^–1.     

Low temperature synthesis of Li5La3Nb2O12 with cubic garnet-type structure by sol–gel process

A cubic Li₅La₃Nb₂O₁₂ phase with a garnet framework was synthesized by the sol–gel process, in which lithium hydroxide, niobium oxide and acetic lanthanum were used as starting materials, while water was used as solvent. Pure garnet-like Li₅La₃Nb₂O₁₂ powders were obtained after heating the gel precursor at 700 °C for 6 h with 10 % excess lithium salt. The calcination temperature is nearly 250 °C lower than that by the solid state reaction. The phase transforms from cubic to tetragonal symmetry with loss of lithium at 717 °C, but the garnet framework remains stable to above 900 °C. A pellet annealed at 900 °C for 6 h had a room-temperature Li⁺-ion conductivity σ_Li (22 °C) = 1.0 × 10^?5 S cm^?1, a little higher than that attained by solid-state synthesis. The Li₅La₃Nb₂O₁₂ compound was chemically stable against two commonly used cathode materials, LiMn₂O₄ and LiCoO₂, up to 900 °C and against metallic lithium.     

Comparative study on uni-univalent and uni-bivalent ion-exchange reaction on Doulite A-116

Determination of ion-exchange equilibrium constant (K) for Cl⁻/I⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 25 to 45°C and by varying concentration of iodide and oxalate ion solution. For both uni-univalent and uni-bivalent exchange systems, using 0.5 g of ion-exchange resin DUOLITE A-116 (in chloride form), the value of K increases with rise in temperature i.e., from 13.0 at 25°C to 19.05 at 45°C for Cl⁻/I⁻ system and 33.0 at 25°C to 63.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion-exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution.     

Electrical Properties of Sm‐doped Ceria (SDC) and SDC Carbonate Composite

This study prepared a dense Sm‐doped ceria (SDC) and an SDC carbonate composite (abbreviated as SDC‐C). The latter was prepared by immersing porous SDC with a formula of (Ce_0.8Sm_0.2)O_1.9 and a relative density of approximately 65‐70% into a molten mixture of carbonates containing 1:1 molar ratio of Li₂CO₃ and Na₂CO₃ at 500 °C. The relative density of the SDC‐C was close to 100%. In addition, SDC oxide without carbonates, which also has a relative density of close to 100%, was heat treated at 1600 °C. At 500 °C, the electrical conductivity and ionic transference number (t_i) of the SDC oxide were 1.79(5) × 10^?3 S·cm^?1 and 0.99(2), respectively, such that electronic conduction could be disregarded. Increasing the temperature caused a gradual decrease in the t_i of SDC. Following the addition of carbonates to SDC, the electrical conductivity reached 1.23(9) × 10^?1 S·cm^?1 at 500 °C. After 14 days (340 h), the electrical conductivity of the SDC‐C at 490 °C, leveled off at about 6 × 10^?2 S·cm^?1. SDC‐C could be used as a potential electrolyte in solid oxide fuel cells (SOFCs) at temperatures below 500 °C.