Phase equilibria in the binary system lead fluoride [PbF2]-calcium fluoride [CaF2]

The phase diagram of the binary system lead fluoride [PbF₂]-calcium fluoride [CaF₂] was determined over the whole composition range. The investigations were carried out by means of thermal microscopic, X-ray and dilatometric analyses. It was concluded that the components did not form chemical compounds.     

氟离子对TiO2/膨润土光催化降解酸性桃红的影响

研究了在紫外光照射下, 添加氟离子对P25(锐钛矿)和TiO2/膨润土光催化降解酸性桃红(SRB)的影响. 紫外可见光谱测定结果表明无氟的反应体系, pH值越小, 光降解速率越快; pH值固定, 添加氟离子越多, 反应速率越快, 在TiO2/膨润土催化剂上, 当氟离子浓度达到一定程度时, 反应速率不再变化. 在P25和TiO2/膨润土催化剂上, 添加氟离子对H2O2的产生量影响不同, 通过电子顺磁共振(EPR)技术探测到了超氧自由基和羟基自由基, 这两个体系添加氟离子对其产生强度影响不同, 这可能是因为TiO2/膨润土催化剂为层状结构, BET 比表面积较大, 经XRD和TEM测试表明其晶粒直径约为57.9 nm. TiO2/膨润土催化剂连续循环使用11次, 光催化活性基本不变, 这个现象说明TiO2/膨润土催化剂既易于从分散体系中分离出来, 而且其稳定性也好, 它是一个有应用前途的催化剂.     

Synthesis of Boron-containing Complexes of 1-(2-hydroxyphenyl)-3-phenyl-2-propen-1-one

Condensation of o-hydroxyacetophenone with benzaldehyde in alcohol in the presence of a triple excess of a sodium hydroxide solution leads to 2'-hydroxychalcone sodium salt. The latter was heated with boron trifluoride etherate in toluene to a 2'-hydroxychalcone boron fluoride complex in which the boron atom is coordinated to the carbonyl oxygen atom. The same complex was obtained by boiling of the o-hydroxyacetophenone boron fluoride complex with benzaldehyde in acetic anhydride.     

Determination of Fluoride by Alf-MAS in N2O-C2H2 Flame: Application to Toothpaste

A new chemical method for the determination of fluoride in samples with high fluoride content such as toothpaste is reported. It is based on the formation of the AlF molecule in a N₂O-C₂H₂ flame. This radical absorbs radiation at 227.45 nm from a Pt hollow cathode lamp. The developed method is very fast and relatively free from interference and has been applied to determine ionic and covalently bound fluoride in toothpaste.     

Convenient,One-Step Syntheses of 2-Fluoroveratrole And 2-Fluoroveratraldehyde

Metalated veratraldehyde and veratrole were quenched with perchloryl fluoride to provide one-step syntheses of 2-fluoroveratraldehyde and 2-fluoroveratrole, respectively. Previous syntheses of these precursors to 2-fluorodopamine and 5-fluoronorepinephrine are multi-step processess which involve introduction of fluorine at an early stage. Perchloryl fluoride is a potentially hazardous reagent, and should be used only on an appropriate (millimolar) scale with precautions.     

Phase Equilibria in the Binary System Lead Fluoride [PbF2]-Cadmium Fluoride [CdF2]

Phase dependences in the binary system lead fluoride [PbF₂]—cadmium fluoride [CdF₂] were examined and the phase diagram of this system was established. The occurrence of solid continuous solutions with a minimum melting point of 750°C and a CdF₂content of 35 mol% was confirmed. Thermal, dilatometric, microscopic and X-ray analytical methods were used during the investigations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reaction of alkyl 2-chloro-1,1,2-irifluoroethyl ethers with lewis acids

Ethyl 2-chloro-1,1,2-trifluoroethyl ether heated with boron trifluoride etherate gave ethyl fluoride and chlorofluoroacetyl fluoride. When heated with aluminum chloride, it afforded a mixture of ethyl fluoride, ethyl chloride, chlorofluoroacetyl fluoride, and chlorofluoroacetyl chloride. Treatment of the acyl halides with ethanol yielded ethyl chloro- fluoroacetate. Butyl and octyl 2-chloro-1,1,2-trifluoroethyl ethers gave directly butyl and octyl chlorofluoroacetates, respectively, under similar conditions.     

Fluoride ion-mediated nucleophilic fluoroalkylation of alkyl halides with Me3SiCF2SPh: Synthesis of PhSCF2- and CF2H-containing compounds

A facile and highly efficient nucleophilic (phenylthio)difluoromethylation of alkyl halides has been achieved via fluoride ion-mediated substitution reaction using [difluoro(phenylthio)methyl]trimethylsilane (Me₃SiCF₂SPh). The reaction proceeds well with primary alkyl bromides (or alkyl iodides) in DME solvent when CsF/15-crown-5 was used as the fluoride source/additive. The PhSCF₂-containing products can be readily transformed into CF₂H-containing compounds via a free-radical desulfurization method.     

阳极氧化法制备TiO_2纳米管及其光催化性能

纳米TiO_2对诸多环境污染物有显著的光催化降解作用,光催化已发展成为新型环境污染治理技术.本文采用阳极氧化法制备出TiO_2纳米管,对比了四种电解液组成(A氟化铵+硫酸铵+水;B氟化铵+硫酸铵+乙酸+水;C氟化铵+硫酸铵+甘油+水;D氢氟酸+二甲基亚砜(DMOS)+乙醇)对催化剂表面形貌及光催化性能的影响.结果表明,电解液A和C都制备出了形貌清晰的TiO_2纳米管,管径约为60～74 nm.样品经400℃煅烧,TiO_2晶型主要为锐钛矿相;经500℃煅烧,出现少量金红石相;经700℃煅烧,晶型全部为金红石相.具有良好形貌的TiO_2纳米管同时具有良好的紫外光吸收能力.当亚甲基蓝初始浓度为10mg·L~(-1),经500℃煅烧的TiO_2纳米管光催化活性最佳,光照30 min亚甲基蓝的降解率达89.98%.亚甲基蓝光催化降解反应符合一级反应动力学,反应速率常数为0.079 30.     

TBAF-catalyzed cyclization of 6-hydroxyhex-2-ynoates and 7-hydroxyhept-2-ynoates

Tetrabutyl ammonium fluoride(TBAF) was found to be capable of catalyzing the intramolecular hydroalkoxylation of 6- hydroxyhex-2-ynoates and 7-hydroxyhept-2-ynoates.The reaction could be used to prepare 2,5-substituted THF rings and 2,6- substituted THP rings.     

STRUCTURE OF [W(H)_2(F)(OH_2)(PMe_2)_4]F

<正> Mr = 546.3, orthorhombic, space group Cmc21, a = 14.223(4), b = 12.907(3), c = 12.343(4) A, V = 2265.746 A3, Z = 4, DC = 1.601 Mg.m-3, λ= 0.7106 A, μ(MoK(?)) = 56.86 cm-1, F(OOO) = 1048. Final R = 0.044 for 1937 observed reflections. Cation [W(H)2(F)(OH2)(PMes)4]4 has a mirror symmetry, an equatorial belt of four PMe3 groups and mutually syn fluoride and water Ugands. The mean W-P length is 2.462 (A) and P-C 1.83 (A). From the dimensions of the metal, fluoride and water system ( W(1)-F(1) = 2.08(1), W(1)-0(1) - 2.084(9), F(2)-O(1) = 2.59(2) A and F(2)-W(1)-O(1) - 76.7(4)°) an in-terligand hydrogen bond was assumed. The ligand water molecule also makes an H-bonded contact with the fluoride counter ion.     

Fourier transform IR product study of the reaction of CFO radicals with O2 at 298 K

Experimental results are presented of a Fourier transform IR product study at 298 K of the reaction system CFO+O₂ at oxygen pressures between 3 and 250 mbar. Pulsed photolysis of oxalyl fluoride (CFO)₂ or formyl fluoride (CHFO) at 193 nm was used to produce CFO. As stable products we detected bis-fluoroformyl peroxide, carbonyl fluoride and carbon dioxide. The yields of the peroxide and of CF₂O were measured as a function of [O₂]/[precursor] and are discussed qualitatively.     

Synthesis of 2'-C-beta-fluoromethyluridine

[reaction: see text] 2'-C-beta-Fluoromethyluridine (17) represents both a potentially important biological agent and a tool for biochemical analysis. Here we describe the first synthesis of this compound starting from uridine. The key steps include protection of the uracil base with methoxyethoxymethyl (MEM) chloride, conversion to the corresponding 2'-C-alpha-epoxide, and regioselective opening of the oxirane ring with potassium fluoride/hydrogen fluoride. Subsequent acetylation of the 3'- and 5'-hydroxyl groups enables MEM removal using B-bromocatecholborane. Deacetylation generates the parent nucleoside, 2'-C-beta-flurormethyluridine.     

Synthesis of Perfluoro- and 2-Trifluoromethylpentafluorodihydrofurans and Their Epoxy Derivatives

Perfluorotetrahydrofuran-2-carboxylic acid was converted through a series of transformations into perfluoro-2,3-dihydrofuran and perfluoro-2,5-dihydrofuran; likewise, from (2-perfluorotetrahydrofuryl)difluoroacetic acid 2-trifluoromethylpentafluoro-2,3-dihydrofuran was obtained. Perfluoro-2,3-dihydrofuran and 2-trifluoromethylpentafluoro-2,3-dihydrofuran underwent isomerization into perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran by the action of cesium fluoride. Treatment of perfluoro-2,5-dihydrofuran with SbF₅ resulted in ring opening and formation of cis-perfluoro-2-butenoyl fluoride, while 2-trifluoromethylpentafluoro-2,3-dihydrofuran was converted into 2-trifluoromethylpentafluoro-2,5-dihydrofuran under the same conditions. Perfluoro-3,4-epoxytetrahydrofuran and 2-trifluoromethyl-3,4-epoxypentafluorotetrahydrofuran containing fused oxirane and tetrahydrofuran rings were synthesized by reactions of perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran, respectively, with sodium hypochlorite.     

Cascade iodination-fluorination synthesis of 2-fluorothiophene and 5-fluoro-2-thienyliodonium salts

The first synthesis of fluorine-containing 2-thienyliodonium salts was accomplished using cascade iodination-fluorination. According to this methodology, thiophene is first converted to bis(2-thienyl)iodonium hexafluorophosphate using an electrophilic iodination reaction. Upon heating with potassium fluoride, this salt undergoes regioselective fluorination producing 2-fluorothiophene. 2-Fluorothiophene is then iodinated again to yield fluorothienyliodonium salts.     

MgF2 as a non-conventional catalyst support

This review reports progress in the study of the surface structure of MgF₂ and its use as a support of catalytically active phases. Magnesium fluoride was applied first as a support in catalysis for systems containing individual oxides of transition metals (Mo, V, W, Cu, Cr) and then two different oxide phases (Cu-Cr, Cu-Mn), a metal phase (Ru, Pd) or heteropolyacids. Its use as a support enabled determination of the structure and surface properties of these catalysts. The MgF₂-supported catalysts are characterized by high activity and selectivity in such processes as: hydrodechlorination of chlorofluorocarbons (CFCs), hydrodesulfurization of organic compounds and purification of fuel combustion products from nitrogen oxides. Magnesium fluoride has been also used in MgF₂-doped chromium or aluminum fluoride catalysts for Cl/F exchange on hydrochlorocarbons.     

Effects of polyoxometalate and fluoride on adsorption and photocatalytic degradation of organic dye X3B on TiO2: the difference in the production of reactive species

It has been reported that addition of polyoxometalates (POM) or fluoride anions into the TiO(2) dispersions can significantly enhance the photocatalytic degradation (PCD) of weakly adsorptive organic pollutants in water such as chlorophenol. In this work, however, contradictory effects of POM and fluoride were observed on the PCD of highly adsorptive substrate X3B, an anionic organic dye, under similar conditions. The total rate of X3B PCD, determined by total loss of X3B both in solution and on the catalyst surface, was increased in the presence of fluoride, but the rate was decreased in the presence of POM. In both cases, the dark adsorption of X3B on TiO(2) was greatly decreased, ascribed to competitive adsorption of POM or fluoride that reduces the positive charges on the catalyst surface. The spectral analysis and the kinetic study using tert-butyl alcohol as hydroxyl radical scavenger revealed that the PCD of X3B on naked TiO(2) was predominately initiated by direct hole transfer, whereas addition of POM or fluoride into the TiO(2) dispersions enhanced the degradation of X3B via hydroxyl radical pathway. It is proposed that the surface occupation of POM on TiO(2) accelerates the production of surface-bound hydroxyl radicals, due to enhanced charge separation, whereas the fluoride replacement of surface hydroxyl groups of TiO(2) increases the production of free hydroxyl radicals in solution, due to enhanced hole availability for water oxidation. Assume that the relative reactivity among various active follows the order of free hydroxyl radicals > subsurface holes > surface-bound hydroxyl radicals, the proposal could account for the observed effects of POM and fluoride on the PCD of both weakly and highly adsorptive organic substrates over TiO(2) such as chlorophenol and X3B.     

Synthesis and single-crystal X-ray diffraction analysis of 2-sulfamoyladenosine (6-amino-9-β-D-ribofuranosylpurine-2-sulfonamide)

2-Amino-9-β-D-ribofuranosylpurine-2-sulfonamide (2-sulfamoyladenosine, 4 ), a congener of sulfonosine ( 3 ), was synthesized by four different routes. Acid catalyzed fusion of 6-chloropurine-2-sulfonyl fluoride ( 5 ) with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose ( 8 ) gave a good yield of 6-chloro-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine-2-sulfonyl fluoride ( 9 ). Ammonolysis of 9 furnished 4 . Lewis acid catalyzed glycosylation of the trimethylsilyl derivative of either 6-chloropurine-2-sulfonamide ( 6 ) or 6-aminopurine-2-sulfonamide ( 7 ) with 8 gave the corresponding N9-glycosylated products, 10 and 11 , respectively, which on ammonolysis gave 4 . Amination of 2-thioadenosine ( 12 ) with chloramine solution gave the sulfenamide derivative 13 , which on subsequent oxidation with m-chloroperoxybenzoic acid furnished an alternate route to 4 . The structure of 4 was established by single-crystal X-ray diffraction studies. 2-Sulfamoyladenosine ( 4 ) is devoid of significant inhibitory activity against L1210 leukemia in mice.     

Darstellung von [(C2H5)2NH2]3[PS3F]F und [(C2H5)2NH2]3[PS2SeF]F und Kristallstruktur der selenhaltigen Phase

Preparation of [(C₂H₅)₂NH₂]₃[PS₃F]F and [(C₂H₅)₂NH₂]₃ [PS₂SeF]F and Crystal structure of the Phase with Selenium The title compounds were prepared by reaction of diethylammon ium-trithiophosphite with fluoride ions (as diethylammonium fluoride) and sulfur and selenium, respectively. The crystal structure of the selenium containing phase was determined. It does not represent a phosphoranate with a [PS₂SeF₂]^3? anion, but a double salt of [PS₂SeF]^2? with F^?.     

Graphite anode reaction in the KF2HF melt

Effects of traces of water on the graphite anode reaction have been investigated in the KF2HF melt at 100 °C. Cyclic voltammetry shows that with increasing water content from 0.01% to 0.05%, anode potentials for the formation of graphite oxide and graphite fluoride films on graphite electrodes are shifted to lower potentials. This may be ascribed to increase in the reaction of discharged oxygen with graphite and the subsequent decomposition of graphite oxide film by attack of discharged fluorine, which gives ultimately graphite fluoride film on a graphite electrode. When the water content is 0.05 %, the anode effect is thus caused in a short time by graphite fluoride film with a low surface energy. However, when it is 0.01-0.02%, a stage 4 intercalation compound of graphite, C_n⁺HF₂^- was prepared. Addition of 3-6 wt% LiF to the melt gave a stage 3 C_XF(HF)_y without occurrence of anode effect.