Preparation of chloropentafluoroethane from dichlorotetrafluoroethane - note 1.

Gaseous fluorination with hydrogen fluoride at atmospheric pressure of the two isomers CClF₂CClF₂ and CCl₂FCF₃ was carried out continuously on a chromic oxide based catalyst. The fluorinated derivative, obtained in a yield greater than 90%, was chloropentafluoroethane. Hexafluoroethane and an isomeric mixture of trichlorotrifluoroethane were obtained as by-products. The latter was recycled with unconverted C₂Cl₂F₄ for further fluorination. Both conversion of C₂Cl₂F₄ and selectivity to the formation of C₂ClF₅ were affected by temperature, contact time and molar ratio of the reagents. The catalytic activity of chromic oxide was adversely affected by small amounts of water in the hydrogen fluoride. A difference was also observed in the reactivity of the two isomersCCl₂FCF₃ and CClF₂OClF₂ The formation of C₂Cl₃F₃ as a by-product was due to the disproportionating activity of chromic oxide upon C₂Cl₂F₄.     

Thermal chlorofluorination of propyne and propadiene II

Propyne and propadiene have been previously reported to readily undergo vapor phase catalyzed chlorofluorination at temperatures to 285 °C to form C₃F₄Cl₄ mixtures that are primarily CFCl₂-CF₂-CFCl₂. Continued fluorination at temperatures up to 485 °C produce the rearranged C₃F₆Cl₂ isomers CF₃-CCl₂-CF₃ and CF₂Cl-CFCl-CF₃.     

Electrochemical fluorination of chlorine-containing amines

The electrochemical fluorination of chlorine-containing alkylamines has been studied. It was found that, in general, the carbon-chlorine bond in the alkylamines is retained during electrochemical fluorination is anhydrous hydrogen fluoride, yielding chlorine-containing polyfluoroalkylamines. Perfluoroalkylamines and fluorocarbons were also produced.By the use of this method, several new chloropolyfluoroamines such as (CF₃)₂NCF₂CClF₂, (C₂F₅)₂NCF₂CClF₂, (CF₃)(C₂F₅)NCF₂CClF₂, (CClF₂CF₂)₂NCF₃, (CClF₂CF₂)₂NC₂F₅, (C₂F₅)(CClF₂CF₂)NF, (CClF₂CF₂)₂NF, (CF₃)₂NCF₂CF₂CClF₂, $\text{CF}{}_2\text{(CF}{}_2\text{)}{}_3\text{N}$CF₂CClF₂, and $\text{CF}{}_2\text{CF}{}_2\text{OC}{}_2\text{F}{}_4\text{N}$CF₂CClF₂ have been isolated and characterized.     

Fluorination of chlorofluoroethanes by hydrogen [18F]-fluoride in the presence of a chromia catalyst

An ¹⁸F tracer study of the fluorination of CCl₂FCClF₂ or C₂Cl₂F₄ isomers by hydrogen fluoride over a chromia catalyst, indicates that a surface fluoride species is involved. The interaction of HF with chromia is substantial, and evidence for three different fluoride species is presented.     

Catalytic Gas‐phase Fluorination of Hexachlorobutadiene to 1,2‐Dichlorotetrafluorocyclobutene over Cr/Zn‐based Catalysts

In this paper, the gas‐phase fluorination of hexachlorobutadiene (HCBD) to synthesize 1,2‐dichlorotetrafluorocyclobutene (DTB) was carried out over a series of Cr/M/Zn catalysts (M = Ni, Co, Cu, In, Al). The influence of prefluorination by different fluorinating agents (HF, 95%HF + 5%Cl₂, 95%HF + 5%O₂, CF₂O, CF₂Cl₂) on catalytic performance of Cr/Co/Zn sample was also investigated. The addition of prompters to the Cr/Zn catalyst improved remarkably its catalytic properties. The Cr/Ni/Zn catalyst exhibited the best catalytic activity (1.318 mmol/h/g) at 390 °C and the Cr/Co/Zn catalyst showed the best DTB selectivity (42.5%) at 350 °C. Compared to that of gaseous HF, the catalytic performance of the Cr/Co/Zn catalyst after treatment by HF + O₂ and CF₂O increased considerably, whereas for HF + Cl₂ and CF₂Cl₂ it showed little effect. In order to identify the different species (Cr─O, Cr─F, CrO _xF _y) present on catalysts’ surface and determine their exact role, these catalysts before and after the reaction were characterized by X‐ray photoelectron spectroscopy. It was found that the concentration of the various species was responsible for the activity and lifetime of catalysts. Moreover, a possible reaction route is proposed based upon the product distribution. The most feasible formation pathway of DTB proceeded via the cyclization of C₄Cl₄F₂ or C₄Cl₃F₃ to yield c‐C₄Cl₄F₂ and c‐C₄Cl₃F₃ followed by further the Cl/F exchange.     

19F NMR analysis of the fluorides of perfluorocyclohexane-sulphonic acid and of 3-trifluoromethylperfluorocyclopentane-1-sulphonic acid

From the electrochemical fluorination of the chloride and the fluoride of benzenesulphonic acid, in addition to the main product C₆F₁₁SO₂F, the side products C₅F₈(CF₃)SO₂F, a structural isomer of the main product and C₆F₁₀Cl? SO₂F are also obtained. The NMR analysis of these products was performed. Chemical shift and coupling constant values were obtained for all the compounds. The NMR parameters of the main product are compared with those of perfluoromethylcyclohexane according to the data of Jolley, Sutcliffe and Walker. From the NMR parameters of C₅F₈(CF₃)SO₂F it was possible to demonstrate that substitution on the ring for —SO₂F and CF₃— is of the 1,3 and not the 1,2 type.     

Preparation of CF3COCl: investigation of operating parameters

The preparation of CF₃COCl through reaction between CF₃CCl₃ and SO₃ was investigated with particular reference to the following operating parameters: catalyst type and concentration, molar ratio C₂Cl₃F₃/SO₃ and composition of the isomeric mixture CF₃CCl₃/CClF₂CCl₂F.Such preparation was first investigated either batchwise or semi-continuously, in order to define at best the above parameters. It was then effected continuously on proper equipment, which allowed to separate the CF₃COCl at a degree of purity adequate to its direct use in the preparation of trifluoroacetic compounds.     

The vertical distribution of halocarbons in the stratosphere

Summary By means of cryogenic sampling and subsequent gas-chromatographic analysis vertical profiles of CCl₄, CCl₃F, CCl₂F₂, CClF₃, CF₄, C₂Cl₃F₃, C₂Cl₂F₄, C₂ClF₅, C₂F₆, CH₃Cl and CH₃CCl₃ were derived for stratospheric heights up to 35 km. Vertical profiles of halocarbons computed by means of one-dimensional and two-dimensional models fall off less rapidly in the stratosphere than the measured profiles, this systematic discrepancy being due to deficiencies in the radiation and transport schemes of present models. It is shown that measured profiles of fully halogenated hydrocarbons provide a tool for systematically studying these deficiencies and thus improving the models. Sources and sinks of halocarbons are discussed, and an assessment of past and future sources of organically bound chlorine in the atmosphere is made.

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Die vertikale Verteilung halogenierter Kohlenwasserstoffe in der stratosphäre

Zusammenfassung Die vertikalen Profile von CCl₄, CCl₃F, CCl₂F₂, CClF₃, CF₄, C₂Cl₃F₃, C₂Cl₂F₄, C₂ClF₅, C₂F₆, CH₃Cl und CH₃CCl₃ wurden für stratosphärische Höhen bis zu 35 km mit Hilfe kryogener Probenahme und anschließender gas-chromatographischer Analyse bestimmt. Die mit Hilfe von ein- und zweidimensionalen Modellen berechneten Profile fallen in der Stratosphäre weniger schnell ab als die gemessenen. Dieser systematische Unterschied ist auf Mängel in den Strahlungs- und Transportmechanismen der gegenwärtigen Modelle zurückzuführen. Es wird gezeigt, daß die gemessenen Profile der vollhalogenisierten Kohlenwasserstoffe dazu dienen können, diese Mängel zu untersuchen und die Modelle zu verbessern. Ursprung und Verbleib der halogenierten Kohlenwasserstoffe werden beschrieben und vergangene und zukünftige Quellen organisch gebundenen Chlors in der Atmosphäre diskutiert.

     

The fluorination of methane and related compounds by copper(II) fluoride and other metal fluorides

Methane reacted with MnF₃ between 350-650°C affording hydrogen fluoride, MnF₂, the fluoromethanes CH₃F, CH₂F₂, CHF₃ and CF₄ and a complex mixture of less volatile fluorocarbons.Methane reacted with FeF₃ between 650-950°C giving the fluoromethenes CH₃F, CH₂F₂ and CHF₃, C₂H₄ and carbon, as well as hydrogen fluoride and FeF₂.A more detailed study of the CuF₂-CH₄ reaction between 600-850°C showed that copper metal, hydrogen fluoride and CH₃F were always obtained, other products including CH₂F₂, CHF₃, CF₄, C₂H₄, C₂H₆, C₂F₆ and carbon. Yields of the fluoromethanes were enhanced by using relatively large amount of CuF₂ and by adding CaF₂ as an inert support. A nearly constant reaction rate occurred at a fixed temperature. Dilution of methane with nitrogen decreased yields of carbon and CH₃F but increased yields of C₂H₄ and C₂H₆.A brief study of the reactions with CuF₂ and some of the CH₄-CuF₂ reaction products was also made. Ethane and ethene both afforded traces of trifluoromethane and relatively large yields of carbon and hydrogen fluoride. That the fluorination of methane to tetrafluoromethane could take place sequentially was demonstrated by reactions with CH₃F, CH₂F₂ and CHF₃. Some pyrolysis of CH₂F₂ and CHF₃ also occurred under the chosen reaction conditions.The CH₄-CuF₂ reaction was made part of a cyclic process in which generation of the CuF₂ in situ from copper metal by successive reaction with oxygen at 400°C and hydrogen fluoride at temperatures rising to 600°C was followed by reaction with methane; 68% coversion to fluorinated products occurred. The cycle was completed by re-conversion of the copper metal residue back to CuF₂ and further reaction with methane when almost identical yields of fluorocarbons and hydrogen fluoride were obtained.     

Pentafluorphenylioddifluorid: alternative Darstellungsmethoden,Molekülstruktur und Eigenschaften

Pentafluorophenyliodine(III) Compounds. 3 Pentafluorophenyliodinedifluoride: Alternative Preparations, Molecular Structure, and Properties The formation of C₆F₅IF₂ ( 1 ) by oxidative fluorination of C₆F₅I ( 2 ) using ClF, CF₃OCl, BrF₅, C₆F₅BrF₂, and C₆F₅BrF₄ is described. Highest purity and yield of 1 was achieved by a modified low temperature fluorination with F₂. Thermolysis of 1 delivered perfluoroiodocyclohexadiene‐1,4 and perfluoroiodocyclohexene besides 2 . X‐ray structural analysis of 1 exhibits the fluoride donor and acceptor ability. 1 is spectroscopically characterized by NMR (¹⁹F, ¹³C), IR and Ra. The influence of the change in the oxidation number of iodine in 2 , 1 and C₆F₅IF₄ ( 3 ) on spectroscopic and structural results will be discussed. Minimum energy geometries and charge distributions are calculated (RHF, LANL2DZ) for 1 , 2 and related compounds.     

Synthesen und Eigenschaften von Tetrakis(perfluoralkyl)tellur Te(Rf)4 (Rf = CF3, C2F5, C2F5, C3F7, C4F9)

Synthesis and Properties of Tetrakis(Perfluoroalkyl)Tellurium Te(R_f)₄ (R_f = CF₃, C₂F₅, C₃F₇, C₄F₉) Te(CF₃)₄ is obtained from the reaction of Te(CF₃)Cl₂ with Cd(CF₃)₂ complexes as a complex with e. g. CH₃CN, DMF. It is a light and temperature sensitive hydrolysable liquid. The reaction with fluorides yields the complex anion [Te(CF₃)₄F]⁻, with fluoride ion acceptors the complex cation [Te(CF₃)₃]⁺. With traces of water an acidic solution is formed. Te(CF₃)₄ acts as a trifluoromethylation reagent. The reaction with XeF₂ gives hints for the formation of Ye(CF₃)₄F₂. Properties and NMR spectra are discussed. The much more stable complexes of Te(R_f)₄ (R_f = C₂F₅, C₃F₇, C₄F₉) are formed from the reaction of TeCl₄ with the corresponding Cd(R_f)₂ complexes.     

Formation of selectivity in molecular isomerization by the IR multiphoton excitation

The formation mechanism of the selectivity of IR laser isomerization induced by vibrational multiphoton excitation is considered. The effective and highly selective isomerization of perfluorodimethyl ketene (CF₃)₂C=C=O into perfluoromethacrylic acid fluoride F₂C=C(CF₃)COF and perfluorocyclobutene into perfluorobutadiene upon pulse irradiation with a CO₂ laser and its second harmonic was performed. The conversion of (CF₃)₂C=C=O into F₂C=C(CF₃)COF was higher than 99%. A record-breaking conversion of 99.8% of the parent substance into the isomer was achieved in the case of perfluorocyclobutene isomerization into perfluorobutadiene. It was shown that the high selectivity of the laser-induced chemical reactions is mainly associated with the different levels of the vibrational excitation of the parent molecules and their isomers. The latter is due to the difference in the IR absorption spectra of different isomers, which allows for the excitation of the necessary component with a high selectivity.     

Die elektrofluorierung von α-chlorethylsulfochlorid

The electrochemical fluorination von CH₃CHClSO₂Cl was studied at different conditions. Besides methane- and ethane- derivates, SO₂F₂ and SF₆, the products formed are the two sulfonylfluorides C₂F₅SO₂F and CF₃CFClSO₂F.The yield of CF₃CFClSO₂F was greater at low temperature, low concentration, and low current density.     

Fluorocyclohexanes. Part XVI. The six H-trifluoromethyldecafluoro- and two of the 2H,4H-trifluoromethylnonafluoro-cyclohexanes

Fluorination of benzotrifluoride by cobaltic fluoride at 260–280° gave, besides the fluorocarbon, the six possible tridecafluoromethylcyclohexane isomers, and two 2H,4H-dodecafluorides. Of the C₇HF₁₃ compounds, only the cis?2H-, and the cis- and trans-4H-isomers could be isolated pure. The two 3H-isomers were made by pyrolysis of perfluoro(1-methyl-3-isopropylcyclohexane) in the presence of toluene. The trans-2H-isomer was made by further fluorination of one of the 2H,4H-dodecafluorides. Aqueous potash and the cis-2H-tridecafluoride gave 1-trifluoromethylnonafluorocyclohex-1-ene, which with stronger alkali hydrolysed to 1-carboxynonafluorocyclohex-1-ene. The cis- and trans- 2H and 4H-tridecafluorides were dehydrofluorinated by sodium fluoride at 320–380° (the cis-isomer of each pair reacted faster than the trans- : axial versus equatorial hydrogen) to give, respectively, the 1-trifluoromethylnonafluoro-ene and the 4-trifluoromethyl-isomer. The latter was isomerised to the former by sodium fluoride at 500–600°. The 1?CF₃-ene gave hexafluoroglutaric acid on oxidation with alkaline potassium permanganate.     

Density Functional Study of Two Seven-Membered Unconventional Fullerenes C58F17CF3 and C58F18

The density functional method is used to study the structure, electronic properties, static linear polarizabilities, and optical absorption spectra of two seven‐membered unconventional fullerene derivatives C₅₈F₁₇CF₃ and C₅₈F₁₈. It is calculated that three sites chosen to locate the CF₃ are isoenergetic. The energy gaps of C₅₈F₁₈ and C₅₈F₁₇CF₃ are much larger than that of C₅₈, indicating the fluorination and trifluoromethylation of C₅₈ can remarkably enhance the kinetic stability. The density of states explore that the influence of CF₃ to the energy levels is mainly distributed in the energy range from ?10 to ?2 eV. However, when the CF₃ substitutes for F in C₅₈F₁₈, the bond lengths, energy gaps, static linear polarizabilities, and optical absorption spectra all show small variety.     

Preparation and properties of perfluorochloromethyl-mercaptophosphoryldichlorides and -chlorophosphanes

In Arbuzov-type reactions CF_nCl_3?nSCl reacts with ROPCl₂ (R = CH₃, C₂H₅) to give CF_nCl_3?nSP(O)Cl₂ (n = 3,2,1,0). The corresponding reaction with CF₃SeX (X = Cl, Br) produces CF₃SeP(O)Cl₂ in good yields only in the presence of catalysts such as SbCl₅ or BCl₃. Reactions between P₄ and the sulfenylchlorides produce (CF_nCl_3?nS)_xPCl_3?n (n = 3,2,1 and x = 1,2). On heating CF_n′ Cl_3?n′ SP(O)Cl₂ (n′ = 2,1,0) decompose to P(O)Cl₃ and SCF_n′ Cl_2?n′. During this process fluorination of P(O)Cl₃ to P(O)F₃ by SCF₂ is observed. A Cl/Br exchange between CF_nCl_3?nSP(O)Cl₂ (n = 3,2) and PBr₃ was proved ¹⁹F? and ³¹P-NMR-spectroscopically.Chemical and physical properties of the newly synthesized compounds will be discussed.     

Fluoration de telomeres polyhalogenes par le fluorure de potassium: synthese d'olefines perfluorees

Action of potassium fluoride on chlorofluorinated telomers of general formula Cl-(CFCl-CF₂)_n-CCl₃ leads to a mixture of perfluorinated cis isomers of internal olefins with the more substitued isomer being preponderant. The influence of temperature and solvant has also been studied. Only reactions carried out in tetramethylene sulfone or preferably in dimethylsulfoxide lead to perfluorinated alkenes. We suggest a mechanism with elimination followed by fluorination.     

Synthesis of Tris‐ and Tetrakis(pentafluoroethyl)silanes

The synthesis and complete characterization of functional, highly Lewis acidic tris(pentafluoroethyl)silanes as well as tetrakis(perfluoroalkyl)silanes Si(C₂F₅)₄ and Si(C₂F₅)₃CF₃ by direct fluorination is described. The reaction of SiCl₄ with LiC₂F₅ invariably affords (pentafluoroethyl)fluorosilicates. To avoid silicate formation by fluoride transfer from LiC₂F₅ the Lewis acidity of the silane has to be decreased by electron‐donating substituents, such as dialkylamino groups. The easily accessible Si(C₂F₅)₃NEt₂ is a valuable precursor for a series of tris(pentafluoroethyl)silanes.     

Hydrogenolysis of dichlorotetrafluoroethane isomeric mixtures for obtaining 1.1.1.2 - tetrafluoroethane

1.1.1.2 - Tetrafluoroethane was prepared from isomeric mixture of dichlorotetrafluoroethanes through selective hydrogenolysis of CF₃  CCl₂F catalyzed by Pd/C. The other isomer CClF₂  CClF₂ appeared more stable to hydrogenolysis and at most it was converted at a low degree to the monohydrogenated derivative CHF₂CClF₂.Influence of the three meaningful operating parameters was definided on the basis of a statistical testing program.The mathematical elaboration of the experimental data allowed to define some relations, by which it is possible to foresee conversion of CF₃CCl₂F, yield in CF₃CH₂F end concentration of reaction products, such as CF₃CH₃, CF₃CH₂F, CF₃ CHClF end CClF₂CHF₂ versus the above reported operating parameters.     

Reaktion von Lanthanfluorid mit Halogenalkanen

Reactions of Lanthanum Fluoride with Halogenoalkanes Reactions are reported on lanthanum fluoride as a fluorinating reagent and as a catalyst for the fluorination and dismutation of halogenoalkanes. Carbon tetrachloride, monofluorotrichlormethane, and chloroform are partially fluorinated by lanthanum fluoride. In the presence of HF, lanthanum fluoride acts as catalyst the fluorine transfer to CCl₄, CHCl₃ and C₂F₃Cl₃. Monofluorotrichloromethane, difluorodichloromethane, and trifluorotrichloroethane dismutate on lanthanum fluoride. Results on the thermal decomposition of the above-mentioned fluorochloroalkanes are communicated.