Downloads & Free Reading Options - Results

Freon E Series Fluorocarbons - Du Pont 1966

The purpose of this project is to conduct research for the preparation of unsaturated organic com pounds containing F and to prepare various fluoro olefins which may give oil and fuel resistant elastomers which retain elasticity at low temper atures. The reaction of CF2CFCH2Si(CHI and CF2CFSi(CH3)3 II with butadiene was studied. A cyclobutyl derivative was formed from the butenylsilane. Nitrosyl chloride reacted with I to give CF2ClCFNOCH2-CH2Si(CH3)3. I also formed a cyclobutyl dimer on heating. Trifluoroaceto phenone treated with ethylene chlorohydrin gave 2-trifluoromethyl-2-phenyl-1,3-dioxolane. Lithium methylacetylide reacted with a number of fluoroolefins to give compounds containing both double and triple bonds.

The objective of this project was to synthesize and study the chemistry of an array fluorocarbons and fluorocarbon derivatives in order to further understanding of fluorine as substituent in organic chemistry. Target molecules, all of which incorporated conjugation and/or strain, were chosen on the basis of unusual and/or interesting structural features. This investigation has accomplished the synthesis of many new fluorocarbons and derived molecules, and has included exploration of new synthetic methodology in fluorocarbon chemistry, determination of thermodynamic and kinetic parameters for fluorocarbon valence isomerizations, study of negative hyperconjugation, and examination of mechanisms of fluorocarbon reactions. Much has been learned about how to synthesize perfluorinated annulenes and their relatives, and much information has been acquired about potential energy surfaces for fluorocarbon valence isomerizations. A study of rotational barriers in alpha-fluoramines has revealed that negative hyperconjugation can have powerful energetic consequences even in neutral molecules. Insights into fluorocarbon reaction mechanisms, both thermal and photochemical, have emerged from synthetic explorations as well as from explicitly mechanistic studies. Keywords: Fluorocarbons; Organic synthesis; Annulenes; Ring strain; Dynamic NMR; Valence isomers; Negative hyperconjugation; Thermodynamic parameters; Kinetic parameters; Reaction mechanisms.

A study has been made of the reaction of sodium nitrosyl with hexafluorobenzene but no nitroso pentafluorobenzene was formed. Two silanes containing the trifluorovinyl group have been synthesized. One of these, CF2CF(CH2)2Si(CH3)3 has been treated with NOCl but no nitroso compound was formed. Gas-phase additions of NOCl with fluoroolefins has been continued. Trifluoro vinyllithium did not react with hexafluorobenzene to give perfluorostyrene. A study was made of the reaction of perfluoroallyl chloride with mercurous nitrate. Some acryloyl fluoride was obtained but not enough for a practical synthesis. Perfluoroallyl iodide has been coupled to 1,5-perfluorohexadiene via the mercury allyl.

This volume was digitized and made accessible online due to deterioration of the original print copy.

Concern with the effects of fluorides on plants has been devoted to that resulting from dry deposition (mainly with reference to gaseous HF and secondarily with particulate forms). The occurrence of precipitation as rain or mist and the presence of dew or free water on the foliage has mainly been considered with respect to their effects on the accumulation of air-borne fluoride and not with fluoride in wet deposition. That is, precipitation has been viewed primarily with respect to its facilitation of the solution and subsequent absorption of deposits by the foliar tissues or its elution of deposited fluoride from foliage. Accordingly, our evaluation of inorganic fluoride from fluorocarbon degradation rests upon a comparison with what is known about the effects of industrial emissions and what could be considered the natural condition.

Concern with the effects of fluorides on plants has been devoted to that resulting from dry deposition (mainly with reference to gaseous HF and secondarily with particulate forms). The occurrence of precipitation as rain or mist and the presence of dew or free water on the foliage has mainly been considered with respect to their effects on the accumulation of air-borne fluoride and not with fluoride in wet deposition. That is, precipitation has been viewed primarily with respect to its facilitation of the solution and subsequent absorption of deposits by the foliar tissues or its elution of deposited fluoride from foliage. Accordingly, our evaluation of inorganic fluoride from fluorocarbon degradation rests upon a comparison with what is known about the effects of industrial emissions and what could be considered the natural condition.

A study was made to develop the best preparative method for nitroso compounds by adding nitrosyl chloride to a fluoroolefin in the presence of AlCl3 and dimethylformide in solution. The gas phase reaction of nitrosyl chloride with olefins in sunlight was investigated and nitroso compounds were obtained. A number of fluoroalkylnitroso compounds were reacted with butadienes to give oxazines.

The purpose of this project is to conduct the necessary research for the preparation of unsaturated organic compounds containing fluorine and, when synthetic methods have been developed, to prepare various fluoro-olefins which may give elastomers which are oil and fuel resistant and which retain their elasticity at low temperatures. CF2=CH-CF2NO and CF2=CF-CF2NO have been prepared in 24.5% and 34% yield respectively by reacting the corresponding polyfluoroallyl iodide with nitric oxide in the presence of mercury. Polyfluoroallyl chlorides and iodides react with nitrogen dioxide in the presence of mercury to give high yields of the corresponding polyfluoroacrylic acid fluorides.

This grant was issued under the DOD University Research Instrumentation for the purpose of upgrading equipment at the universities in order to perform research in support of National Defense. The instrument acquired was a Jeol FX-90Q(II) Fourier Transform (FT) Multi-Nuclear Magnetic Resonance Spectrometer System with the 'Omni Probe'. The instrument also contains variable temperature observation, internal and external lock systems and computer control of irradiation frequencies.

Journal of Research of the National Bureau of Standards

The current knowledge of atmospheric degradation of hydrogen containing chlorofluorocarbons (HCFC 22 (CHClF2), HCFC 123 (CHCl2CF3), HCFC 124 (CHClFCF3), HCFC 141b (CFCl2CH3), HCFC 142b (CF2ClCH3)) and fluorocarbons (HFC 125 (CHF2CF3), HFC 134a (CH2FCF3), HFC 152a (CHF2CH3)) is assessed. Except for the initiation reaction by OH radicals, there are virtually no experimental data available concerning the subsequent oxidative breakdown of these molecules. However, from an analogy to the degradation mechanisms of simple alkanes, some useful guidelines as to the expected intermediates and final products can be derived. A noteable exception from this analogy, however, appears for the oxi-radicals. Here, halogen substitution induces new reaction types (C-Cl and C-C bond ruptures) which are unknown to the unsubstituted analogues and which modify the nature of the expected carbonyl products. Based on an evaluation of these processes using estimated bond strength data, the following simplified rules with regards to the chlorine content of the HCFC's may be deduced: (1) HCFC's containing one chlorine atom such as 22 and 142b seem to release their chlorine content essentially instantaneous with the initial attack on the parent by OH radicals, and for HCFC 124, such release is apparently prevented; (2) HCFC's such as 123 and 141b with two chlorine atoms are expected to release only one of these instantaneously; and the second chlorine atom may be stored in potentially long-lived carbonyl compounds such as CF3CClO or CClFO.

The current knowledge of atmospheric degradation of hydrogen containing chlorofluorocarbons (HCFC 22 (CHClF2), HCFC 123 (CHCl2CF3), HCFC 124 (CHClFCF3), HCFC 141b (CFCl2CH3), HCFC 142b (CF2ClCH3)) and fluorocarbons (HFC 125 (CHF2CF3), HFC 134a (CH2FCF3), HFC 152a (CHF2CH3)) is assessed. Except for the initiation reaction by OH radicals, there are virtually no experimental data available concerning the subsequent oxidative breakdown of these molecules. However, from an analogy to the degradation mechanisms of simple alkanes, some useful guidelines as to the expected intermediates and final products can be derived. A noteable exception from this analogy, however, appears for the oxi-radicals. Here, halogen substitution induces new reaction types (C-Cl and C-C bond ruptures) which are unknown to the unsubstituted analogues and which modify the nature of the expected carbonyl products. Based on an evaluation of these processes using estimated bond strength data, the following simplified rules with regards to the chlorine content of the HCFC's may be deduced: (1) HCFC's containing one chlorine atom such as 22 and 142b seem to release their chlorine content essentially instantaneous with the initial attack on the parent by OH radicals, and for HCFC 124, such release is apparently prevented; (2) HCFC's such as 123 and 141b with two chlorine atoms are expected to release only one of these instantaneously; and the second chlorine atom may be stored in potentially long-lived carbonyl compounds such as CF3CClO or CClFO.

The ignition characteristics of NF3 were studied with several hydrocarbons and fluorocarbons at various initial pressures and reactant concentrations. All tests were conducted statically in an instrumented high-pressure reaction vessel with the use of either spark or hot-wire ignition sources. Product gases were analyzed in order to determine combustion efficiency. Ignition delay, over-pressures, and temperature rise were determined for each test. The optimum oxidizer/fuel ratio for the most complete reaction of NF3 was determined for mixtures of NF3 and C2H4; NF3 and 1, 3 -C4H6; NF3 and C5H6; and NF3 and C2H2F2. The feasibility of using N2F4 as an injected additive for firing spontaneously spark-ignitable mixtures of NF3 and C2H4 at concentrations of up to 10% N2F4 in helium was investigated with negative results. (Author)

Journal of Research of the National Bureau of Standards

In the present assessment, the hydrogen containing halocarbons being considered as alternatives to the the presently used chlorofluorocarbons are the hydrochlorofluorocarbons (HCFCs) 123 (CF3CHCl2), 141b (CFCl2CH3), 142b (CF2ClCH3), 22 (CHF2Cl) and 124 (CF3CHFCl) and the hydrofluorocarbons (HFCs) 134a (CF3CH2F), 152a (CHF2CH3) and 125 (CF3CHF2). All of these HCFCs and HFCs will react with the hydroxyl (OH) radical in the troposphere, giving rise to haloalkyl radicals which then undergo a complex series of reactions in the troposphere. These reactions of the haloalkyl radicals formed from the initial OH radical reactions with the HCFCs and HFCs under tropospheric conditions are the focus here.

A gas-liquid chromatographic separation of some low molecular weight fluorocarbons is described. The separation has been effected at 0 C with a partially fluorinated acrylate as the liquid phase. As an adjunct to gas-liquid chromatography separation, separations were also carried out by gas-solid chromatography on a silica gel column under programmed temperature conditions.

Possible consequences of stratospheric ozone reduction due to fluorocarbon contamination are evaluated. The fluorocarbon industry, economic factors, and Federal roles in this area are also discussed.

Tropospheric chemical transformations of alternative hydrofluorocarbons (HCF's) and hydrochlorofluorocarbons (HCFC's) are governed by hydroxyl radical initiated oxidation processes, which are likely to be analogous to those known for alkanes and chloroalkanes. A schematic diagram is used to illustrate plausible reaction mechanisms for their atmospheric degradation, where R, R', and R'' denote the F- and/or Cl-substituted alkyl groups derived from HCF's and HCFC's subsequent th the initial H atom abstraction by HO radicals. At present, virtually no kinetic data exist for the majority of these reactions, particularly for those involving RO. Potential degradation intermediates and final products include a large variety of fluorine- and/or chlorine-containing carbonyls, acids, peroxy acids, alcohols, hydrogen peroxides, nitrates and peroxy nitrates, as summarized in the attached table. Probably atmospheric lifetimes of these compounds were also estimated. For some carbonyl and nitrate products shown in this table, there seem to be no significant gas-phase removal mechanisms. Further chemical kinetics and photochemical data are needed to quantitatively assess the atmospheric fate of HCF's and HCFC's, and of the degradation products postulated in this report.

Tropospheric chemical transformations of alternative hydrofluorocarbons (HCF's) and hydrochlorofluorocarbons (HCFC's) are governed by hydroxyl radical initiated oxidation processes, which are likely to be analogous to those known for alkanes and chloroalkanes. A schematic diagram is used to illustrate plausible reaction mechanisms for their atmospheric degradation, where R, R', and R'' denote the F- and/or Cl-substituted alkyl groups derived from HCF's and HCFC's subsequent th the initial H atom abstraction by HO radicals. At present, virtually no kinetic data exist for the majority of these reactions, particularly for those involving RO. Potential degradation intermediates and final products include a large variety of fluorine- and/or chlorine-containing carbonyls, acids, peroxy acids, alcohols, hydrogen peroxides, nitrates and peroxy nitrates, as summarized in the attached table. Probably atmospheric lifetimes of these compounds were also estimated. For some carbonyl and nitrate products shown in this table, there seem to be no significant gas-phase removal mechanisms. Further chemical kinetics and photochemical data are needed to quantitatively assess the atmospheric fate of HCF's and HCFC's, and of the degradation products postulated in this report.

Journal of Research of the National Bureau of Standards

A screening program has been initiated for the purpose of exploring the possibility that the inhalation exposure of rodents to selected halogenated hydrocarbons may affect enzymes of the hepatic smooth endoplasmic reticulum, the so-called microsomal drug-metabolizing enzymes. The materials of interest to the Air Force which have come under investigation include bromotrifluoromethane, trichlorotrifluoroethane, and dibromotetrafluoroethane. Some work with halothane has also been done for comparative purposes.

New, unusual perfluorinated organic molecules have been synthesized and their chemistry has been examined. Reaction mechanisms of fluorocarbon derivatives have been investigated, and new synthetic methodology has been developed. The nature and chemistry of excited states as well as ground states have been explored.... Fluorocarbons, Organofluorine chemistry, Synthesis, Mechanisms, Excited states.

New, unusual perfluorinated organic molecules have been synthesized and their chemistry has been examined. Reaction mechanisms of fluorocarbon derivatives have been investigated, and new synthetic methodology has been developed. The nature and chemistry of excited states as well as ground states have been explored.... Fluorocarbons, Organofluorine chemistry, Synthesis, Mechanisms, Excited states.

While the chlorofuorocarbons (CFCs) such as CFC-11 (CFCl3) and CFC-12 (CF2Cl2) are chemically inert in the troposphere, the hydrogen-containing halocarbons being considered as their replacements can, to a large extent, be removed in the troposphere by the HO radical. These alternative halocarbons include the hydrochlorofluorocarbons (HCFCs) 123 (CF3CHCl2), 141b (CFCl2CH3), 142b (CF2ClCH3), 22 (CHF2Cl), and 124 (CF3CHFCl) and the hydrofluorocarbons (HCFs) 134a (CF3CH2F), 152a (CHF2CH3) and 125 (CF3CHF2). Listed are the rate constants (k) for the HO radical reaction of these compounds and their estimated chemical lifetimes in the troposphere. In this table, values of the lifetimes of these selected HCFCs and HCFs are seen to vary by more than a factor of more than ten ranging from 1.6 years for HFC 152a and HCFC 125 to as long as 28 years for HFC 125. Clearly, from the standpoint of avoiding or minimizing impact on stratospheric O3, those halocarbons with short tropospheric lifetimes are the desirable alternates. However, potential environmental consequences of their degradation in the troposphere should be assessed and taken into account in the selection process.

238 p. 20 cm

The preparation of thermally stable fluoropolymers was investigated using three approaches, each based on the synthesis of a different type of fluorocarbon alkoxide monomer. Two of these alkoxides were prepared by the reaction of potassium fluoride with bis(fluorosulfonate) COMPOUNDS. One alkoxide is extremely stable, whereas the other is formed only as a transient intermediate. Neither polymerized with perfluorocyclobutene. A prototype of the third type of monomer was prepared, but it too failed to react with perfluorocyclobutene. Results indicate that the reactivity of perfluorinated alkoxides is extremely sensitive to structure.

The preparation of thermally stable fluoropolymers was investigated using three approaches, each based on the synthesis of a different type of fluorocarbon alkoxide monomer. Two of these alkoxides were prepared by the reaction of potassium fluoride with bis(fluorosulfonate) COMPOUNDS. One alkoxide is extremely stable, whereas the other is formed only as a transient intermediate. Neither polymerized with perfluorocyclobutene. A prototype of the third type of monomer was prepared, but it too failed to react with perfluorocyclobutene. Results indicate that the reactivity of perfluorinated alkoxides is extremely sensitive to structure.

Equations and computer code are given for the thermodynamic properties of gaseous fluorocarbons in chemical equilibrium. In addition, isentropic equilibrium expansions of two binary mixtures of fluorocarbons and argon are included. The computer code calculates the equilibrium thermodynamic properties and, in some cases, the transport properties for the following fluorocarbons: CCl2F, CCl2F2, CBrF3, CF4, CHCl2F, CHF3, CCL2F-CCl2F, CCLF2-CClF2, CF3-CF3, and C4F8. Equilibrium thermodynamic properties are tabulated for six of the fluorocarbons(CCl3F, CCL2F2, CBrF3, CF4, CF3-CF3, and C4F8) and pressure-enthalpy diagrams are presented for CBrF3.

Equations and computer code are given for the thermodynamic properties of gaseous fluorocarbons in chemical equilibrium. In addition, isentropic equilibrium expansions of two binary mixtures of fluorocarbons and argon are included. The computer code calculates the equilibrium thermodynamic properties and, in some cases, the transport properties for the following fluorocarbons: CCl2F, CCl2F2, CBrF3, CF4, CHCl2F, CHF3, CCL2F-CCl2F, CCLF2-CClF2, CF3-CF3, and C4F8. Equilibrium thermodynamic properties are tabulated for six of the fluorocarbons(CCl3F, CCL2F2, CBrF3, CF4, CF3-CF3, and C4F8) and pressure-enthalpy diagrams are presented for CBrF3.

Equations and computer code are given for the thermodynamic properties of gaseous fluorocarbons in chemical equilibrium. In addition, isentropic equilibrium expansions of two binary mixtures of fluorocarbons and argon are included. The computer code calculates the equilibrium thermodynamic properties and, in some cases, the transport properties for the following fluorocarbons: CCl2F, CCl2F2, CBrF3, CF4, CHCl2F, CHF3, CCL2F-CCl2F, CCLF2-CClF2, CF3-CF3, and C4F8. Equilibrium thermodynamic properties are tabulated for six of the fluorocarbons(CCl3F, CCL2F2, CBrF3, CF4, CF3-CF3, and C4F8) and pressure-enthalpy diagrams are presented for CBrF3.

Solar photolysis is likely to contribute to the stratospheric destruction of those alternative fluorocarbons (HFC's) which have two or more chlorine atoms bonded to the same carbon atom. Two of the eight HFC's considered here fall into this category, namely HFC-123 and HFC141b. For these two species there is good agreement among the various measurements of the ultraviolet cross sections in the wavelength region which is important for atmospheric photodissociation, that is, around 200 nm. There is also good agreement for HFC-124, HFC-22 and HFC-142b. These are the three species which contain one chlorine atom per molecule. The agreement in the measurements is poor for the other species, i.e., those that do not contain chlorine, except in so far as to corroborate that solar photolysis should be negligible relative to destruction by hydroxyl radicals.

Reactions of Xenon fluoride and Trimethyl silyl Nitride at low temperatures gave Trimethyl silyl fluoride and possibly Xenon di nitride as indicated by subsequent decomposition to Xenon and Nitrogen. These reactions were erratic in either solventless of Difluoro dichloro methane solvent systems. Trapping the azide radical from the decomposition with a fluoroolefin was not realized. The interaction of Potassium perchlorate and Trimethyl silicon chloride gave Potassium chloride but the expected Me3SiClO3 was not isolated. It was not possible to duplicate the claimed synthesis of nitryl azide from alkali metal oxides Nitrous boron tetra fluoride. An alternate synthesis of Nitrous nitride from HN3 and FNO2 in anhydrous HF apparently resulted in an equilibrium involving Nitrile Azide and NO2HF2. Pentafluorosulfuroxide containing fluorocarbons were prepared by the addition of SF5OCl to unsymmetrical fluoroethylenes and also by the addition of SF5OF to CFC1 = CFC1. These new compounds were throughly characterized. Numerous unsuccessful attempts were made to dehalogenate SF5OCFClCF2Cl using zinc and other reducing agents in a variety of solvents and without solvent. Perfluorovinyl cadmium iodide was prepared in DMF solvent and reacted with FNO2.

Auburn University Profiles was a weekly radio program produced by Auburn University's Office of University Relations. Each daily program covered a topic of university, local, or national interest. Programs were about 4 1/2 minutes long and featured students, faculty, administrators, visiting scholars and celebrities.

Click here to view the University of Florida catalog record