Fluoroform properties

Goswami and Sarkar3 claimed to have prepared methyl and ethyl fluoroformates by the action of thallium fluoride on the corresponding chloroformates. These fluoroformates were described as powerful lacrimators. We found that no appreciable reaction took place between potassium fluoride and ethyl chloroformate in boiling carbon tetrachloride or nitrobenzene. Ethyl fluoroformate could, however, be readily produced by the action of potassium fluoride on ethyl chloroformate by using the autoclave technique. It was found not to have the lacrimatory properties claimed for it, and was non-toxic in comparison with M.F.A. This non-toxicity was to be expected, as the fluoroformate contains the COF and not the CH2F- group. 

Many solvent properties are related to density and vary with pressure in a SCF. These include the dielectric constant (er), the Hildebrand parameter (S) and n [5], The amount a parameter varies with pressure is different for each substance. So, for example, for scC02, which is very nonpolar, there is very little variation in the dielectric constant with pressure. However, the dielectric constants of both water and fluoroform vary considerably with pressure (Figure 6.3). This variation leads to the concept of tunable solvent parameters. If a property shows a strong pressure dependence, then it is possible to tune the parameter to that required for a particular process simply by altering the pressure [6], This may be useful in selectively extracting natural products or even in varying the chemical potential of reactants and catalysts in a reaction to alter the rate or product distributions of the reaction. 

Fluorodisulfuric acid, salts of, 2 127 Fluoro(fluorosulfuryl) peroxide, 16 138-140 preparation of, 16 138, 139 properties of, 16 139 reactions of, 16 139, 140 Fluoroform, 3 379-380 Fluoroimines, preparation, 33 185 Fluorooximes, reaction with hexafluoroacetone, 30 271... 

Properties Colorless gas. Noncorrosive. Fp -168C, bp -58C, d at bp 8.71 g/L. Nonflammable. Derivation Bromination of fluoroform or perfluoro-propane in nonmetallic reactor. 

Enzyme reactions have been successfully operated in a variety of organic solvents (Table 8.4) as well as in supercritical fluids (e.g., carbon dioxide and fluoroform) and gases. - The latter two categories offer some intriguing possibilities and potential advantages relative to solvents, including enhanced substrate diffusivity, tunable solvent phase properties (via temperature and pressure), reduced solvent... 

There have been many reports on the use of supercritical fluid extraction (SFE) to extract PCBs, phenols, PAHs and other organic compounds from various solid wastes [20,161,162,167-175]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [176, 177]. The supercritical fluids that have been used have low viscosities, high diffusion coefficients and low flammabihties, which are all clearly superior to the organic solvents normally used. Carbon dioxide (COj) [89,90] is the most common supercritical fluid used for SFE, since it is inexpensive and has a low critical temperature (31.3 °C) and pressure (72.2 bar). Other less commonly used fluids include nitrous oxide (N2O), ammonia, fluoroform, methane, pentane, methanol, ethanol, sulfur hexafluoride (SFg) and dichlorofluoromethane [89-91]. Most of these fluids are clearly less attractive as solvents in terms of toxicity or as environmentally benign chemicals. Commercial SFE systems are available, but some workers have also made inexpensive modular systems, as follows ... 

Moreover, Atobe et al. successfully prepared polythiophene nano-brush using template electrochemical polymerization in supercritical fluoroform [12]. In this work, nanoporous alumina membranes (60 pm thick, 200 nm pore size) coated on one side with evaporated Pt (ca. 500 nm thick) were employed as a template electrode for polythiophene electrodeposition into pores. The use of the special properties of the fluids such as higher diffusivity and lower viscosity enabled the effective monomer transport into the porous template and the nanoprecise filling with the polymers. Consequently, the solid polythiophene nano-brush could be obtained after removal of the alumina membrane (Fig. 3). 

Abstract - This work is concerned with the origin of effects on rate equilibrium processes when reactions are performed in dipolar aprotic media such as dimethyl sulfoxide and dimethyl-formamide compared to typical hydroxylic media. An example of processes studied in our laboratory is the competition between proton abstraction and a-complex (Meisenheimer adduct) formation in the interaction of nitroaromatic compounds with basic systems (e.g. 1,3-dinitrobenzene in DMF-D20-Na0D). Other reactions studied are the base catalyzed isotopic exchange of D2 in aqueous DMSO mixtures, and also isotopic exchange of fluoroform. It has been found possible in certain cases to dissect the initial state and transition state contributions to the reaction rates from the kinetically measured enthalpies of activation and the thermodynamically evaluated enthalpies of transfer of the reactants. This procedure affords insight into transition state properties and behaviour. 

At the present time, Freon-23 (trifluoromethane or fluoroform) is considered to be a thoroughly investigated substance (Tables 41 and 42). Meanwhile, information about its thermodynamic properties is absent in the reference books [0.8-0.10]. Review reference [0.34] gives only summaries of articles from journals published up to 1967. 

Several research groups have used pyrene as a fluorescent probe in the study of supercritical fluid properties (2,3,40-48). In particular, the density dependence of the Py scale has been examined systematically in a number of supercritical fluids such as CO2 (2,3,40-43,45,46), ethylene (40,41,47), fluoro-form (3,40,41,43,47), and C02-fluoroform mixtures (43). The Py values obtained in various supercritical fluids correlate well with the polarity or polarizability parameters of the fluids (3,40,41,43,47). For example, Brennecke et al. (40) found that the Py values obtained in fluoroform were consistently larger than those obtained in CO2, which were, in turn, consistently larger than those found in ethylene over the entire density region examined. In addition, the Py values obtained in the liquid-like region (reduced density 1.8) indicate that the local polarity of fluoroform is comparable to that of liquid methanol, CO2 with xylenes, and ethane with simple aliphatic hydrocabons (15,16). 

Unimolecular reactions that have been used to investigate the solvation properties of supercritical fluids include tautomeric reactions (67-71), rotational isomerization reactions (72-78), and radical reactions (79-83). O Shea et al. used the tautomeric equilibrium of 4-(phenylazo)-l-naphthol to examine the solvent strength in supercritical ethane, CO2, and fluoroform and to determine its dependence on density (67). The equilibrium is strongly shifted to the azo tautomer in supercritical ethane and the hydrazone tautomer in supercritical chloroform and... 

These properties are similar to those of germanium tetrafluoride. Aqueous sodium hydroxide reacts at room temperature with the three CFsGeXa compounds to give fluoroform. Similar behavior is shown by perfluoroalkyl derivatives of tin and lead. With cold water the Cp3GeX3 derivatives afford stable clear solutions, although the iodo compound is not immediately miscible. On addition of potassium fluoride solution the novel salt K2[CF3GeF5] is produced, but unlike K[CF3BF3] it is unstable to base. 

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