1.2- Dichlorofluoromethane

Pyrolytic routes to hexafluorobenzene have also attracted attention but have not been commercialized. Pyrolysis of tribromofluoromethane [353-54-8] CBr F, at 630—640°C in a platinum tube gives hexafluorobenzene in 55% yield (251—253). The principal disadvantage of this process is the low weight yield of product 90% of the costly CBr F that is charged is lost as bromine. Of economic potential is the related copyrolysis of dichlorofluoromethane [754-34-0] and chlorofluoromethane [593-70-4] (254,255). 

Condensatron between lithium acetylides and dibromodifluoromethane [124] or dichlorofluoromethane [125] leads to fluorohaloacetylenes (equation 107) Sodium alkyl malonates are also alkylated by dihalogenodifluoromethanes [124] (equation 108) These reactions involve difluorocarbene as intermediate (for the mechanism of the Cp2Br2 condensation, see equation 15)... 

ChLorofluorocarbene generated by the thermal decomposition of dichlorofluoro-methylphenylmercury reacts with 2,3-dimethylindole to give 3-fluoro-2,4-di-methylquinoline, 3-chloro-2,4-dimethylqumoline and 3-(chlorofluoromethyl)-2,3-dimethylindole [f] (equation 1). Similar results are obtained when the chloro-fluorocarbene is generated from dichlorofluoromethane by base-catalyzed de-hydrohalogenation using a phase-transfer catalyst in an aqueous-organic solvent system [21 (equation 1). 

In the context of Scheme 11-1 we are also interested to know whether the variation of K observed with 18-, 21-, and 24-membered crown ethers is due to changes in the complexation rate (k ), the decomplexation rate (k- ), or both. Krane and Skjetne (1980) carried out dynamic 13C NMR studies of complexes of the 4-toluenediazo-nium ion with 18-crown-6, 21-crown-7, and 24-crown-8 in dichlorofluoromethane. They determined the decomplexation rate (k- ) and the free energy of activation for decomplexation (AG i). From the values of k i obtained by Krane and Skjetne and the equilibrium constants K of Nakazumi et al. (1983), k can be calculated. The results show that the complexation rate (kx) does not change much with the size of the macrocycle, that it is most likely diffusion-controlled, and that the large equilibrium constant K of 21-crown-7 is due to the decomplexation rate constant k i being lower than those for the 18- and 24-membered crown ethers. Izatt et al. (1991) published a comprehensive review of K, k, and k data for crown ethers and related hosts with metal cations, ammonium ions, diazonium ions, and related guest compounds. 

COMPOUND NAME CHLORODIFLUOROMETHANE DICHLOROFLUOROMETHANE CHLOROFORM HYDROGEN CYANIDE DIBROMOMETHANE DICHLOROMETHANE FORMALDEHYDE FORMIC ACID METHYL BROMIDE METHYL CHLORIDE METHYL FLUORIDE METHYL IODIDE NITROMETHANE METHANE METHANOL METHYL MERCAPTAN METHYL AMINE METHYL HYDRAZINE METHYL SILANE... 

Some of the fluorinated hydrocarbons—e.g., trifluoromethane 44), 1,1-difluoroethane 45), and difluorodichloromethane 82)—are known to be chemically inactive and physiologically inert. Stepwise replacement of the chlorine atoms in chloroform by fluorine yields the dichlorofluoromethane and chlorodifluoromethane, neither of which is as toxic as the original substance (7). 

Dichloroethyl ether Dichlorofluoromethane Dichloromethane, see Methylene chloride 1,1 -Dichloro-1 -nitroethane 2,2 -Dichioro-4,4 -niethyiene dianiline... 

Trichlorofluoromethane and dichlorofluoromethane have been determined in seawater using headspace analysis and gas chromatography with electron capture detection [226]. 

Dichloroethylene cis-1,2-Dichloroethylene trans-1,2-Dichloroethylene Dichlorofluoromethane (Freon 21) Dichloromethane... 

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel [379]. Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments [362, 363, 380-389]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [390]. Supercritical fluids, which have been used, have low viscosities, high diffusion coefficients, and low flammabilities, which are all clearly superior to the organic solvents normally used. Carbon dioxide (C02, [362,363]) 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 (N20), ammonia, fluoro-form, methane, pentane, methanol, ethanol, sulfur hexafluoride (SF6), and dichlorofluoromethane [362, 363, 391]. 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 [390]. 

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