Fluorine aerosol fluorination

Aerosol-Based Direct Fluorination. A technology that works on Hter and half-Hter quantities has been introduced (40—42). This new aerosol technique, which functions on principles similar to LaMar direct fluorination (Fig. 5), uses fine aerosol particle surfaces rather than copper filings to maintain a high surface area for direct fluorination. The aerosol direct fluorination technique has been shown to be effective for the synthesis of bicycHc perfluorocarbon such as perfluoroadamantane, perfluoroketones, perfluoroethers, and highly branched perfluorocarbons. 

The popularity of aerosols has been declining. A widely used group of propellants, the fluorinated hydrocarbons, have been restricted in use since it was found that they can harm the environment by reducing the o2one layer of the upper atmosphere (see AiRPOLLUTlON ATMOSPHERIC MODELING Ozone). 

In a few cases extensive cleavage of the substrate molecule occurs The case documented [JS] involves beta cleavage of tetramethylorthocarbonate and tri-methylorthoacetate The mechanism of this reaction involves the formation of a radical which can form a more stable radical by eliminating a stable molecule by beta cleavage Interestingly tetramethylorthocarbonate seems to suffer less cleav age by the LTG method [9] Examples of beta cleavage during direct fluorination are shown in equahons 6-9, where AF is aerosol direct fluorination procedure... 

Primary alkyl chlorides are fairly stable to fluorine displacement. When fluorinated, 1-chloropropane is converted to 1-chloroheptafluoropropane and 1-chloto-2-methylbutane produces 39% l-chlorononafluoro-2-methylbutane and 19% perfluoro-2-methylbutane. Secondary and tertiary alkyl chlorides can undergo 1,2-chlorine shifts to afford perfluonnated primary alkyl chlorides 2-Chloro-2-methylpropane gives l-chlorononafluoro-2-methylpropane, and three products are obtained by the fluorination of 3-chloropentane [7] (equation 1). Aerosol fluorina-tion of dichloromethane produces dichlorodifluoromethane which is isolated in 98% purity [4 (equation 2). If the molecule contains only carbon and halogens, the picture is different. Molecular beam analysis has shown that the reaction of fluorine with carbon tetrachlonde, lodotrichloromethane, or bromotrichloromethane proceeds first by abstraction of halogen to form a trichloromethyl radical [5]... 

Aerosol Fluorination of Dimethoxymethane, 111 Fluorination with Cesium Fluoroxysulfate... 

The principal laws for the fluorination of polymeric hydrocarbons are the same as those described above for the simple case. Direct fluorination has been used extensively in organic chemistry (but only since the early 1970s) in low-temperature methods, where the fluorine is strongly diluted with some inert gas (helium, argon, nitrogen, krypton). One can note the La Mar, aerosol-based, and liquid-phase fluorination methods. 

Freon is a commercial trademark for a series of fluorocarbon products used in refrigeration and air-conditioning equipment, as aerosol propellants, blowing agents, fire extinguishing agents, and cleaning fluids and solvents. Many types contain chlorine as well as fluorine, and should be called chlorofluorocarbons (CFCs) [85,86]. 

Aviado DM, Zakheri S, Watanabe T Non-Fluorinated Propellants and Solvents for Aerosols, pp 49-81. Cleveland, OH, CRC Press,... 

HF In die presence of fluorinating agents, such. as antimony tri- and penta-fluorides. Used as aerosol propint, refrigerant and fire extinguisher... 

The Aerosol Fluorination process [42] (Aerosol) is operated on the principle that the substrate is absorbed onto the surface of fine sodium fluoride particles in the fluorination apparatus in which the fluorine concentration and the temperature increases along the length of the reaction vessel. A U.V. photo-fluorination finishing stage completes the perfluorination process which has the advantage that it is a continuous flow method. 

Detailed studies concerning the perfluorination of haloalkanes by the aerosol fluorination technique have recently been conducted by Adcock and co-workers... 

---