Fluorine scavengers

One should then consider the fact that the fluorine deficiency can be caused by a fluorine scavenger at high CF4 concentration. 

Reactions of alcohols with sulfur tetrafluoride, because of decomposition and/or polymerization, usually do not give fluorinated products However, in the presence of a hydrogen fluoride scavenger like triethylamine or pyridine, even such sensitive substrates as benzylic alcohols [555], 2-phenylethanol, and 2-furylmethanol [554] can be fluorinated to give the expected fluoro derivatives (equation 73)... 

Many classes of perfluoroethers such as acyclic [63], cyclic [64, 65], glymes [66,67], highly branched [63],macrocyclic [68-73], orthoformates [74-76] and poly-ethers [15, 77], have been succesfully prepared in high yield by direct fluorination techniques (Figs. 19 and 20). Carbon-oxygen bond cleavage is minimised in these processes by the addition of an HF scavenger, such as sodium fluoride, to the reaction mixture [14,45,46]. 

Although the concentration of fluorine is the most important quantity in the control of the reaction rate and must be maintained within certain limits, in practice the stoichiometry, the molecular fluorine to substrate H-atom molar ratio, is used to determine the reaction parameters leading to a successful and efficient perfluorination. AF is most successful when sublimable solids are introduced into the hydrocarbon evaporator unit of the aerosol fluorinator as solutions by a syringe pump. This now common procedure emphasizes the individual molecule s isolation as it is fluorinated using AF. No intermolecular reactions between solute and solvent have been observed Choice of the solvent is important as it must not boil at a temperature below the melting point of the solute in order to prevent solid deposition in the tubes feeding the evaporator. It must also fluorinate to a material easily separable from the solid reactant after perfluorination. In most cases it has been found that aliphatic hydrochlorocarbons are excellent choices, but that carbon tetrachloride and chloroform and other radical-scavenging solvents are not (sec ref 6). 

Fluorination and hydroxylation are observed in reactions with substituted adamantanes 15, while the product distribution and number of products depend on the reaction conditions (with or without the HF scavenger Na2C03).21... 

In effect, the hydrogen serves to scavenge any free fluorine in the plasma, thereby promoting the deposition reaction. 

As discussed above, simple alcohols are not usually fluorinated with sulfur tetrafluoride with good results. For example, the attempted synthesis of 2-(fluoromethyl)furan and l-fluoro-2-phenylethanc from (2-furyl)mcthanol and 2-phcnylethanol at — 50 C in the presence of triethylamine or pyridine as a hydrogen fluoride scavenger gives the desired products in yields of only 20 and 35%, respectively.- ... 

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