Perfluorocarbon/amine

In the Liquid-Phase Photofluorination [39,44] process the reactant is injected at a very slow constant rate into an inert fluorocarbon solvent which is saturated by fluorine and under U.V. irradiation. Conditions are chosen to ensure that the concentration of fluorine and fluorine radicals is always much higher than the concentration of the substrate. This method is only suitable for the perfluorination of substrates, such as partially fluorinated ethers (see Section 2.5) and amines (see Section 2.7), that are both soluble in perfluorocarbon solvents and can withstand such vigorous reaction conditions. 

Conversely, fluorine or fluorocarbon groups have a major effect in reducing the base strength of amines, ethers and carbonyl compounds for example, 2,2,2-trifluoroethylamine (pKb = 3.3) is ca. 10 times less basic than ethylamine. Also, pentafluoropyridine is only protonated in strong acid [6], whereas hexafluoroacetone is not protonated even in superacids [7-9] and perfluorinated tertiary amines and ethers are sufficiently non-basic for them to be used as inert fluids interchangeably with perfluorocarbons. 

Building on related work in C-H bond activation chemistry [42], Crabtree and Burdeniuc [41] have discovered two metal based photochemical systems which are useful for the functionalization of perfluorocarbons. Under Hg photosensitization, saturated perfluorocarbons react with ammonia to afford amine, imine and cyano-derivatives [41] (Scheme 5). 

Their pronounced ability to dissolve molecular oxygen in combination with their non-toxicity and complete physiological inertness makes perfluorocarbon fluids attractive for applications as respiratory fluids and as components of artificial blood substitutes [102] (Scheme 4.44). Many perfluorocarbons and perfluorinated amines can dissolve up to 40-50% v/v oxygen at 1 atm and 37 °C. It has been speculated that this unusual oxygen-dissolving capacity is related to the molecular shape and the occurrence of "cavities in perfluorocarbon fluids [103]. 

Although perfluorocarbon sulfonic acid groups are very stable chemically as well as thermally, perfluorocarbon sulfonyl halide, especially sulfonyl chloride groups, are quite reactive. For example, sulfonyl chloride groups react with oxidants, reductants, various amines, phenol compounds, iodine compounds, etc. and give carboxylic acid, sulfinic acid, sulfonic acid amide, -CF2I and so forth. Some examples of how this feature can be used to generate various kinds of membranes will next be described... 

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