Organic fluorination reactions

Olah GA, Welch IT, Vankar YD et al (1979) Synthetic methods and reactions. 63. Pyridinium poly (hydrogen fluoride) (30% pyridine-70% hydrogen fluoride) a convenient reagent for organic fluorination reactions. J Org Chem 44 3872-3881... 

Organic fluorine compounds were first prepared in the latter part of the nineteenth century. Pioneer work by the Belgian chemist, F. Swarts, led to observations that antimony(Ill) fluoride reacts with organic compounds having activated carbon—chlorine bonds to form the corresponding carbon—fluorine bonds. Preparation of fluorinated compounds was faciUtated by fluorinations with antimony(Ill) fluoride containing antimony(V) haUdes as a reaction catalyst. 

The fluorination reaction is best described as a radical-chain process involving fluorine atoms (19) and hydrogen abstraction as the initiation step. If the molecule contains unsaturation, addition of fluorine also takes place (17). Gomplete fluorination of complex molecules can be conducted using this method (see Fluorine compounds, organic-direct fluorination). 

Thus, for a successful fluorination process involving elemental fluorine, the number of coUisions must be drasticaUy reduced in the initial stages the rate of fluorination must be slow enough to aUow relaxation processes to occur and a heat sink must be provided to remove the reaction heat. Most direct fluorination reactions with organic compounds are performed at or near room temperature unless reaction rates are so fast that excessive fragmentation, charring, or decomposition occurs and a much lower temperature is desirable. 

Many fluorides are corrosive to glass and some metals Even the very corrosive anhydrous fluorides, however, can be handled at room temperature in steel, stainless steel, copper, and Teflon equipment For reactions at higher temperature, nickel and Monel metal are indispensable More data on corrosion of matenals are given in pages 22 and 23 of Chemistry of Organic Fluorine Cowjpoundi, published in 1676... 

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