Fluorin , reaction with organic compounds

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. 

The halogen fluorides are binary compounds of bromine, chlorine, and iodine with fluorine. Of the eight known compounds, only bromine trifluoride, chlorine trifluoride, and iodine pentafluoride have been of commercial importance. Properties and appHcations have been reviewed (1 7) as have the reactions with organic compounds (8). Reviews covering the methods of preparation, properties, and analytical chemistry of the halogen fluorides are also available (9). 

However, the proponents of the Radical Mechanism would argue that, whatever the actual agent, the fact remains that the process provides a means of generating fluorine at a rate, and in a form which is conducive to controlled reaction with organic compounds, probably constrained on a favourable, possibly catalytic [189] heat-sink surface, in such a way as to overcome the two principal problems inherent in all elemental fluorinations [190], namely... 

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. 

Moissan, and others after him, made no progress in this area and only after 1930 were smooth reactions of elemental fluorine with organic compounds realized by careful control of conditions. Good mixing and dissipation of the heat evolved were vital. There are reviews (see e.g., refs 9, 29, 38-40) listing these advances highlights are noted below, in chronological order. 

Reactions of sulfur tetrafluoride with organic compounds proceeding with substitution of hydrogen by fluorine are considered anomalous, but there are increasing numbers of reports describing such reactions. The classic example is anthracen-9(10//)-onc which on treatment with sulfur tetrafluoride and hydrogen fluoride, instead of the expected 9,9-difluoro-9,10-di-... 

Similar insertion reactions are known with organic compounds. For example, the reaction with methyl fluoride yields fluorinated methylpolysilanes18 ... 

The reactions of halogen fluorides with organic compounds have been reviewed [174, 175] but their usefulness for the preparation of highly fluorinated substrates is limited to reactions with the corresponding perhalo-organic compounds [176] (Figure 2.28). 

Fluorine attacks all organic compounds except CF4. The inorganic compounds that react with fluorine include many, such as asbestos, that are relatively stable to the other halogens. Reaction with water often leads even to explosions. Metals react with fluorine at room temperature some form an impermeable fluorine layer on the surface which protects them against further corrosion, in particular Monel metal, nickel, aluminum, magnesium, iron, and steel. Glass is not attacked by fluorine if it is free from HF and dry. 

Meshri DT, Hage DB (1999) Fluorine reactions with structured carbon. In Houben-Weyl (ed) methods in organic chemistry, vol ElO. organo-fluorine compounds, 4th edn. Thieme Medical... 

The introduction of a fluorine atom to bioactive compounds can modify their activity, so much effort has been invested in the development of selective fluorination reactions. Many bioactive compounds that have double bonds are known, and their analogs, which have a fluorine atom at their double bond, have been attracting the attention of biochemists and organic chemists [ 1 -4-]. In order to induce an effect on the activity of bioactive compounds, a fluorine atom must be introduced to the desired position at the double bond with the correct stereochemistry. The stereoselective synthesis of fluoroalkene is therefore important. There have been articles written recently that concern fluoroalkene synthesis [5-7] so I would like to introduce the recent development in the stereoselective synthesis of mono-fluorinated alkenes. 

Volume II of Organic Reac tions an annual series that reviews reactions of interest to organic chemists contains the statement Most organic compounds burn or explode when brought in contact with fluorine... 

---