REACTIONS OF FLUORINE COMPOUNDS

Kinetic experiments involving chemical reactions of inorganic fluorine compounds with other inorganic non-metallic species are difficult to perform since they generally involve extremely reactive fluorine atoms or fluorine containing species or at the opposite extreme involve exceptionally stable and unreactive fluorine compounds. As a result, the reactions are very rapid or very slow. Frequently, heterogeneous phenomena preclude any determination of homogeneous rate coefficients. As a result very few kinetic data are available on this type of fluorine system. 

The fluorination of hydrogen-methane mixtures in both inconel and fused silica reaction vessels has been studied by Mercer and Pritchard They noted rather severe complications from surface interactions but were able to evaluate the rate coefficient ratio k jk = 2.4 0.2 for 

Clark and Tedder have studied the fluorination of carbon tetrachloride by flowing together F2 and CCI4, both diluted in nitrogen. FCl was converted to HF and HCl followed by titration of fluoride and spectrophotometric determination of the chloride. Experiments at 20 °C are interpreted in terms of the mechanism 

The low overall activation energy of this reaction renders it considerably different from the reaction of NO with Brj or CI2 where the low temperature rate is dominated by a termolecular mechanism. 

Theoretical analysis of models of transition states in bimolecular and termolecular reactions of NO with F2 indicates that the termolecular rate would be eight orders of magnitude lower than the observed rate even if the activation energy of the termolecular reaction were zero. The bimolecular model yields a pre-exponential factor which is in agreement with the experimental results. Therefore, the reaction between NO and F2 is bimolecular even at dry-ice temperatures. 

---

Elimination reactions of fluorine compounds are not limited to the removal of simple molecules Frequently, large molecules or combination of smaller ones are formed as by-products, especially in pyrolytic reactions For example perhalo genated acid chlorides lose not only carbon monoxide but also chlorine fluoride [106, 107] (equations 74 and 75)... 

Those Concerned Mainly with the Reactions of Fluorinated Compounds... 

Some Transition Metal-Catalyzed Reactions of Fluorine Compounds ... 

Some of the fluorinated compounds possess unique properties. Although most reactions of fluorine compounds resemble those of chlorine, bromine, and iodine, in many cases fluorinated compounds show peculiar dissimilarities. Such dissimilarities are the subject of this volume. 

Very little quantitative data on other hydrogen-halogen systems is available. The H2-F2 reaction is discussed in section 7 (Reactions of fluorine compounds) and the only other quantitative data on these systems is for the H2-ICI reaction. 

A number of detailed kinetic studies on the thermal reactions of fluorine compounds has been made in recent years by Atkinson and associates " at the Imperial College of Science and Technology, London. The static method has been largely used, with nickel, stainless steel, and occasionally, pyrex glass reaction vessels suitably aged after several decompositions of the fluorine compound. Glass vessels are attacked by fluorine compounds at high temperatures presumably with the formation of carbon monoxide and silicon fluoride -... 

One of the best-known thermal reactions of fluorine compounds is the pyrolysis of chlorodifluoromethane to tetrafluoroethylene as used in the production of Teflon polymer. This reaction was described by Park et in 1947, and Nor-ton" in 1957 reported an activation energy of 49 kcal.mole for the decomposition over silica at 425-525 °C. More recently, Gozzo and Patrick have made a kinetic study of the process using a helium flow system at 670-750 °C with a surface conditioned platinum tubular reactor. HCl is found to retard the raction and the following mechanism has been proposed... 

The halogen fluorides are best prepared by the reaction of fluorine with the corresponding halogen. These compounds are powerful oxidising agents chlorine trifluoride approaches the reactivity of fluorine. In descending order of reactivity the halogen fluorides are chlorine pentafluoride [13637-63-3] 1 5 chlorine trifluoride [7790-91-2] 3 bromine pentafluoride [7789-30-2], BrF iodine heptafluoride [16921 -96-3], chlorine... 

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 Preparation and Reactions of Fluoromethyleiies Fluorinated Isocyanates and Their Denvatives as Intermediates for Biologically Active Stibsianccs (Ccr) Radical Reactions of Polyfliioroaromatic Compounds (Russ )... 

Some Peculianties of Radical Reactions of Polyfluoroaromatic Compounds Kobnna, L S J Fluorine Chem 42, 301-344 73 o 5... 

Kinetics of Nucleophilic Substitution Reactions of Polyfluoroaromatic Compounds Rodionov, P P, Furin, G G J Fluorine Chem 47. 361 34 105 ... 

Hypochlorites- are obtained by reaction of fluorinated carbonyl compounds, such as carbonyl lluonde, with an alkali metal fluoride and chlorine fluoride f62, 720]... 

Reactions of polyhydroxyl compounds such as carbohydrates with DAST lead to replacement of one or two hydroxyl groups by fluorine, more fluorine atoms are not introduced even when a large excess of the reagent is used [132, 139, 147] Although diethylaminosulfur tnfluonde (DAST) is the most popular, other dialkylaminosulfuranes, such as diisopropylamino- [95] pyrrolidino [95 109 /27], dimethylamino- [148], piperidino- [148] and particularly morpholinosulfur trifluonde [148,149, ISO], are also used as fluonnating agents to convert alcohols into fluorides... 

Rate constants have been measured for the reactions of boron compounds with a series of bromomethanes and bromofluoromethanes. Previously it was shown that the reactivity of the chlorine in chlorofluoromethane is substantially reduced by increasing fluorine substitution. The corresponding decrease in the reactivity of bromolluoromethane u as not observed [ifS]. 

Londry KL, PM Fedorak (1993) Use of fluorinated compounds to detect aromatic metabolites from m-cresol in a methanogenic consortium evidence for a demethylation reaction. Appl Environ Microbiol 59 2229-2238. 

Fusion of fluorinated compounds with sodium for qualitative analysis requires a high temperature for reaction because of their unreactivity. When reaction does occur, there is often an explosion and precautions must be taken. 

Bekiaris et al. have studied the reaction of fluorinated pentane-2,4-diones and phosphanes and have reported the formation of bicyclic compounds and phosphaadamantanes <1997CB1547>. Compounds 167 and 168 were formed in a diasteroselective manner (Scheme 13) and their structures were determined by single crystal X-ray structure analysis. 

The metathesis reaction of fluorinated alkyl iodides with reagents such as CdMe2 is a well-established procedure for the synthesis of fluoroalkyl cadmium derivatives. A recent application of this method has allowed for the synthesis of compound 186, as shown in Scheme 22.248 This reaction is accompanied by formation of 187, which results from the insertion of the difluorocarbene in the methyl-cadmium bond. Presumably, the difluorocarbene is generated by a radicalar process involving HCF2I and CdMe2. 

This section focuses on the preparation of fluorinated compounds through asymmetric hydrogenation/reduction reactions and nucleophilic additions by listing some examples. The first successful example of catalytic asymmetric hydrogenation of a fluoro-compound was reported by Konig et al.81... 

In contrast to the cathodic reduction of organic tellurium compounds, few studies on their anodic oxidation have been performed. No paper has reported on the electrolytic reactions of fluorinated tellurides up to date, which is probably due to the difficulty of the preparation of the partially fluorinated tellurides as starting material. Quite recently, Fuchigami et al. have investigated the anodic behavior of 2,2,2-trifluoroethyl and difluoroethyl phenyl tellurides (8 and 9) [54]. The telluride 8 does not undergo an anodic a-substitution, which is totally different to the eases of the corresponding sulfide and selenide. Even in the presence of fluoride ions, the anodic methoxylation does not take place at all. Instead, a selective difluorination occurs at the tellurium atom effectively to provide the hypervalent tellurium derivative in good yield as shown in Scheme 6.12. 

Bis(pentafluoroselenium) oxide, F5SeOSeF5 (mp -82.1°C, bp 55.2°C), is produced besides F5SeOOSeF5 by the reaction of fluorine with selenium dioxide (141, 182). Bis(pentafluorotellurium) oxide, F5TeOTeF5 (mp - 36.6°C, bp 59.8°C) is prepared by the method shown in Eq. (22) (58). This compound has been obtained several times since 1933, but was always mistakenly characterized as Te2F10. The proposed existence of Te2F10, which in fact has not been prepared to date,... 

Tris(fluorosulfuroyl)fluoromethane (329) reacted with bis(diethylamido)benzyl phosphite to yield an intermediate (330) which extruded a molecule of SO2 to give as final product the bis(fluorosulfonyl) compound (331). The kinetics and mechanism of the reaction of fluorinated tricoordinate phosphorus compounds (332) and aryl 2,2,2-trifluoroethyl sulfenates (333) have been reviewed. ... 

---