Direct Fluorination with

Fluorofullerenes have been prepared by reaction with halogen fluorides, by direct fluorination with F2 or by fluorination with noble gas fluorides [7,8,14], The reaction with high valence metal fluorides is the most versatile route for the synthesis of CsoFnH. 

Fluorination with Noble Cas Fluorides and Halogen Fluorides 

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For example, direct fluorinations with elemental fluorine are kept imder control in this way, at very low conversion and by entrapping the molecules in a molecular-sieve reactor. As with some other aromatic substitutions they can proceed by either radical or electrophilic paths, if not even more mechanisms. The products are dif ferent then this may involve position isomerism, arising from different substitution patterns, when the aromatic core already has a primary substituent further, there may be changed selectivity for imdefined addition and polymeric side products (Figure 1.31). It is justified to term this and other similar reactions new , as the reaction follows new elemental paths and creates new products or at least new... 

Direct fluorinations with elemental fluorine still are not feasible on an industrial scale today they are even problematic when carried out on a laboratory-scale [49-53]. This is caused by the difficulty of sustaining the electrophilic substitution path as the latter demands process conditions, in particular isothermal operation, which can hardly be realized using conventional equipment. As a consequence, uncontrolled additions and polymerizations usually dominate over substitution, in many cases causing large heat release which may even lead to explosions. 

Although the formation of fully fluorinated fullerene C6o was firstly reported in 1991 based on the sharp singlet of 19F NMR spectrum of the product in tetrahydrofuran solution [29], the preparation in macroamount has not been confirmed in the late 1990s. The fully fluorinated C6oF60 has been detected only in mass spectra of the products obtained by direct fluorination with elemental fluorine [30,31]. 

By the direct fluorination with elemental fluorine, it is still difficult to prepare pure compounds C6oF.v and C70F of specific fluorine content because the reaction between fluorine gas and solid state C6o and C70 proceeds under heterogeneous conditions and, therefore, lacks control. Attempts to prepare stoichiometrically pure compounds have become successful using solid phase reactions between fullerenes and metal fluorides. These are described in the next section. It has been unsuccessful so far, but efforts are being made to produce fluorinated fullerenes C6oF v of lower fluorine content (x < 18) [24],... 

The direct fluorination with elemental fluorine at — 78 "C of trimethylsilyl enol ethers derived from diketones results in the formation of the corresponding monofluoro diketones 11 in moderate yield. The trimethylsilyl ethers from cyclic diketones undergo smooth fluorination to give the enol forms, c.g. 12, and not the keto forms.Higher yields are generally observed for the analogous reactions of silyl derivatives of esters, carboxylic acids, malonates, dimethyl amides and lactones (Table 4). ... 

Methods for the chlorination of secondary amines, secondary amides and imides have been reviewed. Secondary alkylamines can be chlorinated by f-butyl hypochlorite at low temperature, or by sodium hypochlorite or IV-chlorosuccinimide. A/-Bromination and IV-iodination can be brought about by using the appropriate halogen, but these A/-halodialkylamines are unstable and are rarely isolated. A -Flu-oroamines and -fluoroamides are also rare. The A/-fluoroimide (CP3S02)2NF, has, however, been prepared by direct fluorination with fluorine. It is a stable liquid which shows promise as a fluorinating agent for aromatic compounds. ... 

A diazonium salt reacts with fluoroboric acid (HBF4) to form an aryl fluoride. This is a useful reaction because aryl fluorides cannot be produced by direct fluorination with F2 and a Lewis acid catalyst, as F2 reacts too violently (Section 18.3). 

Earlier syntheses of 8-fluoropurines are limited to a few reports involving nucleophilic displacement, Schiemann reactions, halogen-exchange reactions, and electrochemical oxidations. Recently, the first direct fluorination with elemental fluorine has been reported for the synthesis of 8-fluoroguanines, e.g. 

Direct fluorinations with elemental fluorine and other powerful fluorinating agents can be carried out, but they are, to say the least, inconvenient. They are also potentially very hazardous for the inexperienced chemist and are best left to a fluorine specialist. Such reactions are, of course, carried out industrially, but using dedicated special equipment with rigorous safety control.)... 

Again the question arises on the bmit to exhaustive halogenation. Due to its size, fluorine should be the halogen best suitable to a dense covering of the fuller-ene s surface. The compound undoubtedly characterized by now is C )F48, which is obtained by direct fluorination with F2. 

Fluorination of ketones. Direct fluorination with reagent (1) often proceeds in... 

Direct fluorination with dilute elemental [ F]p2 was used to prepare 8-[ F] fluoroguanine, a positron emission tomography (PET) scanning probe that was used... 

Fig. 8 Direct fluorination with elementary fluorine to synthesize perfluoro compounds. PERFECT means PERFluorination of Esterified Compounds then Thermal elimination...

Li B, Gao J, Wang X, Fan C, Wang H, Liu X (2014) Surface modification of polypropylene battery separator by direct fluorination with different gas components. Appl Surf Sci 290 137-141... 

Different from PTFE and ETFE, cost reduction of the PS VE polymer is one of the problems for prevailing perfluorinated membranes. Recently, a new direct fluorina-tion process with elementary fluorine was reported to produce perfluorinated fluo-rosulfonyl polymers, as shown in Fig. 2.4 [47], This new process eonsists of the following features and is free from explosion in the gas phase and the difficulty in finding solvents with stability to fluorine gas and solubUity for hydrocarbon com-poimds, these problems having limited the application of the eonventional direct fluorination methods (1) decomposition of the ester and regeneration of RFCOF into an ester (RFCOOR) that is not very volatile and soluble in RFCOF (2) direct fluorination with elementary fluorine gas and (3) deeomposition of the ester and regeneration of RFCOF. This proeess ean offer wide seleetion of the synthetie routes of precursor hydrocarbon, shorter steps, and low-cost produetion of the perfluorinated polymers [52]. 

Direct fluorination with elemental fluorine is not practical for commercial synthesis of fluorinated surfactants. Elemental fluorine is extremely reactive and difficult to handle. The heat of formation of the C—bond (about 460 kJ/mol or 110 kcal/mol) and the H—F bond (566 kJ/mol or 135 kcal/mol) exceeds that of the C—C bond (about 348 kJ/mol or 83 kcal/mol) [1]. Hence, the fluorination with elemental fluorine leads to a violent fragmentation of the substrate unless the reaction is carefully controlled and the reaction heat effectively dissipated [2,3]. Commercially important pathways to fluorinated surfactants are electrochemical fluorination, telomerization, and oligomerization of tetrafluoroethylene [4-6]. 

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