Fluorine species

This reaction has often reached explosive proportions in the laboratory. Several methods were devised for controlling it between 1940 and 1965. For fluorination of hydrocarbons of low (1—6 carbon atoms) molecular weight at room temperature or below by these methods, yields as high as 80% of perfluorinated products were reported together with partially fluorinated species (9—11). However, fluorination reactions in that eta involving elemental fluorine with complex hydrocarbons at elevated temperatures led to appreciable cleavage of the carbon—carbon bonds and the yields invariably were only a few percent. 

Fluorination and iodination reactions are used relatively littie in dye synthesis. Fluorinated species include the trifluoromethyl group, which can be obtained from the trichi oromethyl group by the action of hydrogen fluoride or antimony pentafluoride, and various fluorotria2iQyl and pyrimidyl reactive systems for reactive dyes, eg, Cibacron F dyes. 

A new thermal preparation ot fluorinated species is copyrolysis Copyrolysis of fluorinated compounds like perfluorobenzene, fluorinated aromatic anhydndes, and fluorinated heteroaromatics with tetrafluoroethylene or other fluonnated olefins is a useful method of preparing fluorinated olefins [88 89], functionalized fluoroaromatics [90 91 92, 93, 94, 95], fluonnated benzocycloalkanes [80, 96, 97, 98, 99, 700], fluorinated heterocycles [80, 93, 101, 102, 103], and fluonnated polycyclic compounds [104] (equations 19 and 20)... 

The thenoyltrifluoroacetate (tta) complex, [Sc tta)3 OP(OBu)3)], has been prepared. Scandium also afforded, with l,2-dihydroxybenzene-3,5-disodium sulphonate (Tiron), a monoprotonated chelate below pH 2.5, but above pH 6.0 hydrolysis afforded a monohydroxo-Sc-Tiron complex. Ligand-exchange equilibria for the piperidium salts of [Y(ffac)4] and [Y(tfac)4] have been studied by n.m.r. spectroscopy. The fully fluorinated ligands appear to exchange faster than the partially fluorinated species, and the mixed compounds, [Y(Hffac) (tfac)4 ] , n = 0 — 4, were obtained. 

Spectrophotometric studies of the reaction between Np and 1,3-dikelones in water revealed that 1 1 and 1 2 adducts were formed, except with fluorinated species which preferred only to form 1 1 complexes. The stability of Np02 complexes was lower than that of the corresponding UOj species. 

The different PFCLs used as interoperative tools can be categorised as a group of compounds with more or less uniform behaviour. On the contrary, the partially fluorinated species have to be regarded as individuals each. This is due to the hybrid character of these compounds, which combine the behaviours of alkanes and perfluoroalkanes. Especially, the toxicological behaviour cannot be optimised by simple modifications of the degree of fluorination. If the two molecule parts are combined in the right balance, the cytotoxic behaviour of the alkyl chain can be overcompensated by the inert perfluorinated part of the compound. But each compound should be tested individually to ensure its suitability as a candidate for ophthalmic use. 

Within the O—MgBr group are at least three subcategories the alkoxy and phenoxy, the carboxy and the fluorinated species. Within the alkoxy subgroup, the endothermic... 

An exception is perfluoro(2-methylpropene) (perfluoroisobutylene, PFIB), which is the most toxic fluorinated species known so far and is particularly dangerous due to delayed development of lethal lung edema, not starting until 1-2 days after the cessation of the exposure. 

The in situ preparation of the active fluorinating species lead diacctate difluoride from lead(I V) acetate (dissolved in chloroform) and hydrogen fluoride at 0 C was described in an earlier report.48 The crystalline lead diacetate difluoride could be isolated by a modified preparation.49... 

The 19F NMR spectra of the commercial BF3 NH2C2H5 samples are illustrated in Fig. 5. The major components identified in the 19F spectra were BF3 NH2C2H5, BF4, and BF3(OH) species and an unidentified highly reactive BF3 species with an NMR peak in the region of BF3(OH). The fluorine species observed in the commercial samples are illustrated in Table 1, in which several other observed 19F NMR peaks are combined under the Miscellaneous heading. 

Table 2. Effect of thermal annealing on the fluorine species in BF3 NH2C2H5 from 19F NMR...

F NMR studies, illustrated in Table 4, indicate that the TGDDM epoxide enhances BF4 salt formation in DMSO solution. For example, after exposure to 115 °C for 1 h, all the BF3 NH2C2HS species have disappeared in the presence of TGDDM. However, in DMSO solution in the absence of TGDDM, 50% of the total fluorine species are still in the form of BF3 NH2C2H5 after 1 h exposure at 115 °C (Table 3). 

The fluorine species observed in five different lots of Fiberite 934 were identified and tabulated in Table 5. A typical spectrum is illustrated in Fig. 6. The catalyst in... 

We associate the various additional fluorine peaks observed in the NMR spectra with principally the products of epoxide-active fluorine species reactions. The total fluorine in the form of these products is relatively constant from prepreg lot to lot (28.2 to 36.3%). 

Organo-fluorine compounds have a diverse, often unanticiptated chemistry. The chemical behavior of fluorinated species is much more comprehensible if the effects of fluorination on reactivity are rationalized. It is the effect of fluorine on reactive intermediates that in turn governs the outcome of reactions. The principal properties of fluorine which have the most profound influence on bonding and, therefore, reactivity are the pronounced electronegativity of fluorine1 and its associated low polarizability,2 the availability of three nonbonded electron pairs, and the excellent overlap that is possible between the 2s and 2p orbitals of fluorine and those of carbon.3... 

The importance of hyperconjugation in anionic fluorinated species has been questioned, 3,74 with the proposal that the effects of fluorination can be rationalized by involving polarization effects alone. A study of the relative rates of the deuteration of tris(trifluoromethyl)methane (1), l//-undecafluorobicyclo[2.2.1]heptane (2), and l//-tridecafluorobicyclo[2.2.2]octane (3) clearly illustrates that deuteration occurs much more rapidly with tris(trifluoromethyl)melhane... 

HF is extremely stable and accumulates in the Middle Atmosphere. Its present abundance is equivalent to the accumulated fluorine amount liberated from fluorine bearing halocaibons up to present, and it increases at the pace of ongoing fluorine species entering the stratosphere. As HF is not a natural atmospheric constituent, the HF budget of the Middle Atmosphere is an important piece of evidence showing the fate and effect of fluorinated halocarbons. 

FIC Ratio Model. The fluorine-to-carbon ratio (F/C) of the active species can be used (92) to explain the observed etch results (Figure 8). This model does not consider the specific chemistry occurring in a glow discharge but, rather, views the plasma as a ratio of fluorine species to carbon species that can react with a silicon surface. The generation or elimination of the active species by various processes or gas additions then modifies the initial F/C ratio of the inlet gas. 

Mass Calibration The process by which the mass analyzer is calibrated such that a measured and displayed m/z is accurate. Well-characterized calibration compounds are utilized, and measured m/z values for these compounds are compared to theoretical m/z values. Calibrants commonly used include various polymeric species (such as polypropylene glyol, or PPGs poly tyrosine (poly-t)) or fluorinated species (perfluorokerosene or PFK) but can be any compound or mixture (Nal/KI) of compounds properly characterized for MS. 

Ci rkva, V., Bohm, S., and Paleta, O. (2000) Radical addition reactions of fluorinated species. Part 8. Regioselectivity of radical additions to perfluoroalkylefhylenes... 

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