Other Fluorinated Solvents

3-Methyl-2-oxazolidinone (NMO) is isostructural with EC with an N-CH3 group substituted for one of the EC ring oxygen atoms. It is a highly polar solvent (er=78 at 25 °C) and was once used in primary lithium cells [54]. However, its oxidation potential on a glassy carbon is much lower than that of PC [55]. To increase its 

The electrolytic conductivity of 1 moldm LiPF6/DFNMOmix was much lower than that of NMO due to the high viscosity and low permittivity. The oxidation potential of DFNMOmix on Pt was increased but still lower than that of PC. The addition of DFNMOmix to 1 moldm LiPF6/EC-DEC equimolar binary solution suppressed discharge capacity fading in a Li/LiCo02 cell. 

The direct fluorination of A -methylpyrrolidinone (NMP) was also carried out to afford a-fluoro-A -methylpyrrolidinone (a-F-NMP). Its relative permittivity (70) and viscosity (3.6) were almost doubled those of NMP (32, 1.7), respectively. The electrolytic conductivity of 1 moldm LiPF6/a-F-NMP solution at 25 °C was 2.5 mScm less than half of that of NMP (6.1) [58]. 

The enhancement of both energy density and cell safety of rechargeable lith-ium(-ion) batteries is important for electric vehicle and power grid applications. Therefore, partially fluorinated organic compounds are expected as a good solvent 

---

The synthesis of fluoropolymers in C02 is of particular interest since these polymers have historically been prepared in chlorofluorocarbons (CFCs) and other fluorinated solvents, as well as in water. Due to the association of CFCs with ozone-layer depletion, these solvents have been banned and replacement solvents must be found. Alternative fluorinated solvents are expensive and also have environmental concerns. 

That s the good news. The bad news is that recovery must be excellent because this solvent, among other fluorinated solvents, is highlypriced. 

Chemical Properties. A combination of excellent chemical and mechanical properties at elevated temperatures result in high performance service in the chemical processing industry. Teflon PEA resins have been exposed to a variety of organic and inorganic compounds commonly encountered in chemical service (26). They are not attacked by inorganic acids, bases, halogens, metal salt solutions, organic acids, and anhydrides. Aromatic and ahphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, amines, esters, chlorinated compounds, and other polymer solvents have Httle effect. However, like other perfluorinated polymers,they react with alkah metals and elemental fluorine. 

Like many organic solvents, including hexane, heptane, ben2ene, xylene, toluene, gasoline, and particularly some of the other chlorinated and fluorinated solvents, methylene chloride may cause cardiac arrhythmias in the presence of elevated epinephrine when inhaled at concentrations as high as 20,000 ppm (36). 

Other fluorinated derivatives of acetylacetone are trifluoroacetylacetone (CF3COCH2COCH3) and hexafluoroacetylacetone (CF3COCH2COCF3), which form stable volatile chelates with aluminium, beryllium, chromium(III) and a number of other metal ions. These reagents have consequently been used for the solvent extraction of such metal ions, with subsequent separation and analysis by gas chromatography [see Section 9.2(2)]. 

The term fluorous biphase has been proposed to cover fully fluorinated hydrocarbon solvents (or other fluorinated inert materials, for example ethers) that are immiscible with organic solvents at ambient conditions. Like ionic liquids the ideal concept is that reactants and catalysts would be soluble in the (relatively high-boiling) fluorous phase under reaction conditions but that products would readily separate into a distinct phase at ambient conditions (Figure 5.5). 

Various other biphasic solutions to the separation problem are considered in other chapters of this book, but an especially attractive alternative was introduced by Horvath and co-workers in 1994.[1] He coined the term catalysis in the fluorous biphase and the process uses the temperature dependent miscibility of fluorinated solvents (organic solvents in which most or all of the hydrogen atoms have been replaced by fluorine atoms) with normal organic solvents, to provide a possible answer to the biphasic hydroformylation of long-chain alkenes. At temperatures close to the operating temperature of many catalytic reactions (60-120°C), the fluorous and organic solvents mix, but at temperatures near ambient they phase separate cleanly. Since that time, many other reactions have been demonstrated under fluorous biphasic conditions and these form the basis of this chapter. The subject has been comprehensively reviewed, [2-6] so this chapter gives an overview and finishes with some process considerations. 

As shown in Table 17.3 and Fignres 17.6 and 17.7, the other polar solvents yielded significantly different spectra. For the amic acids prepared in DMSO and m-cresol, the 6F region was essentially identical to the NMP-prepared sample however, for the aromatic regions, fonr peaks were observed instead of two. The strnctnres in Table 17.3 can aid in this discnssion. Each of the p,p- and m, m-isomers shonld yield one signal in the F-NMR spectra since the aryl fluorine atoms on all of these molecules are equivalent. For the m,p-isomer, the two fluorines are not chemically equivalent to each other and should thus yield two peaks. 

Fifolt [ 130] reported this chemical shift additivity method for fluorobenzenes in two deuterated solvents d6 acetone and d6 dimethyl sulfoxide (DMSO) Close correlations between experimental and calculated fluorine chemical shifts were seen for 50 compounds Data presented in Table 18 result from measurements in deuterochloroform as (he solvent [56] Fluorine chemical shifts calculated by this additivity method can be used to predict approximate values for any substituted benzene with one or more fluorines and any combination of the substituents, to differentiate structural isomers of multisubstituted fluorobenzenes [fluoromtrotoluenes (6, 7, and 8) in example 1, Table 19], and to assign chemical shifts of multiple fluorines in the same compound [2,5 difluoroamline (9) in example 2, Table 19] Calculated chemical shifts can be in error by more than 5 ppm (upfield) in some highly fluonnated systems, especially when one fluonne is ortho to two other fluorines Still, the calculated values can be informative even in these cases [2,3,4,6-tetrafluorobromobenzene (10) in example 3, Table 19]... 

The selective oxidation of C—H bonds in alkanes under mild conditions continues to attract interest from researchers. A new procedure based upon mild generation of perfluoroalkyl radicals from their corresponding anhydrides with either H2O2, m-CPBA, AIBN, or PbEt4 has been described. Oxidation of ethane under the reported conditions furnishes propionic acid and other fluorinated products.79 While some previously reported methods have involved metal-mediated functionalization of alkanes using trifluoroacetic acid/anhydride as solvent, these latter results indicate that the solvent itself without metal catalysis can react as an oxidant. As a consequence, results of these metal-mediated reactions should be treated with caution. The absolute rate constants for H-abstraction from BU3 SnH by perfluorinated w-alkyl radicals have been measured and the trends were found to be qualitatively similar to that of their addition reactions to alkenes.80 a,a-Difluorinated radicals were found to have enhanced reactivities and this was explained as being due to their pyramidal nature while multifluorinated radicals were more reactive still, owing to their electrophilic nature.80... 

These reaction conditions using fluorinated solvents have also been applied to the construction of other spirocyclic systems. 

Perfluoroelastomers, i.e., elastomers based on perfluoromethyl vinyl ether (PMVE) and TFE, exhibit a virtually unmatched resistance to a broad class of chemicals except fluorinated solvents. On the other hand, they are adversely affected by hydraulic fluid, diethyl amine, and fumed nitric acid resulting in swelling of the elastomer by 41, 61, and 90%, respectively.10... 

The thermal decomposition of salts of fluorinated acids gives tw o different types of products. depending on the reaction conditions and the type of cation. When the decarboxylation of alkali and alkaline earth metal salts is carried out in the presence of proton donors, such as water, alcohol, aniline, pyridine or other basic solvents, the product of the reaction is a fluorocarbon hydride. This is a general procedure for the preparation of 1 /Z-perfluoroalkanes. ... 

---