Fluorinated Cyclic Carbonates

Section 2.2 mainly reviews the papers on novel fluorinated organic solvents, which include fluorinated lactones, fluorinated linear carboxylates, fluorinated cyclic carbonates, fluorinated linear carbonates, fluorinated monoethers, fluorinated diethers, and others. The physicochemical properties of typical fluorinated compounds are summarized in comparison with nonfluorinated counterparts. 

Besides FEC and TFPC, more advanced stmctures of fluorinated cyclic carbonates have also been synthesized and evaluated in Li-ion batteries. Two examples of such molecules are given in Fig. 2. These molecules have traditionally been used in specialized applications such as coolants and supercapacitors, and their use in Li-ion batteries is relatively new [5, 6, 74, 78]. Regardless, these molecules have shown increased stability toward oxidation, better thermal stability, and low flammability. 

Compared with fluorinated cyclic carbonates, less research has been conducted on fluorinated linear carbonates due to their limited availability. The stmcture variation of the fluorinated linear carbonates are much more diverse than that of... 

Addition of fluorine and carbon to nucleophilic olefins is little studied, a rare example being the photochemical addition of benzotrifluonde to electron-rich cyclic olefins [202] (equation 40)... 

Merritt et al. [124,170-174] carried out some of the earliest additions of fluorine to carbon-carbon double bonds. The fluorination of cis and trans propenyl benzene in a nonpolar solvent at low temperature gave predominantly erythro and threo difluorides respectively. More recently, Rozen [175] carried out similar reactions, but used a more polar solvent (trichlorofluoro methane, chloroform and ethanol) and a very low concentration of fluorine. Thus, in the fluorination of cis and trans 3-hexene- l-ol acetate (Fig. 72), syn addition occured to give exclusively the erythro and threo difluoro compounds respectively. Corresponding results were obtained in the addition of fluorine to other alkenes, including cyclic alkenes and cyclic enones. 

Esters of carboxylic acids are, in general, not suitable starting materials for the synthesis of fluorides because the ester group cannot be substituted by fluorine. However, ft- and y-fluoro alcohols 1 and 2 can be obtained by treatment of the cyclic carbonates of 1.2- and 1,3-glycols, respectively, with anhydrous potassium fluoride. 

ETHYLENE GLYCOL CYCLIC CARBONATE (96-49-1) Combustible liquid (flash point 289°F/143°C). Reacts with strong oxidizers. Incompatible with fluorine, germanium, lead diacetate, magnesium, mercurous chloride, nitrates, silicon, silver nitrate, titanium. 

Five- and six-membered cyclic ethers, lactones, and cyclic carbonates do not undergo cleavage during anodic fluorination in methylene chloride in the presence of EtsN SHF or Et4NF HF (k = 4, 5). The reaction leads to monofluorinated cyclic products (02TL1503). 

FIGURE 2.38 Structure of (a) fluorinated carbonates and (b) cyclic carbonates studied in Reference 438. (Reproduced by permission of The Electrochemical Society from Chiba, K. et al. 2011. Journal of the Electrochemical Society 158 A1320-A1327.)... 

Selective Electrochemical Fluorination, Scheme 18 Solvent-free electrochemical fluorination of lactone and cyclic carbonate in poly HF salt... 

Cyclic carbons with fluorine atom in NMR C spectra of boronfluoride salt of 2,4-difluoro-6-(l,3-diisopropyl-4,5-dimefliylimidazolyl-2)-l,3,5-triazine are fixed in the form of a multiplet at 170.6-172.9 ppm [9]. NMR spectra of difluoro-sulphonamido-l,3,5-triazines in THF-t/g at different temperatures (Table 2) reveal that at the room temperature and atoms are equivalent, and at low temperatures rotation of the substituent round exocyclic C-N bond slows down so that and atoms become magnetically nonequivalent [10]. 

Fluorine-substituted carbonates have lower melting points than unsubstituted carbonates, and they have improved oxidation stability, which favors formation of a dense passivation SEl film on carbon negative electrode material. Some linear fluorine-containing carbonates are methyl 2,2,2-tri-fluoroethyl carbonate, ethyl 2,2,2-trifluoroethyl carbonate, propyl 2,2,2-tri-fluoroethyl carbonate, methyl 2,2,2-2, 2, 2 -hexafluoroisopropyl carbonate, ethyl 2,2,2-2, 2, 2 -hexafluoroisopropyl carbonate, and di-2,2,2-trifluoroethyl carbonate. Some cyclic fluorine-containing carbonates include fluoro-methyl ethylene carbonate (CH2F-EC), difluoromethyl ethylene carbonate (CHF2-EC), and trifluoromethyl ethylene carbonate (CF3-EC). They are miscible with EC, PC, and other organic solvents. The fluorinated cyclic... 

Many classes of perfluoroethers such as acyclic [63], cyclic [64, 65], glymes [66,67], highly branched [63],macrocyclic [68-73], orthoformates [74-76] and poly-ethers [15, 77], have been succesfully prepared in high yield by direct fluorination techniques (Figs. 19 and 20). Carbon-oxygen bond cleavage is minimised in these processes by the addition of an HF scavenger, such as sodium fluoride, to the reaction mixture [14,45,46]. 

The products of the electrochemical perfluorination of aliphatic or cyclic ethers are the corresponding perfluorinated ethers. Byproducts are perfluorinated ethers with shorter carbon chains, perfluoroalkanes, perfluorocarboxylic acid fluorides and oxygen difluoride. Cyclic perfluorinated ethers can be produced by electrochemical fluorination of alcohols,32 aliphatic carboxylic acids33 or of their acid halides34 containing not less than four carbon atoms in the chain. 

By a similar mechanism, fluorine is replaced in cyclic l//-perfluoroalkenes. The primary hydride attack is directed to the more positive carbon atom of the C = C bond 44... 

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