Fluorinated 1,3-dioxolanes, preparation

This and other fluorous acetal derivatives are prepared from diols bearing 13 or more F atoms to make them soluble in fluorinated hydrocarbons. They are prepared by the standard methods of heating the ketone with the diol in the presence of an acid such as TsOH or pyridinium tosylate. As with most 1,3-dioxanes and 1,3-dioxolanes, they can be cleaved with aqueous acid. ... 

Oxidative addition of elemental fluorine to appropriate 1,3-dicarbonyl compounds provides a convenient synthesis of perfluorinated 1,2-dioxolanes. In this way (20) may be formed from difluoromalonyl fluoride, F2C(COF)2 <92JST(274)163>, and (39) is similarly prepared from either hexafluoroacetylacetone or the copper(II) or nickel(II) chelate of trifluoroacetylacetone with concomitant replacement of all remaining hydrogen atoms by fluorine <65JOCI429>. 

Ethylene carbonate (EC) and propylene carbonate (PC) have favorable physical and electrochemical properties such as high relative permittivity, high donicity, and relatively wide potential window. The direct fluorination of EC was successfully carried out to provide 4-fluoro-l,3-dioxolan-2-one (fluoroethylene carbonate, FEC) as shown in Scheme 2.3 [20], The fluorination of EC was strongly dependent on a choice of a reaction medium and no solvent was preferred from the viewpoint of conversion. FEC was further fluorinated to give three di-fluorinated derivatives. On the other hand, FEC was also prepared from 4-chloroethylene carbonate by exchange with KF [21], FEC was tested as an electrolyte additive for rechargeable lithium cells [21, 22] and is now practically used [23, 24],... 

Preparation. 2,2-Bistrifluoromethyl difluoro-l,3-dioxole (PDD) monomer is synthesized in four steps (2). In the first step, hexafluoroacetone and ethylene oxide are reacted to form 2,2-bistrifluoromethyl-4,5-dichloro-4,5-difluoro-l,3-dioxolane. This product is then fully chlorinated and subsequently partially fluori-nated to difluoro-l,3-dioxolane. In the last step, the fluorinated product is dechlo-rinated to obtain the final product, PDD. 

Bis(iluoroformyl) peroxide, prepared from carbon monoxide, oxygen, and fluorine at 55 cyclizes to the cyclic peroxide (77) when left in contact with potassium fluoride at — 80 °C, presumably via a mechanism of the type proposed for fluoride-initiated conversion of the bis(acyi) fluoride CKCFjCOF) into perfluoro-j3-oxa-8-valerolactone (see Vol. 1, p. 76) use of caesium fluoride at -40 °C gives a mixture of the acyclic peroxides (CFs-0-0)sC0 and CFj-O-O COF, possibly via attack of F on the CF group of (77). The 1,2-dioxolan (78) can be obtained by direct fluorination of the copper chelate of l,l,l,5,5,5-hexafluoropraitane-2,4-dione at —20... 

Copolymers of the Teflon AF series are prepared in four steps starting with hexafluoro-acetone (HFA) and ethylene oxide (EO). Condensation reactions of HFA and EO result in 2,2-bis-trifluoromethyl-l,3-dioxolane, which is successively chlorinated, fluorinated, and dechlorinated to give the 2,2-bis-trifluoromethyl-4,5-difluoro-l,3-dioxole (TFMDFD) monomer (Hung, 1993 Resnick, 1976). This monomer copolymerizes with tetrafluoro-ethylene (TFE). The physical properties of these amorphous copolymers vary according to the relative amoimts of the co-monomers, TFMDFD and TFE. Currently, DuPont is producing two commercial grades, AF-1600 and AF-2400. Teflon AF-2400 and AF-1600 are the names of copolymers for which n = 0.87 and 0.65, respectively, where n is the percentage of the TFMDFD monomer (see Fig. 24.9). Table 24.4 summarizes physical properties of the two fluoropolymers. 

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