Patent GB-784727-A (GB)
Title: Improvements in or relating to carboxylic acids
IPC: C07C53/21
Filed: 1955-07-29
Abstract: Telomers obtained by polymerizing e.g. in a solvent, a perhalogenated olefin in the presence of a telogen, e.g. a sulphuryl halide or a bromoperhalogenated methane, are converted into carboxylic acids (see Group IV (b)).  The perhalogenated olefin may be tetrafluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene alone, or admixed with vinylidene fluoride, or trifluoroethylene.  The telomer products include generally those of formula CCl3-(CF2-CXaXb)n-Br, Cl(CF2CXaXb)n-Cl, Cl(CF2.CFCl)n-1CF2. CCl3, and may contain at least one CCl3, CCl2Br, CBr2Cl, or CBr3 group, such products being obtained by treating products from sulphuryl chloride having a F in the end group with Friedel-Crafts metal halides, n being 1-16.  Specified telogens are bromotri-fluoromethane, bromochlorodifluoromethane, bromodichlorofluoromethane, dibromodifluoromethane, dibromochlorofluoromethane, sulphuryl chloride and bromide, fluorosulphuryl chloride and bromosulfuryl chloride.  The catalyst for the polymerization may be benzoyl peroxide, di-t-butyl peroxide or dichlorobenzoyl peroxide.  The polymerization solvent may be carbon tetrachloride or tetrachloroethylene.  The hydrolysis of the telomers to mono- or di-acids is effected by treatment with concentrated sulphuric acid containing sulphur trioxide at elevated temperatures.ALSO:The invention comprises fluoroperhalogenated carboxylic acids having the formula Z.(CFClCF2)n-2CF2.COOH, and esters, anhydrides and metal and ammonium salts thereof, in which Z is COOH.CF2.CFCl-, COOH.CFCl-, COOH.CF2-, perhalomethylene-CF2-CFCl-, or halo-CF2.CFCl-, the atomic weight of the terminal perhalomethyl group being not more than 146.5 and n being 2-16, and a method of obtaining them by the action of fuming sulphuric acid on telomers obtained by telomerizing a fluorinated olefin in presence of sulphuryl chloride or with a perhalogenated methane containing bromine, or by the action of fuming sulphuric acid on such a telomer which has been further treated with Friedel-Crafts metal halides. The CFClBr group at the end or ends is hydrolysed to COOH and the telomer must not contain perhalomethyl groups more readily hydrolysed than this.  The CFCl2 group may also be hydrolysed by the method. Telomers produced by other telogens such as fluorosulphuryl chloride, having the desired end groups may also be used.  In examples, sulphuric acid of various percentages of free SO3 reacts with the telomers CCl3(CF2 CFCl)2Br, CCl3(CF2-CFCl)3Br, C7 and C9 telomers obtained from chlorotrifluoroethylene and bromotrifluoromethane, C11 and C13 similar fractions, Cl(CF2CFCl)4Cl and other telomers, to give products such as CCl3.CF2.CFCl.CF2.COOH, COOH.CF2.CFCl.CF2.COOH, COOH. (CF2.CFCl)2.CF2COOH, other similar diacids having 3, 4 and 5 groups (CF2.CFCl), an anhydride of 3-chloro-pentafluoroglutaric acid, the anhydride (CCl3.CF2.CFCl.CF2COO)2O, Cl.(CF2.CFCl)2CF2.COOH, CF2Cl(CFCl.CF2)3.COOH, COOH(CFCl-CF2)3.COOH and similar products. Cyclic anhydrides may be formed from 5-carbon dicarboxylic acids. Salts of some of the acids are specified.  The fluorine atom in the end group of a telomer obtained with sulphuryl chloride may first be replaced by the action of a Friedel-Crafts metal chloride before treatment of the telomer with fuming sulphuric acid.  Thus the telomer Cl(CF2.CXaXb)nCl in which XaandXb are Cl or F is converted by AlCl3 into the telomer CF2Cl(CXaXb.CF2)n-1C.Cl3, and, where both ends of the molecule are affected, into such products as CCl3(CFCl.CF2)n-1.CCl3.  When the telomer products contain the end groups CBrClF, CBrF2 and an opposite end group CF3, CClF2, CCl2F, CBrF2 and CBrClF, these groups, except CF3, may be converted to CCl3, CCl2Br, CBr2Cl and CBr3 end groups by this method, depending on the starting materials. An example of the conversion of Cl(CF2.CFCl)3Cl to Cl(CF2CFCl)2CF2CCl3 with AlCl3 is given, followed by its hydrolysis with acid as above to ClCF2(CFCl-CF2)2.COOH.  The end-group converted by Friedel-Craft halides is more reactive than the one it replaces.  Esters and salts of the acids claimed may be prepared.  Other telomers which may be used (see Group IV (a)) are described with general formul .