Patent GB-579897-A (GB)
Title: The manufacture of organic compounds containing fluorine
Filed: 1944-02-21
Abstract: Salts of fluorine containing organic compounds are prepared by reacting a polyfluoroethylene containing at least two fluorine atoms, two of which are attached to one carbon atom, with a L  water-soluble inorganic sulphurous acid salt and water at a temperature above 0 DEG C. and below that at which pyrolytic decomposition of the organic reactants or products occurs.  This is preferably carried out by using an aqueous solution of an inorganic sulphurous acid salt, in particular alkali metal and alkaline earth metal sulphites and bisulphites such as those of sodium, potassium, ammonium, lithium, magnesium and calcium.  The reaction may be effected under pressure and in a batchwise or continuous manner and in the presence or absence of catalysts comprising oxygen and peroxygen compounds. Inorganic salts such as borax or disodium phosphate may be added as buffers.  By the above process, a mixture of salts of polyfluoroethanesulphonic acids and halo-acetic acid salts is obtained which may be partially separated by first removing inorganic salts from the reaction mixture by extracting with alcohol and then carrying out a fractional crystallization.  Complete separation may be effected by fractional distillation after the salts have been converted into the corresponding acids by acidifying with a strong mineral acid such as sulphuric or phosphoric acid.  The polyfluorosulphonic acids form salts with bases such as ammonia, amines, such as methylamine, dimethylamine, trimethylamine, aniline, a -naphthylamine, N-monomethyl aniline, morpholine, dodecylamine, hexamethylenediamine, amino acids and hydrazines; and with hydroxides and basic salts of sodium, potassium, lithium, calcium, barium, aluminium, zinc, iron, copper, lead, bismuth, magnesium and nickel. The polyfluoroethanesulphonates or the acids may be converted into the corresponding sulphonyl chlorides by reaction with phosphorus chlorides such as phosphorus pentachloride.  The sulphonyl chloride can be reacted with ammonia or primary or secondary amines to produce sulphonamides.  In the examples: (1) aqueous sodium sulphite solution is heated in an autoclave with tetrafluoroethylene under pressure. The reaction mixture is purified by evaporating to dryness followed by extraction of the residue with hot alcohol.  The resultant solution is evaporated to dryness.  The residue is treated with aqueous sulphuric acid and filtered, the filtrate being extracted with ether.  The ether extract is fractionally distilled giving pure tetrafluoroethane sulphonic acid monohydrate.  This is warmed with thionyl chloride to give the anhydrous acid, which is converted to the sulphonyl chloride, by adding it to phosphorus pentachloride. (2) Tetrafluoroethylene is heated under pressure in an autoclave with an aqueous solution of sodium bisulphite, borax and benzoyl peroxide. The product is worked up as in example (1).  (3) Tetrafluoroethylene is heated under pressure in an autoclave with an aqueous solution of potassium sulphite and benzoyl peroxide.  The product is worked up as in example (1). The resulting acid is reacted with solid sodium carbonate giving sodium tetrafluoroethanesulphonate which is purified.  The aniline salt of the acid is prepared by adding the acid to aniline and also by reacting tetrafluoroethane sulphonic acid monohydrate with phenylisocyanate.  (4) Aqueous sodium sulphite solution is heated in an autoclave with vinylidene fluoride and the product purified. Other polyfluoroethylenes which may be used as starting materials are stated to be: trifluorochloroethylene, trifluorobromoethylene, trifluoroethylene, 1 : 1-difluoro-2 : 2-dichloroethylene and 1 : 1-difluoro-2-chloroethylene.  The products of the invention may be used in place of sulphuric acid, for example, as catalysts, in reactions in which sulphuric acid produces charring.