TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The method involves oxidizing omega-halo perfluoro alkyl sulfonyl fluoride of formula (1') (X-(CF2)mSO2F), to obtain omega-fluoro sulfonyl compound of formula (3') (FCO(CF2)m-1SO2F). The obtained omega-fluoro sulfonyl compound is reacted with hexafluoro propylene oxide, to obtain an acid fluoride compound of formula (4') (CF3CF(COF)O(CF2CF(CF3)O)n'(CF2)mSO2F). The obtained acid fluoride compound is then converted to omega-fluorosulfonyl perfluoroalkyl vinyl ether of formula (2') (CF2=CFO(CF2CF(CF3)O)n'(CF2)mSO2F. The oxidizing agent is SO3 or fuming sulfuric acid. A reaction mixture containing compound of formula (3) and sulfonyl fluoride compound of formula (5) (FSO2O-CFY-Rf-SO2F), is contacted with an alkali metal salt, alkaline-earth metal salt or Lewis base, such that the sulfonyl fluoride compound is converted to omega-fluorosulfonyl compound. The sulfonyl fluoride compound of formula (5) in reaction residue, is converted into omega-fluoro sulfonyl compound of formula (3), by contacting with alkali metal salt, alkaline-earth metal salt or Lewis base. A reaction mixture containing compound of formula (3') and sulfonyl fluoride compound of formula (5') (FSO2O(CF2)mSO2F), is contacted with an alkali metal salt, alkaline-earth metal salt or Lewis base, such that the sulfonyl fluoride compound is converted to omega-fluorosulfonyl compound. Separation removal of compound of formula (3 or 3') is performed. Compounds of formulae (3,4') are reacted in the presence of a fluorine ion-containing compound, in mixed solvent containing an ether solvent and a carboxylic acid dinitrile type solvent of formula (6) (R1O(R2O)pR1), to obtain an acid fluoride compound of formula (4") (CF3CF(COF)O(CF2)mSO2F). The mixed solvent contains 30-99 mass% of compound of formula (6). The acid fluoride compound of formula (4") is converted into carboxylate salt and is thermally decomposed, to obtain omega-fluorosulfonyl perfluoro alkyl vinyl ether of formula (2") (CF2=CFO(CF2)mSO2F). The generation ratio of byproduct in the reaction is given by the relation, (s)/(r+s) less than 0.1, where r is generation number-of-moles of compound of formula (2") and s is the generation number-of-moles of compound of formula (4"). The carboxylate salt of acid fluoride compound of formula (4"), is potassium salt of formula (7) (CF3CF(CO2K)O(CF2)mSO2F). Thermal decomposition of the carboxylate salt is performed by maintaining the salt in a solid-phase. Alternately, an alkali metal salt-type, alkaline-earth metal salt-type, quaternary-ammonium salt-type or quaternary phosphonium salt-type dithionite is mixed with alpha,omega-dihalo perfluoro alkane of formula (8) (X(CF2)mX) and stirred, to obtain omega-halo perfluoro alkyl-sulfinic-acid salt of formula (9) (X(CF2)mSO2M. The obtained salt is separated from the reaction mixture and is reacted with a chlorinating agent, to obtain omega-halo perfluoro alkyl sulfonyl chloride of formula (10) (X(CF2)mSO2Cl). The obtained sulfonyl chloride compound is processed with a fluorine ion-containing compound, to obtain omega-halo perfluoro alkyl sulfonyl fluoride of formula (1'). The omega-halo perfluoro alkyl-sulfinic-acid salt of formula (9) is separated from the reaction product containing compound of formula (9) and compound of formula (11) (MO2S(CF2)mSO2M). Unreacted compounds of formulae (8,9) are removed from the reaction solution containing perfluoro alkyl compound of formula (11) and compounds of formulae (8,9). The compound of formula (9) is separated from the reaction mixture containing compounds of formulae (9,11) or reaction mixture containing compounds of formulae (8,10). After separating the compound of formula (9), the reaction residue containing at least one mineral salt selected from inorganic iodide or bromide, is dissolved in aqueous solution of perfluoro alkyl-alpha,omega-bis sulfinate, and processed with a chlorinating agent, to obtain a perfluoro alkyl-alpha,omega-bis-sulfonyl chloride of formula (12) (ClO2S(CF2)mSO2Cl). Extraction processing of the obtained reaction mixture is performed with a poor-water-soluble organic solvent, to obtain compound of formula (8) and/or compound of formula (10).Rf = 1-9C bivalent perfluoro carbon group;X = I or Br;Y = fluorine atom, 1-3C perfluoro alkyl group or 1-3C coupling group with Rf;-CFY-Rf = 3-10C bivalent perfluoro carbon group;n = 0-2;R1 = 1-5C alkyl group;R2 = C2H4 or C3H6;p = 0-10;m = 3-10;M = Ma, Mb1/2, quaternary ammonium radical or quaternary phosphonium radical;Ma = alkali metal;andMb = alkaline-earth metal. Preferred Definitions:    m=4-8, preferably 4-6;    n or n'=0;and    X=iodine atom.    EXAMPLE - Acetone (2250 mL), water (750 mL) and I(CF2)4I (in g) (1000) were introduced into a reactor. Na2S2O4 (287) was added for 15 minutes and stirred at room temperature for 2 hours. Acetone and I(CF2)4I were distilled from the reaction mixture, to obtain a solid-like residue. Water was added to the residue and extraction process was performed for 3 times using ethyl acetate. The obtained ethyl-acetate extraction solution (445) contained I(CF2)4SO2Na at a yield of 36%. Extraction separation process was performed, and water (1000 mL) was added and stirred. Chlorine was introduced until two layers were separated. The lower layer was separated and analyzed. The lower layer contained I(CF2)4SO2Cl at a yield of 99.7%. Acetonitrile (700 mL) was added and heated at 50degreesC. I(CF2)4SO2Cl (665) was added for 2 hours and stirred at 50degreesC. After reaction completion, water was added until two layers were separated. The lower layer contained I(CF2)4SO2F (606.8) at a yield of 99.4%, which was removed by distillation. 65 mass% fuming sulfuric acid was added to I(CF2)4SO2F and heat-refluxed under normal pressure for 40 hours. Liquid separation was performed and the upper layer was washed for 3 times using concentrated sulfuric acid. Distillation was performed to obtain FOC(CF2)3SO2F (570) at a yield of 74.4%. Using the obtained compound, omega-fluorosulfonyl perfluoroalkyl vinyl ether of formula CF2=CFO(CF2)4SO2F, was manufactured at a yield of 82.2%. The structure of the obtained compound was confirmed by 19F-NMR spectrum.