TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The Hammett function H0 for the superacidic ionic liquid comprises aluminum chloride (-16 to -20). The inorganic anion is Al2Cl7- or Al2Cl6Br-.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The olefin is a linear or branched and/or cyclic 2-14C (preferably 2-10C) olefin (preferably monoolefin, especially ethene, 2-methyl-1-butene, 2-methyl-2-butene or 1-methylcyclopentene). The hydrocarbon to be isomerized is a linear or branched and/or cyclic 4-18C (preferably 5-8C) hydrocarbon. The organic cation is an ammonium ion, optionally 1-4C alkyl-substituted pyridinium ion or optionally 1-4C alkyl-substituted imidazolium ion (preferably trimethylammonium ion, triethylammonium ion, unsubstituted pyridinium ion or 1-ethyl-3-methylimidazolium ion). Preferred Method: The isomerization is performed in the presence of olefin (0.01-5, preferably 0.1-3 wt.%) based on the saturated hydrocarbon used. In the method, a tertiary carbon atom of the hydrocarbon is converted to a secondary carbon atom in the course of isomerization. The isomerization is performed at -20 to 150 degrees C. The isomerization is performed at an absolute pressure of 1-10 bar. The hydrocarbon to be isomerized is used in a concentration of 1-90 wt.%. The molar ratio of aluminum trichloride to Lewis base is 1-3. EXAMPLE - Trimethylammonium-Al2Cl7 as ionic liquid (IL) (150 ml) was initially charged in stirred vessel under argon, and the methylcyclopentane (MCP)-containing 2-methyl-1-pentene (0.1 wt.%) as organic mixture to be isomerized (30 ml) was introduced into the feed vessel. After heating all reactants to 60 degrees C, the entire contents of the feed vessel were transferred by opening Teflon tap within 1-2 seconds into the stirred vessel containing the IL while stirring. At defined time interval, 5 ml of sample were taken each time by using 30 cm cannula and syringe through sampling stub with septum. After approximately 2 minutes, the lighter organic phase containing pure MCP with 2-methyl-1-pentene (0.1 wt.%) which had separated out was introduced from the syringe into approximately 5 ml of 10 wt.% of aqueous sodium-EDTA solution and shaked. The phases were then separated. The organic phase was diluted with methylene chloride (2 ml) and, after drying with anhydrous sodium sulfate, analyzed by using GC. The time until attainment of reaction equilibrium (RE) of 70 minutes for 80% MCP conversion.