Mixtures of straight-chain perfluoroolefins and perfluoroparaffins and process for preparing them

The perfluoroolefins having terminal and internal double bonds and trifluoromethyl groups are, in a mixture with perfluoroparaffins of the same chain length and corresponding structure, thermally stable and can be used, for example, as solvents, coolants or dielectrics. They are industrially important intermediates, for example for preparing surface-active compounds. These mixtures are prepared by exposing highly fluorinated organic substances such as, for example, highly fluorinated polymers, in an irradiation chamber purged with inert gas, to high-energy radiation, preferably electron beams, having an energy density of 0.3 to 3.0 W/cm , so that they are degraded thereby to give mixtures which can be distilled or sublimed.