Hoechst Aktiengesellschaft

Alfons Gisser

Konrad Von Werner

Heiner Debrodt

Wilfried Becker

Joachim Naumann

A mixture of isomers of the formula C.sub.6 F.sup.12, which contains at least 80% by weight of the trans isomer of perfluoro-4-methyl-2-pentene and at most 3% by weight of perfluoro-2-methyl-2-pentene, is suitable as a cooling and insulating medium and can be used as a substitute 1,1,2-trichloro-1,2,2-trifluoroethane.

Perfluoroisohexene as a cooling and insulating medium

Process for the preparation of hexafluoropropene dimers having a high proportion of perfluoro-(4-methyl-2-pentene) The dimerization of hexafluoropropene produces almost exclusively dimers having a high content of perfluoro-(4-methyl-2-pentene) if the dimerization is carried out in an aprotic solvent in the presence of an adduct of an amine, which contains no NH groups, and a metal fluoride.

Process for the preparation of hexafluoropropene dimers having a high

Saturated perfluoroalkane-1-carboxylic acids having 6 to 14 C atoms are prepared by reacting the corresponding 1-iodoperfluoroalkanes at temperatures of 100.degree. to 180.degree. C. with fuming sulfuric acid containing 15 to 45% by weight of dissolved sulfur trioxide. The two liquid phases which are formed are separated. The lighter phase is mixed with 0.3 to 6% of its weight of water and is distilled at a pressure of 0.3 to 100 kPa. The heavier phase is mixed with 0.7 to 1.5 moles of water per mole of sulfur trioxide employed and is cooled to 0.degree. to +30.degree. C. and the precipitated iodine is filtered off. After the addition of sulfur trioxide, the liquid filtrate can be re-used. Perfluoroalkan-1-oic acids are obtained in a high state of purity and the bulk of the iodine is recovered in the elementary form.

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Burgkirchen, Germany

Alfons Gisser