Clark and Gollan's discovery triggered the investigation on the possible use of PFC as oxygen-carrying fluids and Slovitor and Geyer's breakthrough using PFC in an emulsified form has made it realistic. One of the most important factors relating to the realization of such oxygen-carrying fluids is the synthesis of PFC which are non-toxic, have high oxygen and carbon dioxide solubilities, are stable as an emulsion for 2 years even at room temperature; and are easily removable from the body in an unchanged form after accomplishing its role with the formation of the natural blood.
Various PFC are disclosed in patents, wherein they are described as being suitable as an oxygen and carbon dioxide carrier. Almost all of the PFC patented are prepared by the electrochemical fluorination method or the cobalt trifluoride method. The cobalt trifluoride method, which is excellent in preparing perfluorohydrocarbon, is too vigorous to fluorinate ethers. That is, degradation products are caused by the cleavage of oxygen and carbon bonds. The electrochemical fluorination method, which is excellent in preparing perfluoro amine, has limited utility in preparing perfluoro cyclic ethers. Therefore, in general, perfluorocyclic ethers, which are believed to be suitable as an oxygen and carbon dioxide carrier, remain to be synthesized. The exception are the ones synthesized by the electrochemical fluorination method, such as those set forth below: ##STR1## described by Abe et al (e.g., T. Abe, E. Hayashi, H. Baba and S. Nagase: J. Fluorine Chem. 25:419 (1984), and Japanese Patent Application (OPI) Nos. 119449/79, 119471/79, 128566/79 and 44071/80.
In the present invention, the substrates followed by the prefix "perfluoro" mean substrates having all of the hydrogens replaced by fluorine atoms but containing no halogens such as chlorine, bromine and iodine, and they may be cyclic or straight-chain compounds. Furthermore, polyfluorinated compounds with a few chlorine atoms denote substrates wherein the hydrogens are mostly replaced by fluorines, but the rest of the hydrogens, usually one or two hydrogens, are replaced by chlorine atoms.