are typically charged into an autoclave with such inhibitors as phenothiazine u03b2 pinene and the like and the mixture is heated at a suitable temperature e g at 150 u00b0 c for 12 hours under autogenous pressure when the reaction is complete the autoclave is cooled and gaseous substances are evacuated through a cold trap the liquid contents are then removed and subjected to a preliminary distillation followed by final purification by means of preparatory scale vapor phase chromatography or by other suitable techniques compounds of sufficiently high purity for anesthetic use are obtained in this manner some of the ethlenic compounds that may be employed to synthesize the anesthetic products of the invention are listed in table i along with some of the physical properties of the products it should be noted that the cyclobutyl ethers used in this invention may also be obtained from different pairs of ethylenic compounds with or without further post cyclization halogenation for instance the ether of example i may be synthesized by the cyclization of u03b2 chlorodifluorovinylmethyl ether with tetrafluoroethylene table 1______________________________________synthesis and physical properties of anesthetic compounds boilingex cyclobutane reactants density point______________________________________1 1 cl 2 f sub 2 c cf o ch sub 3 1 521 sup 27 5 89 u00b0 cmethoxy hexafluoro f sub 2 c cfcl2 1 cl 2 h sub 2 c ch o ch sub 3 1 323 sup 24 120 8 u00b0 methoxy 1 4 4 trifluoro f sub 2 c cfcl3 1 br 2 f sub 2 c cf o ch sub 3 1 780 sup 25 104 u00b0 methoxyhexafluoro.