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Hexafluorobenzene, readily prepared by pyrolysis of tribromofluoromethane, has been converted into pentafluorophenol under mild conditions and in good yield; derivatives and properties of pentafluorophenol are described. Infrared spectroscopy reveals a characteristic ring vibration near 1520 cm.-l for pentafluorophenyl derivatives and suggests that appreciable aromatic character is associated with the ring. The decreased basicity of oxygen in pentafluorophenol causes less intermolecular hydrogen bonding than with phenol, and is reflected in its relatively low b. p. (143') ; the possibility of intramolecular hydrogen bonding to the ortho fluorine atoms is considered.ALTHOUGH many per-and poly-fluoroalkyl compounds are now known, very few compounds of type ArFX, where ArF is a perfluoroaryl group and X is a functional group, have been synthesised. Hexafluorobenzene was prepared by McBee et aZ.l but the route followed is unsatisfactory for synthesis on a larger scale. Earlier work by Dkirant, only recently published,2 provides the best method for the synthesis of hexafluorobenzene : 630-640"CFBr, -C6F, Pt tubeHexafluorobenzene has since been obtained by dehydrofluorination of a nonafluorocyclohexane, but the preparation of suitable pure precursors of this type is tedious.

Elcctrolysisof solutions of alkanesulphonyl chlorides CH3*[CH2],,*S02C1 (n = 1-7) in anhydrous hydrogen fluoride gives the perfluoroalkanesulphonyl fluorides CFS*[CF2],*S02F in 25-80% yield ; the fluorides arc readily converted into the corresponding sulphonic acids CF,*[CF21n*S0,H. Certain of the by-products from the electrolysis of n-octanesulphonyl chloride have been identified. Salts and other derivatives of the acids have been prepared, and a survey has been made of the chemical and physical properties of these compounds.A GENERAL method for the preparation of the acid fluorides of perfluoroalkanesulphonic acids by electrolysis of the correspmding alkanesulphonyl chloride or fluoede was described in Part IV and exemplified by trifluoromethanesulphonic acid. Preparation of the homologues containing 2-8 carbon atoms is now recorded. Since this work was completed a patent has dealt with related studies (cf. the Experimental part below).Electrochemical fluorination of an alkanesulphonyl chloride gives smoothly the pzrfluoroalkanesulphonyl fluoride, which can be converted into the corresponding Acid :