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Only the following fluorine derivatives of fluorene have been prepared : 4-fluoro-5-nitro-lmethylfluorene, 2-fluorofluorenone and its oxime, 2.3 2-fluoro-9,9-dichlorofluorene and several 9,9-condensation products, and peduorofluorane ( C U F~~) .~Since the 9-position in fluorene has aliphatic properties and has never been fluorinated independently of the rest of the molecule, it seemed of interest to attempt the preparation of 9,9-difluorofluorene. The difluoro compound was selected because it seemed doubtful if the allylic character of the 9-carbon6 would permit the preparation of 9-monofluorofluorene.Little difficulty was expected in the preparation of 9,9-difluorofluorene because Heme and Lei-cester6 had reported the preparation of diphenyldifluoromethane in yields of 60%.We treated 9,9-dichlorofluorene with hydrogen fluoride in the presence of mercuric oxide. To reduce the violence of the reaction, toluene or chlorobenzene was used as a diluent. The products that were obtained from the reaction were fluorenone, toly lmercuric chloride and mercuric chloride.It is not clear whether the formation of fluorenone is the primary reaction. It is possible that hydrogen fluoride reacted with mercuric oxide to produce water and that 9,9-dichlorofluorene was subsequently hydrolyzed to fluorenone. 2HF + HgO + H2O + HgFz Other catalysts such as antimony tri-and pentafluoride and zinc fluoride also gave fluorenone or intractable tars as did the use of uncatalyzed hydrogen fluoride. Impure 9,9-fluorochlorofluorene may have been present in some of these products. The monofluorochloro derivatives are generally less stable than the difluoro compounds. ' Despite the fact that hydrous mercuric fluoride was entirely unsuitable as a catalyst, Hemes later found that it was not necessary to isolate mercuric fluoride but simply passed a stream of hydrogen fluoride into the mixture of mercuric oxide and the substance. This was the first method tried and it led to the formation of fluorenone.The inconvenient preparation of mercuric fluoride from mercuric chloride and fluorine and the bad effects of mercuric oxide in the second method might both be avoided by passing hydrogen fluoride into a mixture of mercuric chloride and the substance to be fluorinated. Daudt and Youker, U. S. Patent 2,005,707, disclose the use of mercuric chloride in vapor phase hydrofluorination a t elevated temperatures but give no experimental details.On carrying out this experiment at 70°, we obtained the desired 9,9-difluorofluorene in addition to some of the unstable material obtained previously and thought to be 9,9-fluorochlorofluorene.An attempt to increase the yield by operating at 100 pounds pressure produced a sponge-like rubbery hydrocarbon mass of approximately 2800 molecular weight. 9,9-Difluorofluorene formed white crystals that melted a t 47-48' and analyzed correctly for fluorine and had the required molecular weight. After standing for two weeks in a desiccator evidence of decomposition was apparent.It is thus seen that mercuric chloride and hydr...

Received 8.viii.69 f r o m the Department of Pediatric Pathologu, Karolinska sjuk-Requests for reprints should be addressed to Bengt Robertson, RI. D., Department huset, Stockh,olm, Sweden. o f Pcdiatric Pathology, Karolinska sjulihnset, S-104 01 Stockholm, Sweden. Received 25.vi.69 from the Department of Pathologu, Maria Hospital, Helsinki/ Helsingfors 18, Finland and the Department of Anatomu, Uniuersitu of Helsinki, Helsinki 17. Finland.