158 THE FORMATION OF CYCLIC KETONESgen fluoride, although better yields have been obtained by the Friedel-Crafts method (Table II, examples 8, 9, 10, 11). The cyclization ofy-phenylbutyric acid to tetralone-1 (Table III) is perhaps best effected bythis new method.General Procedure.Liquid hydrogen fluoride (b.p. 19.4°) containingonly 0.1-0.2% of water is available commercially in steel cylinders. It ishighly corrosive to tissue,1820and the vapors are very toxic. Conse-quently, it should be handled with care; goggles and rubber gloves mustbe worn. With heed to these precautions hydrogen fluoride can behandled safely and easily.The reactions may be carried out in the hood in an open containerwithout provision for reflux. Platinum vessels appear to be most satis-factory, although copper flasks also may be used.183The vessel contain-ing the acid to be cyclized is tared on a rough balance in the hood andfilled with 7 to 30 parts (based on the weight of acid) of hydrogen fluoridefrom the inverted tank through a copper tube.
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