The friedel–crafts acetylation of phenanthrene

Abstract

The Friedel–Crafts acetylation of phenanthrene affords mixtures of 1-, 2-, 3-, 4-, and 9-acetylphenanthrenes, the proportions of which (determined by gas chromatography) vary widely according to the conditions. In ethylene dichloride the major product is the 9-isomer (54% yield); in nitrobenzene (65%), nitromethane (64%), benzene (47%), and carbon disulphide (39–50%) it is the 3-isomer. In chloroform equal amounts (37%) of the 0- and the 9-isomer are formed. The proportion of 1-isomer ranges from 2%(in ethylene dichloride) to 18%(in chloroform); of the 2-isomer from 4%(in ethylene dichloride) to 27%(in nitromethane); and of the 4-isomer from 0·5%(in chloroform) to 8%(in carbon disulphide). In a reaction.carried out in carbon disulphide the 9- and the 1-ketone are gradually converted into the 3- and the 2-isomer, and more slowly the 3-ketone into the 2-ketone. Reversibility is not, however, responsible for the initial formation of the 3- and 2-isomers. Relative reactivities: 1-naphthyl 1·00, 3-phenanthryl 0·643, 9-phenanthryl 0·616, 1-phenanthryl 0·293, 2-naphthyl 0·278, 2-phenanthryl 0·122, and 4-phenanthryl 0·0085 have been determined by competitive Perrier acetylation of phenanthrene and naphthalene in chloroform solution.