AbstractFriedel‐Crafts acetylation of phenanthrene (1a) insym‐tetrachloroethane yields mixtures of 2‐, 3‐ and 9‐acetylphenanthrenes (2a, 3a, 4). The distribution of isomers is found to depend strongly upon the method of mixing the reagents. Acetylation of 9‐chlorophenanthrene (1b), performed by a variety of methods and solvents, led mainly to 3‐acetyl‐9‐chlorophenanthrene (3b) (≥85%). Previously unreported 2‐acetyl‐9‐chlorophenanthrene (2b) was found to form up to a ma