Friedel–Crafts acylations of aromatic hydrocarbons. Part XV. Acetylation of 2-methylnaphthalene

Abstract

In the Friedel–Crafts acetylation of 2-methylnaphthalene all seven possible isomers are formed, their proportions depending on the experimental conditions. The yields of the isomers vary within the limits given in parentheses : 1 -(0·3–33%), 3-(0·8–14%), 4-(0·8–5·5%). 5-(0·4–2·0%), 6-(7·4–73%), 7-(4·2–58%), and 8-(9–59%). Competitive acetylation experiments in chloroform solution at 20° gave the following positional reactivities : 1-naphthyl 1·00, 2-naphthyl 0·31, 2-methyl-1-naphthyl 11·4, 2-methyl-3-naphthyl 0·31, 2-methyl-4-naphthyl 1·37, 2-methyl-5-naphthyl 0·19, 2-methyl-6-naphthyl 7·02, 2-methyl-7-naphthyl 1·78, and 2-methyl-8-naphthyl 16·1; the corresponding values obtained in nitromethane solution were: 1·00, 8·3, 6·9, 10·8, 6·1, 11·0, 177, 32·6, and 42·3, respectively. Overall and positional reactivities of 2,3-, 2,6-, and 2,7-dimethylnaphthalenes were calculated, and compared with results from earlier experiments.