Abstract The double effect of ethylaluminium sesquichloride on ω-phenylcarboxylic acid chlorides with a chain length of C 3 to C 6, namely alkylation and Friedel-Crafts cyclization was investigated. It was established that the two alternatives are possible only with 4- phenylbutyryl chloride. Depending on the reaction conditions, both alkylation and cyclization yield 6-phenyl-3-hexanone, as well as 1-tetralone. The other three ω-phenylcarboxylic ...