PhOH was condensed with EtOCO(CH(2))(2)COMe to 4,4'-bis-(p,p'-hydroxyphenylpentanoic acid in 1-n-alkyl-3-methylimidazolium tetrachloroaluminate ionic liqs. (alkyl = Et, Bu, hexyl or octyl) for 3 h at room temp. The highest yield of bisphenol (72.39%) was achieved when the hexyl contg. ionic liq. was used as the reaction medium. The yield was even higher than in the case of the std. HCl catalysts (51.62%). As by-product, isomeric 4-(p-hydroxyphenyl)-4-(o-hydroxyphenyl)pentanoic acid was obtained by rearrangement of the resp. lactone.