Alkylations of a-methyl naphthalene with long-chain alkenes have been investigated in the presence of various cations bromochloroaluminate room temperature ionic liquids like 1-ethyl-3-methylimidazolium bromochloroaluminate (EMIMBr-AlCl3), butylpyridinium bromochloroaluminate (BuPyBr-AlCl3) and organic polycation ionic liquid, methylenedipyridinium bromochloroaluminate (MeDiPyCl-AlCl3). Effects of anions in ionic liquids on their catalytic performance are also studied. It is found that the BuPyBi-AlCl3 (0.67-0.75 molar fraction of AlCl3) ionic liquid exhibits outstanding catalytic properties. The influences of various reaction parameters such as dosage of catalyst, reaction temperature and reaction time on the alkylation catalyzed by BuPyBr-AlCl3 were investigated. Under the optimum reaction conditions, higher than 90% conversion of alkenes and 100% selectivity for the desired products were obtained. After reaction, the upper organic layer is separated, and the left ionic liquid is reused three times only with a slight decrease in its catalytic activation. (c) 2005 Elsevier B.V. All rights reserved.