Methanesulfonic acid (MSA) was used as catalyst for the electrophilic addition of long-chain olefins such as 1-dodecene to benzene. The influence of the temperature, the ratios of the reactants, the amount of MSA, and the stirring of the reaction mixture were investigated. After a 3 h reaction time at 80 C, a selectivity to the phenyldodecanes of more than 90% was obtained at 98% dodecene conversion. MSA could be recycled at least five times after a treatment with water and dichloromethane and a subsequent water removal. The presence of water in the reaction mixture was found to be detrimental for the activity of MSA. The inhibitory products formed during the reaction, as well as the crude organic phase, have been proved also as responsible for MSA deactivation. This method represents an environmentally benign alkylation route, because MSA could easily be separated from the reaction mixture via decantation and because it could be reused. In addition to that, MSA is biodegradable. (C) 2004 Elsevier Inc. All rights reserved.