Selective Tert-Butylation of p-Cresol with Acidic Ionic Liquids

Uses of antioxidants in composite propellants formulation is unavoidable. These materials are added to propellants to afford stability during storage time. In this paper, synthesis of 2-t-butyl p-cresol intermediate for the preparation of A.O.2246 using Bronsted acidic ionic liquids as catalyst and solvent were investigated. Methyl-tert-butyl ether was used for tert butylation of para cresol and variable reaction parameters such as temperature, mole ratio, type and catalyst composition and time were optimized. Tert butylation of p-cresol gives two products, 2-tert-butyl p-cresol and 2,6-di-tert-butyl p-cresol. Among ionic liquids, triphenyl(butyl-4-sulphonyl) phosphonium sulfonate, irrespective of the alkylating agent, is the most active catalyst. In the presence of triphenyl(butyl-4-sulphonyl) phosphonium sulfonate, 2-t-butyl p-cresol was the main product of reaction with 91.7% of selectivity and 73.2% of p-cresol conversion.