pH Measurements of 1-alkyl-3-methylimidazolium chloride in alcohols

This paper reports the pH of binary systems containing 1-butyl-3-methylimidazolium chloride, [bmim][Cl], and alcohols [ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol, 2-butanol, 2-methyl-2-propanol (tert-butyl alcohol)] in a range of ionic liquid concentrations (c1) from 0.7 × 10−2 mol dm−3 to 3.51 × 10−2 mol dm−3 in the temperature range from 290 to 348.15 K. In this work, the pH of solutions of 1-butyl-3-methylimidazolium chloride, [bmim][Cl], or 1-octyl-3-methylimidazolium chloride, [C8mim][Cl], or 1-decyl-3-methylimidazolium chloride, [C10mim][Cl], or 1-dodecyl-3-methylimidazolium chloride, [C12mim][Cl] + ethanol are also presented, which allows us to show the effect of the alkyl chain length of the cation in the investigated ionic liquids on the solutions' pH. Our investigation permits us to find the required range of the pH values from 3.0 to 8.5. It can be noted that the pH value of binary systems consisting of a chloride ionic liquid and an alcohol is dependent on temperature, the nature of the alcohol, the alkyl chain length substituted at the imidazolium ring and the concentration of [alkylmim][Cl]. The investigated ionic liquids also exhibit superacidity properties. The acidity of the solution increases with an increase of the alkyl chain substituted at the imidazolium ring.