A new series of nitrile-functionalized room-temperature ionic liquids (RTILs), incorporating different anions, namely, dioctylsulfosuccinate, dodecylsulfate, benzenesulfonate, sulfobenzoate, and triflouromethanesulfonate, have been prepared and characterized using FTIR-ATR, 1H NMR, and elemental analysis. Their physical properties such as density, viscosity, refractive index, and thermal stability were measured and reported for a temperature range from (293.15 to 353.15) K at atmospheric pressure. © 2011 American Chemical Society.