A sulfonate's a salt or ester of a sulfonic acid. It contains the functional group R-SO2O-. Sulfonate salts Anions with the general formula RSO2O− are called sulfonates. They're the conjugate bases of sulfonic acids with formula RSO2OH. As sulfonic acids tend to be strong acids, the corresponding sulfonates are weak bases. Due to the stability of sulfonate anions, the cations of sulfonate salts such as scandium triflate have application as Lewis acids. A classic organic reaction for the… (More on Sulfonate)