A specific acidic group (SO3H) which gives certain cation exchange resins their ion exchange capability.

n acid derived from sulphuric acid

an often used cation exchange functional group

(-SO2OH) A specific acidic group which forms the exchange site active group in certain cation exchange resins and gives these resins their ion exchange capability.

Sulfonic acid is an hypothetical acid with formula H-S(=O)2-OH. This compound is a tautomer of sulfurous acid HO-S(=O)-OH, but less stable, and would likely convert to that very quickly if it were formed. Although this compound is unimportant, there are many derived compounds, with formula R-S(=O)2-OH for various R.