The Hinsberg test, which can distinguish primary, secondary, and tertiary amines, is based upon sulfonamide formation. In the Hinsberg test, an amine is reacted with benzene sulfonyl chloride. If a product forms, the amine is either a primary or secondary amine, because tertiary amines do not form stable sulfonamides.
The data curve for OCI-/H3O appears to be similar to C2H3O2-/H3O because protons have not dissociated with conjugate base. This conjugate base is strong and hold proton in solution while acids try to dissociate it.
