# Acidity of 2-sulfopropanedioic acid in water

Sulfuric acid is a strong acid ($$\mathrm{p}K_\mathrm{a}$$ value below that of $$\ce{H3O+}$$: completely dissociated in water) at its first deprotonation, but is a weak acid ($$\mathrm{p}K_\mathrm{a}$$ value over that of $$\ce{H3O+}$$) in its second one.

Does it also hold for 2-sulfopropanedioic acid too, being a strong acid at its first deprotonation and being weak acids at its second to fourth deprotonations?

• Probably you get a weak second stage. Second deprotonation has to come from a carboxyl group -> expected to be a weak acid. Nov 28 '19 at 11:58
• Yes, the rest of pKa values should be only a bit lower then for malonic acid. There's no 4th value to speak of though. Nov 28 '19 at 18:15
• I think the 4th deprotonation should be deprotonation from the alpha-carbon. Dec 2 '19 at 1:25