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?

  • 1
    $\begingroup$ Probably you get a weak second stage. Second deprotonation has to come from a carboxyl group -> expected to be a weak acid. $\endgroup$ Nov 28, 2019 at 11:58
  • 1
    $\begingroup$ 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. $\endgroup$
    – Mithoron
    Nov 28, 2019 at 18:15
  • $\begingroup$ I think the 4th deprotonation should be deprotonation from the alpha-carbon. $\endgroup$ Dec 2, 2019 at 1:25


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