Since all compounds with an accessable free lone pair can act as a Brønsted-Lowry base, I was wondering if there was any specific example of a substance that when it loses a proton, it cannot accept a proton but can donate another proton.

Please note that I am not considering something like sulfuric acid which is a strong diprotic acid, as $\ce{HSO^{-}_{4}}$ still accepts a proton even if its to a limited extent.

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    $\begingroup$ What you ask for is a contradiction in terms. If your hypothetical acid exists in the protonated form in the first place, then of course it get protonated after being deprotonated. There is no going around it. True, superacids might be pretty reluctant to protonate, but what I said above still applies. $\endgroup$ Mar 25, 2019 at 7:39
  • $\begingroup$ I thought there might be a compound that upon deprotonation forms a base that is very unstable and breaks down into something else in a very one way manner? $\endgroup$
    – sab hoque
    Mar 25, 2019 at 7:47
  • $\begingroup$ If there were cooperativity you could imagine a case where the acid loses two protons or none, but not one. I don’t know of such a case. sciencedirect.com/science/article/abs/pii/… $\endgroup$
    – Karsten
    Mar 25, 2019 at 11:19
  • $\begingroup$ @sabhoque That felse like a different thing than what is asked in the question. You may want to look for anionic rearrangements. I think that one could design a molecule from which two hydrogens could theoretically be abstracted, but after the first one, it undergoes rapid rearrangement, possibly preventing the second from being abstracted. $\endgroup$
    – TAR86
    Mar 25, 2019 at 17:28

1 Answer 1


The conjugate base of sulfuric acid, bisulfate ion, shows little amphoteric character in water solution. Unless you drop the pH to about 2 or below, it is only an acid, and a moderately strong one at that.

  • $\begingroup$ what do you mean by > moderately strong one at that Do you mean that it is only a moderately strong acid at a pH less than 2? $\endgroup$
    – sab hoque
    May 2, 2019 at 8:40

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