Looking at the examples in Tautomer on Wikipedia, it seems that the hydrogen needs to travel a significant distance (~20Å) for the interconversion to take place. What lets it happen so fast? Why interconversion is preferred over maintaining its position?

Tautomer examples (source)

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    $\begingroup$ I think this is too similar to your other question to deserve its own entry. You can just edit the other question adding a small sentence asking about tautomerisation kinetics. $\endgroup$ Apr 4, 2015 at 18:06
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    $\begingroup$ 1) tautomerisation isn't quick 2)where did you found sth like 20A ? $\endgroup$
    – Mithoron
    Apr 4, 2015 at 19:43
  • $\begingroup$ Tautomerisation doesn't proceed by an intramolecular mechanism generally, and it is also rarely fast. $\endgroup$
    – J. LS
    Apr 5, 2015 at 7:49
  • $\begingroup$ @J.LS, on Wikipedia it says "Because of the rapid interconversion, tautomers are generally considered to be the same chemical compound.", but I don't really know what "rapid" actually means in this context. $\endgroup$
    – Sparkler
    Apr 6, 2015 at 15:23
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    $\begingroup$ I think that refers to the fact that interconversion is fast enough that you get equilibrium population of tautomers. $\endgroup$
    – J. LS
    Apr 6, 2015 at 18:10

1 Answer 1


If you are using a protic solvent (the most common situation when you're dealing with polar functional groups), then you are "cheating" because the solvent can generate its own proton transfers, making the reaction look rapid.


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