I'm asking this because I found a link for imidazole-HCl buffer: , but from what I understand, a buffer is a weak acid or base with its corresponding salt. Would imidazole-HCl buffer be a salt solution, or does it have a weak acid or base as well (if it does, what is the weak acid/base)? Also, I found two different pictures for imidazole hydrochloride:
Which one is correct? Is imidazole-HCl a salt or a buffer?
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$\begingroup$ Welcome to chemistry.SE! If you had any questions about the policies of our community, please visit the help center. Nice question, BTW! $\endgroup$– M.A.R.Jul 31, 2015 at 19:45
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1 Answer
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The correct structure of the salt is as shown above. This structure is more stable than the one that has two hydrogens on the same nitrogen - due to electron delocalization.
If you have a water solution of about 50/50 imidazole base and the hydrochloride salt, you get the maximum buffer capacity, due to the fact that both acid and base forms are present, and a small amount of a strong acid or base subsequently added to the mixture will react with these imidazole species, and therefore have little effect on the pH.
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1$\begingroup$ It may be worth adding that since the lone pair in the other nitrogen is a part of the pi-cloud (aromatic sextet) and therefore the basicity of this nitrogen would be low. $\endgroup$– WYSIWYGAug 19, 2015 at 11:48