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This question is from the National Standard Examination in Chemistry, India, 2019

My take on this question : a total of 5 moles of $\ce{CH3I}$ should be consumed.

  1. The oxygen atoms in the $\ce{2 OH}$ groups each have a lone pair of electrons. They should displace $\ce{I-}$ from methyl iodide via an $\ce{S_N2}$ reaction.

  2. The two nitrogen atoms in the tertiary amino moieties also should react with a total of 2 moles of $\ce{CH3I}$ .

  3. The $\ce N$ atom in the pyridine moiety should also consume a mole, as the lone pair of electrons on it is not in conjugation with the benzene nucleus.

However, as I checked the answer, it's provided as 3. What may be the fallacy in my reasoning?

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    $\begingroup$ The OH groups will not methylate without being deprotonated first, there is no base present strong enough to do this. $\endgroup$ – Waylander Mar 25 at 7:51
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    $\begingroup$ Please note that the proper term for "number of moles" is amount of substance. The former would be the same as referring to the mass as "number of kilograms". It makes it even worse seeing this on the picture of a textbook question. I am sad now. $\endgroup$ – Martin - マーチン Mar 25 at 18:01
  • $\begingroup$ Why so? A mole of CH3I is equal to a gram equivalent of CH3I. $\endgroup$ – Aabesh Ghosh Mar 26 at 5:37

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