Textbook 6.21

[Gabriel Wolf 3I]

Question: the structure of one of DNA's bases, thymine, is shown. How many protons can this base accept? Draw the structure of each conjugate acid that can be formed. Mark with an asterisk any structure that can show amphiprotic behavior in an aqueous solution.

For this one you need to look in the textbook at the structure. Could somebody walk me through this? Why can't the oxygens accept protons with their lone pairs? What does it mean by draw the structure of the conjugate acid? Also, I thought amphiprotic behavior was only for elements on that weird diagonal between transition metals and nonmetals?

[jennaj3k]

Oxygen is more electronegative than Nitrogen so it's unlikely to share its electrons. If it did, then thymine would have a positive charge which isn't stable. Nitrogen is less electronegative and more likely to share its electrons, so its going to accept those protons.