Question on Problem 6.21

[AChoudhry_1L]

The two strands of the nucleic acid DNA are held together by hydrogen bonding between four organic bases. The structure of one of these bases, thymine, is shown below. (a) How many pro- tons can this base accept? (b) Draw the structure of each conjugate acid that can be formed. (c) Mark with an asterisk any structure that can show amphiprotic behavior in aqueous solution.

When drawing the conjugate acids, why do the protons only attach to the NH groups and not the oxygens?

[Cynthia Gong 1L]

This is because oxygen is more electronegative and less likely to share its electrons with a proton