6.21

[rita_h]

In the textbook, Why does the compound only accept protons at the level of Nitrogens and not at the level of oxygen?
Can someone explain what electronegativity has to do with this? ( I get that oxygen is much more electronegative than nitrogen, but why exactly can't it accept the protons)?

[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. You always want to look for the most stable structure. Nitrogen is less electronegative and more likely to share its electrons, so its going to accept those protons.