Answer to Question #23216 in Organic Chemistry for Michelle

Question

How can the amino group NH3 in an amino acid accept an H+ if it already has a full valence shell?

Answer 1

Amino acids are both amphiprotic (can accept ordonate protons) and amphoteric (can react with acids or bases).Amine groups are basic (proton acceptor), carboxylic acid groups are acidic (proton donator).(amino group NH₂ not NH₃). In case of NH₂ group it has an unshared pair of electrons, and as per VSEPR the four electron groups around a central atom will be directed towards the corners of tetrahedron to give maximum separation and this pair of electrons is the reason why amino group can accept an H⁺.