The pKa's of the side chain group and the α-carboxyl group of glutamate are 4.1 and 2.1,respectively.Which statement accounts for this difference?
A)The side chain has more possible resonance structures.
B)The α-carboxyl group has less steric hindrance and is therefore ionized more easily.
C)The side chain is a different functional group than the α-carboxyl group.
D)The α-carboxyl group is closer to the α-amino group than the side chain is.

Question

Quizplus · Accepted Answer

The α-carboxyl group is closer to the α-amino group, which can stabilize the carboxylate ion through intramolecular interactions, making it easier to ionize and thus lowering its pKa compared to the side chain carboxyl group.

The PKa's of the Side Chain Group and the α-Carboxyl