In following reaction chain HO-C(=O)-CH2-CH(NH3+)-COOH (Aspartic acid) ⇌ HO-C(=O)-CH2-CH(NH3+)-COO- (Zwitterion) [pKa1 = 1.9] ⇌ -O-C(=O)-CH2-CH(NH3+)-COO- [pKa2 | AITS & Test Series — Chem-Mantra | Chem-Mantra