2.1. Crystal data

The title compound, C5H9NO4, crystallized as a zwitterion. There is an intramolecular N—H O hydrogen bond involving the trans-succinic acid and the ammonium group, forming an S(6) ring motif. In the crystal, molecules are linked by O—H O hydrogen bonds, forming C(7) chains along the c-axis direction. The chains are linked by N—H O and C— H O hydrogen bonds, forming sheets parallel to the bc plane. Further N—H O hydrogen bonds link the sheets to form a three-dimensional framework