In the title compound, C4H10NO3+C2HO4-, the DL-threonine molecule exists as
a cation and the oxalic acid molecule in the mono-ionized state. The molec
ules aggregate into infinite parallel layers which extend along the diagona
l of the ac plane. These layers have no hydrogen-bonded interactions betwee
n them, only van der Waals interactions. The semi-oxalate ion deviates far
from planarity. No classic head-to-tail hydrogen bonds are observed.