1-Aza­niumyl­cyclo­butane-1-carboxyl­ate monohydrate

In the title compound, C₅H₉NO₂·H₂O, the amino acid is in the usual zwitterionic form involving the α-carboxyl­ate group. The cyclo­butane backbone of the amino acid is disordered over two conformations, with occupancies of 0.882 (7) and 0.118 (7). In the crystal, N—H...O and O—H...O hydrogen bonds link the zwitterions [with the water molecule involved as both acceptor (with the NH₃⁺) and donor (through a single carboxylate O from two different aminocyclobutane carb­oxylate moities)], resulting in a two-dimensional layered structure lying parallel to (100).