(2S)-1-Carbamoylpyrrolidine-2-carboxylic acid

In the title compound, also known as N-carbamoyl-L-proline, C₆H₁₀N₂O₃, the pyrrolidine ring adopts a half-chair conformation, whereas the carboxyl group and the mean plane of the ureide group form an angle of 80.1 (2)°. Mol­ecules are joined by N-H...O and O-H...O hydrogen bonds into cyclic structures with graph-set R²₂(8), forming chains in the b-axis direction that are further connected via N-H...O hydrogen bonds into a three-dimensional network.

Hydrogen-bonded networks in trans-3-(3-pyrid­yl)acrylic acid and rctt-3,3′-(3,4-dicarboxy­cyclo­butane-1,2-diyl)­dipyridinium dichloride

The structure of trans-3-(3-pyridyl)acrylic acid, C₈H₇NO₂, (I), possesses a two-dimensional hydrogen-bonded array of supra­molecular ribbons assembled via heterodimeric synthons between the pyridine and carboxyl groups. This compound is photoreactive in the solid state as a result of close contacts between the double bonds of neighbouring mol­ecules [3.821 (1) Å] along the a axis. The crystal structure of the photoproduct, rctt-3,3′-(3,4-dicarboxy­cyclo­butane-1,2-diyl)­dipyridinium dichloride, C₁₆H₁₆N₂O₄²⁺·2Cl⁻, (II), consists of a three-dimensional hydrogen-bonded network built from crosslinking of helical chains integrated by self-assembly of dipyridinium cations and Cl⁻ anions via different O—H...Cl, C—H...Cl and N⁺—H...Cl hydrogen-bond inter­actions.

(S)-5-Benzyl­imidazolidine-2,4-dione monohydrate

The crystal structure of the title compound, C₁₀H₁₀N₂O₂·H₂O, also known as L-5-benzylhydantoin monohydrate, is described in terms of two-dimensional supra­molecular arrays built up from infinite chains assembled via N-H...O and O-H...O hydrogen bonds among the organic mol­ecules and solvent water mol­ecules, with graph-set R³₃(10)C(5)C²₂(6). The hydrogen-bond network is reinforced by stacking of the layers through C-H...[pi] inter­actions.