R. K. Rajaram

Reinvestigation of the crystal structure of diglycine hydrochloride

A reinvestigation of the crystal structure of diglycine hydrochloride, (NH2CH2COOH)2HCl, was carried out. The structure is orthorhombic, space group Fly2{lx, with a = 5.2992(6), b = 8.083(2), c = 17.973(2) A and Ζ = 4. Three-dimensional intensity data collected on a CAD 4 diffractometer using CuKa radiation was used for the structure elucidation and refinement. The final R value is 0.055 for 779 reflections. All the hydrogen atoms have been located in the present study. The glycine molecules are held together by a network of N —H...C1, Ν—H...O and Ο—Η... Ο hydrogen bonds. One of the glycine molecules exists as a zwitterion whereas the other one in the cationic form.

l-Valinium picrate

In the title compound, C5H12NO2+·C6H2N3O7−, the carboxyl group of the valinium residue is engaged in a strong hydrogen bond with the picrate anion. The amino group of the l-valinium cation and the picrate anion are held together by an intermolecular hydrogen bond. The valine residue is involved in a zigzag (Z1) head-to-tail sequence.

Bis(l‐proline) hydrogen nitrate

In the title compound, 2C5H9NO2·H+·NO3−, the two proline residues are linked by a strong O—H⋯O hydrogen bond, with an O⋯O distance of 2.414 (3) A. In one of the residues, the pyrrolidine ring adopts an envelope conformation, while in the other it adopts a half-chair conformation. N—H⋯O hydrogen bonds link the two residues to form double-chain structures down the a axis, which are interlinked by N—H⋯O hydrogen bonds involving the O atoms of the nitrate ions.

l‐Leucine l‐leucinium picrate

The asymmetric unit of the title compound, C6H13NO2·C6H14NO2+·C6H2N3O7−, contains two unprotonated leucine residues, two protonated leucinium cations and two picrate anions. The leucine residues show a class II hydrogen-bonding scheme and the leucinium residues show a class I hydrogen-bonding scheme. The leucine and leucinium residues form infinite hydrogen-bonded chains running along the a axis.

Bis(l-proline) hydrogen(1+) perchlorate

In the title compound, 2C5H9NO2·H+·ClO4−, two proline residues are linked by a strong O—H⋯O hydrogen bond with an O⋯O distance of 2.474 (6) A. Conformational disorder is observed in the pyrrolidine rings of the two proline residues. In one of the residues, both the major and minor conformers adopt conformations intermediate between half-chair and envelope, whereas in the other residue, they adopt envelope conformations. The crystal structure is stabilized by a number of N—H⋯O hydrogen bonds.

dl‐Methio­nine dl‐methio­ninium picrate

The asymmetric unit of the title compound, (C5H11NO2SC5H12NO2S+.C6H2N3O7-)-C-., is composed of two crystallographically independent methionine residues and a picrate anion. The methionine and protonated methioninium residues are bonded through a strong O-(HO)-O-... hydrogen bond, and an inversion-related DL1 head-to-tail sequence along the a axis is observed in the zwitterion. The amino groups of two residues connect to the lone oxygen of two inversion-related picrate anions. Hydrophobic layers are observed in the y = 0 plane.

β-Alanine β-alaninium picrate

In the title compound, C3H7NO2·C3H8NO2+·C6H2N3O7−, each β-alanine residue forms an asymmetric O—H⋯O hydrogen bond with its inversion-related partner [O⋯O = 2.477 (4) and 2.472 (4) A], involving disorder of carboxylic acid and carboxylate groups. The crystal structure is further stabilized by N—H⋯O hydrogen bonds.

Bis(β-alanine) hydrogen nitrate

In the title compound, 2C3H7NO2.H+·NO3−, both the alanine residues, related by a center of symmetry, are linked by a strong symmetric O—H⋯O hydrogen bond with an O⋯O distance of 2.467 (2) A. The N atom and one of the O atoms of the nitrate anion lie on the twofold axis.

Hydrogen‐bonding patterns in 2‐amino‐4,6‐dimethyl­pyrimidine–cinnamic acid (1/2)

In the title compound, C(6)H(9)N(3)center dot 2C(9)H(8)O(2), an aminopyrimidine-cinnamic acid 1:2 cocrystal, the 2-amino-4,6dimethyl-pyrimidine molecule forms two eight-membered hydrogen-bonded rings R-2(2)(8) motif] with the carboxylic acid groups from two independent cinnamic acid molecules via N-H center dot center dot center dot O and O-H center dot center dot center dot N hydrogen bonds. The cinnamic acid molecules are linked by C-H center dot center dot center dot O hydrogen bonds to form chains along two axes.

l-Valine l-valinium perchlorate monohydrate

In the title compound, C5H12NO2+·ClO4−·C5H11NO2·H2O, the valine as a zwitterion and valinium are bonded through a strong O—H⋯O hydrogen bond. Their ammonium groups and the perchlorate ion are held together by hydrogen bonds. Both valine and valinium show gauche-II forms.