In the title mol-ecule, C13H21ClO2, there is an intra-molecular C-H⋯Cl hydrogen bond. The conformation about the C=C bond is E and the six-membered ring has a chair conformation. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming inversion dimers, which are consolidated by C-H⋯O hydrogen bonds. The dimers are linked via C-H.·O hydrogen bonds, forming chains along [1...

The supra-molecular structure of the title compound, C(9)H(11)N(3)O(3)S(2), is defined by two inter-molecular hydrogen bonds. Pairs of N-H⋯N hydrogen bonds link the mol-ecules into centrosymmetric dimers and N-H⋯O hydrogen bonds link the dimers into a tubular chain structure running parallel to the a axis.

In the title salt, C2H5N4 (+)·C2HO4 (-), the hydrogen oxalate anions form corrugated chains parallel to the c axis, linked by inter-molecular O-H⋯O hydrogen bonds. The 5-amino-1H-1,2,4-triazol-4-ium cations are connected into centrosymmetric clusters via weak C-H⋯N hydrogen bonds forming nine-membered rings with an R 3 (3)(9) motif. These clusters are inter-connected via anions through N-H⋯O hy...

Mol-ecules of the title compound, C(14)H(13)N(3)O(2)S, are linked by inter-molecular O-H⋯O hydrogen bonds into centrosymmetric dimers forming R(2) (2)(4) rings which are further linked by O-H⋯S hydrogen bonds and weaker N-H⋯S and N-H⋯O hydrogen bonds to form a three-dimensional network.

The title compound, C(21)H(28)N(2)O(5), has two intra-molecular N-H⋯O hydrogen bonds. Inter-molecular N-H⋯O hydrogen bonds [graph-set motif R(2) (2)(8)] give rise to a dimer. Weak N-H⋯N hydrogen bonds between neighboring dimers further extend the crystal structure, which exhibits an infinite chain motif.

A total of 19 835 polar residues from a data set of 250 non-homologous and highly resolved protein crystal structures were used to identify side-chain main-chain (SC-MC) hydrogen bonds. The ratio of the number of SC-MC hydrogen bonds to the total number of polar residues is close to 1:2, indicating the ubiquitous nature of such hydrogen bonds. Close to 56% of the SC-MC hydrogen bonds are local ...

In the title compound, C18H18N4O4S2, the mean planes passing through the tosyl benzene rings form dihedral angles of 48.42 (9) and 15.1 (1)° with the amino-pyrimidine ring. In the crystal, mol-ecules associate via N-H⋯N and N-H⋯O hydrogen bonds, forming extended hydrogen-bonded sheets that lie parallel to the bc plane. The N-H⋯N hydrogen bonds propagate along the b-axis direction, while the N-H...

In the title molecular salt, 3C5H12N(+)·HSO4 (-)·SO4 (2-), each cation adopts a chair conformation. In the crystal, the hydrogen sulfate ion is connected to the sulfate ion by a strong O-H⋯O hydrogen bond. The packing also features a number of N-H⋯O hydrogen bonds, which lead to a three-dimensional network structure. The hydrogen sulfate anion accepts four hydrogen bonds from two cations, where...

The title compound, 2C(2)H(8)N(+)·C(30)H(12)N(2)O(12) (2-)·2H(2)O, comprises dimethyl-ammonium cations, 3,3'-dicarb-oxy-5,5'-(5,7,12,14-tetra-oxo-6,13-diaza-tetra-cyclo-[6.6.2.0(4,16).0(11,15)]hexa-deca-1,3,8,10,15-penta-ene-6,13-di-yl)dibenzoate dianions and water mol-ecules. The dianion is situated on a crystallographic inversion centre. Two very strong symmetry-restricted O⋯H⋯O hydrogen bond...