In the crystal structure of the title compound, C(10)H(12)O(4), O-H⋯O hydrogen bonds incorporating R(2) (2)(10) and R(2) (2)(14) motifs link mol-ecules into chains along [1[Formula: see text]0]. An intra-molecular O-H⋯O hydrogen bond is also observed.

In the title compound, C(16)H(21)BrO(2), the cyclo-hexane ring adopts a chair conformation. The hy-droxy and carbonyl groups are involved in an intra-molecular O-H⋯O hydrogen bond. In the crystal, weak C-H⋯O inter-actions link the mol-ecules into zigzag chains along [010].

In the title compound, C(22)H(26)OS(2), prepared from (-)-1R-cis-caronaldehyde, the 1,3-dithiane ring adopts a chair conformation. An intra-molecular O-H⋯S hydrogen bond influences the mol-ecular conformation. In the crystal, weak inter-molecular C-H⋯S and C-H⋯O hydrogen bonds link the mol-ecules into chains propagating along [010].

In the crystal structure of the title compound, C(6)H(9)N(2) (+)·C(3)H(3)O(4) (-), all the amino H atoms are involved in inter-molecular N-H⋯O hydrogen bonds, which link the ions into double chains parallel to [101]. In the anion, an intra-molecular O-H⋯O hydrogen bond is observed.

The title compound, C(5)H(9)NO(2), is almost planar (r.m.s. deviation for the non-H atoms = 0.036 Å) and an intra-molecular N-H⋯O hydrogen bond generates an S(6) ring. In the crystal, N-H⋯O inter-actions link the mol-ecules into C(6) chains propagating along [010].

In the title compound, C(21)H(18)N(2)O(2), the amino group is involved in an intra-molecular N-H⋯O hydrogen bond. The rings make dihedral angles of 37.9 (2), 64.4 (2) and 83.6 (2)°. In the crystal, inter-molecular O-H⋯N and O-H⋯O hydrogen bonds link the mol-ecules into chains running along [100].

In the title mol-ecule, C12H11NO2S, the dioxane-type ring adopts a half-chair conformation. The thio-phene ring forms a dihedral angle of 12.53 (6)° with the benzene ring. In the crystal, N-H⋯O, hydrogen bonds link mol-ecules, forming chains along the c-axis direction. A weak intra-molecular C-H⋯O hydrogen bond is observed.

In the title compound, C11H15N3O2S·C2H3N, the dihedral angle between the benzene ring and the mean plane of the hydrazinecarbothio-amide group is 75.1 (2)°. In the crystal, the main mol-ecule is linked to the solvent mol-ecule by a weak N-H⋯N hydrogen bond while O-H⋯S hydrogen bonds link the mol-ecules into columns along [100].

In the title compound, C(12)H(14)O(4), a derivative of caffeic acid [(E)-3-(3,4-dihy-droxy-phen-yl)-2-propenoic acid], an intra-molecular O-H⋯O hydrogen bond forms an S(5) ring. In the crystal, inter-molecular O-H⋯O hydrogen bonds link mol-ecules into chains propagating in [110].

The title compound, C(5)H(6)ClN(3), was synthesized by the reaction of 2,3-dichloro-pyridine and hydrazine hydrate. An intra-molecular N-H⋯Cl hydrogen bond results in the formation of a planar (mean deviation 0.038 Å) five-membered ring. In the crystal, inter-molecular N-H⋯N hydrogen bonds link the mol-ecules into a three-dimensional network.