4-(Prop-2-yn-1-yl­oxy)benzaldehyde

In the title mol­ecule, C₁₀H₈O₂, all non-H atoms are essentailly coplanar (r.m.s. deviation = 0.0192 Å), indicating an effective conjugation of the carbonyl group, the benzene ring and the lone pair of the propyn­yloxy O atom. In the crystal, π–π stacking inter­actions [centroid–centroid distance = 3.5585 (15) Å] connect mol­ecules into inversion dimers which are linked by Csp—H...O=C hydrogen bonds, forming a ladder-like structure.

A second monoclinic polymorph of N-(2,4-dinitro­phen­yl)-2,4-dinitro­aniline

The title compound, C₁₂H₇N₅O₈, was previously described in space group P2₁/n with Z = 4 [Wu et al. (2007). Acta Cryst. E63, o4194]. The current monoclinic P2₁/c polymorph was obtained from a mixed solution of dichloro­methane and hexane. The dihedral angle between the benzene rings is 44.16 (5)°, smaller than in the previously reported polymorph [56.3 (2)°]. As a result of the steric hinderance of the nitro groups, hydrogen bonding is limited intramolecularly. The dihedral angles between the phenyl rings and their attached nitro groups are 18.97 (6) and 17.71 (5)° at the 2-position, and 18.52 (6) and 32.41 (6)° at the 4-position.

2-(2,5-Dimethyl­phen­oxy)ethanol

There are two independent mol­ecules in the asymmetric unit of the title phen­oxy­ethanol derivative, C₁₀H₁₄O₂, Each molecule has an approximately planar structure except for the hy­droxy groups (r.m.s. deviations = 0.0281 and 0.0144 Å). The ethyl­enedi­oxy groups have a gauche conformation. In the crystal, the mol­ecules form O—H...O hydrogen-bonded chains along the a axis.

N,N-Bis(4-nitro­phen­yl)acetamide

In the title compound, C₁₄H₁₁N₃O₅, the dihedral angles between the amide group (r.m.s. deviation = 0.0429 Å) and the two benzene rings are 39.66 (6) and 63.04 (7)°. The dihedral angle between the benzene rings is 86.04 (7)°. The benzene rings form dihedral angles of 4.42 (5) and 8.91 (5)° with the adjacent nitro groups. In the crystal, mol­ecules are linked via a pair of C—H...O hydrogen bonds, forming inversion dimers, which are linked via a second pair of C—H...O hydrogen bonds, forming chains propagating along [100].

(Z)-9-(1,2-Dichloro­vin­yl)-9H-carbazole

There are two independent mol­ecules in the asymmetric unit of the title compound, C₁₄H₉Cl₂N, in which the dihedral angles between the dichloro­vinyl unit (r.m.s. deviations = 0.0003 and 0.0009 Å), and the carbazole ring are 87.77 (3) and 72.90 (3)°.

A new polymorph of 1,3-bis­(penta­fluoro­phen­yl)urea

The title compound, C₁₃H₂F₁₀N₂O, has been previously described in the space group Pbca with Z = 8 [Jai-nhuknan et al. (1997). Acta Cryst. C53, 455–457]. The current P2₁2₁2₁ polymorph was obtained from a tetra­hydro­furan solution. The penta­fluoro­phenyl rings make dihedral angles of 50.35 (6) and 54.94 (6)° with the urea fragment, in close accord with those reported for the first polymorph. In the crystal, both of the N—H groups donate H atoms to the same carbonyl O atom, forming a one-dimensional mol­ecular array along the a axis. There are close contacts between perfluoro­phenyl C atoms within the array [3.228 (3) Å] and halogen bonds are also observed between the arrays [F...F = 2.709 (2) and 2.7323 (18) Å].

2-Methyl-3-(10H-pheno­thia­zin-10-yl)buta-1,3-diene-1,1,4,4-tetra­carbo­nitrile

In the title compound, C₂₁H₁₁N₅S, the pheno­thia­zine unit has a butterfly structure, and the central six-membered ring adopts a boat conformation. The dihedral angle between the benzene rings is 127.64 (6)°, which is smaller than those reported for similar compounds because of the steric repulsion between the pheno­thia­zine and its tetra­cyano-1,3-butadiene substituent. The di­cyano­vinyl groups are almost orthogonal to one another, making a dihedral angle of 80.58 (6)°. In the crystal, the mol­ecules are aligned along the b axis. Four kinds of weak C—H...N inter­actions are recognized, one of which connects the mol­ecules into a one-dimensional array and the remaining three link these arrays.