Introduction.

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The crystal structure of benzanilide has been determined from Weissenberg photographs using Cu Kα radiations and refined to an R value of 0.075 for 766 independent reflections. The crystals are monoclinic, space group C2/c, Z=4, with a=24.34(4), b=5.325(3), c=8.012(8) Å, β=107.2(3)°, Dm=1.32 and Dx=1.321 g cm−3. Dihedral angle between the benzene rings is 62.6°, and each benzene ring makes dihedral angle of 31.3 and 31.6° with the plane of amido group as found in Kevlar and Nomex polymers. The molecules related by a b-translation are linked together by N–H…O hydrogen bond [N…O 3.112(6), H…O 2.03 Å, N–H…O 157°] to form a chain along b. The chains are held together primarily by dipole forces of carbonyl groups of the molecules related by inversion centers to form a sheet parallel to the bc plane. The sheets are stacked along a with disorder by van der Waals interactions.

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The origin of the crystallographic pedigree [Haisa (1978). Acta Cryst. A34, 753-759] by the balance of the interactions between the neighbors of atomic contents which can be estimated from the lifting of the degeneracy of the nearest-neighbor distances, or the coordination index. When the interactions become out of balance, a descent of the space group through Pm3m, Im3m and P63/mmc to their subgroups occurs to form the crystallographic pedigree.

The crystal and molecular structure of p-hydroxybenzoic acid monohydrate has been determined by a single crystal X-ray analysis. The crystals are monoclinic, space group P21⁄a, Z=4, with a=17.79, b=6.39, c=6.79 Å, and β=105.6°. The structure was solved by the Patterson and Fourier methods, and refined by the block-diagonal least-squares method to a final R value of 0.086 for 806 non-zero reflections. Pairs of acid molecules form dimers by the hydrogen bonds between carboxyl groups (2.678 Å). The dimers are held together by the hydrogen bonds between phenolic hydroxyl groups and water molecules (2.595 and 2.823 Å); these hydrogen bonds extend around two-fold screw axes to make up layers of the dimers parallel to the (401). The layers are linked by the additional hydrogen bonds between carbonyl oxygens and water molecules (2.823 Å).

The crystal structures of the N-aromatic amides p-acetanisidide [ N-(4-methoxyphenyl)

Isomorphous crystals of 5-chloro-7-iodo- and 5,7-dibromo-8-quinolinols have been examined by X-ray analysis. Both compounds crystallize in the monoclinic space group P2⁄a with four formula units in the unit cell. The cell dimensions are: a=16.98; b=4.16; c=14.84 Å, and β=112.0° for 5-chloro-7-iodo-8-quinolinol, and a=16.34, b=4.02, c=15.52 Å, and β=115.6° for 5,7-dibromo-8-quinolinol. The structure of the former, chinoform, has been determined by the Patterson methods from data collected with MoKα radiation on Weissenberg photographs, and refined by the block-diagonal least-squares method, with anisotropic temperature factors. The final R value is 0.081 for 836 observed reflections. The quinolinol molecule is nearly planar. In the crystals, the molecules related by two-fold axis are held together by hydrogen bonds to form bent dimers, which are stacked closely by van der Waals forces along the b axis.