Structure determination of forms I and II of phenobarbital from X-ray powder diffraction.
From pure powders of forms I and II of phenobarbital, X-ray diffraction patterns were recorded at room temperature. The starting crystal structural models were found by a Monte-Carlo simulated annealing method. The structures of the two forms were obtained through Rietveld refinements. Soft restraints were applied on bond lengths and bond angles, all H-atom positions were calculated. The cell of form I is monoclinic with the space group P2(1)/n, Z=12, Z'=3. Form II has a triclinic cell, with the space group P1 , Z=6, Z'=3. For both forms, the crystal cohesion is achieved by networks of N-H...O hydrogen bonds along [101]. The broadening of the Bragg peak profiles is interpreted in terms of isotropic strain effects and anisotropic size effects.
Platteau
Cyril
C
Laboratoire de Dynamique et Structure des Matériaux Moléculaires (UMR CNRS 8024), UFR de Physique, Bâtiment P5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq CEDEX, France.
Lefebvre
Jacques
J
Hemon
Stephanie
S
Baehtz
Carsten
C
Danede
Florence
F
Prevost
Dominique
D
D007536:Isomerism; D008958:Models, Molecular; D015394:Molecular Structure; D010634:Phenobarbital / Q000737:chemistry*; D033362:Powder Diffraction; D014961:X-Ray Diffraction
D010634:Phenobarbital