Ab initio structure determination of the hygroscopic anhydrous form of alpha-lactose by powder X-ray diffraction.
Annealing of alpha-lactose monohydrate at 408 K yielded a mixture of this compound with hygroscopic anhydrous alpha-lactose. A powder X-ray diffraction pattern of this mixture was recorded at room temperature. The starting structural model of hygroscopic alpha-lactose was found by a Monte Carlo simulated-annealing method. The final structure was obtained through Rietveld refinements, with soft restraints on interatomic bond lengths and bond angles, and crystalline energy minimization to locate the H atoms of the hydroxy groups. The crystalline cohesion is achieved by networks of O-H...O hydrogen bonds that differ from those of the monohydrate phase. The width of the Bragg peaks is interpreted by a phenomenological microstructural approach in terms of isotropic size effects and anisotropic strain 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 Cédex, France.
Lefebvre
Jacques
J
Affouard
Frederic
F
Derollez
Patrick
P
D006860:Hydrogen Bonding; D007785:Lactose / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011208:Powders; D013816:Thermodynamics; D014961:X-Ray Diffraction
D011208:Powders; D007785:Lactose