title: Formation of isomorphic desolvates: creating a molecular vacuum.
abstract: The objective of this work was to investigate a common but poorly understood category of crystalline organic substances: isomorphic desolvates. When solvent is lost from a crystal lattice but the lattice retains its three-dimensional order, a lattice is created which is in a high-energy state relative to the original solvate structure. The desolvated lattice can reduce its internal energy by either resorbing solvent or by relaxation processes which increase the packing efficiency of the solid by reducing the unit cell volume. In the following paper, solid-state properties of isomorphic desolvates of cephalexin, cefaclor, erythromycin A, and spirapril hydrochloride hydrates are investigated. The hygroscopicity of the compounds are evaluated using a vacuum moisture balance, and structural relaxation is measured using a combination of X-ray powder diffraction and isothermal microcalorimetry. The study results are explained in terms of Kitaigorodski's close packing principle.
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, Indiana 46285, USA. Stephenson_GregoryA@lilly.com
authors.forename: G A
authors.initials: GA
authors.lastname: Stephenson
authors.forename: E G
authors.initials: EG
authors.lastname: Groleau
authors.forename: R L
authors.initials: RL
authors.lastname: Kleemann
authors.forename: W
authors.initials: W
authors.lastname: Xu
authors.forename: D R
authors.initials: DR
authors.lastname: Rigsbee
mesh_terms: D000042:Absorption; D002151:Calorimetry; D002433:Cefaclor / Q000737:chemistry*; D002506:Cephalexin / Q000737:chemistry*; D004656:Enalapril / Q000031:analogs & derivatives* / Q000737:chemistry; D004917:Erythromycin / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011208:Powders; D012995:Solubility; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D011208:Powders; D014867:Water; D004917:Erythromycin; D002433:Cefaclor; D004656:Enalapril; C052555:spirapril; D002506:Cephalexin