title: Solid tryptophan as a pseudoracemate: physicochemical and crystallographic characterization.
abstract: The crystalline nature of solid tryptophan has been characterized by X-ray single crystal and powder diffraction analyses, differential scanning calorimetry, as well as measurement of solid-liquid equilibrium in water/isopropanol solution. Both the thermodynamic and crystallographic investigations have demonstrated unambiguously that solid tryptophan crystallizes in the form of a pseudoracemate (i.e., solid solution) with maximum melting over the entire enantiomeric composition range. Comparative single-crystal X-ray studies show that the crystal structures of racemic and enantiomeric tryptophan give very similar solid-state packing geometries dictated by hydrogen bonding interactions. Our results indicate that the insignificant difference between homochiral and heterochiral interactions accounts for the formation of a pseudoracemate for this system.
authors.affiliation: Faculty of Engineering & Applied Science, Memorial University of Newfoundland, St Joh's, NL, Canada.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Yuming
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D002152:Calorimetry, Differential Scanning; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D013237:Stereoisomerism; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D014364:Tryptophan
keywords: X-ray crystallography; phase diagram; racemic modification; solid solution; tryptophan