Structures for polymorphs of triphenylchloromethane. Triphenylacetic acid illustrates the isomorphous stable modification

Bart Kahr, Randall L. Carter

Research output: Contribution to journalArticle

Abstract

Triphenylacetic acid is isomorphous with the published structure of triphenylchloromethane (I). It crystallizes in the trigonal system, space group P3, with a=b=14.105(3)Å c=13.121(2)Å, V=2261(1)Å3, Z=6 at 175K. The structure was solved by direct methods and refined to R(Fo)=0.062. We determined the structures for two triclinic polymorphs of triphenylchloromethane, II and III. The three forms were obtained from pentane evaporated at room temperature. Phases I and III were isolated from particular solvent systems. Crystal data (II): triclinic system, space group P1, with a=13.028(l)Å, b=13.559(2)Å, c=13.969(3)Å, α=l 17.67(1)°, β=92.67(l)°, γ=91.43(l)°, V=2179.9Å3, Z=6 at 228K. The structure was solved by direct methods and refined to R(Fo)=0.045. Crystal data (III): triclinic system, space group P1, with a=14.1562(4)Å, b=21.3190(7)Å, c=13.0654(5)Å, α=99.92(3)°, β=92.68(3)°, γ=106.15(2)°, V=3712(2)Å3, Z=10 at 248K. The structure was solved by direct methods and refined to R(Fo)=0.064. A batch of crystals from pentane showed three peaks in the DSC thermogram at 99°C (III), 108°C (II), and 111°C (I). Phase III melts without being transformed to phase II or phase I. Phase II could not be isolated for calorimetric studies.

Original languageEnglish (US)
Pages (from-to)79-100
Number of pages22
JournalMolecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals
Volume219
Issue number1
DOIs
Publication statusPublished - Aug 1 1992

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Keywords

  • Differential scanning calorimetry
  • Polymorphism
  • Triphenylacetic Acid
  • Triphenylchloromethane
  • X-ray structure determination

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Chemistry(all)

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