Polymorphism in 2-4-6 trinitrotoluene

R.M. Vrcelj, J.N. Sherwood, A.R. Kennedy, Hugh Gerald Gallagher, T. Gelbrich

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119 Citations (Scopus)

Abstract

Two crystal structures of 2-4-6 trinitrotoluene (TNT) are given, the monoclinic form (a0 ) 1.49113 (1) nm, b0 ) 0.60340 (1) nm, c0 ) 2.08815(3) nm, â ) 110.365 (1)°, V ) 1.76137 (4) nm3, space group ) P21/a, T ) 100 K) and the orthorhombic form (a0 ) 1.4910 (2) nm, b0 ) 0.6031 (2) nm, c0 ) 1.9680 (4) nm, V ) 1.7706 (7) nm3, space group ) Pca21, T ) 123 K). Of these two forms, the most stable is the monoclinic and the less stable is the orthorhombic form. These two polymorphs are shown to be orientational, rather than configurational in character. Due to their restricted molecular motifs, no strong hydrogen bonding exists and the crystalline form is dominated by van der Waals type forces. The two structures are shown to be closely related and an analysis of the two structures shows that they are effectively large scale polytypes. Calorimetric studies show that the two polymorphs are monotropic and that the enthalpy of transformation is very low, concurring with the similarity shown by the diffraction data and calculated lattice energies. The thermal expansion coefficients are defined, and it is shown that both polymorphs have similar thermal expansions.
Original languageEnglish
Pages (from-to)1027-1032
Number of pages5
JournalCrystal Growth and Design
Volume3
Issue number6
DOIs
Publication statusPublished - 5 Nov 2003

Keywords

  • 2-4-6 trinitrotoluene
  • TNT
  • monoclinic
  • orthorhombic
  • polymorphs
  • hydrogen bonding
  • crystalline
  • van der Waals
  • Calorimetric studies
  • monotropic
  • form

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