Polymorphism in 2,4,6-trinitrotoluene crystallized from solution

Vrcelj, Ranko M., Gallagher, Hugh G. and Sherwood, John N. (2001) Polymorphism in 2,4,6-trinitrotoluene crystallized from solution. Journal of the American Chemical Society, 123 (10). pp. 2291-2295. ISSN 0002-7863

Full content URL: http://dx.doi.org/10.1021/ja0031422

Polymorphism in 2,4,6-trinitrotoluene crystallized from solution

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An examination has been made of the role of solvent type in the definition of the polymorphic
nature of 2,4,6-trinitrotoluene precipitated from solution. A combination of calorimetric and structural techniques
including in situ crystallization studies using synchrotron radiation has shown that the variations in polymorphic
form following precipitation from solution do not arise specifically from any stereospecific guidance that the
nature of the solvent might impose on the structural form. Rather the differences are linked to the variations
in solubility and hence supersaturation which might build up prior to nucleation and growth and to the isolation
of the metastable orthorhombic phase from the solvent. The final conclusion is that the changes fit well with
Ostwald’s Law of Stages with the orthorhombic form always precipitating initially followed by its conversion
to the stable monoclinic form. The previously observed tendency for some solvents to yield one or the other
form then becomes attributable to kinetics in solution rather than structural control. It can be associated with
the solubility of the material in the solvent used and the role of this factor in a solvent-mediated phase
transformation. On this basis rules can be formulated for the isolation of the metastable forms of this and
similarly related polymorphic systems.

Keywords:Crystallization, Polymorphism, TNT
Subjects:F Physical Sciences > F130 Structural Chemistry
Divisions:College of Science > School of Pharmacy
ID Code:16743
Deposited On:20 Feb 2015 09:10

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