Polymorphism and aging in terephthalic acid
- 1 February 1985
- journal article
- research article
- Published by Wiley in Crystal Research and Technology
- Vol. 20 (2) , 201-208
- https://doi.org/10.1002/crat.2170200215
Abstract
The role of the polymorphic transformation was investigated by X‐Ray diffraction in the habit modification process of terephthalic acid reported earlier (Gaines, Myerson). Contrary to the expectations it was found that only one of the two polymorphs described in the literature (Bailey, Brown) was present. Using an interatomic function derived (Derissen, Smit) to approximate the crystallographic properties of this class of organic acids, we calculated the lattice energies of the two proposed polymorphs of terephthalic acid. These were found to be 41.02 and 39.99 kcal/mole for the polymorphs I and II, respectively. The heat of transition calculated (1.03 kcal/mole) is small enough to be overcome by an increase of the enthropy term and the polymorphic transition is realizable.Keywords
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