Crystallization of Mefenamic Acid from Dimethylformamide Microemulsions: Obtaining Thermodynamic Control through 3D Nanoconfinement

Crystals

Catherine E. Nicholson¹ 

[1]id="af1-crystals-01-00195">Department of Chemistry, University Science Laboratories, South Road, Durham, DH1 3LE, UK. E-Mail: [e-mail].u

关键词: mefenamic acid;    crystallization;    polymorph;    microemulsion;    thermodynamic control;   

DOI  :  10.3390/cryst1030195

来源: mdpi

【 摘 要 】

Recently we showed how crystallization in microemulsions could lead directly to the most stable polymorph, thereby leapfrogging Ostwald's rule of stages. Here we consider in more details the crystallization of mefenamic acid from dimethylformamide microemulsions. Crystallization of mefenamic acid from bulk DMF has previously been shown to produce only the metastable Form II irrespective of the supersaturation or temperature. In contrast, we show that stable Form I can be produced from DMF microemulsions provided the lowest supersaturations that can achieve crystallization are used; these correspond to initial supersaturations that are significantly higher than those commonly used in bulk solution crystallizations, owing to the large decrease in supersaturation that occurs when a nuclei grows in a 3D-nanoconfined droplet. Increasing the supersaturation above the minimum required for crystallization leads to increasing proportions of metastable Form II crystals. In compositions crystallizing a mixture of Form I and Form II crystals, the Form I crystals can nevertheless be obtained exclusively by slowly heating the microemulsions.

【 授权许可】

CC BY   
© 2011 by the authors; licensee MDPI, Basel, Switzerland.