(744d) Determination of Crystal Growth Rate of Racemic Ibuprofen Crystals from Enantiomerically Enriched Solutions

The influence of foreign molecules on crystallization kinetics has been widely investigated [1,2]. When growing crystals of pure enantiomers, the presence of the counter-enantiomer is known to typically reduce the crystallization kinetics of the preferred enantiomer [3,4]. For the case of racemic compounds, such investigations are rarely reported. However, if a retarding or promoting effect is determined in such an investigation it could lead to valuable insights about the underlying crystallization mechanisms. For instance, carefully investigating the effect of an enantiomeric enrichment in the solution on the crystallization kinetics of racemic crystals, could clarify whether interactions in the solution or interactions of the enantiomers on the crystalline surfaces are responsible for the change in kinetics.

In this work, we established the ternary phase diagram of the chiral molecule Ibuprofen in n-Heptane at various temperatures and described the thermodynamics using an activity coefficient model. Following this, batch desupersaturation experiments were carried out at different initial supersaturations, temperatures and enantiomeric excesses in the liquid phase with the aim of determining the growth kinetics of (R,S)-Ibuprofen crystals. We estimated the growth kinetics by fitting a population balance equation model to concentration profiles obtained by ATR-FTIR spectroscopy. The obtained growth kinetics provide insightful information about the crystal growth behavior of crystals of the racemic compound from enriched solutions.

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