Resolution of (±)ibuprofen using S-α-Methylbenzylamine in pure ethanol leads to the enriched S-IBU/S-αMBA diastereomeric salt which crystallizes as very fine needles. In order to improve the filterability and processability of the solid phase, water can be added to the medium and lead to more equant particles that are still elongated. A high fraction of the resulting platelets display on both ends a fluid inclusion containing both liquid and a large bubble of gas. A detailed analysis of the particles reveals that they are not really single crystals but more an ordered association of fibers defined as fibrous crystal. A domain of partial solid solution is evidenced near the pure less soluble diastereomer and its impact on the formation of fibrous crystals is demonstrated. When pure S-IBU/S-αMBA diastereomeric salt is recrystallized in the same medium (e.g., ethanol–water) the crystallinity is improved, but fluid inclusions can still be observed.

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