The crystal structure of the molecular complex of camphoramic acid with mandelic acid: A partial separation of a racemic mixture of mandelic acid by (1R,3S)-camphoramic acid

Abstract

From an ethanol/water solution containing (1R,3S)-camphoramic acid and a racemic mixture of mandelic acid, the title complex crystallizes in the space group P2₁2₁2₁ with a = 8.015(2), b = 11.041(2), c = 21.781(4) Å. Both molecular complexes, the (1R,3S)-camphoramic acid (S)-mandelic acid complex and the (1R,3S)-camphoramic acid (R)-mandelic acid complex, randomly distribute in a disordered crystal structure with an approximate molar ratio of 3:1, thus a 3:1 separation of the mandelic acid enantiomers was achieved. Molecules of (S)-mandelic and (R)-mandelic acid form very similar intermolecular interactions with adjacent camphoramic acid and water molecules in the structure. This results in the formation of a cocrystal containing two diastereomers. The crystal structure consists of camphoramic acid layers and mandelic acid layers. An extensive H-bonding network occurs within and between the layers.