Separation and Structure of Chiral S ‐Malic Acid Hydrate

Crystals of the chiral malic acid hydrate (C 4 H 6 O 3 · H 2 O) were unexpectedly obtained from an ethanol/water solution containing racemic D, L ‐malic acid and L ‐asparagine. The crystal belongs to orthorhombic space group P 2 1 2 1 2 1 with cell dimensions of a = 0.5576(1), b = 0.9818(2), c = 1.1793(2) nm, V = 0.6455(2) nm 3 , Z = 4, μ(Mo K a =0.152 mm −1 , F (000) = 320, D c = 1.565 g·cm −3 , R = 0.051, wR = 0.136 for 657 observed reflections [ I < 2σ( I )]. The significant difference in bond distances for carboxyl groups suggests that the crystal consist of malate anion and protonized crystalline water. This is a report for direct separation of racemic mixture, i.e ., without the formation of a molecular complex of raceme with a chiral separating reagent.