Molecular mechanism of DCR phenomenon observed in (RS)-1-cyclohexylethylamine–mandelic acid resolution system

In the resolution system of (RS)-1-cyclohexylethylamine (CHEA) with (S)-mandelic acid (MA), the DCR (dielectrically controlled resolution) phenomenon was clearly observed. (S)-CHEA and (R)-CHEA were obtained as less-soluble salts from 2-propanol (ε = 18) and water (ε = 78), respectively. Although (S)-MAs pack similarly in the crystals of both of the salts, the chiral spaces formed between the columns of (S)-MAs are significantly different in shape. The present study showed that these chiral spaces are crucial to molecular recognition and their shapes are greatly influenced by the dielectric property of the solvent employed.

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