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Issue 22, 2011
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Enantiomeric crystallization of (±)-trans-1,2-diaminocyclohexane under pressure

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Abstract

The isothermal and isochoric crystallizations of (±)-trans-1,2-diaminocyclohexane, C6H10(NH2)2, (±)-DACH, yield enantiomeric conglomerates of orthorhombic symmetry, space groupP21212, the same as obtained by isobaric crystallization. Despite the compression to 73% of ambient pressure volume, no racemic compound of DACH was formed. This contradicts for this compound the possibility of reverse causality between density and preferred enantiomorphic/racemic crystallization in Wallach's rule. The crystal structures have been determined at 0.36, 0.52, 0.65, 1.19 and 2.04 GPa at 296 K by single-crystal X-ray diffraction. It has been established that the enantiomeric-conglomerate crystallization of DACH at ambient pressure is mainly due to the molecular arrangement, governed by the close-packing rule in the crystal. High pressure enhances the close packing, and it does not change the course of crystallization of (±)-DACH. The shortest intermolecular contacts, NH⋯N and CH⋯N, become most compressed between 0.36 and 2.04 GPa, indicating that such weak hydrogen bonds are enhanced by pressure. The phase diagram of (±)-DACH has been outlined to 2.04 GPa.

Graphical abstract: Enantiomeric crystallization of (±)-trans-1,2-diaminocyclohexane under pressure

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Publication details

The article was received on 12 May 2011, accepted on 12 Aug 2011 and first published on 08 Sep 2011


Article type: Paper
DOI: 10.1039/C1CE05553D
Citation: CrystEngComm, 2011,13, 6742-6746
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    Enantiomeric crystallization of (±)-trans-1,2-diaminocyclohexane under pressure

    W. Cai and A. Katrusiak, CrystEngComm, 2011, 13, 6742
    DOI: 10.1039/C1CE05553D

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