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Structures of piperazine, piperidine and morpholine
Andrew Parkin1, Iain D H Oswald, Simon Parsons
1School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, Scotland.
Acta Crystallographica. Section B, Structural Science
|March 16, 2004
Summary
This study reveals that piperazine, piperidine, and morpholine crystal structures form NH...N hydrogen-bonded chains. These chains interleave and stack in layered arrangements, similar to cyclohexane, but with molecular rotations due to hydrogen bonding.
Area of Science:
- Crystallography
- Chemical Physics
- Materials Science
Background:
- Piperazine, piperidine, and morpholine are cyclic organic compounds with significant applications.
- Understanding their solid-state structures is crucial for predicting their physical and chemical properties.
- Previous studies have established basic structural features, but detailed crystallographic analysis at low temperatures provides deeper insights.
Purpose of the Study:
- To determine the precise crystal structures of piperazine, piperidine, and morpholine at 150 K.
- To analyze the intermolecular interactions, particularly hydrogen bonding, within these crystal structures.
- To compare the observed structures with known related compounds, such as cyclohexane-II, using topological analysis.
Main Methods:
- Single-crystal X-ray diffraction at 150 K.
- Crystallographic structure determination and refinement.
- Topological analysis of crystal packing and intermolecular interactions (hydrogen bonding, CH...O interactions).
Main Results:
- All three compounds exhibit NH...N hydrogen-bonded chains.
- Piperazine forms interleaved sheets, while piperidine and morpholine adopt layered structures resembling hexagonal close-packing.
- Morpholine structures also feature weak CH...O interactions.
- The observed structures are topologically related to cyclohexane-II, with molecular rotations accommodating inter-layer interactions.
Conclusions:
- The crystal structures of piperazine, piperidine, and morpholine are characterized by specific hydrogen-bonding motifs and layered arrangements.
- These structures show clear relationships to cyclohexane-II, highlighting the influence of hydrogen bonding on molecular packing.
- The findings provide a detailed understanding of the solid-state behavior of these important cyclic amines.