Molecular packing modes. Part V. Crystal and molecular structures of fumaramic acid
- 1 January 1972
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 12,p. 1758-1763
- https://doi.org/10.1039/p29720001758
Abstract
The crystal structure of the title compound has ben solved from X-ray diffractometer data by direct methods and refined by least-squares to R 0·038 for 1182 independent reflections. Crystals are monoclinic, space group P21, with Z= 2 in a unit cell of dimensions: a= 7·367(1), b= 9·041(1), c= 3·742(1)Å, β= 99·39(1)°. The mean σ for bond lengths not involving hydrogen is 0·002 Å. The hydrogen-bond network is two-dimensional. The amide and carboxy-groups of molecules related by translation form cyclic hydrogen-bonded (asymmetric) pairs (OH O, 2·660; NH O, 2·838 Å) generating chains which are interlinked, along the 21 axis, by NH O (2·935 Å) bonds. The conformations of the groups C:C·C(NH2):O and C:C·C(OH):O are syn-planar, in contrast to the antiplanar C:C·C:O arrangements in the α- and β-forms of fumaric acid. The bond lengths are: CC 1·320, C(OH)–C 1·497, C(NH2)–C 1·486, C(OH)O 1·209, C(NH2)O 1·247, C–OH 1·310, and C–NH2 1·323 Å.Keywords
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