Structural studies of analgesics and their interactions. Part 4. Crystal structures of phenylbutazone and a 2 : 1 complex between phenylbutazone and piperazine

Singh, Tej Pal and Vijayan, Mamannamana (1977) Structural studies of analgesics and their interactions. Part 4. Crystal structures of phenylbutazone and a 2 : 1 complex between phenylbutazone and piperazine. In: Journal of The Chemical Society-Perkin Transactions 2, 2 (5). pp. 693-699.

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Abstract

The X-ray crystal structures of 4-butyl-1,2-diphenylpyrazolidine-3,5-dione (phenylbutazone)(I). and its 2 : 1 complex (II) with piperazine have been determined by direct methods and the structures refined to R 0.096 (2 300 observed reflections measured by diffractometer) and 0.074 (2 494 observed reflections visuallyestimated). Crystals are monoclinic, space group P21/c; for (I)a= 21.695(4), b= 5.823(2), c= 27.881(4)Å, = 108.06 (10)°, Z= 8, and for (II)a= 8.048(4), b= 15.081(4), c= 15.583(7)Å, = 95.9(3)°, Z= 2. The two crystallographically independant molecules in the structure of (I) are similar except for the conformation of the butyl group, which is disordered in one of the molecules. In the pyrazolidinedione group, the two C–C bonds are single and the two C–O bonds double. The two nitrogen atoms in the five-membered ring are pyramidal with the attached phenyl groups lying on the opposite sides of the mean plane of the ring. The phenylbutazone molecule in (II) exists as a negative ion owing to deprotonation of C-4. C-4 is therefore trigonal and the orientation of the Bu group with respect to the pyrazolidinedione group is considerably different from that in (I); there is also considerable electron delocalization along the C–O and C–C bonds. These changes in geometry and electronic structure may relate to biological activity. The doubly charged cationic piperazine molecule exists in the chair form with the nitrogen atoms at the apices. The crystal structure of (II) is stabilized by ionic interactions and N–H O hydrogen bonds.

Item Type:	Journal Article
Publication:	Journal of The Chemical Society-Perkin Transactions 2
Publisher:	Royal Society London
Additional Information:	Copyright of this article belongs to Royal Society London.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit Division of Physical & Mathematical Sciences > Physics
Date Deposited:	03 Feb 2010 12:28
Last Modified:	19 Sep 2010 05:51
URI:	http://eprints.iisc.ac.in/id/eprint/24572

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