organic papers Acta Cryst. (2005). E61, o3287–o3288 doi:10.1107/S1600536805028709 Ali et al.  C 15 H 11 N 3 O 2 o3287 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 Isatin 3-benzoylhydrazone: an orthorhombic form Hapipah M. Ali, Siti Nadiah Abdul Halim and Seik Weng Ng* Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia Correspondence e-mail: seikweng@um.edu.my Key indicators Single-crystal X-ray study T = 295 K Mean (C–C) = 0.006 A ˚ R factor = 0.058 wR factor = 0.191 Data-to-parameter ratio = 8.1 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2005 International Union of Crystallography Printed in Great Britain – all rights reserved The amine N atom of the isatin portion of the title compound (systematic name: 2-oxo-2,3-dihydro-1H-indole-3-carbalde- hyde benzoylhydrazone), C 15 H 11 N 3 O 2 , forms a hydrogen bond with the amide O atom of the benzoylhydrazone portion of a symmetry-related molecule to give rise to a hydrogen- bonded chain structure that propagates by a twofold screw axis along the a axis of the orthorhombic unit cell. Comment The preceeding report describes the structure of the mono- clinic form of isatin 3-benzoylhydrazone (Ali et al., 2005). In the orthorhombic form, the chain formed by hydrogen- bonded molecules propagates by twofold screw axial transla- tions (Fig. 1), whereas in the monoclinic form the chain formed by hydrogen-bonded molecules propagates by glide planes. The orthorhombic form is significantly denser (density = 1.467 Mg m 3 ) than the monoclinic form (density = 1.392 Mg m 3 ), as the polymeric chain is more flexible owing to a more adaptable, helical construction. Experimental Isatin 3-benzoylhydrazone (0.50 g, 1.9 mmol) and zinc acetate (0.20 g, 0.9 mmol) were refluxed for 5 h. The yellow solid that precipitated was collected and recrystallized from pyridine to give yellow–orange blocks. The color is distinctly different from that of the monoclinic polymorph. Received 6 September 2005 Accepted 12 September 2005 Online 17 September 2005 Figure 1 ORTEPII (Johnson, 1976) plot of C 15 H 11 N 3 O 2 . Displacement ellipsoids are drawn at the 50% probability level, and H atoms are shown as spheres of arbitrary radii. Hydrogen bonds are shown as dashed lines.