Acta Cryst. (2013). C69, 407-411 [ doi:10.1107/S0108270113005325 ]
Abstract: The title compounds, C11H11BrO3, (I), and C11H11NO5, (II), respectively, are derivatives of 6-hydroxy-5,7,8-trimethylchroman-2-one substituted at the 5-position by a Br atom in (I) and by a nitro group in (II). The pyranone rings in both molecules adopt half-chair conformations, and intramolecular O-HBr [in (I)] and O-HOnitro [in (II)] hydrogen bonds affect the dispositions of the hydroxy groups. Classical intermolecular O-HO hydrogen bonds are found in both molecules but play quite dissimilar roles in the crystal structures. In (I), O-HO hydrogen bonds form zigzag C(9) chains of molecules along the a axis. Because of the tetragonal symmetry, similar chains also form along b. In (II), however, similar contacts involving an O atom of the nitro group form inversion dimers and generate R22(12) rings. These also result in a close intermolecular OO contact of 2.686 (4) Å. For (I), four additional C-HO hydrogen bonds combine with - stacking interactions between the benzene rings to build an extensive three-dimensional network with molecules stacked along the c axis. The packing in (II) is much simpler and centres on the inversion dimers formed through O-HO contacts. These dimers are stacked through additional C-HO hydrogen bonds, and further weak C-HO interactions generate a three-dimensional network of dimer stacks.
Formula: C11H11BrO3 and C11H11NO5
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