Synthesis and crystal structures of two isomeric nitro-α-resorcylic acids |
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Authors: | Ilija Čorić Dalibor Milić Dubravka Matković-Čalogović Linda Tomašković |
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Institution: | (1) Laboratory of Organic Chemistry, Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, Zagreb, Croatia;(2) Chemistry Department, GlaxoSmithKline Research Centre Zagreb Ltd., Prilaz Baruna Filipovića 29, Zagreb, Croatia;(3) Laboratory of General and Inorganic Chemistry, Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, Zagreb, Croatia |
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Abstract: | Nitration of α-resorcylic acid (3,5-dihydroxybenzoic acid) to 3,5-dihydroxy-2-nitrobenzoic acid (1) and 3,5-dihydroxy-4-nitrobenzoic acid (2), their separation, and crystallization is described. Crystal structures of 1, 1 · 3H2O, and 2 were determined by X-ray single-crystal diffraction analysis and compared with DFT-calculated structures. An intramolecular
hydrogen bond between the nitro group and o-hydroxyl group(s) occurs in all investigated structures. Intermolecular hydrogen bonds and π···π stacking interactions determine
the molecular packing. Additionally, N···O interactions have a crucial role in arrangement of the molecules in the crystal
structures of 1 and 2. DFT calculations in the gas phase and in the solution reveal that minor product 2 is a more stable regioisomer than 1, the major product in the nitration reaction. |
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Keywords: | 3 5-Dihydroxy-2-nitrobenzoic acid 3 5-Dihydroxy-4-nitrobenzoic acid α -Resorcylic acid X-ray structure Aromatic nitration |
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