(E)-2-(2-Nitroprop-1-enyl)furan

Crystals of the title compound, C7H7NO3, under Mo Kα radiation sublime in less than 1h at room temperature. However, it was possible to collect data at 100K. It crystallized as the E isomer only. A double-bond conjugation in the furan ring is extended to the nitroalkenyl group. Molecular associations were realized in the crystal through N⋯π [3.545 (2) Å] interactions involving the furan ring and C—H⋯O hydrogen bonds.

We thank the SCCYT (Universidad de Cá diz) for theX-ray data collection and the Consejería de Innovació n, Ciencia y Empresa de la Junta de Andalucía, for financial support. ZRN thanks the AUIP and Aula Iberoamericana for the stay at UCA.
Experimental 2-(2-Nitro-propen-1-yl)-furan, also called UC-244, was obtained using the Knoevenagel's condensation method by reaction of furfural, an aromatic compound from acid hydrolysis of sugar cane residuals (straw, sawdust, etc.) and nitroethane in the presence of isobutylamine as a catalyst. To obtain a product with purity higher than 99% the method was optimized studying temperature, contact and reaction times as variables. The purification was achieved using activated coal and ethanol. The

Refinement
All H atoms were positioned geometrically and treated as riding (C-H = 0.99Å for methylene and C-H = 0.93Å otherwise).
U iso (H) = 1.2 U eq (C) of the carrier atom. In the absence of any significant anomalous scatters, the Friedel pairs were merged before final refinements. Fig. 1. ORTEP representation of I with the atom labelling scheme and displacement ellipsoids at the 50% probability level.

Special details
Experimental. Refinement of F 2 against unique set of reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. Refinement. Refinement of F 2 against unique set of reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.  (6)  C5 0.0199 (7) 0.0173 (7) 0.0206 (6) 0.0013 (5) 0.0034 (5) 0.0010 (5)  C6 0.0217 (7) 0.0164 (6) 0.0211 (7) 0.0014 (5) 0.0047 (5) 0.0005 (5)  C7 0.0292 (8) 0.0254 (7) 0.0224 (7) 0.0037 (6) −0.0014 (6) −0.0020 (6) Geometric parameters (Å, °)