2-Iodo-5-nitrothiophene

The title compound, C4H2INO2S, was synthesized by nitration of iodothiophene with acetyl nitrate. The molecule is essentially planar, withthe nitro group tilted by 1.78 (19)° and the iodine atom displaced by 0.0233 (2) Å with respect to the thiophene ring. In the crystal structure, adjacent molecules are linked through weak I⋯O interactions [3.039 (2)Å], forming chains extending along the b axis.


Structure Reports Online
The molecule of the title compound ( Fig. 1) is essentially planar, with the nitro group tilted by 1.78 (19)° and the iodine atom displaced by 0.0233 (2) Å with respect to the thiophene ring. In the crystal structure, adjacent molecules are linked through weak I···O interactions to form chains extending along the b axis. (Fig. 2).
Experimental Iodothiophene (6.5 g, 31 mmol) dissolved in 10 ml of acetic anhydride was introduced into a round flask, provided with a stirrer and a cooling device. Acetyl nitrate was added dropwise in forty-five minutes and the temperature was kept under 273 K. When the addition was over, the mixture was stirred for half an hour continuously at the same temperature. The nitrating flask was then surrounded with ice and kept in a refrigerator for 24 hours. The product was poured, with stirring, into finely crushed ice. After filtration, the precipitate was collected as a yellow solid. The impure product was dissolved in methanol, pale yellow monoclinic crystals suitable for X-ray analysis (m.p. 348 K, 67% yield) grew over a period of five days on slow evaporation of the solvent at room temperature.

Refinement
All non-H atoms were refined with anisotropic displacement parameters. The H atoms were positioned geometrically (C-H = 0.95 Å) and refined using a riding model, with U iso = 1.2 U eq (C). Fig. 1. The molecular structure of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds supplementary materials sup-3 in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL 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 Rfactors(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.