2-(2-Methyl-5-nitro-1H-imidazol-1-yl)ethyl methanesulfonate

The asymmetric unit of the title compound, C7H11N3O5S, contains two independent molecules with virtually identical conformations. The imidazole rings of both molecules are essentially planar (r.m.s. deviations = 0.0019 and 0.0038 Å), with a dihedral angle 9.25 (19)° between them. The nitro groups are oriented at 4.5 (2) and 6.44 (13)° with respect to the imidazole rings. In the crystal, molecules are linked to form a three-dimensional framework by C—H⋯O and C—H⋯N hydrogen bonds.

The asymmetric unit of the title compound, C 7 H 11 N 3 O 5 S, contains two independent molecules with virtually identical conformations. The imidazole rings of both molecules are essentially planar (r.m.s. deviations = 0.0019 and 0.0038 Å ), with a dihedral angle 9.25 (19) between them. The nitro groups are oriented at 4.5 (2) and 6.44 (13) with respect to the imidazole rings. In the crystal, molecules are linked to form a three-dimensional framework by C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds.
The title compound contains two independent molecules in an asymmetric unit ( Fig. 1) with identical conformations.

Experimental
The title compound was synthesized by adding methane sulfonyl chloride (16 mmol) drop wise into an ice-cooled solution of metronidazole (10 mmol) and triethylamine (16 mmol) in dry dichloromethane (DCM) with continuous stirring. The reaction mixture was further stirred in the ice bath for 4 h. The separated thick material was filtered and washed with water (20 ml X 3) to obtain a cream coloured solid which was dissolved and recrystallized from DCM by slow evaporation to give pure crystals of the title compound (82% yield), suitable for single-crystal X-ray diffraction studies. All chemicals were purchased from Sigma-Aldrich.

Refinement
H atoms on methyl, methylene and methine were positioned geometrically with C-H = 0.96, 0.97 and 0.93 Å respectively, and constrained to ride on their parent atoms with U iso (H)= 1.2U eq (CH and CH 2 ) and 1.5U eq (CH 3 ). A rotating group model was applied to the methyl groups.

Computing details
Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), PARST (Nardelli, 1995) and PLATON (Spek, 2009    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 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.