2-(3-Nitrophenoxy)quinoxaline

In the title molecule, C14H9N3O3, the dihedral angle between the quinoxaline and benzene rings is 77.13 (9)°. The molecule is twisted about the ether–benzene O—C bond, with a C—O—C—C torsion angle of −102.8 (2)°. In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming layers in the ab plane, with one nitro O atom accepting two such interactions. The layers stack along the c-axis direction via weak C—H⋯π interactions.

The molecule in (I), Fig. 1, is bent as the quinoxaline ring [r.m.s. deviation = 0.025 Å] forms a dihedral angle of 77.13 (9) ° with the benzene molecule. The twist in the molecule is seen in the value of the C1-O1-C9-C14 torsion angle of -102.8 (2) °. Overall the conformation of the molecule matches those found in the polymorphic phenyl quinoxalin-2-yl ether compound (Hassan et al., 2008;. In (I), the nitro group is slightly twisted out of the plane of the benzene ring to which it is bonded as seen in the O2-N3-C13-C12 torsion angle of 12.6 (3) °.
The bifurcated nitro-O2 atom is pivotal in the crystal packing, forming two close C-H···O interactions, Table 1, leading to the formation of layers in the ab plane, Fig. 2. These stack along the c axis, being connected by C-H···π interactions, Fig. 3.
Experimental 3-Nitrophenol (5 mmol) was dissolved in tetrahydrofuran (100 ml) to which was added 2-chloroquinoxaline with a stoichiometric amount of NaOH. The solution was refluxed for 4 h. The mixture was extracted using 5% sodium hydroxide solution (5 ml), then chloroform (20 ml), washed with distilled water (30 ml), and dried over anhydrous sodium hydroxide.
Evaporation of the solvent gave a red solid and recrystallization was from its ethanol solution to yield red prisms of (I).

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.95 Å) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2U equiv (C). In the absence of significant anomalous scattering effects, 1199 Friedel pairs were averaged in the final refinement. In the final refinement a low angle reflection evidently effected by the beam stop were omitted, i.e. 0 0 1. Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(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.