Methyl 4-chloro-3-nitrobenzoate

In the title compound, C8H6ClNO4, the molecules are linked by C—H⋯O interactions to form a chain parallel to the a axis. The chains are further connected by slipped π–π stacking between symmetry-related benzene rings, with a centroid-to-centroid distance of 3.646 (2) Å and an interplanar distance of 3.474 Å, resulting in an offset of 1.106 Å.

In the title compound, C 8 H 6 ClNO 4 , the molecules are linked by C-HÁ Á ÁO interactions to form a chain parallel to the a axis. The chains are further connected by slippedstacking between symmetry-related benzene rings, with a centroid-tocentroid distance of 3.646 (2) Å and an interplanar distance of 3.474 Å , resulting in an offset of 1.106 Å .

Structure Reports Online
The molecules of (I) are linked by C-H···O interactions to form a chain parallel to the a axis (Table 1, Fig. 2). The chains are further connected by slippest π-π stacking between symmetry related phenyl rings with a centroit to centroid distance Cg1···Cg1i (Symmetry code: (i) 1 − x, 1 − y, 1 − z) of 3.646 (2) Å and an interplanar distance of 3.474 Å resulting in an offset of 1.106 Å.
Experimental 4-Chloro-3-nitrobenzoic acid (35.0 g, 0.174 mol) was suspended in methanol (150 ml) and cooled to 0°. Concentrated sulfuric acid (15 ml) was slowly added with stirring, and then the mixture was heated at reflux for 17 h. Upon cooling to room temperature, a precipitate formed, which was collected by filtration and washed with cold methanol (2*50 ml) and hexane (2*50 ml) to afford the methyl ester as a white solid (31.8 g, 85%) (Andrews & Ladlow, 2003;Jönssen et al., 2004). Pure compound (I) was obstained by crystallizing from methanol. Crystals of (I) suitable for X-ray diffraction were obstained by slow evaporation of an methanol solution.

Refinement
All H atoms were placed geometrically and treated as riding on their parent C atoms with C-H = 0.93 Å (Caromatic) and 0.96 Å (Cmethyl) with U iso (H) = 1.2(Caromatic) or 1.5(methyl)U eq (C). Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii.

Data collection
Enraf-Nonius CAD-4 diffractometer R int = 0.019 Radiation source: fine-focus sealed tube θ max = 26.0º Monochromator: graphite θ min = 2.2º T = 293(2) K h = 0→9 ω/2θ scans k = −9→8 Absorption correction: ψ scan (North et al., 1968) l = −11→11 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 > 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.