2,5-Dimethyl-1,3-dinitro­benzene

Dean H Johnston; Heather M Crather

doi:10.1107/S1600536811031424

. 2011 Aug 11;67(Pt 9):o2276–o2277. doi: 10.1107/S1600536811031424

2,5-Dimethyl-1,3-dinitrobenzene

Dean H Johnston ^a,^*, Heather M Crather ^a

PMCID: PMC3200820 PMID: 22058925

Abstract

The title compound, C₈H₈N₂O₄, was prepared via the nitration of p-xylene. The molecules are stacked along the c axis in an antiparallel manner. The two nitro groups are rotated relative to the benzene ring with dihedral angles of 44.50 (7) and 31.67 (8)°. The tilt of the nitro groups allows the formation of C—H⋯O interactions between the ring C—H and nitro groups of adjacent molecules creating puckered sheets perpendicular to the c axis. The H atoms of the methyl group in the 5-position are disordered (60° rotation) with an occupancy of 0.616 (19) for the major component. The crystal was found to be a non-merohedral twin with a twin law [−1 −0.002 0.005, 0.00031 −1 0.002, 0.118 −0.007 1] corresponding to a rotation of 180° about the reciprocal axis (001) and refined to give a minor component fraction of 0.320 (2).

Related literature

For the synthesis and properties of dinitro derivatives of p-xylene, see: Kobe & Hudson (1950 ▶); Johnson & Northcott (1967 ▶); Liu et al. (2005a ▶). For single-crystal diffraction studies of dinitrotoluene, see: McCrone (1954 ▶); Nie et al. (2001 ▶); Hanson et al. (2004 ▶). For single-crystal diffraction studies of nitro derivatives of simple aromatic compounds, see: Ori et al. (1989 ▶); Graham et al. (2004 ▶); Liu et al. (2005b ▶); Demartin et al. (2004 ▶). For discussions of non-conventional hydrogen bonding in nitroaromatics and other compounds, see: Desiraju (2005 ▶); Gagnon et al. (2007 ▶).

Experimental

Crystal data

C₈H₈N₂O₄
M _r = 196.16
Monoclinic,
a = 12.582 (3) Å
b = 9.3868 (17) Å
c = 7.3565 (14) Å
β = 91.963 (6)°
V = 868.3 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 200 K
0.40 × 0.40 × 0.30 mm

Data collection

Bruker SMART X2S benchtop diffractometer
Absorption correction: multi-scan (TWINABS; Bruker, 2009 ▶) T _min = 0.76, T _max = 0.96
2868 measured reflections
1540 independent reflections
1307 reflections with I > 2σ(I)
R _int = 0.043

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.103
S = 1.04
1540 reflections
132 parameters
H-atom parameters constrained
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Data collection: APEX2 and GIS (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶) and OLEX2 (Dolomanov et al., 2009 ▶); molecular graphics: PLATON (Spek, 2009 ▶), Mercury (Macrae et al., 2008 ▶) and POV-RAY (Cason, 2004 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811031424/zl2394sup1.cif

e-67-o2276-sup1.cif^{(18.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811031424/zl2394Isup2.hkl

e-67-o2276-Isup2.hkl^{(76KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811031424/zl2394Isup3.mol

Supplementary material file. DOI: 10.1107/S1600536811031424/zl2394Isup4.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯O1ⁱ	0.95	2.41	3.340 (2)	165
C5—H5⋯O3ⁱⁱ	0.95	2.47	3.207 (2)	134

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This work was supported in part by the National Science Foundation through grant CHE-0532510.

supplementary crystallographic information

Comment

Nitro-derivatives of para-xylene have been prepared as synthetic intermediates and as energetic materials. There are three possible isomers for the dinitro derivative of p-xylene, with studies showing that the major product is the 2,3-dinitro isomer, with exact amounts dependent on reaction conditions (Kobe & Hudson, 1950, Johnson & Northcott, 1967).

The title compound was prepared as a solid derivative of para-xylene for a qualitative organic analysis laboratory course. The intended product was the mono-nitro derivative, but it appears the major product was the dinitro product. Large (~1 cm) needle crystals were obtained by vapor diffusion of n-pentane into a diethyl ether solution of the compound. The lower solubility of the 1,3-dinitro product relative to the other isomers (Kobe & Hudson, 1950) likely favored formation of crystals of the single isomer.

The dihedral angles between the plane of the benzene ring (Fig. 1) and the two nitro groups are 44.50 (7) and 31.67 (8)°, within the range observed for similar methyl-substituted nitrobenzene derivatives (Demartin, et al., 2004, Liu, et al. 2005a). The molecules are packed along the c axis (Fig. 2) with the rings nearly parallel to each other with an interplane angle of 0.63 (2) ° and interplane spacings (centroid to plane) of 3.648 Å and 3.659 Å. The positioning of the nitro groups enables the formation of non-conventional hydrogen bonds (Desiraju, 2005) between the aromatic C—H and nitro group oxygen atoms of adjacent molecules as illustrated in Figures 3 and 4 (for measurements see Table 1). This type of C—H···O interaction is often found in the structures of simple nitroarenes (Gagnon et al., 2007). These interactions combine to create a network of puckered sheets perpendicular the c axis.

Experimental

Concentrated nitric acid (4 ml) and concentrated sulfuric acid (4 ml) were placed in a round-bottom flask equipped with a Claisen adapter, thermometer and condenser. Approximately 4.5 ml of p-xylene was slowly added to the nitric/sulfuric acid mixture, ensuring that the internal temperature did not exceed 323–328 K. After the addition was complete, the mixture was heated for an additional 15 min at 323–328 K. The reaction mixture was cooled to room temperature, poured into 40 ml of cold water and cooled to produce the crystals of the crude nitration product.

The product was recrystallized by vapor diffusion of n-pentane into a diethyl ether solution. Large translucent needles formed after two weeks. The melting point of this crystal was determined to be 398.4 (1) K by DSC, in agreement with literature values (Johnson & Northcott, 1967, Liu et al., 2005a).

A small, optically clear crystal was cut and selected from the larger crystal under a polarizing microscope. Data sets on three separate crystals selected from different parts of the larger crystal all showed significant non-merohedral twinning.