2,4-Dichloro-6-nitro­benzoic acid

Abstract

The title compound, C₇H₃Cl₂NO₄, was prepared by the reaction of 2,4-dichloro-6-nitro­toluene with 20% HNO₃ solution at 430 K. The carboxyl and nitro groups are twisted by 82.82 (12) and 11.9 (2)°, respectively, with respect to the benzene ring. The crystal structure is stabilized by O—H⋯O hydrogen bonding between carboxyl groups and weak C—H⋯O hydrogen bonding between the nitro group and the benzene ring of an adjacent mol­ecule.

Related literature

For general background, see: Jacobson (1997 ▶); Langer et al. (2006 ▶); Li & Zhu (2007 ▶).

Experimental

Crystal data

• C₇H₃Cl₂NO₄

• M _r = 236.00

• Triclinic,

• a = 4.6930 (7) Å

• b = 7.5590 (11) Å

• c = 13.0721 (19) Å

• α = 97.120 (2)°

• β = 95.267 (2)°

• γ = 100.631 (2)°

• V = 449.11 (11) ų

• Z = 2

• Mo Kα radiation

• μ = 0.71 mm⁻¹

• T = 295 (2) K

• 0.40 × 0.30 × 0.20 mm

Data collection

• Bruker SMART CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2002 ▶) T _min = 0.765, T _max = 0.872

• 2415 measured reflections

• 1641 independent reflections

• 1457 reflections with I > 2σ(I)

• R _int = 0.011

Refinement

• R[F ² > 2σ(F ²)] = 0.032

• wR(F ²) = 0.086

• S = 1.06

• 1641 reflections

• 127 parameters

• H-atom parameters constrained

• Δρ_max = 0.22 e Å⁻³

• Δρ_min = −0.34 e Å⁻³

Data collection: SMART (Bruker, 2002 ▶); cell refinement: SAINT (Bruker, 2002 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

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
O4—H4A⋯O3i	0.90	1.77	2.664 (2)	173
C3—H5⋯O2ii	0.93	2.56	3.453 (2)	160

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

Comment

Ortho-nitro aromatic acids have been used as intermediates of dyes, pharmaceuticals and agrochemicals (Jacobson, 1997; Langer et al., 2006). The title compound is an important chemical intermediates of a kind of synthetic dyes, pharmaceuticals (Li & Zhu, 2007). Its crystal structure is reported here.

The molecular structure of the title compound is shown in Fig. 1. The molecule displays a non-planar structure. The carboxyl and nitro groups are twisted with respect to the benzene ring by 82.82 (12) and 11.9 (2)°, respectively. Within the carboxyl group, the O3—C7 bond distance is appreciably shorter than the O4—C7 bond distance (Table 1). The crystal structure is stabilized by O—H···O hydrogen bonding between carboxyl groups and weak C—H···O hydrogen bonding between nitro group and benzene ring of adjacent molecules (Table 2).

Experimental

The title compound was prepared by a reaction of 2-nitro-4,6-dichlorotoluene (1 mmol) with 20% HNO₃ solution (15 ml) in an autoclave at 430 K for 20 h. Single crystals suitable for X-ray data collection were obtained by recrystallization from a methanol solution.

Refinement

Carboxyl H atom was located in a difference Fourier map and refined as riding in as-found relative position with U_iso(H) = 1.5U_eq(O). Other H atoms were placed in calculated positions with C—H = 0.93 Å and refined in riding mode, U_iso(H) = 1.2U_eq(C).

Figures

Fig. 1.

The molecular structure of the title compound with 40% probability displacement ellipsoids.

Crystal data

C7H3Cl2NO4	Z = 2
Mr = 236.00	F000 = 236
Triclinic, P1	Dx = 1.745 Mg m−3
Hall symbol: -P 1	Mo Kα radiation λ = 0.71073 Å
a = 4.6930 (7) Å	Cell parameters from 2069 reflections
b = 7.5590 (11) Å	θ = 2.8–27.5º
c = 13.0721 (19) Å	µ = 0.71 mm−1
α = 97.120 (2)º	T = 295 (2) K
β = 95.267 (2)º	Prism, colorless
γ = 100.631 (2)º	0.40 × 0.30 × 0.20 mm
V = 449.11 (11) Å3

Data collection

Bruker SMART CCD area-detector diffractometer	1641 independent reflections
Radiation source: fine-focus sealed tube	1457 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.011
T = 295(2) K	θmax = 25.5º
φ and ω scans	θmin = 2.8º
Absorption correction: multi-scan(SADABS; Bruker, 2002)	h = −5→5
Tmin = 0.765, Tmax = 0.872	k = −9→9
2415 measured reflections	l = −15→15

Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.032	H-atom parameters constrained
wR(F2) = 0.087	w = 1/[σ2(Fo2) + (0.0463P)2 + 0.1228P] where P = (Fo2 + 2Fc2)/3
S = 1.06	(Δ/σ)max < 0.001
1641 reflections	Δρmax = 0.22 e Å−3
127 parameters	Δρmin = −0.34 e Å−3
Primary atom site location: structure-invariant direct methods	Extinction correction: none

Special details

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

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.66419 (15)	0.23838 (7)	0.04930 (4)	0.0620 (2)
Cl2	0.19170 (13)	0.45919 (8)	0.38873 (4)	0.0611 (2)
N1	0.8796 (4)	0.9077 (2)	0.20929 (13)	0.0425 (4)
O1	0.8119 (3)	1.03193 (18)	0.26405 (12)	0.0542 (4)
O2	1.0647 (4)	0.9276 (2)	0.15015 (13)	0.0651 (5)
O3	0.7264 (3)	0.86356 (19)	0.45830 (10)	0.0456 (3)
O4	0.3076 (3)	0.9004 (2)	0.37628 (11)	0.0540 (4)
H4A	0.2886	0.9850	0.4282	0.081*
C1	0.5569 (4)	0.6891 (2)	0.29482 (13)	0.0335 (4)
C2	0.4126 (4)	0.5107 (3)	0.29348 (14)	0.0388 (4)
C3	0.4410 (4)	0.3708 (2)	0.21800 (15)	0.0428 (5)
H5	0.3413	0.2525	0.2182	0.051*
C4	0.6193 (4)	0.4107 (3)	0.14305 (15)	0.0413 (4)
C5	0.7657 (4)	0.5858 (3)	0.14027 (15)	0.0410 (4)
H3	0.8852	0.6117	0.0889	0.049*
C6	0.7292 (4)	0.7212 (2)	0.21587 (14)	0.0346 (4)
C7	0.5340 (4)	0.8318 (2)	0.38368 (14)	0.0352 (4)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cl1	0.0958 (5)	0.0399 (3)	0.0486 (3)	0.0164 (3)	0.0174 (3)	−0.0113 (2)
Cl2	0.0633 (4)	0.0609 (4)	0.0532 (3)	−0.0092 (3)	0.0264 (3)	0.0033 (3)
N1	0.0503 (9)	0.0346 (8)	0.0403 (9)	0.0024 (7)	0.0099 (7)	0.0021 (7)
O1	0.0708 (10)	0.0309 (7)	0.0605 (9)	0.0096 (6)	0.0189 (7)	−0.0021 (6)
O2	0.0816 (11)	0.0478 (9)	0.0627 (10)	−0.0061 (8)	0.0389 (9)	0.0017 (7)
O3	0.0431 (7)	0.0502 (8)	0.0388 (7)	0.0098 (6)	−0.0012 (6)	−0.0080 (6)
O4	0.0438 (8)	0.0655 (10)	0.0506 (8)	0.0230 (7)	0.0038 (6)	−0.0162 (7)
C1	0.0319 (9)	0.0341 (9)	0.0326 (9)	0.0062 (7)	0.0029 (7)	−0.0017 (7)
C2	0.0370 (10)	0.0418 (10)	0.0349 (9)	0.0026 (8)	0.0064 (8)	0.0013 (8)
C3	0.0490 (11)	0.0306 (9)	0.0442 (11)	0.0003 (8)	0.0042 (9)	0.0003 (8)
C4	0.0531 (11)	0.0346 (10)	0.0347 (10)	0.0106 (8)	0.0054 (8)	−0.0047 (7)
C5	0.0496 (11)	0.0385 (10)	0.0354 (10)	0.0088 (8)	0.0131 (8)	0.0008 (8)
C6	0.0388 (9)	0.0301 (9)	0.0330 (9)	0.0040 (7)	0.0056 (7)	0.0007 (7)
C7	0.0327 (9)	0.0372 (10)	0.0341 (9)	0.0048 (7)	0.0077 (7)	−0.0009 (7)

Geometric parameters (Å, °)

Cl1—C4	1.7309 (18)	C1—C2	1.390 (3)
Cl2—C2	1.7277 (19)	C1—C7	1.510 (2)
N1—O2	1.216 (2)	C2—C3	1.388 (3)
N1—O1	1.217 (2)	C3—C4	1.372 (3)
N1—C6	1.472 (2)	C3—H5	0.9300
O3—C7	1.235 (2)	C4—C5	1.381 (3)
O4—C7	1.266 (2)	C5—C6	1.377 (2)
O4—H4A	0.8961	C5—H3	0.9300
C1—C6	1.386 (3)
O2—N1—O1	124.25 (16)	C3—C4—C5	121.65 (17)
O2—N1—C6	117.96 (16)	C3—C4—Cl1	119.64 (15)
O1—N1—C6	117.79 (16)	C5—C4—Cl1	118.71 (15)
C7—O4—H4A	117.5	C6—C5—C4	117.98 (18)
C6—C1—C2	116.50 (16)	C6—C5—H3	121.0
C6—C1—C7	124.11 (16)	C4—C5—H3	121.0
C2—C1—C7	119.26 (16)	C5—C6—C1	123.15 (17)
C3—C2—C1	122.11 (17)	C5—C6—N1	117.00 (16)
C3—C2—Cl2	118.41 (15)	C1—C6—N1	119.84 (15)
C1—C2—Cl2	119.48 (14)	O3—C7—O4	126.27 (17)
C4—C3—C2	118.60 (17)	O3—C7—C1	117.77 (15)
C4—C3—H5	120.7	O4—C7—C1	115.83 (15)
C2—C3—H5	120.7

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4A···O3i	0.90	1.77	2.664 (2)	173
C3—H5···O2ii	0.93	2.56	3.453 (2)	160

Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x−1, y−1, z.