A redetermination of 2-nitro­benzoic acid

The crystal structure of the title compound, C₇H₅NO₄, was first reported by Kurahashi, Fukuyo & Shimada [(1967). Bull. Chem. Soc. Jpn, 40, 1296]. It has been re-examined, improving the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar independent mol­ecule, as the nitro and the carb­oxy substituents force each other to be twisted away from the plane of the aromatic ring by 54.9 (2) and 24.0 (2)°, respectively. The mol­ecules form a conventional dimeric unit via centrosymmetric inter­molecular hydrogen bonds.

Related literature

For the previous structure determination, see: Kurahashi et al. (1967); Sakore et al. (1967); Tavale & Pant (1973). For the effect of nitro and carboxy substitution on the geometry of polysubstituted benzene rings, see: Colapietro et al. (1984); Domenicano et al. (1989). For the formation of hydrogen-bonded dimers in monocarboylic acids, see:Leiserowitz (1976). For computation of ring patterns formed by hydrogen bonds in crystal structures, see: Etter et al. (1990); Bernstein et al. (1995); Motherwell et al. (1999).

Experimental

Crystal data

• C₇H₅NO₄

• M_r = 167.12

• Triclinic,

• a = 5.0147 (15) Å

• b = 7.527 (2) Å

• c = 10.620 (2) Å

• α = 69.41 (2)°

• β = 86.07 (2)°

• γ = 71.01 (3)°

• V = 354.35 (18) ų

• Z = 2

• Mo Kα radiation

• μ = 0.13 mm⁻¹

• T = 298 K

• 0.15 × 0.15 × 0.10 mm

Data collection

• Oxford Diffraction Xcalibur S CCD diffractometer

• Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) T_min = 0.879, T_max = 0.980

• 3862 measured reflections

• 1872 independent reflections

• 1087 reflections with I > 2σ(I)

• R_int = 0.050

Refinement

• R[F² > 2σ(F²)] = 0.077

• wR(F²) = 0.148

• S = 1.07

• 1872 reflections

• 113 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.26 e Å⁻³

• Δρ_min = −0.20 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O1^i	0.90 (3)	1.77 (4)	2.660 (3)	173 (3)
Symmetry code: (i) -x+2, -y+1, -z+1.

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Supporting information

S1. Comment

o-Nitrobenzoic acid was determined more than 40 years ago (Kurahashi et al., 1967), but the final refinement was carried only to R=0.18. Subsequently, a new X-ray structure determination was reported (Sakore et al., 1967). In this study, 1250 unique reflections were collected at ambient temperature on an equi-inclination Weissenberg camera using Cu Kα radiation. Data were corrected for Lp effects as well as for the effect of spot extension, but not for absorption [µ(Cu Kα)= 135 mm^-1]. 694 visually estimated reflections having values significantly above background were used in the isotropic least-squares refinement. The final calculations led to R = 0.142 for 49 refined parameters, as the H atoms were not localized. A further anisotropic refinement of the structure was eventually carried out (Tavale & Pant, 1973). In this calculation, based on the same data set but with the inclusion of H atoms. the R factor decreased to 0.104, with a data-to-parameter ratio of 5.6, and average standard deviations of 0.013Å in C—C bond lengths and 0.9° in bond angles.

The asymmetric unit of (I) comprises a non-planar independent molecule, as the nitro and carboxy substituents force each other to be twisted away from the plane of the aromatic ring by 54.9 (2) and 24.0 (2)°, respectively (Fig. 1). The pattern of bond lengths and bond angles is consistent with those reported in previous structural investigations concerning the effect of the nitro and the carboxy groups on the geometry of polysubstituted benzene rings (Colapietro et al., 1984; Domenicano et al., 1989). Analysis of the crystal packing of (I), (Fig. 2), shows that the molecular components form the conventional dimeric units observed in monocarboylic acids (Leiserowitz, 1976). The structure is stabilized by very short [2.660 (3) Å] intermolecular O—H···O interactions of descriptor R²₂(8) (Etter et al., 1990; Bernstein et al., 1995; Motherwell et al., 1999) (Table 1) between the OH moiety and the carbonyl O atom (O1ⁱ) [symmetry code: (i) -x + 2, -y + 1, -z + 1].

Related literature

For the previous structure determination, see: Kurahashi et al. (1967); Sakore et al. (1967); Tavale & Pant (1973). For related literature, see: Leiserowitz (1976); Colapietro et al. (1984); Domenicano et al. (1989). For computation of ring patterns formed by hydrogen bonds in crystal structures, see: Etter et al. (1990); Bernstein et al. (1995); Motherwell et al. (1999).

S2. Experimental

o-Nitrobenzoic acid (0.1 mmol, Sigma Aldrich at 95% purity) was dissolved in water (5 ml) and gently heated under reflux for 1 h. After cooling the solution to an ambient temperature, crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of the solvent after few days.

S3. Refinement

All H atoms were found in a difference map and then treated as riding atoms, with C—H = 0.93Å and U_iso values equal to 1.2U_eq(C, phenyl). The remaining H atom of the carboxy group was freely refined.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacements ellipsoids are at the 50% probability level.
	Fig. 2. Crystal packing diagram for (I) viewed approximately down a. All atoms are shown as small spheres of arbitrary radii. For the sake of clarity, H atoms not involved in hydrogen bonding have been omitted. Hydrogen bonding is indicated by dashed lines.

2-nitrobenzoic acid

Crystal data

C7H5NO4	Z = 2
Mr = 167.12	F(000) = 172
Triclinic, P1	Dx = 1.566 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.0147 (15) Å	Cell parameters from 861 reflections
b = 7.527 (2) Å	θ = 3.0–32.5°
c = 10.620 (2) Å	µ = 0.13 mm^−1
α = 69.41 (2)°	T = 298 K
β = 86.07 (2)°	Tablets, colourless
γ = 71.01 (3)°	0.15 × 0.15 × 0.10 mm
V = 354.35 (18) Å^3

Data collection

Oxford Diffraction Xcalibur S CCD diffractometer	1872 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1087 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.050
Detector resolution: 16.0696 pixels mm^-1	θmax = 29.0°, θmin = 3.0°
ω and ϕ scans	h = −6→6
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	k = −10→10
Tmin = 0.879, Tmax = 0.980	l = −14→14
3862 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.077	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.148	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0536P)^2 + 0.0451P] where P = (Fo^2 + 2Fc^2)/3
1872 reflections	(Δ/σ)max < 0.001
113 parameters	Δρmax = 0.26 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

Experimental. Absorption correction: CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.29 (release 10-06-2008 CrysAlis171 .NET) (compiled Jun 10 2008,16:49:55) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

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
O1	0.8083 (4)	0.3762 (3)	0.6058 (2)	0.0471 (6)
O2	1.2483 (4)	0.2482 (3)	0.5512 (2)	0.0481 (6)
H2	1.221 (7)	0.378 (5)	0.504 (3)	0.068 (11)*
O3	0.7790 (4)	0.2147 (3)	0.8921 (2)	0.0537 (6)
O4	0.4118 (4)	0.1514 (3)	0.8517 (2)	0.0533 (6)
N1	0.6642 (5)	0.1288 (3)	0.8481 (2)	0.0344 (5)
C1	1.0287 (5)	0.0235 (3)	0.6923 (2)	0.0305 (6)
C2	0.8416 (5)	−0.0231 (4)	0.7933 (2)	0.0297 (6)
C3	0.8224 (6)	−0.2123 (4)	0.8508 (3)	0.0381 (7)
H3	0.6904	−0.2375	0.9147	0.046*
C4	1.0025 (6)	−0.3648 (4)	0.8123 (3)	0.0450 (7)
H4	0.9927	−0.4941	0.8503	0.054*
C5	1.1971 (6)	−0.3249 (4)	0.7172 (3)	0.0440 (8)
H5	1.3219	−0.4286	0.6933	0.053*
C6	1.2084 (6)	−0.1327 (4)	0.6572 (3)	0.0393 (7)
H6	1.3386	−0.1080	0.5922	0.047*
C7	1.0188 (5)	0.2327 (4)	0.6144 (3)	0.0334 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0457 (12)	0.0296 (10)	0.0542 (13)	−0.0083 (9)	0.0228 (10)	−0.0080 (9)
O2	0.0461 (13)	0.0350 (12)	0.0543 (13)	−0.0151 (9)	0.0236 (10)	−0.0071 (10)
O3	0.0600 (14)	0.0563 (13)	0.0657 (14)	−0.0290 (11)	0.0177 (11)	−0.0391 (12)
O4	0.0361 (12)	0.0638 (14)	0.0638 (15)	−0.0131 (10)	0.0160 (10)	−0.0321 (12)
N1	0.0411 (14)	0.0319 (12)	0.0275 (12)	−0.0140 (10)	0.0117 (10)	−0.0071 (10)
C1	0.0335 (14)	0.0287 (14)	0.0275 (13)	−0.0088 (11)	0.0023 (11)	−0.0090 (11)
C2	0.0312 (13)	0.0300 (14)	0.0270 (13)	−0.0084 (10)	0.0045 (11)	−0.0106 (11)
C3	0.0486 (17)	0.0355 (15)	0.0323 (15)	−0.0205 (12)	0.0114 (13)	−0.0097 (12)
C4	0.062 (2)	0.0263 (14)	0.0437 (17)	−0.0150 (13)	0.0056 (15)	−0.0079 (13)
C5	0.0530 (18)	0.0312 (15)	0.0436 (17)	−0.0052 (12)	0.0085 (14)	−0.0169 (13)
C6	0.0402 (16)	0.0393 (16)	0.0357 (15)	−0.0105 (12)	0.0132 (13)	−0.0138 (13)
C7	0.0392 (15)	0.0320 (14)	0.0304 (14)	−0.0148 (12)	0.0131 (12)	−0.0116 (11)

Geometric parameters (Å, º)

O1—C7	1.222 (3)	C2—C3	1.372 (3)
O2—C7	1.310 (3)	C3—C4	1.380 (3)
O2—H2	0.90 (3)	C3—H3	0.9300
O3—N1	1.208 (3)	C4—C5	1.381 (4)
O4—N1	1.221 (3)	C4—H4	0.9300
N1—C2	1.474 (3)	C5—C6	1.379 (4)
C1—C6	1.381 (3)	C5—H5	0.9300
C1—C2	1.402 (3)	C6—H6	0.9300
C1—C7	1.485 (3)
C7—O2—H2	108 (2)	C3—C4—C5	119.8 (2)
O3—N1—O4	124.6 (2)	C3—C4—H4	120.1
O3—N1—C2	118.2 (2)	C5—C4—H4	120.1
O4—N1—C2	117.1 (2)	C6—C5—C4	120.6 (2)
C6—C1—C2	117.2 (2)	C6—C5—H5	119.7
C6—C1—C7	119.9 (2)	C4—C5—H5	119.7
C2—C1—C7	122.7 (2)	C5—C6—C1	120.9 (2)
C3—C2—C1	122.5 (2)	C5—C6—H6	119.6
C3—C2—N1	116.4 (2)	C1—C6—H6	119.6
C1—C2—N1	121.1 (2)	O1—C7—O2	123.4 (2)
C2—C3—C4	118.9 (2)	O1—C7—C1	122.2 (2)
C2—C3—H3	120.6	O2—C7—C1	114.4 (2)
C4—C3—H3	120.6
C6—C1—C2—C3	−3.7 (4)	C2—C3—C4—C5	−0.1 (4)
C7—C1—C2—C3	169.9 (3)	C3—C4—C5—C6	−1.9 (4)
C6—C1—C2—N1	173.2 (2)	C4—C5—C6—C1	1.1 (4)
C7—C1—C2—N1	−13.3 (4)	C2—C1—C6—C5	1.6 (4)
O3—N1—C2—C3	122.6 (3)	C7—C1—C6—C5	−172.1 (3)
O4—N1—C2—C3	−53.9 (3)	C6—C1—C7—O1	152.9 (3)
O3—N1—C2—C1	−54.5 (3)	C2—C1—C7—O1	−20.5 (4)
O4—N1—C2—C1	129.1 (3)	C6—C1—C7—O2	−23.9 (4)
C1—C2—C3—C4	2.9 (4)	C2—C1—C7—O2	162.7 (2)
N1—C2—C3—C4	−174.1 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1^i	0.90 (3)	1.77 (4)	2.660 (3)	173 (3)

Symmetry code: (i) −x+2, −y+1, −z+1.