A monoclinic polymorph of 2-(4-nitro­phen­yl)acetic acid

A new monoclinic form of 4-nitro­phenyl­acetic acid, C₈H₇NO₄, (I), differs from the known ortho­rhom­bic form both in its mol­ecular conformation and in its inter­molecular contacts. The conformation is different as the plane of the carb­oxy­lic acid group in (I) is more nearly perpendicular to the plane of the aromatic ring [dihedral angle = 86.9 (3)°] than in the previous form (74.5°). Both polymorphs display hydrogen-bonded R₂²(8) carb­oxy­lic acid dimeric pairs, but in (I), neighbouring dimers inter­act through nitro–nitro N...O dipole–dipole contacts rather than the nitro–carbonyl contacts found in the ortho­rhom­bic form.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.054
• wR factor = 0.130
• Data-to-parameter ratio = 14.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT905_ALERT_3_C Negative K value in the Analysis of Variance ...     -2.239 Report
PLAT905_ALERT_3_C Negative K value in the Analysis of Variance ...     -0.026 Report
PLAT978_ALERT_2_C Number C-C Bonds with Positive Residual Density.          0 Note

Alert level G
PLAT012_ALERT_1_G N.O.K. _shelx_res_checksum found in CIF ........     Please Check
PLAT910_ALERT_3_G Missing # of FCF Reflection(s) Below Theta(Min)           1 Note
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600         14 Note
PLAT955_ALERT_1_G Reported (CIF) and Actual (FCF) Lmax Differ by .          1 Units

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   3 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   4 ALERT level G = General information/check it is not something unexpected

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

2-(4-Nitrophenyl)acetic acid

Crystal data

C8H7NO4	F(000) = 376
Mr = 181.15	Dx = 1.517 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.1364 (5) Å	Cell parameters from 2414 reflections
b = 5.1034 (4) Å	θ = 3.2–28.7°
c = 25.458 (3) Å	µ = 0.12 mm^−1
β = 95.937 (8)°	T = 150 K
V = 792.98 (13) Å^3	Tablet, colourless
Z = 4	0.32 × 0.18 × 0.13 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer	1814 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1076 reflections with I > 2σ(I)
Detector resolution: 16.0727 pixels mm^-1	Rint = 0.090
ω scans	θmax = 27.5°, θmin = 3.2°
Absorption correction: multi-scan CrysAlis PRO (Agilent, 2014)	h = −7→7
Tmin = 0.880, Tmax = 1.000	k = −6→6
15530 measured reflections	l = −33→32

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.054	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.130	w = 1/[σ^2(Fo^2) + (0.0414P)^2 + 0.2348P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
1814 reflections	Δρmax = 0.24 e Å^−3
122 parameters	Δρmin = −0.26 e Å^−3

Special details

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

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

	x	y	z	Uiso*/Ueq
O2	0.1037 (3)	0.8022 (4)	0.03062 (7)	0.0364 (5)
O3	0.8335 (3)	−0.2053 (3)	0.23833 (7)	0.0349 (5)
O4	1.0830 (3)	−0.1662 (4)	0.18470 (7)	0.0371 (5)
O1	0.2209 (3)	0.3888 (3)	0.03653 (7)	0.0337 (5)
N1	0.9081 (3)	−0.1028 (4)	0.20049 (8)	0.0274 (5)
C4	0.7826 (4)	0.1092 (5)	0.17228 (9)	0.0229 (5)
C1	0.5454 (4)	0.5029 (5)	0.11899 (9)	0.0243 (6)
C6	0.4753 (4)	0.3949 (5)	0.16427 (9)	0.0267 (6)
H6	0.3449	0.4582	0.1770	0.032*
C8	0.2380 (4)	0.6189 (5)	0.04973 (9)	0.0252 (6)
C5	0.5924 (4)	0.1965 (5)	0.19118 (9)	0.0265 (6)
H5	0.5431	0.1218	0.2220	0.032*
C3	0.8571 (4)	0.2132 (5)	0.12774 (9)	0.0288 (6)
H3	0.9886	0.1511	0.1155	0.035*
C2	0.7366 (4)	0.4104 (5)	0.10109 (10)	0.0297 (6)
H2	0.7858	0.4833	0.0701	0.036*
C7	0.4160 (4)	0.7176 (5)	0.08958 (10)	0.0284 (6)
H7A	0.3497	0.8298	0.1154	0.034*
H7B	0.5173	0.8280	0.0713	0.034*
H2O	−0.009 (7)	0.741 (8)	0.0027 (16)	0.099 (13)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O2	0.0362 (11)	0.0257 (10)	0.0427 (11)	0.0049 (9)	−0.0178 (9)	0.0012 (9)
O3	0.0359 (11)	0.0336 (11)	0.0346 (10)	0.0010 (9)	0.0003 (8)	0.0081 (9)
O4	0.0291 (10)	0.0390 (12)	0.0430 (11)	0.0141 (9)	0.0033 (8)	−0.0006 (9)
O1	0.0353 (11)	0.0213 (10)	0.0416 (11)	−0.0006 (8)	−0.0095 (8)	−0.0026 (8)
N1	0.0262 (12)	0.0240 (12)	0.0307 (12)	0.0026 (10)	−0.0032 (9)	−0.0034 (10)
C4	0.0213 (12)	0.0217 (13)	0.0242 (13)	0.0034 (11)	−0.0050 (9)	−0.0015 (11)
C1	0.0237 (13)	0.0225 (13)	0.0250 (13)	−0.0016 (11)	−0.0056 (10)	−0.0032 (10)
C6	0.0236 (13)	0.0296 (14)	0.0264 (13)	0.0053 (11)	0.0005 (10)	−0.0038 (11)
C8	0.0250 (14)	0.0241 (14)	0.0260 (13)	0.0009 (11)	0.0008 (10)	0.0032 (11)
C5	0.0276 (13)	0.0268 (13)	0.0251 (13)	0.0008 (12)	0.0021 (10)	−0.0004 (11)
C3	0.0214 (13)	0.0337 (15)	0.0315 (14)	0.0054 (12)	0.0038 (10)	−0.0002 (12)
C2	0.0264 (14)	0.0349 (15)	0.0277 (14)	−0.0013 (12)	0.0026 (11)	0.0045 (12)
C7	0.0277 (14)	0.0244 (13)	0.0309 (14)	−0.0004 (11)	−0.0071 (11)	−0.0026 (11)

Geometric parameters (Å, º)

O2—C8	1.307 (3)	C1—C7	1.506 (3)
O2—H2O	0.99 (4)	C6—C5	1.382 (3)
O3—N1	1.226 (3)	C6—H6	0.9500
O4—N1	1.228 (2)	C8—C7	1.499 (3)
O1—C8	1.223 (3)	C5—H5	0.9500
N1—C4	1.472 (3)	C3—C2	1.384 (3)
C4—C3	1.372 (3)	C3—H3	0.9500
C4—C5	1.382 (3)	C2—H2	0.9500
C1—C2	1.385 (3)	C7—H7A	0.9900
C1—C6	1.386 (3)	C7—H7B	0.9900
C8—O2—H2O	114 (2)	C6—C5—C4	118.6 (2)
O3—N1—O4	123.7 (2)	C6—C5—H5	120.7
O3—N1—C4	118.6 (2)	C4—C5—H5	120.7
O4—N1—C4	117.7 (2)	C4—C3—C2	118.7 (2)
C3—C4—C5	121.9 (2)	C4—C3—H3	120.7
C3—C4—N1	119.0 (2)	C2—C3—H3	120.7
C5—C4—N1	119.1 (2)	C3—C2—C1	120.9 (2)
C2—C1—C6	119.0 (2)	C3—C2—H2	119.5
C2—C1—C7	120.4 (2)	C1—C2—H2	119.5
C6—C1—C7	120.6 (2)	C8—C7—C1	113.7 (2)
C5—C6—C1	120.9 (2)	C8—C7—H7A	108.8
C5—C6—H6	119.6	C1—C7—H7A	108.8
C1—C6—H6	119.6	C8—C7—H7B	108.8
O1—C8—O2	123.5 (2)	C1—C7—H7B	108.8
O1—C8—C7	123.0 (2)	H7A—C7—H7B	107.7
O2—C8—C7	113.5 (2)
O3—N1—C4—C3	−175.6 (2)	C5—C4—C3—C2	−0.3 (4)
O4—N1—C4—C3	4.7 (3)	N1—C4—C3—C2	179.2 (2)
O3—N1—C4—C5	3.9 (3)	C4—C3—C2—C1	0.4 (4)
O4—N1—C4—C5	−175.8 (2)	C6—C1—C2—C3	0.0 (4)
C2—C1—C6—C5	−0.5 (4)	C7—C1—C2—C3	180.0 (2)
C7—C1—C6—C5	179.5 (2)	O1—C8—C7—C1	−10.7 (3)
C1—C6—C5—C4	0.6 (4)	O2—C8—C7—C1	169.3 (2)
C3—C4—C5—C6	−0.2 (4)	C2—C1—C7—C8	93.1 (3)
N1—C4—C5—C6	−179.7 (2)	C6—C1—C7—C8	−86.9 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O1^i	0.99 (4)	1.69 (4)	2.672 (2)	170 (3)

Symmetry code: (i) −x, −y+1, −z.