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

Kennedy, A.R.; Silva de Moraes, L.

doi:10.1107/S2414314616019325

organic compounds

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ISSN: 2414-3146

Volume 1| Part 12| December 2016| x161932

https://doi.org/10.1107/S2414314616019325

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

Alan R. Kennedy ^a ^* and Lygia Silva de Moraes ^a

^aWestChem, Department of Pure & Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland
^*Correspondence e-mail: a.r.kennedy@strath.ac.uk

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 19 November 2016; accepted 2 December 2016; online 9 December 2016)

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.

Keywords: crystal structure; polymorphism; carboxylic acid; hydrogen bonding; nitro–nitro dipole interactions.

CCDC reference: 1520553

Structure description

An orthorhombic polymorph of 4-nitrophenylacetic acid was crystallized from ethanol solution and structurally described by Grabowski et al. (1990 ). The new polymorph described herein, (I), features a molecular structure with a nitro group that is essentially coplanar with the aromatic ring [dihedral angle = 3.9 (3) °] and a carboxylic acid group that approaches the perpendicular with respect to the aromatic ring [dihedral angle = 86.9 (3)°], see Fig. 1. The previously known orthorhombic polymorph also features near coplanarity of the nitro and aromatic groups, but the carboxylic acid group lies further from the perpendicular (74.5°).

Figure 1
The molecular structure of (I). Displacement ellipsoids are drawn at the 50% probability level.

In the crystal structure of (I), strong O—H⋯O hydrogen bonds (Table 1) occur between carboxylic acid groups, creating the classic dimeric $[R_{2}^{2}]$ (8) motif (Fig. 2). This motif is also present in the orthorhombic polymorph. A difference is that in (I) these dimers interconnect through nitro-to-nitro dipole-to-dipole contacts [O3⋯N1ⁱⁱ 2.923 (3) Å, symmetry code: (ii) 2 − x, − $[{1\over 2}]$ + y, $[{1\over 2}]$ − z] to form an extended chain (Wozniak et al., 1994 ). However, in the orthorhombic form of 4-nitrophenylacetic acid, the nitro group forms nitro-to-carbonyl dipole–dipole contacts instead. A similar set of intermolecular contacts to that found in (I) is found in the polymorph of 4-nitrobenzoic acid described by Groth (1980 ). Interestingly, that structure also has a unit cell that is similar to that found for (I) (a = 5.403, b = 5.153, c = 24.692 Å, β = 96.89°, space group P2₁/c).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2O⋯O1ⁱ	0.99 (4)	1.69 (4)	2.672 (2)	170 (3)
Symmetry code: (i) -x, -y+1, -z.

Figure 2
The crystal structure of (I) displays the classic $[R_{2}^{2}]$ (8) carboxylic acid dimeric hydrogen-bonding motif. Neighbouring dimers interact through nitro-to-nitro contacts to form a chain.

Synthesis and crystallization

The crystallization of 4-nitrophenylacetic acid occurred during an attempt to synthesize a salt form of N-methylephedrine by reaction with the acid (Kennedy et al., 2011 ): 1.27 mmol of 4-nitrophenylacetic acid was dissolved in 5 ml of deionized water and the added to a slurry of 1 mmol of base in 5 ml of deionized water. The resulting solution was stirred at 323 K for 30 minutes and filtered. The solution was then put into a test tube and left to slowly evaporate and to cool to room temperature: monoclinic 4-nitrophenylacetic acid in the form of colourless tablets crystallized on the walls of the test tube.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₈H₇NO₄
M_r	181.15
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	150
a, b, c (Å)	6.1364 (5), 5.1034 (4), 25.458 (3)
β (°)	95.937 (8)
V (Å³)	792.98 (13)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.12
Crystal size (mm)	0.32 × 0.18 × 0.13

Data collection
Diffractometer	Oxford Diffraction Xcalibur Eos
Absorption correction	Multi-scan CrysAlis PRO (Agilent, 2014 )
T_min, T_max	0.880, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	15530, 1814, 1076
R_int	0.090
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.054, 0.130, 1.06
No. of reflections	1814
No. of parameters	122
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.24, −0.26
Computer programs: CrysAlis PRO (Agilent, 2014), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), ORTEP-3 for Windows (Farrugia, 2012 ) and Mercury (Macrae et al., 2008 ).

Structural data

CCDC reference: 1520553

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314616019325/hb4100sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314616019325/hb4100Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314616019325/hb4100Isup3.cml

checkCIF report

Computing details top

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 top

Crystal data top

C₈H₇NO₄	F(000) = 376
M_r = 181.15	D_x = 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) Å³	Tablet, colourless
Z = 4	0.32 × 0.18 × 0.13 mm

Data collection top

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	R_int = 0.090
ω scans	θ_max = 27.5°, θ_min = 3.2°
Absorption correction: multi-scan CrysAlis PRO (Agilent, 2014)	h = −7→7
T_min = 0.880, T_max = 1.000	k = −6→6
15530 measured reflections	l = −33→32

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.054	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.130	w = 1/[σ²(F_o²) + (0.0414P)² + 0.2348P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max < 0.001
1814 reflections	Δρ_max = 0.24 e Å⁻³
122 parameters	Δρ_min = −0.26 e Å⁻³

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
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 (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
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) top

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) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O1ⁱ	0.99 (4)	1.69 (4)	2.672 (2)	170 (3)

Symmetry code: (i) −x, −y+1, −z.

Acknowledgements

The financial support of a PhD studentship by CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologici) and the advice of GSK are gratefully acknowledged.

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