2,3-Difluoro­benzoic acid

Knapik, A.A.; Minor, W.; Chruszcz, M.

doi:10.1107/S1600536808001232

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 64| Part 2| February 2008| Page o466

doi:10.1107/S1600536808001232

Open

access

2,3-Difluorobenzoic acid

Aleksandra A. Knapik,^a Wladek Minor ^a and Maksymilian Chruszcz ^a ^*

^aUniversity of Virginia, Department of Molecular Physiology and Biological Physics, 1340 Jefferson Park Avenue, Charlottesville, VA 22908, USA
^*Correspondence e-mail: maks@iwonka.med.virginia.edu

(Received 11 December 2007; accepted 11 January 2008; online 18 January 2008)

2,3-Difluorobenzoic acid, C₇H₄F₂O₂, forms dimers that are stabilized by hydrogen bonds. The dimers are stacked and the stacks are held together by weak C—H⋯F and C—H⋯O interactions.

Related literature

For related literature, see: Juhler & Mortensen (2002 ); Malone et al. (2006 ); Potrzebowski & Chruszcz (2007 ).

Experimental

Crystal data

C₇H₄F₂O₂
M_r = 158.10
Monoclinic, P 2₁ /c
a = 3.761 (1) Å
b = 6.520 (1) Å
c = 26.521 (2) Å
β = 92.27 (1)°
V = 649.8 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.15 mm⁻¹
T = 293 (2) K
0.15 × 0.15 × 0.02 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (Otwinowski et al., 2003 ) T_min = 0.98, T_max = 1.00 (expected range = 0.977–0.997)
25713 measured reflections
1881 independent reflections
1371 reflections with I > 2σ(I)
R_int = 0.031

Refinement

R[F² > 2σ(F²)] = 0.043
wR(F²) = 0.133
S = 1.06
1881 reflections
116 parameters
All H-atom parameters refined
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.13 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯O1ⁱ	0.94 (2)	2.65 (2)	3.509 (2)	153 (2)
O2—H2⋯O1ⁱⁱ	1.03 (3)	1.60 (3)	2.625 (2)	173 (3)
C6—H6⋯O2ⁱⁱⁱ	0.95 (2)	2.67 (2)	3.498 (2)	146 (1)
C4—H4⋯F2^iv	0.95 (2)	2.65 (2)	3.513 (2)	151 (2)
Symmetry codes: (i) x-1, y-1, z; (ii) -x+1, -y+1, -z; (iii) -x, -y, -z; (iv) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: HKL-2000 (Otwinowski & Minor, 1997 ); cell refinement: HKL-2000; data reduction: HKL-2000; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ) and HKL-3000SM (Minor et al., 2006 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and HKL-3000SM; molecular graphics: HKL-3000SM, Mercury (Macrae et al., 2006 ), ORTEPIII (Burnett & Johnson, 1996 ) and ORTEP-3 (Farrugia, 1997 ); software used to prepare material for publication: HKL-3000SM.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808001232/om2199sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808001232/om2199Isup2.hkl

checkCIF report

Comment top

2,3-Difluorobenzoic acid (I) (Fig. 1) is used as a tracer for determining the extent of recovery of materials injected into oil wells (Malone et al., 2006) or for observing water movment in soil (Juhler & Mortensen, 2002). 2,3-Difluorobenzoic acid crystallized, like 3,5-difluorobenzoic acid (Potrzebowski & Chruszcz, 2007), in the space group P2₁/c with one molecule per asymmetric unit. Both (I) and 3,5-difluorobenzoic acid form dimers in the crystal lattice (Fig. 2), but the dimers of the two compounds pack differently. The molecules of (I) pack more tightly in the crystal, as the crystal density is 8% higher than in case of 3,5-difluorobenzoic acid. The dimers of (I) are stabilized by hydrogen bonds (Table 1). The dimers are arranged in stacks that are held together by weak C—H···F and C—H···O interactions (Fig. 2).

Related literature top

For related literature, see: Juhler & Mortensen (2002); Malone et al. (2006); Potrzebowski & Chruszcz (2007).

Experimental top

2,3-Difluorobenzoic acid (98%) was purchased from Aldrich, and dissolved in 1-propanol. Single crystals suitable for X-ray diffraction study were obtained by slow evaporation at 293 K.

Computing details top

Data collection: HKL-2000 (Otwinowski & Minor, 1997); cell refinement: HKL-2000 (Otwinowski & Minor, 1997); data reduction: HKL-2000 (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008) and HKL-3000SM (Minor et al., 2006); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and HKL-3000SM (Minor et al., 2006); molecular graphics: HKL-3000SM (Minor et al., 2006), Mercury (Macrae et al., 2006), ORTEPIII (Burnett & Johnson, 1996) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: HKL-3000SM (Minor et al., 2006).

Figures top

	Fig. 1. An asymmetric unit of 2,3-difluorobenzoic acid. Displacement ellipsoids are drawn at the 50% probability level, while hydrogen atoms are drawn as spheres of an arbitrary radius.
	Fig. 2. The packing of 2,3-difluorobenzoic acid shown along [010]. Hydrogen bonds are marked with blue, dashed lines. Weak C—H···F and C—H···O interactions are shown as light-blue, dashed lines.

2,3-difluorobenzoic acid top

Crystal data top

C₇H₄F₂O₂	F(000) = 320
M_r = 158.10	D_x = 1.616 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71074 Å
Hall symbol: -P 2ybc	Cell parameters from 25713 reflections
a = 3.761 (1) Å	θ = 3.1–30.0°
b = 6.520 (1) Å	µ = 0.15 mm⁻¹
c = 26.521 (2) Å	T = 293 K
β = 92.27 (1)°	Plate, colorless
V = 649.8 (2) Å³	0.15 × 0.15 × 0.02 mm
Z = 4

Data collection top

Rigaku R-AXIS RAPID diffractometer	1881 independent reflections
Radiation source: fine-focus sealed tube	1371 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.031
Detector resolution: 10 pixels mm^-1	θ_max = 30.0°, θ_min = 3.1°
ω scans with χ offset	h = −5→5
Absorption correction: multi-scan (Otwinowski et al., 2003)	k = −9→9
T_min = 0.98, T_max = 1.00	l = −37→37
25713 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.044	Hydrogen site location: difference Fourier map
wR(F²) = 0.133	All H-atom parameters refined
S = 1.06	w = 1/[σ²(F_o²) + (0.0665P)² + 0.0891P] where P = (F_o² + 2F_c²)/3
1881 reflections	(Δ/σ)_max < 0.001
116 parameters	Δρ_max = 0.29 e Å⁻³
0 restraints	Δρ_min = −0.13 e Å⁻³

Crystal data top

C₇H₄F₂O₂	V = 649.8 (2) Å³
M_r = 158.10	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 3.761 (1) Å	µ = 0.15 mm⁻¹
b = 6.520 (1) Å	T = 293 K
c = 26.521 (2) Å	0.15 × 0.15 × 0.02 mm
β = 92.27 (1)°

Data collection top

Rigaku R-AXIS RAPID diffractometer	1881 independent reflections
Absorption correction: multi-scan (Otwinowski et al., 2003)	1371 reflections with I > 2σ(I)
T_min = 0.98, T_max = 1.00	R_int = 0.031
25713 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.044	0 restraints
wR(F²) = 0.133	All H-atom parameters refined
S = 1.06	Δρ_max = 0.29 e Å⁻³
1881 reflections	Δρ_min = −0.13 e Å⁻³
116 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.3028 (3)	0.18896 (18)	0.09787 (4)	0.0453 (3)
C2	0.3710 (3)	0.2435 (2)	0.14793 (5)	0.0507 (3)
C3	0.2895 (4)	0.1088 (2)	0.18600 (5)	0.0580 (3)
C4	0.1428 (4)	−0.0797 (2)	0.17592 (6)	0.0607 (4)
C5	0.0737 (4)	−0.1357 (2)	0.12626 (6)	0.0587 (3)
C6	0.1521 (3)	−0.0033 (2)	0.08785 (5)	0.0517 (3)
C7	0.3892 (3)	0.32666 (19)	0.05550 (5)	0.0485 (3)
F1	0.5159 (3)	0.42443 (14)	0.16134 (3)	0.0748 (3)
F2	0.3611 (3)	0.16829 (19)	0.23412 (3)	0.0893 (4)
O1	0.5592 (3)	0.48801 (16)	0.06313 (4)	0.0673 (3)
O2	0.2818 (3)	0.26822 (19)	0.01143 (4)	0.0742 (4)
H2	0.330 (8)	0.372 (4)	−0.0169 (13)	0.158 (11)*
H4	0.090 (5)	−0.174 (3)	0.2020 (8)	0.087 (6)*
H5	−0.026 (5)	−0.264 (3)	0.1183 (7)	0.079 (5)*
H6	0.104 (4)	−0.037 (3)	0.0534 (6)	0.057 (4)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0441 (6)	0.0446 (6)	0.0472 (6)	0.0012 (5)	0.0014 (4)	−0.0005 (5)
C2	0.0550 (7)	0.0465 (6)	0.0503 (6)	0.0009 (5)	0.0003 (5)	−0.0037 (5)
C3	0.0635 (8)	0.0653 (8)	0.0451 (6)	0.0066 (6)	0.0024 (5)	0.0018 (6)
C4	0.0593 (7)	0.0625 (8)	0.0607 (8)	0.0018 (6)	0.0074 (6)	0.0151 (6)
C5	0.0565 (7)	0.0494 (7)	0.0699 (9)	−0.0047 (6)	0.0003 (6)	0.0058 (6)
C6	0.0524 (7)	0.0495 (7)	0.0529 (7)	−0.0036 (5)	−0.0017 (5)	−0.0021 (5)
C7	0.0503 (6)	0.0481 (6)	0.0471 (6)	−0.0027 (5)	0.0001 (5)	−0.0024 (5)
F1	0.1091 (7)	0.0572 (5)	0.0576 (5)	−0.0162 (5)	−0.0039 (5)	−0.0095 (4)
F2	0.1270 (9)	0.0956 (8)	0.0449 (5)	−0.0067 (7)	0.0015 (5)	−0.0011 (5)
O1	0.0901 (7)	0.0569 (6)	0.0544 (5)	−0.0240 (5)	−0.0021 (5)	0.0016 (4)
O2	0.1028 (9)	0.0728 (7)	0.0461 (5)	−0.0317 (6)	−0.0058 (5)	0.0013 (5)

Geometric parameters (Å, º) top

C1—C2	1.3885 (17)	C4—H4	0.95 (2)
C1—C6	1.3968 (17)	C5—C6	1.376 (2)
C1—C7	1.4842 (17)	C5—H5	0.94 (2)
C2—F1	1.3415 (16)	C6—H6	0.950 (16)
C2—C3	1.3819 (19)	C7—O1	1.2435 (16)
C3—F2	1.3508 (16)	C7—O2	1.2796 (15)
C3—C4	1.369 (2)	O2—H2	1.03 (3)
C4—C5	1.381 (2)

C2—C1—C6	118.03 (12)	C5—C4—H4	119.0 (12)
C2—C1—C7	122.09 (11)	C6—C5—C4	120.17 (14)
C6—C1—C7	119.88 (11)	C6—C5—H5	119.2 (12)
F1—C2—C3	117.71 (12)	C4—C5—H5	120.6 (11)
F1—C2—C1	122.43 (12)	C5—C6—C1	121.28 (13)
C3—C2—C1	119.86 (12)	C5—C6—H6	122.0 (10)
F2—C3—C4	120.41 (13)	C1—C6—H6	116.8 (10)
F2—C3—C2	117.76 (14)	O1—C7—O2	122.84 (12)
C4—C3—C2	121.82 (13)	O1—C7—C1	121.00 (11)
C3—C4—C5	118.84 (13)	O2—C7—C1	116.15 (11)
C3—C4—H4	122.2 (12)	C7—O2—H2	114.3 (16)

C6—C1—C2—F1	179.84 (11)	C2—C3—C4—C5	−0.2 (2)
C7—C1—C2—F1	0.6 (2)	C3—C4—C5—C6	0.0 (2)
C6—C1—C2—C3	−0.03 (19)	C4—C5—C6—C1	0.2 (2)
C7—C1—C2—C3	−179.23 (12)	C2—C1—C6—C5	−0.17 (19)
F1—C2—C3—F2	0.0 (2)	C7—C1—C6—C5	179.05 (12)
C1—C2—C3—F2	179.88 (12)	C2—C1—C7—O1	7.3 (2)
F1—C2—C3—C4	−179.64 (13)	C6—C1—C7—O1	−171.85 (12)
C1—C2—C3—C4	0.2 (2)	C2—C1—C7—O2	−173.28 (12)
F2—C3—C4—C5	−179.87 (13)	C6—C1—C7—O2	7.53 (18)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O1ⁱ	0.94 (2)	2.65 (2)	3.509 (2)	153 (2)
O2—H2···O1ⁱⁱ	1.03 (3)	1.60 (3)	2.625 (2)	173 (3)
C6—H6···O2ⁱⁱⁱ	0.95 (2)	2.67 (2)	3.498 (2)	146 (1)
C4—H4···F2^iv	0.95 (2)	2.65 (2)	3.513 (2)	151 (2)

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

Experimental details

Crystal data
Chemical formula	C₇H₄F₂O₂
M_r	158.10
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	3.761 (1), 6.520 (1), 26.521 (2)
β (°)	92.27 (1)
V (Å³)	649.8 (2)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.15
Crystal size (mm)	0.15 × 0.15 × 0.02

Data collection
Diffractometer	Rigaku R-AXIS RAPID diffractometer
Absorption correction	Multi-scan (Otwinowski et al., 2003)
T_min, T_max	0.98, 1.00
No. of measured, independent and observed [I > 2σ(I)] reflections	25713, 1881, 1371
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.044, 0.133, 1.06
No. of reflections	1881
No. of parameters	116
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.13

Computer programs: HKL-2000 (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008) and HKL-3000SM (Minor et al., 2006), SHELXL97 (Sheldrick, 2008) and HKL-3000SM (Minor et al., 2006), HKL-3000SM (Minor et al., 2006), Mercury (Macrae et al., 2006), ORTEPIII (Burnett & Johnson, 1996) and ORTEP-3 (Farrugia, 1997), HKL-3000SM (Minor et al., 2006).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O1ⁱ	0.94 (2)	2.65 (2)	3.509 (2)	153 (2)
O2—H2···O1ⁱⁱ	1.03 (3)	1.60 (3)	2.625 (2)	173 (3)
C6—H6···O2ⁱⁱⁱ	0.95 (2)	2.67 (2)	3.498 (2)	146 (1)
C4—H4···F2^iv	0.95 (2)	2.65 (2)	3.513 (2)	151 (2)

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

Acknowledgements

The authors thank Matthew D. Zimmerman for helpful discussions. This work was supported by contract GI11496 from HKL Research Inc.

References

Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA. Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Juhler, R. K. & Mortensen, A. P. (2002). J. Chromatogr. A, 957, 11–16. Web of Science CrossRef PubMed CAS Google Scholar
Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453–457. Web of Science CrossRef CAS IUCr Journals Google Scholar
Malone, S., Broacha, E., Shaw, D. & Hampton, T. (2006). US Patent 7 032 662. Google Scholar
Minor, W., Cymborowski, M., Otwinowski, Z. & Chruszcz, M. (2006). Acta Cryst. D62, 859–866. Web of Science CrossRef CAS IUCr Journals Google Scholar
Otwinowski, Z., Borek, D., Majewski, W. & Minor, W. (2003). Acta Cryst. A59, 228–234. Web of Science CrossRef CAS IUCr Journals Google Scholar
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press. Google Scholar
Potrzebowski, W. & Chruszcz, M. (2007). Acta Cryst. E63, o2754. Web of Science CSD CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar