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2,3-Di­fluoro­benzoic acid

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[Juhler, R. K. & Mortensen, A. P. (2002). J. Chromatogr. A, 957, 11-16.]); Malone et al. (2006[Malone, S., Broacha, E., Shaw, D. & Hampton, T. (2006). US Patent 7 032 662.]); Potrzebowski & Chruszcz (2007[Potrzebowski, W. & Chruszcz, M. (2007). Acta Cryst. E63, o2754.]).

[Scheme 1]

Experimental

Crystal data
  • C7H4F2O2

  • Mr = 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[Otwinowski, Z., Borek, D., Majewski, W. & Minor, W. (2003). Acta Cryst. A59, 228-234.]) Tmin = 0.98, Tmax = 1.00 (expected range = 0.977–0.997)

  • 25713 measured reflections

  • 1881 independent reflections

  • 1371 reflections with I > 2σ(I)

  • Rint = 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

  • Δρmax = 0.28 e Å−3

  • Δρmin = −0.13 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA 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⋯F2iv 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[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.]); cell refinement: HKL-2000; data reduction: HKL-2000; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and HKL-3000SM (Minor et al., 2006[Minor, W., Cymborowski, M., Otwinowski, Z. & Chruszcz, M. (2006). Acta Cryst. D62, 859-866.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and HKL-3000SM; molecular graphics: HKL-3000SM, Mercury (Macrae et al., 2006[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.]), ORTEPIII (Burnett & Johnson, 1996[Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA.]) and ORTEP-3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: HKL-3000SM.

Supporting information


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.

Refinement top

All hydrogen atoms were localized using the difference density Fourier map. Their positions and isotropic displacement parameters were refined.

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
[Figure 1] 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.
[Figure 2] 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
C7H4F2O2F(000) = 320
Mr = 158.10Dx = 1.616 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71074 Å
Hall symbol: -P 2ybcCell parameters from 25713 reflections
a = 3.761 (1) Åθ = 3.1–30.0°
b = 6.520 (1) ŵ = 0.15 mm1
c = 26.521 (2) ÅT = 293 K
β = 92.27 (1)°Plate, colorless
V = 649.8 (2) Å30.15 × 0.15 × 0.02 mm
Z = 4
Data collection top
Rigaku R-AXIS RAPID
diffractometer
1881 independent reflections
Radiation source: fine-focus sealed tube1371 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.031
Detector resolution: 10 pixels mm-1θmax = 30.0°, θmin = 3.1°
ω scans with χ offseth = 55
Absorption correction: multi-scan
(Otwinowski et al., 2003)
k = 99
Tmin = 0.98, Tmax = 1.00l = 3737
25713 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.044Hydrogen site location: difference Fourier map
wR(F2) = 0.133All H-atom parameters refined
S = 1.06 w = 1/[σ2(Fo2) + (0.0665P)2 + 0.0891P]
where P = (Fo2 + 2Fc2)/3
1881 reflections(Δ/σ)max < 0.001
116 parametersΔρmax = 0.29 e Å3
0 restraintsΔρmin = 0.13 e Å3
Crystal data top
C7H4F2O2V = 649.8 (2) Å3
Mr = 158.10Z = 4
Monoclinic, P21/cMo Kα radiation
a = 3.761 (1) ŵ = 0.15 mm1
b = 6.520 (1) ÅT = 293 K
c = 26.521 (2) Å0.15 × 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)
Tmin = 0.98, Tmax = 1.00Rint = 0.031
25713 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.133All H-atom parameters refined
S = 1.06Δρmax = 0.29 e Å3
1881 reflectionsΔρmin = 0.13 e Å3
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
xyzUiso*/Ueq
C10.3028 (3)0.18896 (18)0.09787 (4)0.0453 (3)
C20.3710 (3)0.2435 (2)0.14793 (5)0.0507 (3)
C30.2895 (4)0.1088 (2)0.18600 (5)0.0580 (3)
C40.1428 (4)0.0797 (2)0.17592 (6)0.0607 (4)
C50.0737 (4)0.1357 (2)0.12626 (6)0.0587 (3)
C60.1521 (3)0.0033 (2)0.08785 (5)0.0517 (3)
C70.3892 (3)0.32666 (19)0.05550 (5)0.0485 (3)
F10.5159 (3)0.42443 (14)0.16134 (3)0.0748 (3)
F20.3611 (3)0.16829 (19)0.23412 (3)0.0893 (4)
O10.5592 (3)0.48801 (16)0.06313 (4)0.0673 (3)
O20.2818 (3)0.26822 (19)0.01143 (4)0.0742 (4)
H20.330 (8)0.372 (4)0.0169 (13)0.158 (11)*
H40.090 (5)0.174 (3)0.2020 (8)0.087 (6)*
H50.026 (5)0.264 (3)0.1183 (7)0.079 (5)*
H60.104 (4)0.037 (3)0.0534 (6)0.057 (4)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0441 (6)0.0446 (6)0.0472 (6)0.0012 (5)0.0014 (4)0.0005 (5)
C20.0550 (7)0.0465 (6)0.0503 (6)0.0009 (5)0.0003 (5)0.0037 (5)
C30.0635 (8)0.0653 (8)0.0451 (6)0.0066 (6)0.0024 (5)0.0018 (6)
C40.0593 (7)0.0625 (8)0.0607 (8)0.0018 (6)0.0074 (6)0.0151 (6)
C50.0565 (7)0.0494 (7)0.0699 (9)0.0047 (6)0.0003 (6)0.0058 (6)
C60.0524 (7)0.0495 (7)0.0529 (7)0.0036 (5)0.0017 (5)0.0021 (5)
C70.0503 (6)0.0481 (6)0.0471 (6)0.0027 (5)0.0001 (5)0.0024 (5)
F10.1091 (7)0.0572 (5)0.0576 (5)0.0162 (5)0.0039 (5)0.0095 (4)
F20.1270 (9)0.0956 (8)0.0449 (5)0.0067 (7)0.0015 (5)0.0011 (5)
O10.0901 (7)0.0569 (6)0.0544 (5)0.0240 (5)0.0021 (5)0.0016 (4)
O20.1028 (9)0.0728 (7)0.0461 (5)0.0317 (6)0.0058 (5)0.0013 (5)
Geometric parameters (Å, º) top
C1—C21.3885 (17)C4—H40.95 (2)
C1—C61.3968 (17)C5—C61.376 (2)
C1—C71.4842 (17)C5—H50.94 (2)
C2—F11.3415 (16)C6—H60.950 (16)
C2—C31.3819 (19)C7—O11.2435 (16)
C3—F21.3508 (16)C7—O21.2796 (15)
C3—C41.369 (2)O2—H21.03 (3)
C4—C51.381 (2)
C2—C1—C6118.03 (12)C5—C4—H4119.0 (12)
C2—C1—C7122.09 (11)C6—C5—C4120.17 (14)
C6—C1—C7119.88 (11)C6—C5—H5119.2 (12)
F1—C2—C3117.71 (12)C4—C5—H5120.6 (11)
F1—C2—C1122.43 (12)C5—C6—C1121.28 (13)
C3—C2—C1119.86 (12)C5—C6—H6122.0 (10)
F2—C3—C4120.41 (13)C1—C6—H6116.8 (10)
F2—C3—C2117.76 (14)O1—C7—O2122.84 (12)
C4—C3—C2121.82 (13)O1—C7—C1121.00 (11)
C3—C4—C5118.84 (13)O2—C7—C1116.15 (11)
C3—C4—H4122.2 (12)C7—O2—H2114.3 (16)
C6—C1—C2—F1179.84 (11)C2—C3—C4—C50.2 (2)
C7—C1—C2—F10.6 (2)C3—C4—C5—C60.0 (2)
C6—C1—C2—C30.03 (19)C4—C5—C6—C10.2 (2)
C7—C1—C2—C3179.23 (12)C2—C1—C6—C50.17 (19)
F1—C2—C3—F20.0 (2)C7—C1—C6—C5179.05 (12)
C1—C2—C3—F2179.88 (12)C2—C1—C7—O17.3 (2)
F1—C2—C3—C4179.64 (13)C6—C1—C7—O1171.85 (12)
C1—C2—C3—C40.2 (2)C2—C1—C7—O2173.28 (12)
F2—C3—C4—C5179.87 (13)C6—C1—C7—O27.53 (18)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5···O1i0.94 (2)2.65 (2)3.509 (2)153 (2)
O2—H2···O1ii1.03 (3)1.60 (3)2.625 (2)173 (3)
C6—H6···O2iii0.95 (2)2.67 (2)3.498 (2)146 (1)
C4—H4···F2iv0.95 (2)2.65 (2)3.513 (2)151 (2)
Symmetry codes: (i) x1, y1, z; (ii) x+1, y+1, z; (iii) x, y, z; (iv) x, y1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC7H4F2O2
Mr158.10
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)3.761 (1), 6.520 (1), 26.521 (2)
β (°) 92.27 (1)
V3)649.8 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.15
Crystal size (mm)0.15 × 0.15 × 0.02
Data collection
DiffractometerRigaku R-AXIS RAPID
diffractometer
Absorption correctionMulti-scan
(Otwinowski et al., 2003)
Tmin, Tmax0.98, 1.00
No. of measured, independent and
observed [I > 2σ(I)] reflections
25713, 1881, 1371
Rint0.031
(sin θ/λ)max1)0.703
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.133, 1.06
No. of reflections1881
No. of parameters116
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)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···AD—HH···AD···AD—H···A
C5—H5···O1i0.94 (2)2.65 (2)3.509 (2)153 (2)
O2—H2···O1ii1.03 (3)1.60 (3)2.625 (2)173 (3)
C6—H6···O2iii0.95 (2)2.67 (2)3.498 (2)146 (1)
C4—H4···F2iv0.95 (2)2.65 (2)3.513 (2)151 (2)
Symmetry codes: (i) x1, y1, z; (ii) x+1, y+1, z; (iii) x, y, z; (iv) x, y1/2, 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

First citationBurnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA.  Google Scholar
First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
First citationJuhler, R. K. & Mortensen, A. P. (2002). J. Chromatogr. A, 957, 11–16.  Web of Science CrossRef PubMed CAS Google Scholar
First citationMacrae, 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
First citationMalone, S., Broacha, E., Shaw, D. & Hampton, T. (2006). US Patent 7 032 662.  Google Scholar
First citationMinor, W., Cymborowski, M., Otwinowski, Z. & Chruszcz, M. (2006). Acta Cryst. D62, 859–866.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationOtwinowski, Z., Borek, D., Majewski, W. & Minor, W. (2003). Acta Cryst. A59, 228–234.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationOtwinowski, 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
First citationPotrzebowski, W. & Chruszcz, M. (2007). Acta Cryst. E63, o2754.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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