organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

2-Chloro-6-fluoro­benzoic acid

aNelson Mandela Metropolitan University, Summerstrand Campus, Department of Chemistry, University Way, Summerstrand, PO Box 77000, Port Elizabeth 6031, South Africa
*Correspondence e-mail: richard.betz@webmail.co.za

(Received 27 January 2011; accepted 3 May 2011; online 7 May 2011)

The title compound, C7H4ClFO2, is a twofold halogenated derivative of benzoic acid. The C—C—C angles within the aromatic moiety cover a range 116.11 (14)–123.96 (15)°, with the maximum and the minimum value next to each other. In the crystal, O—H⋯O hydrogen bonds form carb­oxy­lic acid dimers, which are further connected by C—H⋯F contacts into undulating sheets perpendicular to the a axis.

Related literature

For the crystal structure of benzoic acid (applying neutron radiation), see: Wilson et al. (1996[Wilson, C. C., Shankland, N. & Florence, A. J. (1996). J. Chem. Soc. Faraday Trans. pp. 5051-5057.]). For the crystal structure of ortho-fluoro­benzoic acid, see: Krausse & Dunken (1966[Krausse, J. & Dunken, H. (1966). Acta Cryst. 20, 67-73.]) and of ortho-chloro­benzoic acid, see: Ferguson & Sim (1961[Ferguson, G. & Sim, G. A. (1961). Acta Cryst. 14, 1262-1270.]); Polito et al. (2008[Polito, M., D'Oria, E., Maini, L., Karamertzanis, P. G., Grepioni, F., Braga, D. & Price, S. L. (2008). CrystEngComm, 10, 1848-1854.]). For graph-set analysis of hydrogen bonds, see: Etter et al. (1990[Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256-262.]); Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]).

[Scheme 1]

Experimental

Crystal data
  • C7H4ClFO2

  • Mr = 174.55

  • Monoclinic, P 21 /c

  • a = 3.7655 (2) Å

  • b = 13.9660 (7) Å

  • c = 13.2300 (7) Å

  • β = 98.034 (3)°

  • V = 688.92 (6) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.51 mm−1

  • T = 200 K

  • 0.51 × 0.19 × 0.15 mm

Data collection
  • Bruker APEXII CCD diffractometer

  • 11312 measured reflections

  • 1671 independent reflections

  • 1267 reflections with I > 2σ(I)

  • Rint = 0.081

Refinement
  • R[F2 > 2σ(F2)] = 0.032

  • wR(F2) = 0.081

  • S = 1.02

  • 1671 reflections

  • 101 parameters

  • H-atom parameters constrained

  • Δρmax = 0.23 e Å−3

  • Δρmin = −0.21 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1⋯O2i 0.84 1.81 2.6436 (17) 172
C5—H5⋯F1ii 0.95 2.46 3.175 (2) 132
Symmetry codes: (i) -x+1, -y+1, -z; (ii) [x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}].

Data collection: APEX2 (Bruker, 2010[Bruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2010[Bruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: ORTEP-3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]) and 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.]); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]).

Supporting information


Comment top

Benzoic acid has found widespread use as a ligand in coordination chemistry for a variety of transition metals and elements from the s- and p-block of the periodic system of the elements. It can act as a neutral or – upon deprotonation – an anionic ligand and serve as mono- or bidentate ligand. By varying the substituents on the phenyl moiety, the acidity of the carboxylic acid group can be fine-tuned. Particular interest rests in benzoic acid derivatives showing an asymmetric pattern of substituents on the aromatic moiety due to different possible orientations of the ligand in coordination compounds and the possible formation of stereoisomeric products. At the beginning of a comprehensive study aimed at rationalizing the coordination behaviour of various benzoic acid derivatives towards a number of transition metals in dependence of the pH value of the reaction batches it seemed interesting to determine the crystal structure of the title compound to enable comparative studies.

C–C–C angles within the phenyl ring span a range of 116.11 (14) ° to 123.96 (15) ° with the smallest angle found on the C-atom bearing the carboxylic acid group. The biggest angle is found on the fluorine-bonded C-atom and thus directly adjacent to the smallest one (Fig. 1).

Possibly due to steric factors, the carboxylic acid group is not in plane with the phenyl ring. The least-squares plane defined by its C-atom and O-atoms encloses an angle of 47.83 (6) ° with the least-squares plane defined by the C-atoms of the carbocycle and the halogen-atoms.

In the crystal structure hydrogen bonds between the OH-group and the carbonylic O-atom of the carboxylic acid group give rise to the formation of dimeric units. These units are further connected by C–F···H contacts (whose ranges fall by more than 0.2 Å below the sum of van-der-Waals radii of the respective atoms) to wave-like sheets perpendicular to the crystallographic a axis. The hydrogen atom involved in the latter contacts is present in para-position to the carboxylic acid group on the aromatic carbocycle (Fig. 2). In terms of graph-set analysis, the descriptor for the hydrogen bonds on the unitary level is R22(8) while the C–F···H contacts necessitate a C11(5) descriptor on the same level. No π-stacking is observed in the crystal structure.

The packing of the title compound is shown in Figure 3.

Related literature top

For the crystal structure of benzoic acid (applying neutron radiation), see: Wilson et al. (1996). For the crystal structure of ortho-fluorobenzoic acid, see: Krausse & Dunken (1966) and of ortho-chlorobenzoic acid, see: Ferguson & Sim (1961); Polito et al. (2008). For graph-set analysis of hydrogen bonds, see: Etter et al. (1990); Bernstein et al. (1995).

Experimental top

The compound was obtained commercially (fluorochem). Crystals suitable for X-ray diffraction were obtained upon slow cooling of a hot aqueous solution of the compound.

Refinement top

Carbon-bound H-atoms were placed in calculated positions (C—H 0.95 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2Ueq(C). The H atom of the carboxylic acid group was allowed to rotate with a fixed angle around the C—O bond to best fit the experimental electron density (HFIX 147 in the SHELX program suite (Sheldrick, 2008)).

Computing details top

Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level).
[Figure 2] Fig. 2. Hydrogen bonds (blue dashed lines) and intermolecular C–F···H contacts (yellow dashed lines), viewed along [-1 0 0]. Symmetry operators: i x, -y + 1/2, z + 1/2; ii x, -y + 1/2, z - 1/2; iii -x + 1, -y + 1, -z.
[Figure 3] Fig. 3. Molecular packing of the title compound, viewed along [-1 0 0] (anisotropic displacement ellipsoids drawn at 50% probability level).
2-Chloro-6-fluorobenzoic acid top
Crystal data top
C7H4ClFO2F(000) = 352
Mr = 174.55Dx = 1.683 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4834 reflections
a = 3.7655 (2) Åθ = 2.9–27.9°
b = 13.9660 (7) ŵ = 0.51 mm1
c = 13.2300 (7) ÅT = 200 K
β = 98.034 (3)°Needle, colourless
V = 688.92 (6) Å30.51 × 0.19 × 0.15 mm
Z = 4
Data collection top
Bruker APEXII CCD
diffractometer
1267 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.081
Graphite monochromatorθmax = 28.3°, θmin = 3.1°
ϕ and ω scansh = 44
11312 measured reflectionsk = 1818
1671 independent reflectionsl = 1717
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)] = 0.032Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.081H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.0326P)2 + 0.237P]
where P = (Fo2 + 2Fc2)/3
1671 reflections(Δ/σ)max = 0.001
101 parametersΔρmax = 0.23 e Å3
0 restraintsΔρmin = 0.21 e Å3
Crystal data top
C7H4ClFO2V = 688.92 (6) Å3
Mr = 174.55Z = 4
Monoclinic, P21/cMo Kα radiation
a = 3.7655 (2) ŵ = 0.51 mm1
b = 13.9660 (7) ÅT = 200 K
c = 13.2300 (7) Å0.51 × 0.19 × 0.15 mm
β = 98.034 (3)°
Data collection top
Bruker APEXII CCD
diffractometer
1267 reflections with I > 2σ(I)
11312 measured reflectionsRint = 0.081
1671 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0320 restraints
wR(F2) = 0.081H-atom parameters constrained
S = 1.02Δρmax = 0.23 e Å3
1671 reflectionsΔρmin = 0.21 e Å3
101 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cl10.56510 (12)0.54455 (3)0.33109 (3)0.03809 (14)
F10.8294 (3)0.24457 (7)0.13846 (8)0.0484 (3)
O10.4025 (4)0.39103 (9)0.06067 (9)0.0441 (3)
H10.35470.42530.00840.066*
O20.7380 (4)0.51658 (9)0.11476 (9)0.0418 (3)
C10.6158 (4)0.43686 (11)0.12879 (12)0.0289 (3)
C20.7161 (4)0.38510 (11)0.22715 (11)0.0254 (3)
C30.7186 (4)0.42864 (11)0.32219 (12)0.0266 (3)
C40.8310 (5)0.37956 (13)0.41170 (13)0.0359 (4)
H40.82760.41000.47580.043*
C50.9477 (5)0.28638 (14)0.40775 (13)0.0391 (4)
H51.03040.25340.46940.047*
C60.9461 (5)0.24039 (13)0.31564 (14)0.0362 (4)
H61.02530.17600.31270.043*
C70.8270 (4)0.29017 (12)0.22850 (12)0.0311 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0461 (3)0.0291 (2)0.0393 (2)0.00636 (18)0.00668 (17)0.00432 (17)
F10.0872 (9)0.0278 (5)0.0328 (6)0.0057 (5)0.0178 (5)0.0044 (4)
O10.0638 (9)0.0349 (7)0.0284 (6)0.0170 (6)0.0120 (6)0.0065 (5)
O20.0631 (8)0.0291 (6)0.0295 (6)0.0149 (6)0.0066 (5)0.0066 (5)
C10.0364 (8)0.0252 (8)0.0241 (8)0.0017 (6)0.0006 (6)0.0004 (6)
C20.0282 (8)0.0244 (7)0.0231 (7)0.0018 (6)0.0021 (6)0.0028 (6)
C30.0255 (7)0.0256 (8)0.0285 (8)0.0010 (6)0.0036 (6)0.0006 (6)
C40.0411 (9)0.0422 (10)0.0239 (8)0.0015 (8)0.0033 (7)0.0017 (7)
C50.0442 (10)0.0412 (10)0.0315 (9)0.0074 (8)0.0039 (7)0.0133 (7)
C60.0417 (9)0.0274 (9)0.0407 (10)0.0078 (7)0.0096 (7)0.0093 (7)
C70.0399 (9)0.0272 (8)0.0274 (8)0.0010 (7)0.0093 (7)0.0007 (6)
Geometric parameters (Å, º) top
Cl1—C31.7285 (16)C3—C41.383 (2)
F1—C71.3519 (18)C4—C51.377 (3)
O1—C11.2902 (19)C4—H40.9500
O1—H10.8400C5—C61.377 (3)
O2—C11.2287 (19)C5—H50.9500
C1—C21.490 (2)C6—C71.367 (2)
C2—C71.389 (2)C6—H60.9500
C2—C31.395 (2)
C1—O1—H1109.5C5—C4—H4120.1
O2—C1—O1123.63 (14)C3—C4—H4120.1
O2—C1—C2121.11 (14)C4—C5—C6120.84 (16)
O1—C1—C2115.24 (13)C4—C5—H5119.6
C7—C2—C3116.11 (14)C6—C5—H5119.6
C7—C2—C1120.86 (13)C7—C6—C5118.00 (16)
C3—C2—C1122.98 (14)C7—C6—H6121.0
C4—C3—C2121.23 (15)C5—C6—H6121.0
C4—C3—Cl1118.11 (12)F1—C7—C6117.50 (15)
C2—C3—Cl1120.62 (12)F1—C7—C2118.51 (14)
C5—C4—C3119.81 (16)C6—C7—C2123.96 (15)
O2—C1—C2—C7131.11 (17)Cl1—C3—C4—C5178.59 (14)
O1—C1—C2—C747.3 (2)C3—C4—C5—C61.6 (3)
O2—C1—C2—C346.4 (2)C4—C5—C6—C70.3 (3)
O1—C1—C2—C3135.22 (17)C5—C6—C7—F1179.46 (15)
C7—C2—C3—C40.9 (2)C5—C6—C7—C21.7 (3)
C1—C2—C3—C4176.64 (15)C3—C2—C7—F1179.95 (14)
C7—C2—C3—Cl1176.68 (12)C1—C2—C7—F12.4 (2)
C1—C2—C3—Cl15.7 (2)C3—C2—C7—C62.3 (2)
C2—C3—C4—C50.9 (3)C1—C2—C7—C6175.35 (16)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O2i0.841.812.6436 (17)172
C5—H5···F1ii0.952.463.175 (2)132
Symmetry codes: (i) x+1, y+1, z; (ii) x, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC7H4ClFO2
Mr174.55
Crystal system, space groupMonoclinic, P21/c
Temperature (K)200
a, b, c (Å)3.7655 (2), 13.9660 (7), 13.2300 (7)
β (°) 98.034 (3)
V3)688.92 (6)
Z4
Radiation typeMo Kα
µ (mm1)0.51
Crystal size (mm)0.51 × 0.19 × 0.15
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
11312, 1671, 1267
Rint0.081
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.081, 1.02
No. of reflections1671
No. of parameters101
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.23, 0.21

Computer programs: APEX2 (Bruker, 2010), SAINT (Bruker, 2010), SHELXS97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2006), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O2i0.841.812.6436 (17)172
C5—H5···F1ii0.952.463.175 (2)132
Symmetry codes: (i) x+1, y+1, z; (ii) x, y+1/2, z+1/2.
 

Acknowledgements

The authors thank Mrs Wilma Nelson for helpful discussions.

References

First citationBernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.  CrossRef CAS Web of Science
First citationBruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.
First citationEtter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256–262.  CrossRef CAS Web of Science IUCr Journals
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First citationPolito, M., D'Oria, E., Maini, L., Karamertzanis, P. G., Grepioni, F., Braga, D. & Price, S. L. (2008). CrystEngComm, 10, 1848–1854.  Web of Science CSD CrossRef CAS
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals
First citationWilson, C. C., Shankland, N. & Florence, A. J. (1996). J. Chem. Soc. Faraday Trans. pp. 5051–5057.  CSD CrossRef

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