2-Chloro-6-fluoro­benzoic acid

Betz, R.; Gerber, T.

doi:10.1107/S1600536811016734

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 67| Part 6| June 2011| Page o1329

doi:10.1107/S1600536811016734

Open

access

2-Chloro-6-fluorobenzoic acid

Richard Betz ^a ^* and Thomas Gerber ^a

^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 ). 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

Crystal data

C₇H₄ClFO₂
M_r = 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)
R_int = 0.081

Refinement

R[F² > 2σ(F²)] = 0.032
wR(F²) = 0.081
S = 1.02
1671 reflections
101 parameters
H-atom parameters constrained
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	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 ); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT; 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 and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811016734/gw2099sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811016734/gw2099Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811016734/gw2099Isup3.cml

checkCIF report

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.

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

	Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level).
	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.
	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

C₇H₄ClFO₂	F(000) = 352
M_r = 174.55	D_x = 1.683 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4834 reflections
a = 3.7655 (2) Å	θ = 2.9–27.9°
b = 13.9660 (7) Å	µ = 0.51 mm⁻¹
c = 13.2300 (7) Å	T = 200 K
β = 98.034 (3)°	Needle, colourless
V = 688.92 (6) Å³	0.51 × 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 tube	R_int = 0.081
Graphite monochromator	θ_max = 28.3°, θ_min = 3.1°
ϕ and ω scans	h = −4→4
11312 measured reflections	k = −18→18
1671 independent reflections	l = −17→17

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)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.081	H-atom parameters constrained
S = 1.02	w = 1/[σ²(F_o²) + (0.0326P)² + 0.237P] where P = (F_o² + 2F_c²)/3
1671 reflections	(Δ/σ)_max = 0.001
101 parameters	Δρ_max = 0.23 e Å⁻³
0 restraints	Δρ_min = −0.21 e Å⁻³

Crystal data top

C₇H₄ClFO₂	V = 688.92 (6) Å³
M_r = 174.55	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 3.7655 (2) Å	µ = 0.51 mm⁻¹
b = 13.9660 (7) Å	T = 200 K
c = 13.2300 (7) Å	0.51 × 0.19 × 0.15 mm
β = 98.034 (3)°

Data collection top

Bruker APEXII CCD diffractometer	1267 reflections with I > 2σ(I)
11312 measured reflections	R_int = 0.081
1671 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.032	0 restraints
wR(F²) = 0.081	H-atom parameters constrained
S = 1.02	Δρ_max = 0.23 e Å⁻³
1671 reflections	Δρ_min = −0.21 e Å⁻³
101 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cl1	0.56510 (12)	0.54455 (3)	0.33109 (3)	0.03809 (14)
F1	0.8294 (3)	0.24457 (7)	0.13846 (8)	0.0484 (3)
O1	0.4025 (4)	0.39103 (9)	0.06067 (9)	0.0441 (3)
H1	0.3547	0.4253	0.0084	0.066*
O2	0.7380 (4)	0.51658 (9)	0.11476 (9)	0.0418 (3)
C1	0.6158 (4)	0.43686 (11)	0.12879 (12)	0.0289 (3)
C2	0.7161 (4)	0.38510 (11)	0.22715 (11)	0.0254 (3)
C3	0.7186 (4)	0.42864 (11)	0.32219 (12)	0.0266 (3)
C4	0.8310 (5)	0.37956 (13)	0.41170 (13)	0.0359 (4)
H4	0.8276	0.4100	0.4758	0.043*
C5	0.9477 (5)	0.28638 (14)	0.40775 (13)	0.0391 (4)
H5	1.0304	0.2534	0.4694	0.047*
C6	0.9461 (5)	0.24039 (13)	0.31564 (14)	0.0362 (4)
H6	1.0253	0.1760	0.3127	0.043*
C7	0.8270 (4)	0.29017 (12)	0.22850 (12)	0.0311 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0461 (3)	0.0291 (2)	0.0393 (2)	0.00636 (18)	0.00668 (17)	−0.00432 (17)
F1	0.0872 (9)	0.0278 (5)	0.0328 (6)	0.0057 (5)	0.0178 (5)	−0.0044 (4)
O1	0.0638 (9)	0.0349 (7)	0.0284 (6)	−0.0170 (6)	−0.0120 (6)	0.0065 (5)
O2	0.0631 (8)	0.0291 (6)	0.0295 (6)	−0.0149 (6)	−0.0066 (5)	0.0066 (5)
C1	0.0364 (8)	0.0252 (8)	0.0241 (8)	−0.0017 (6)	0.0006 (6)	0.0004 (6)
C2	0.0282 (8)	0.0244 (7)	0.0231 (7)	−0.0018 (6)	0.0021 (6)	0.0028 (6)
C3	0.0255 (7)	0.0256 (8)	0.0285 (8)	0.0010 (6)	0.0036 (6)	−0.0006 (6)
C4	0.0411 (9)	0.0422 (10)	0.0239 (8)	0.0015 (8)	0.0033 (7)	0.0017 (7)
C5	0.0442 (10)	0.0412 (10)	0.0315 (9)	0.0074 (8)	0.0039 (7)	0.0133 (7)
C6	0.0417 (9)	0.0274 (9)	0.0407 (10)	0.0078 (7)	0.0096 (7)	0.0093 (7)
C7	0.0399 (9)	0.0272 (8)	0.0274 (8)	−0.0010 (7)	0.0093 (7)	0.0007 (6)

Geometric parameters (Å, º) top

Cl1—C3	1.7285 (16)	C3—C4	1.383 (2)
F1—C7	1.3519 (18)	C4—C5	1.377 (3)
O1—C1	1.2902 (19)	C4—H4	0.9500
O1—H1	0.8400	C5—C6	1.377 (3)
O2—C1	1.2287 (19)	C5—H5	0.9500
C1—C2	1.490 (2)	C6—C7	1.367 (2)
C2—C7	1.389 (2)	C6—H6	0.9500
C2—C3	1.395 (2)

C1—O1—H1	109.5	C5—C4—H4	120.1
O2—C1—O1	123.63 (14)	C3—C4—H4	120.1
O2—C1—C2	121.11 (14)	C4—C5—C6	120.84 (16)
O1—C1—C2	115.24 (13)	C4—C5—H5	119.6
C7—C2—C3	116.11 (14)	C6—C5—H5	119.6
C7—C2—C1	120.86 (13)	C7—C6—C5	118.00 (16)
C3—C2—C1	122.98 (14)	C7—C6—H6	121.0
C4—C3—C2	121.23 (15)	C5—C6—H6	121.0
C4—C3—Cl1	118.11 (12)	F1—C7—C6	117.50 (15)
C2—C3—Cl1	120.62 (12)	F1—C7—C2	118.51 (14)
C5—C4—C3	119.81 (16)	C6—C7—C2	123.96 (15)

O2—C1—C2—C7	−131.11 (17)	Cl1—C3—C4—C5	178.59 (14)
O1—C1—C2—C7	47.3 (2)	C3—C4—C5—C6	−1.6 (3)
O2—C1—C2—C3	46.4 (2)	C4—C5—C6—C7	0.3 (3)
O1—C1—C2—C3	−135.22 (17)	C5—C6—C7—F1	179.46 (15)
C7—C2—C3—C4	0.9 (2)	C5—C6—C7—C2	1.7 (3)
C1—C2—C3—C4	−176.64 (15)	C3—C2—C7—F1	179.95 (14)
C7—C2—C3—Cl1	−176.68 (12)	C1—C2—C7—F1	−2.4 (2)
C1—C2—C3—Cl1	5.7 (2)	C3—C2—C7—C6	−2.3 (2)
C2—C3—C4—C5	0.9 (3)	C1—C2—C7—C6	175.35 (16)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	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+1/2, z+1/2.

Experimental details

Crystal data
Chemical formula	C₇H₄ClFO₂
M_r	174.55
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	200
a, b, c (Å)	3.7655 (2), 13.9660 (7), 13.2300 (7)
β (°)	98.034 (3)
V (Å³)	688.92 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.51
Crystal size (mm)	0.51 × 0.19 × 0.15

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	11312, 1671, 1267
R_int	0.081
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.032, 0.081, 1.02
No. of reflections	1671
No. of parameters	101
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	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···A	D—H	H···A	D···A	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+1/2, z+1/2.

Acknowledgements

The authors thank Mrs Wilma Nelson for helpful discussions.

References

Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. CrossRef CAS Web of Science Google Scholar
Bruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256–262. CrossRef CAS Web of Science IUCr Journals Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Ferguson, G. & Sim, G. A. (1961). Acta Cryst. 14, 1262–1270. CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
Krausse, J. & Dunken, H. (1966). Acta Cryst. 20, 67–73. CSD CrossRef CAS IUCr Journals 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
Polito, 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 Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Wilson, C. C., Shankland, N. & Florence, A. J. (1996). J. Chem. Soc. Faraday Trans. pp. 5051–5057. CSD CrossRef Google Scholar