2,6-Bis(trifluoro­meth­yl)benzoic acid

John M Tobin; Jason D Masuda

doi:10.1107/S1600536809016468

. 2009 May 7;65(Pt 6):o1217. doi: 10.1107/S1600536809016468

2,6-Bis(trifluoromethyl)benzoic acid

John M Tobin ^a, Jason D Masuda ^a,^*

PMCID: PMC2969748 PMID: 21583086

Abstract

The title compound, C₉H₄F₆O₂, contains two molecules in the asymmetric unit, one of which exhibits disorder in both of its trifluoromethyl groups. The dihedral angles between the benzene ring and the carboxyl group are 71.5 (2) and 99.3 (2)° in the two independent molecules. The compound exhibits a catemeric structure resulting from intermolecular O—H⋯O hydrogen bonding between the carboxyl groups.

Related literature

There is only one example in the literature of a crystallographically characterized benzoic acid with trifluoromethyl groups in the ortho position, namely 2-trifluoromethyl-3-pyrrole benzoic acid (see Faigl et al., 1999 ▶). For a recent example of crystal engineering to promote the formation of dimeric or catemeric structures in benzoic acids, see: Moorthy et al. (2002 ▶). For synthesis details, see: Dmowski & Piasecka-Macieiewska (1998 ▶).

Experimental

Crystal data

C₉H₄F₆O₂
M _r = 258.12
Monoclinic,
a = 10.873 (2) Å
b = 15.755 (3) Å
c = 11.561 (2) Å
β = 94.961 (2)°
V = 1973.0 (6) Å³
Z = 8
Mo Kα radiation
μ = 0.20 mm⁻¹
T = 296 K
0.39 × 0.31 × 0.26 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.834, T _max = 0.951
12904 measured reflections
3438 independent reflections
2889 reflections with I > 2σ(I)
R _int = 0.021

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.112
S = 1.02
3438 reflections
331 parameters
H-atom parameters constrained
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); 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 for Windows (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809016468/bi2369sup1.cif

e-65-o1217-sup1.cif^{(19.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809016468/bi2369Isup2.hkl

e-65-o1217-Isup2.hkl^{(168.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2A⋯O4ⁱ	0.82	1.82	2.6340 (19)	169
O3—H3A⋯O1	0.82	1.88	2.6951 (18)	176

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank Saint Mary’s University for providing funding in the form of initial operating funds (JDM) and student funding through the Summer Employment Experience Program (JMT).

supplementary crystallographic information

Comment

The title molecule crystallizes in a catemer motif, a relatively rare form compared to the typical dimeric motif exhibited by benzoic acids resulting from intermolecular hydrogen bonding between the carboxylic acid groups (Moorthy et al., 2002). The sterically bulky o-CF₃ groups result in the carboxylic acid fragments being twisted with respect to the aryl ring. This results in dihedral angles between the aryl ring and carboxylic acid fragments of C7—C2—C1—O1 = 71.5 (2)° and C12—C11—C10—O4 = 99.3 (2)°.

Experimental

The title compound was prepared following the literature methods (Dmowski & Piasecka-Macieiewska, 1998) with a slight modification. The compound crystallized from the oily reaction mixture that remained after acidification of the potassium benzoate salt with concentrated HCl, extraction of the organic components with toluene, drying of the organic fraction with magnesium sulfate and concentration by rotary evaporation.