4,4,4-Trifluoro-3-hy­droxy-3-(trifluoro­meth­yl)butanoic acid

Richard Betz; Thomas Gerber; Henk Schalekamp

doi:10.1107/S1600536811004764

. 2011 Feb 12;67(Pt 3):o616. doi: 10.1107/S1600536811004764

4,4,4-Trifluoro-3-hydroxy-3-(trifluoromethyl)butanoic acid

Richard Betz ^a,^*, Thomas Gerber ^a, Henk Schalekamp ^a

PMCID: PMC3051966 PMID: 21522373

Abstract

The asymmetric unit of the title compound, C₅H₄F₆O₃, a polyfluorinated derivative of β-hydroxybutyric acid, comprises two molecules. Intramolecular O—H⋯O hydrogen bonds occur. In the crystal, intermolecular O—H⋯O hydrogen bonds give rise to the formation of carboxylic acid dimers. Along with these hydrogen bonds, C—H⋯O contacts connect the molecules into infinite strands along the a axis.

Related literature

For the crystal structure of (S)-3-amino-4,4,4-trifluorobutanecarboxylic acid, see: Soloshonok et al. (1993 ▶). For the graph-set analysis of hydrogen bonds, see: Etter et al. (1990 ▶); Bernstein et al. (1995 ▶).

Experimental

Crystal data

C₅H₄F₆O₃
M _r = 226.08
Monoclinic,
a = 5.5031 (2) Å
b = 20.5490 (8) Å
c = 14.0342 (6) Å
β = 98.4543 (14)°
V = 1569.79 (11) Å³
Z = 8
Mo Kα radiation
μ = 0.24 mm⁻¹
T = 200 K
0.59 × 0.45 × 0.33 mm

Data collection

Bruker APEXII CCD diffractometer
25936 measured reflections
3897 independent reflections
3469 reflections with I > 2σ(I)
R _int = 0.014

Refinement

R[F ² > 2σ(F ²)] = 0.038
wR(F ²) = 0.100
S = 1.04
3897 reflections
257 parameters
H-atom parameters constrained
Δρ_max = 0.42 e Å⁻³
Δρ_min = −0.38 e Å⁻³

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 for Windows (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811004764/gk2344sup1.cif

e-67-0o616-sup1.cif^{(18.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811004764/gk2344Isup2.hkl

e-67-0o616-Isup2.hkl^{(191KB, 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
O1—H1⋯O5	0.84	1.83	2.6653 (14)	178
O3—H3⋯O2	0.84	2.01	2.7296 (14)	144
O3—H3⋯O1ⁱ	0.84	2.45	2.9561 (15)	120
O4—H4⋯O2	0.84	1.82	2.6635 (13)	178
O6—H6⋯O5	0.84	2.03	2.7502 (13)	144
O6—H6⋯O4ⁱⁱ	0.84	2.41	2.9276 (13)	121
C2—H2A⋯O3ⁱⁱ	0.99	2.36	3.2773 (16)	153
C7—H7A⋯O6ⁱ	0.99	2.32	3.2340 (14)	153

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

The authors thank Mr Eddie Nelson for helpful discussions.

supplementary crystallographic information

Comment

Chelate ligands have found widespread use in coordination chemistry due to the increased stability of coordination compounds they can form in comparison to monodentate ligands. Most work in this field has been done with chelate ligands capable of forming five-, six- and seven-membered chelate rings. The coordination behaviour of such ligands with respect to reaction products formed (e.g. the coordination number of the central atom) is a function of electronic as well as steric factors. In a larger study aimed at elucidating the coordination chemistry of multiply-fluorinated carboxylic acid derivatives, the structure of the title compound was determined to enable comparisons with reaction products obtained.

The title compound is a symmetric, polyhalogenated derivative of β-hydroxypropanecarboxylic acid which bears two trifluoromethyl-groups at the alcoholic carbon atom. The asymmetric unit (Fig. 1) comprises two molecules of the title compound.

In the crystal structure, intra- as well as intermolecular hydrogen bonds are present. While the intramolecular hydrogen bonds are formed between the alcoholic hydroxyl group and the carbonylic O-atom of the carboxylic group, intermolecular hydrogen bonds can be observed between the carboxylic acid groups' OH-groups and carbonylic O-atoms. The latter interaction connects both molecules of the asymmetric unit to dimers. In terms of graph-set analysis, the descriptor for the intramolecular hydrogen bonds is S(6)S(6) on the unitary level while the intermolecular hydrogen bonds necessitate a R²₂(8) descriptor on the binary level. For the intramolecular hydrogen bond, a bifurcation could be discussed applying the O-atom of another hydroxyl group as acceptor. This would render it a mixed intra-intermolecular hydrogen bond, however, the D–H···A angle of only around 120° for the intermolecular hydrogen bond is comparatively small.

Apart from these hydrogen bonds, C–H···O contacts are present in the crystal structure whose ranges fall more than 0.2 Å below the sum of van-der-Waals radii of the respective atoms. These contacts can be observed between one of the H-atoms of the methylene group and the O-atom of a neighbouring hydroxyl group. Like the possible, bifurcated hydrogen bond mentioned above, these C–H···O contacts connect the molecules to infinite strands along the crystallographic a axis (Fig. 3). The descriptor for the C–H···O contacts on the unitary level is C¹₁(4)C¹₁(4).

Experimental

The structural analysis was done on a single-crystal taken from a commercially obtained (Fluorochem) batch of the title compound.