Racemic 4-(4-tert-butyl­phen­yl)-2,6-dimethyl­cyclo­hex-3-enecarboxylic acid

Songwen Xie; Caryn R O’Hearn; Paul D Robinson

doi:10.1107/S1600536808003309

. 2008 Feb 6;64(Pt 3):o554. doi: 10.1107/S1600536808003309

Racemic 4-(4-tert-butylphenyl)-2,6-dimethylcyclohex-3-enecarboxylic acid

Songwen Xie ^a, Caryn R O’Hearn ^a, Paul D Robinson ^b,^*

PMCID: PMC2960795 PMID: 21201897

Abstract

The chirality of the title compound, C₁₉H₂₆O₂, is solely generated by the presence of the double bond in the cyclohexene ring. This compound was synthesized to study the interaction of the two enantiomers in the solid state. The resultant racemate is made up of carboxylic acid RS dimers. Intermolecular O—H⋯O hydrogen bonds produce centrosymmetric R ₂ ²(8) rings which dimerize the two chiral enantiomers through their carboxyl groups.

Related literature

In similar compounds previously reported (Xie et al., 2002 ▶, 2007a ▶), the racemates also consist of carboxylic acid RS dimers. For related literature, see: Xie et al. (2007b ▶, 2004 ▶); Bernstein et al. (1995 ▶).

Experimental

Crystal data

C₁₉H₂₆O₂
M _r = 286.40
Monoclinic,
a = 24.818 (4) Å
b = 9.4674 (18) Å
c = 7.0105 (12) Å
β = 95.799 (5)°
V = 1638.8 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 100 (2) K
0.36 × 0.29 × 0.09 mm

Data collection

Bruker Kappa APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.793, T _max = 0.993
24559 measured reflections
2912 independent reflections
2230 reflections with I > 2σ(I)
R _int = 0.062

Refinement

R[F ² > 2σ(F ²)] = 0.085
wR(F ²) = 0.244
S = 1.15
2912 reflections
196 parameters
H-atom parameters constrained
Δρ_max = 0.36 e Å⁻³
Δρ_min = −0.34 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT and SADABS (Bruker, 2005 ▶); program(s) used to solve structure: SIR92 (Altomare et al., 1994 ▶); program(s) used to refine structure: LS in TEXSAN (Molecular Structure Corporation, 1997 ▶) and SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶); software used to prepare material for publication: SHELXL97 and PLATON.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808003309/om2210sup1.cif

e-64-0o554-sup1.cif^{(18.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808003309/om2210Isup2.hkl

e-64-0o554-Isup2.hkl^{(143.2KB, 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—H2⋯O1ⁱ	0.82	1.88	2.702 (4)	175

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Symmetry code: (i) Inline graphic .

Acknowledgments

SX and CO are grateful to the departmental fund and for a Grant-in-Aid for Faculty Research from Indiana University Kokomo, as well as a Senior Research Grant from Indiana Academy of Science. The authors thank Professor Nigam P. Rath of the University of Missouri – St. Louis for kindly collecting the low-temperature data set using a diffractometer whose purchase was made possible by funding from the National Science Foundation (CHE-0420497).

supplementary crystallographic information

Comment

The title carboxylic acid, the structure of whose single enantiomer is unknown, was prepared to study the interaction of the two enantiomers in the solid state. We have previously reported the structure of its precursor, which is achiral and also forms hydrogen-bonded dimers (Xie et al., 2007b). The chirality of the title compound is solely generated by the presence of the double bond in the cyclohexene ring (Xie et al., 2004). The resultant racemate is made up of carboxylic acid RS dimers. The structure and atom numbering are shown in Fig. 1, which illustrates the half-chair conformation of the cyclohexene ring. The torsion angles involving atoms C2, C3, C4, C5, and C6 are all near 180°, as are those involving atoms C8, C2, C1, C6, and C9. The carboxyl group is almost perpendicular to the cyclohexene ring with an angle of 81.6 (5) ° between the O1—C7—O2 plane and the C1—C6 ring. The double bond between C3—C4 is not fully conjugated as shown by the C3—C4—C5 plane to benzene ring angle of 30.4 (5) °.

Fig. 2 shows the hydrogen bonding scheme and molecular packing. Atom O2 acts as a donor in an intermolecular hydrogen bond to atom O1. Inversion of this interaction across (1/2, 1/2, 1/2) produces an R₂²(8) ring (Bernstein et al., 1995), thus creating a hydrogen-bonded RS dimer. There is no evidence to suggest that weak directional interactions interconnect the dimers. Hydrogen bond geometry is given in Table 1.

Experimental

The title carboxylic acid was synthesized following a similar method previously reported by Xie et al., 2002. Purified compound was recrystallized from hexane-ethyl acetate as colorless crystals (m.p. 467–468 K).