2,6-Dimethyl-4-m-tolyl­cyclo­hex-3-enecarboxylic acid

Songwen Xie; Holly J Stein; Maren Pink

doi:10.1107/S1600536808027542

. 2008 Sep 6;64(Pt 10):o1869. doi: 10.1107/S1600536808027542

2,6-Dimethyl-4-m-tolylcyclohex-3-enecarboxylic acid

Songwen Xie ^a,^*, Holly J Stein ^a, Maren Pink ^b

PMCID: PMC2959375 PMID: 21201085

Abstract

The title compound, C₁₆H₂₀O₂, was synthesized to study the hydrogen-bonding interaction of the two enantiomers in the solid state. The 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. The chirality of this compound is generated by the presence of the double bond in the cyclohexene ring and a chiral axis due to the meta-methyl substituent on the aromatic ring.

Related literature

In similar compounds previously reported (Xie et al., 2002 ▶, 2007a ▶, 2008 ▶), 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

C₁₆H₂₀O₂
M _r = 244.32
Orthorhombic,
a = 11.2581 (10) Å
b = 8.1055 (7) Å
c = 29.857 (3) Å
V = 2724.5 (4) Å³
Z = 8
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 150 (2) K
0.20 × 0.18 × 0.05 mm

Data collection

Bruker Kappa APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.985, T _max = 0.996
18515 measured reflections
3120 independent reflections
2265 reflections with I > 2σ(I)
R _int = 0.043

Refinement

R[F ² > 2σ(F ²)] = 0.049
wR(F ²) = 0.136
S = 1.03
3120 reflections
170 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.50 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808027542/om2254sup1.cif

e-64-o1869-sup1.cif^{(18.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808027542/om2254Isup2.hkl

e-64-o1869-Isup2.hkl^{(153.2KB, 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
O1—H1O⋯O2ⁱ	1.05 (3)	1.62 (3)	2.6628 (18)	174 (3)

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Symmetry code: (i) Inline graphic .

Acknowledgments

SX and HS are grateful to the departmental fund and the Grant-in-aid for Faculty Research from Indiana University Kokomo, as well as a Senior Research Grant from Indiana Academy of Science.

supplementary crystallographic information

Comment

The title carboxylic acid 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 forms hydrogen-bonded dimers (Xie et al., 2007b). The chirality of the title compound is 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 (Xie et al., 2002, 2007a, 2008). 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 C4, C5, C6, C1, and C2 are all near 180°, as are those involving atoms C13, C2, C3, C4, and C15. The carboxyl group is almost perpendicular to the cyclohexene ring with an angle of 86.5° between the O1—C14—O2 plane and the C1—C6 ring. The double bond between C5—C6 is not fully conjugated with the aromatic ring as shown by the C1—C6—C5 plane to benzene ring angle of 42.4°. Unlike other previously reported para substituted analogs, the molecule also has a chiral axis due to the meta methyl substituent on the aromatic ring.

Fig. 2 shows the hydrogen bonding scheme. Atom O1 acts as a donor in an intermolecular hydrogen bond to atom O2, producing an R₂²(8) ring (Bernstein et al., 1995), thus creating a hydrogen-bonded 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 the similar method reported by Xie et al., 2002. The purified compound was recrystallized from hexane-dichloromethane as colorless plates (m.p. 412–415 K).