organic compounds
4-(3-Methoxyphenyl)-2,6-dimethylcyclohex-3-enecarboxylic acid
aDepartment of Natural, Information, and Mathematical Sciences, Indiana University Kokomo, Kokomo, IN 46904–9003, USA, and bIndiana University Molecular Structure Center, Indiana University, Bloomington, IN 47405–7102, USA
*Correspondence e-mail: soxie@iuk.edu
The racemic title compound, C16H20O3, was synthesized to study the hydrogen-bonding interaction of the two enantiomers in the solid state. In the R and S pairs of the racemate are linked by pairs of intermolecular O—H⋯O hydrogen bonds, producing centrosymmetric R22(8) rings.
Related literature
For similar compounds in which the racemates also consist of carboxylic acid RS dimers, see: Xie et al. (2002, 2007a, 2008a,b). For the structure of the precursor of the title compound, which is achiral and forms hydrogen-bonded dimers, see: Xie et al. (2007b). The of the title compound is solely generated by the presence of the double bond in the cyclohexene ring, see: Xie et al. (2004). For hydrogen-bond motifs, see: Bernstein et al. (1995).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2007); cell 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.
Supporting information
https://doi.org/10.1107/S1600536810018544/fj2304sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810018544/fj2304Isup2.hkl
The title carboxylic acid was synthesized following the similar method reported by Xie et al., 2002. Purified compound was recrystallized from hexane- dichloromethane as colorless plates (m.p. 415-417 K).
The data collection was carried out using synchrotron radiation (λ= 0.44280, diamond 111 monochromator, two mirrors to exclude higher harmonics) with a frame time of 2 second and a detector distance of 6.0 cm. A randomly oriented region of was surveyed to the extent of a hemisphere. Two major sections of frames were collected with 0.50° steps in φ and a detector position of -20° in 2θ. Data to a resolution of 0.84 Å were considered in the reduction. Final cell constants were calculated from the xyz centroids of 2804 strong reflections from the actual data collection after integration (SAINT, Bruker Analytical X-Ray Systems, Madison, WI, 2008). The intensity data were corrected for absorption (SADABS) (Blessing, 1995).
The
Pbca was determined based on intensity statistics and The structure was solved using SIR-2004 (Burla et al., 2005) and refined with SHELXL-97 (Sheldrick, 2008). A direct-methods solution was calculated, which provided most non-hydrogen atoms from the E-map. Full-matrix least squares / difference Fourier cycles were performed, which located the remaining non-hydrogen atoms. All non-hydrogen atoms were refined with anisotropic displacement parameters. The hydrogen atoms were placed in ideal positions and refined as riding atoms with relative isotropic displacement parameters with the exception of the hydroxyl hydrogen atom, which was refined for all parameters. The final full matrix least squares converged to R1 = 0.0368 and wR2 = 0.1190 (F2, all data). The structure was found as proposed. The remaining electron density is minuscule and located on bonds.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
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 (Xie et al., 2002, 2007a, 2008a,b). 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 near 180°. The carboxyl group is almost perpendicular to the cyclohexene ring with an angle of 85.3° between the O1—C14—O2—C3 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 38.7°. Unlike other previously reported para substituted analogs and like other previously reported meta substituted analogs (Xie et al., 2008b), the molecule also has a chiral axis due to the meta methoxy substituent on the aromatic ring.Fig. 2 shows the hydrogen bonding scheme. Atom O2 acts as a donor in an intermolecular hydrogen bond to atom O1, 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.
For similar compounds in which the racemates also consist of carboxylic acid RS dimers, see: Xie et al. (2002, 2007a, 2008a,b). For the structure of the precursor of the title compound, which is achiral and forms hydrogen-bonded dimers, see: Xie et al. (2007b). The
of the title compound is solely generated by the presence of the double bond in the cyclohexene ring, see: Xie et al. (2004). For hydrogen-bond motifs, see: Bernstein et al. (1995).Data collection: APEX2 (Bruker, 2007); cell
SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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 (Sheldrick, 2008).Fig. 1. The molecular structure and atom numbering scheme. | |
Fig. 2. Hydrogen bonded dimer. Dashed lines represent hydrogen bonds. [Symmetry code: #1 -x,-y,-z+1.] |
C16H20O3 | F(000) = 1120 |
Mr = 260.32 | Dx = 1.244 Mg m−3 |
Orthorhombic, Pbca | Synchrotron radiation, λ = 0.44280 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 2804 reflections |
a = 11.032 (2) Å | θ = 2.3–15.3° |
b = 7.8423 (17) Å | µ = 0.05 mm−1 |
c = 32.140 (8) Å | T = 100 K |
V = 2780.7 (11) Å3 | Plate, colorless |
Z = 8 | 0.02 × 0.01 × 0.01 mm |
Bruker Platform goniometer diffractometer | 2173 independent reflections |
Radiation source: synchrotron | 1755 reflections with I > 2σ(I) |
Diamond 1 1 1 monochromator | Rint = 0.050 |
Detector resolution: 83.33 pixels mm-1 | θmax = 15.3°, θmin = 0.8° |
ω and phi scans | h = −11→13 |
Absorption correction: multi-scan (SADABS; Bruker, 2007; Blessing, 1995) | k = −8→6 |
Tmin = 0.999, Tmax = 1.000 | l = −38→26 |
8586 measured reflections |
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)] = 0.037 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.119 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.11 | w = 1/[σ2(Fo2) + (0.0707P)2 + 0.0727P] where P = (Fo2 + 2Fc2)/3 |
2173 reflections | (Δ/σ)max = 0.001 |
179 parameters | Δρmax = 0.17 e Å−3 |
0 restraints | Δρmin = −0.23 e Å−3 |
C16H20O3 | V = 2780.7 (11) Å3 |
Mr = 260.32 | Z = 8 |
Orthorhombic, Pbca | Synchrotron radiation, λ = 0.44280 Å |
a = 11.032 (2) Å | µ = 0.05 mm−1 |
b = 7.8423 (17) Å | T = 100 K |
c = 32.140 (8) Å | 0.02 × 0.01 × 0.01 mm |
Bruker Platform goniometer diffractometer | 2173 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2007; Blessing, 1995) | 1755 reflections with I > 2σ(I) |
Tmin = 0.999, Tmax = 1.000 | Rint = 0.050 |
8586 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.119 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.11 | Δρmax = 0.17 e Å−3 |
2173 reflections | Δρmin = −0.23 e Å−3 |
179 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
O1 | −0.01213 (10) | 0.06346 (16) | 0.54893 (3) | 0.0182 (3) | |
O2 | 0.02685 (11) | 0.22640 (18) | 0.49329 (4) | 0.0209 (3) | |
H2O | 0.018 (2) | 0.122 (4) | 0.4790 (8) | 0.049 (7)* | |
O3 | 0.19151 (12) | 0.77788 (18) | 0.76439 (3) | 0.0250 (4) | |
C1 | −0.07178 (15) | 0.5720 (2) | 0.60649 (5) | 0.0173 (4) | |
H1A | −0.0730 | 0.6650 | 0.5857 | 0.021* | |
H1B | −0.1403 | 0.5909 | 0.6258 | 0.021* | |
C2 | −0.09016 (14) | 0.4018 (2) | 0.58418 (5) | 0.0152 (4) | |
H2 | −0.1031 | 0.3108 | 0.6055 | 0.018* | |
C3 | 0.02669 (14) | 0.3611 (2) | 0.55976 (5) | 0.0141 (4) | |
H3 | 0.0446 | 0.4592 | 0.5409 | 0.017* | |
C4 | 0.13603 (14) | 0.3370 (2) | 0.58944 (5) | 0.0148 (4) | |
H4 | 0.1288 | 0.2227 | 0.6030 | 0.018* | |
C5 | 0.13641 (15) | 0.4715 (2) | 0.62290 (5) | 0.0161 (4) | |
H5 | 0.2066 | 0.4796 | 0.6399 | 0.019* | |
C6 | 0.04532 (15) | 0.5812 (2) | 0.63059 (5) | 0.0152 (4) | |
C7 | 0.05757 (14) | 0.7208 (2) | 0.66193 (5) | 0.0157 (4) | |
C8 | 0.11780 (15) | 0.6918 (2) | 0.69955 (5) | 0.0167 (4) | |
H8 | 0.1500 | 0.5820 | 0.7054 | 0.020* | |
C9 | 0.13098 (15) | 0.8233 (2) | 0.72858 (5) | 0.0181 (4) | |
C10 | 0.08441 (15) | 0.9845 (2) | 0.72076 (5) | 0.0202 (4) | |
H10 | 0.0930 | 1.0736 | 0.7406 | 0.024* | |
C11 | 0.02467 (16) | 1.0126 (3) | 0.68315 (5) | 0.0209 (4) | |
H11 | −0.0067 | 1.1228 | 0.6772 | 0.025* | |
C12 | 0.01008 (15) | 0.8828 (2) | 0.65423 (5) | 0.0189 (4) | |
H12 | −0.0324 | 0.9042 | 0.6291 | 0.023* | |
C13 | −0.20110 (15) | 0.4090 (2) | 0.55581 (5) | 0.0194 (4) | |
H13A | −0.2153 | 0.2962 | 0.5436 | 0.029* | |
H13B | −0.1870 | 0.4920 | 0.5335 | 0.029* | |
H13C | −0.2722 | 0.4433 | 0.5721 | 0.029* | |
C14 | 0.01185 (14) | 0.2031 (2) | 0.53354 (5) | 0.0137 (4) | |
C15 | 0.25486 (15) | 0.3418 (2) | 0.56468 (5) | 0.0183 (4) | |
H15A | 0.3235 | 0.3277 | 0.5837 | 0.027* | |
H15B | 0.2618 | 0.4515 | 0.5503 | 0.027* | |
H15C | 0.2552 | 0.2492 | 0.5442 | 0.027* | |
C16 | 0.19283 (18) | 0.8987 (3) | 0.79772 (5) | 0.0244 (5) | |
H16A | 0.2328 | 0.8483 | 0.8220 | 0.037* | |
H16B | 0.1094 | 0.9297 | 0.8050 | 0.037* | |
H16C | 0.2371 | 1.0010 | 0.7890 | 0.037* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0202 (7) | 0.0155 (9) | 0.0188 (7) | −0.0023 (5) | 0.0004 (5) | −0.0007 (5) |
O2 | 0.0300 (7) | 0.0176 (10) | 0.0153 (7) | −0.0046 (5) | 0.0012 (5) | −0.0023 (5) |
O3 | 0.0342 (8) | 0.0229 (10) | 0.0177 (7) | 0.0040 (5) | −0.0082 (5) | −0.0049 (5) |
C1 | 0.0154 (9) | 0.0176 (13) | 0.0190 (9) | 0.0023 (7) | 0.0011 (7) | −0.0024 (7) |
C2 | 0.0133 (9) | 0.0163 (12) | 0.0161 (8) | 0.0002 (6) | 0.0005 (6) | 0.0001 (6) |
C3 | 0.0147 (9) | 0.0130 (12) | 0.0148 (8) | −0.0001 (6) | −0.0009 (6) | 0.0004 (7) |
C4 | 0.0126 (9) | 0.0149 (12) | 0.0169 (8) | 0.0003 (6) | −0.0016 (6) | 0.0007 (7) |
C5 | 0.0159 (9) | 0.0165 (12) | 0.0159 (8) | −0.0020 (7) | −0.0018 (6) | −0.0007 (7) |
C6 | 0.0162 (9) | 0.0151 (12) | 0.0142 (8) | −0.0016 (7) | 0.0014 (7) | 0.0018 (6) |
C7 | 0.0119 (9) | 0.0179 (13) | 0.0171 (9) | −0.0020 (7) | 0.0038 (6) | −0.0007 (7) |
C8 | 0.0182 (9) | 0.0138 (12) | 0.0181 (9) | 0.0009 (6) | 0.0022 (6) | −0.0004 (6) |
C9 | 0.0175 (9) | 0.0198 (13) | 0.0170 (8) | −0.0018 (7) | 0.0005 (7) | 0.0002 (7) |
C10 | 0.0197 (10) | 0.0204 (13) | 0.0205 (9) | −0.0017 (7) | 0.0028 (7) | −0.0063 (7) |
C11 | 0.0228 (10) | 0.0161 (13) | 0.0239 (10) | 0.0045 (7) | 0.0012 (7) | −0.0020 (7) |
C12 | 0.0172 (9) | 0.0206 (14) | 0.0189 (9) | 0.0025 (7) | −0.0013 (7) | −0.0012 (7) |
C13 | 0.0145 (9) | 0.0199 (13) | 0.0238 (9) | 0.0016 (7) | −0.0021 (7) | −0.0031 (7) |
C14 | 0.0074 (8) | 0.0156 (13) | 0.0181 (9) | 0.0008 (6) | −0.0011 (6) | 0.0011 (7) |
C15 | 0.0151 (9) | 0.0173 (12) | 0.0225 (8) | 0.0000 (7) | −0.0005 (7) | −0.0029 (7) |
C16 | 0.0330 (11) | 0.0235 (14) | 0.0168 (9) | −0.0040 (8) | −0.0029 (8) | −0.0055 (7) |
O1—C14 | 1.230 (2) | C6—C7 | 1.493 (2) |
O2—C14 | 1.317 (2) | C7—C12 | 1.396 (3) |
O2—H2O | 0.94 (3) | C7—C8 | 1.398 (2) |
O3—C9 | 1.378 (2) | C8—C9 | 1.399 (2) |
O3—C16 | 1.430 (2) | C8—H8 | 0.9500 |
C1—C6 | 1.508 (2) | C9—C10 | 1.387 (3) |
C1—C2 | 1.528 (2) | C10—C11 | 1.394 (2) |
C1—H1A | 0.9900 | C10—H10 | 0.9500 |
C1—H1B | 0.9900 | C11—C12 | 1.388 (3) |
C2—C13 | 1.527 (2) | C11—H11 | 0.9500 |
C2—C3 | 1.543 (2) | C12—H12 | 0.9500 |
C2—H2 | 1.0000 | C13—H13A | 0.9800 |
C3—C14 | 1.508 (2) | C13—H13B | 0.9800 |
C3—C4 | 1.549 (2) | C13—H13C | 0.9800 |
C3—H3 | 1.0000 | C15—H15A | 0.9800 |
C4—C5 | 1.507 (2) | C15—H15B | 0.9800 |
C4—C15 | 1.534 (2) | C15—H15C | 0.9800 |
C4—H4 | 1.0000 | C16—H16A | 0.9800 |
C5—C6 | 1.346 (3) | C16—H16B | 0.9800 |
C5—H5 | 0.9500 | C16—H16C | 0.9800 |
C14—O2—H2O | 110.1 (16) | C7—C8—H8 | 119.8 |
C9—O3—C16 | 117.34 (15) | C9—C8—H8 | 119.8 |
C6—C1—C2 | 113.35 (14) | O3—C9—C10 | 124.50 (15) |
C6—C1—H1A | 108.9 | O3—C9—C8 | 114.65 (16) |
C2—C1—H1A | 108.9 | C10—C9—C8 | 120.85 (16) |
C6—C1—H1B | 108.9 | C9—C10—C11 | 118.43 (16) |
C2—C1—H1B | 108.9 | C9—C10—H10 | 120.8 |
H1A—C1—H1B | 107.7 | C11—C10—H10 | 120.8 |
C13—C2—C1 | 110.76 (14) | C12—C11—C10 | 121.27 (18) |
C13—C2—C3 | 111.93 (13) | C12—C11—H11 | 119.4 |
C1—C2—C3 | 107.97 (13) | C10—C11—H11 | 119.4 |
C13—C2—H2 | 108.7 | C11—C12—C7 | 120.36 (16) |
C1—C2—H2 | 108.7 | C11—C12—H12 | 119.8 |
C3—C2—H2 | 108.7 | C7—C12—H12 | 119.8 |
C14—C3—C2 | 111.34 (13) | C2—C13—H13A | 109.5 |
C14—C3—C4 | 109.16 (14) | C2—C13—H13B | 109.5 |
C2—C3—C4 | 111.26 (13) | H13A—C13—H13B | 109.5 |
C14—C3—H3 | 108.3 | C2—C13—H13C | 109.5 |
C2—C3—H3 | 108.3 | H13A—C13—H13C | 109.5 |
C4—C3—H3 | 108.3 | H13B—C13—H13C | 109.5 |
C5—C4—C15 | 110.53 (14) | O1—C14—O2 | 123.06 (15) |
C5—C4—C3 | 110.86 (14) | O1—C14—C3 | 122.03 (14) |
C15—C4—C3 | 110.06 (13) | O2—C14—C3 | 114.91 (15) |
C5—C4—H4 | 108.4 | C4—C15—H15A | 109.5 |
C15—C4—H4 | 108.4 | C4—C15—H15B | 109.5 |
C3—C4—H4 | 108.4 | H15A—C15—H15B | 109.5 |
C6—C5—C4 | 125.23 (15) | C4—C15—H15C | 109.5 |
C6—C5—H5 | 117.4 | H15A—C15—H15C | 109.5 |
C4—C5—H5 | 117.4 | H15B—C15—H15C | 109.5 |
C5—C6—C7 | 121.65 (15) | O3—C16—H16A | 109.5 |
C5—C6—C1 | 120.98 (16) | O3—C16—H16B | 109.5 |
C7—C6—C1 | 117.32 (14) | H16A—C16—H16B | 109.5 |
C12—C7—C8 | 118.65 (15) | O3—C16—H16C | 109.5 |
C12—C7—C6 | 120.89 (15) | H16A—C16—H16C | 109.5 |
C8—C7—C6 | 120.46 (16) | H16B—C16—H16C | 109.5 |
C7—C8—C9 | 120.42 (17) | ||
C6—C1—C2—C13 | −172.40 (14) | C5—C6—C7—C8 | −39.5 (2) |
C6—C1—C2—C3 | −49.53 (18) | C1—C6—C7—C8 | 142.90 (16) |
C13—C2—C3—C14 | −52.46 (19) | C12—C7—C8—C9 | −0.6 (2) |
C1—C2—C3—C14 | −174.62 (13) | C6—C7—C8—C9 | 178.94 (15) |
C13—C2—C3—C4 | −174.47 (15) | C16—O3—C9—C10 | 8.2 (2) |
C1—C2—C3—C4 | 63.37 (17) | C16—O3—C9—C8 | −171.22 (15) |
C14—C3—C4—C5 | −166.45 (14) | C7—C8—C9—O3 | 179.71 (14) |
C2—C3—C4—C5 | −43.19 (19) | C7—C8—C9—C10 | 0.2 (2) |
C14—C3—C4—C15 | 70.95 (17) | O3—C9—C10—C11 | −179.78 (16) |
C2—C3—C4—C15 | −165.78 (14) | C8—C9—C10—C11 | −0.4 (2) |
C15—C4—C5—C6 | 132.37 (18) | C9—C10—C11—C12 | 0.9 (3) |
C3—C4—C5—C6 | 10.1 (2) | C10—C11—C12—C7 | −1.3 (3) |
C4—C5—C6—C7 | −174.49 (16) | C8—C7—C12—C11 | 1.2 (2) |
C4—C5—C6—C1 | 3.0 (3) | C6—C7—C12—C11 | −178.39 (15) |
C2—C1—C6—C5 | 17.8 (2) | C2—C3—C14—O1 | −60.2 (2) |
C2—C1—C6—C7 | −164.57 (14) | C4—C3—C14—O1 | 63.06 (19) |
C5—C6—C7—C12 | 140.02 (18) | C2—C3—C14—O2 | 120.03 (15) |
C1—C6—C7—C12 | −37.5 (2) | C4—C3—C14—O2 | −116.76 (15) |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2O···O1i | 0.94 (3) | 1.71 (3) | 2.6523 (19) | 175 (2) |
Symmetry code: (i) −x, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H20O3 |
Mr | 260.32 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 100 |
a, b, c (Å) | 11.032 (2), 7.8423 (17), 32.140 (8) |
V (Å3) | 2780.7 (11) |
Z | 8 |
Radiation type | Synchrotron, λ = 0.44280 Å |
µ (mm−1) | 0.05 |
Crystal size (mm) | 0.02 × 0.01 × 0.01 |
Data collection | |
Diffractometer | Bruker Platform goniometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2007; Blessing, 1995) |
Tmin, Tmax | 0.999, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8586, 2173, 1755 |
Rint | 0.050 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.119, 1.11 |
No. of reflections | 2173 |
No. of parameters | 179 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.17, −0.23 |
Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SIR2004 (Burla et al., 2005), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2O···O1i | 0.94 (3) | 1.71 (3) | 2.6523 (19) | 175 (2) |
Symmetry code: (i) −x, −y, −z+1. |
Acknowledgements
SX, DN, and HS are grateful for the Grant-in-aid for Faculty Research from Indiana University Kokomo, as well as the Senior Research Grant from Indiana Academy of Science. ChemMatCARS Sector 15 is principally supported by the National Science Foundation/Department of Energy under grant No. CHE-0535644. Use of the advanced Photon Source was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE—AC02-06CH11357. The authors also want to thank the beamline for synchrotron radiation at the Advanced Photon Source, Argonne National Laboratory.
References
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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 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 (Xie et al., 2002, 2007a, 2008a,b). 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 near 180°. The carboxyl group is almost perpendicular to the cyclohexene ring with an angle of 85.3° between the O1—C14—O2—C3 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 38.7°. Unlike other previously reported para substituted analogs and like other previously reported meta substituted analogs (Xie et al., 2008b), the molecule also has a chiral axis due to the meta methoxy substituent on the aromatic ring.
Fig. 2 shows the hydrogen bonding scheme. Atom O2 acts as a donor in an intermolecular hydrogen bond to atom O1, 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.