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The title compound, C18H24O2, was synthesized to study the inter­action of the two enanti­omers in the solid state. The resultant racemate is made up of carboxylic acid RS mol­ecules which are dimerized through their carboxyl groups by O—H...O hydrogen bonds, forming R22(8) rings. The dimers are inter­connected via weak C—H...π(arene) inter­actions, resulting in thick two-dimensional layers.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807041098/om2154sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807041098/om2154Isup2.hkl
Contains datablock I

CCDC reference: 662417

Key indicators

  • Single-crystal X-ray study
  • T = 100 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.058
  • wR factor = 0.150
  • Data-to-parameter ratio = 15.9

checkCIF/PLATON results

No syntax errors found



Alert level B ABSTM02_ALERT_3_B The ratio of expected to reported Tmax/Tmin(RR') is < 0.75 Tmin and Tmax reported: 0.600 0.989 Tmin(prime) and Tmax expected: 0.969 0.989 RR(prime) = 0.619 Please check that your absorption correction is appropriate. PLAT061_ALERT_3_B Tmax/Tmin Range Test RR' too Large ............. 0.62 PLAT220_ALERT_2_B Large Non-Solvent C Ueq(max)/Ueq(min) ... 3.97 Ratio PLAT222_ALERT_3_B Large Non-Solvent H Ueq(max)/Ueq(min) ... 4.87 Ratio PLAT230_ALERT_2_B Hirshfeld Test Diff for C15 - C16 .. 11.16 su
Alert level C PLAT230_ALERT_2_C Hirshfeld Test Diff for C9 - C10 .. 5.15 su PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor .... 2.95 PLAT481_ALERT_4_C Long D...A H-Bond Reported C3 .. CG1 .. 4.07 Ang.
Alert level G PLAT793_ALERT_1_G Check the Absolute Configuration of C2 = ... S PLAT793_ALERT_1_G Check the Absolute Configuration of C5 = ... R PLAT793_ALERT_1_G Check the Absolute Configuration of C6 = ... R
0 ALERT level A = In general: serious problem 5 ALERT level B = Potentially serious problem 3 ALERT level C = Check and explain 3 ALERT level G = General alerts; check 3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 4 ALERT type 2 Indicator that the structure model may be wrong or deficient 3 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check

Comment top

The title carboxylic acid, (I), was prepared to study the interaction of the two enantiomers in the solid state. The resultant racemate is made up of carboxylic acid RS dimers, a phenomenon similar to an analog compound we reported previously (Xie et al., 2002a). The structure and atom numbering of (I) are shown in Fig. 1, which illustrates the twisted chair conformation of the cyclohexene ring. The torsion angles involving atoms C8, C2, C1, C6, and C11 are all near 180°. The C3C4 double bond is not fully conjugated with the benzene ring due to the steric hindrance of the C5-ethyl group, a condition which causes the benzene ring plane to rotate by 44.8 (2)° with respect to the C3—C4—C5 plane. Geometric parameters of interest are given in Table 1.

Fig. 2 shows the hydrogen-bonding scheme, molecular packing and C—H···π(arene) interactions. Atom O2 acts as a donor in an intermolecular hydrogen bond to atom O1. Inversion of this interaction across (1/2, 1/2, 1) produces an R22(8) ring (Bernstein et al., 1995), thus creating a hydrogen-bonded dimer. The dimers are interconnected via weak C—H···π(arene) interactions in both the b and c directions, forming thick two-dimensional layers parallel to (100). Geometry of these two interactions is given in Table 2.

Related literature top

In the 4-p-methoxyphenyl analog (Xie et al., 2002a), the racemate also consists of carboxylic acid RS dimers. For additional related literature, see: Bernstein et al. (1995); Hussain et al. (2006); Xie et al. (2002b, 2007).

Experimental top

The carboxylic acid (I) was synthesized following the same method reported by Xie et al. (2002a). Purified (I) was recrystallized from hexane-ethyl acetate as colorless crystals (m.p. 490.5–492.0 K).

Refinement top

The rotational orientations of the methyl H atoms were refined by the circular Fourier method available in SHELXL97 (Sheldrick, 1997); the hydroxyl H atom position was determined in a similar manner. All H atoms were treated as riding with C—H distances ranging from 0.84 to 1.0 Å and Uiso(H) values equal to 1.5 (hydroxyl and methyl H atoms) or 1.2 times (all other H atoms) Ueq of the parent atom.

Structure description top

The title carboxylic acid, (I), was prepared to study the interaction of the two enantiomers in the solid state. The resultant racemate is made up of carboxylic acid RS dimers, a phenomenon similar to an analog compound we reported previously (Xie et al., 2002a). The structure and atom numbering of (I) are shown in Fig. 1, which illustrates the twisted chair conformation of the cyclohexene ring. The torsion angles involving atoms C8, C2, C1, C6, and C11 are all near 180°. The C3C4 double bond is not fully conjugated with the benzene ring due to the steric hindrance of the C5-ethyl group, a condition which causes the benzene ring plane to rotate by 44.8 (2)° with respect to the C3—C4—C5 plane. Geometric parameters of interest are given in Table 1.

Fig. 2 shows the hydrogen-bonding scheme, molecular packing and C—H···π(arene) interactions. Atom O2 acts as a donor in an intermolecular hydrogen bond to atom O1. Inversion of this interaction across (1/2, 1/2, 1) produces an R22(8) ring (Bernstein et al., 1995), thus creating a hydrogen-bonded dimer. The dimers are interconnected via weak C—H···π(arene) interactions in both the b and c directions, forming thick two-dimensional layers parallel to (100). Geometry of these two interactions is given in Table 2.

In the 4-p-methoxyphenyl analog (Xie et al., 2002a), the racemate also consists of carboxylic acid RS dimers. For additional related literature, see: Bernstein et al. (1995); Hussain et al. (2006); Xie et al. (2002b, 2007).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005) 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, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. The molecular structure and atom numbering scheme for (I), with displacement ellipsoids drawn at the 50% probablilty level.
[Figure 2] Fig. 2. Molecular packing, hydrogen bonding and C—H···π(arene) interactions in (I) as viewed down [010]. Dashed lines between red oxygen atoms represent hydrogen bonds; other dashed lines represent C—H···π(arene) interactions. [Symmetry codes: (i) 1 - x, 1 - y, 2 - z; (ii) x, 3/2 - y, 1/2 + z.]
(RS)-5-ethyl-2,6-dimethyl-4-p-tolyl-3-cyclohexenecarboxylic acid top
Crystal data top
C18H24O2F(000) = 592
Mr = 272.37Dx = 1.199 Mg m3
Monoclinic, P21/cMelting point = 490.5–492 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 16.2786 (14) ÅCell parameters from 2703 reflections
b = 11.472 (1) Åθ = 2.5–28.2°
c = 8.1035 (7) ŵ = 0.08 mm1
β = 94.318 (5)°T = 100 K
V = 1509.0 (2) Å3Irregular fragment, colorless
Z = 40.41 × 0.17 × 0.15 mm
Data collection top
Bruker Kappa APEX II CCD
diffractometer
2952 independent reflections
Radiation source: X-ray tube2211 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.054
φ and ω scansθmax = 26.0°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
h = 2020
Tmin = 0.600, Tmax = 0.989k = 1413
19084 measured reflectionsl = 96
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.058Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.150H-atom parameters constrained
S = 1.03 w = 1/[σ2(Fo2) + (0.0587P)2 + 1.3904P]
where P = (Fo2 + 2Fc2)/3
2952 reflections(Δ/σ)max < 0.001
186 parametersΔρmax = 0.55 e Å3
0 restraintsΔρmin = 0.46 e Å3
Crystal data top
C18H24O2V = 1509.0 (2) Å3
Mr = 272.37Z = 4
Monoclinic, P21/cMo Kα radiation
a = 16.2786 (14) ŵ = 0.08 mm1
b = 11.472 (1) ÅT = 100 K
c = 8.1035 (7) Å0.41 × 0.17 × 0.15 mm
β = 94.318 (5)°
Data collection top
Bruker Kappa APEX II CCD
diffractometer
2952 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
2211 reflections with I > 2σ(I)
Tmin = 0.600, Tmax = 0.989Rint = 0.054
19084 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0580 restraints
wR(F2) = 0.150H-atom parameters constrained
S = 1.03Δρmax = 0.55 e Å3
2952 reflectionsΔρmin = 0.46 e Å3
186 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.40575 (9)0.49053 (13)0.91934 (17)0.0244 (4)
O20.51667 (8)0.52472 (14)0.78147 (17)0.0260 (4)
H20.54060.51830.87650.039*
C10.38654 (12)0.52324 (17)0.6275 (2)0.0194 (4)
H10.42490.53500.53820.023*
C20.33118 (12)0.63081 (17)0.6339 (2)0.0199 (4)
H2A0.29960.62530.73470.024*
C30.27101 (13)0.63237 (18)0.4839 (3)0.0242 (5)
H30.24360.70380.45710.029*
C40.25300 (12)0.54117 (18)0.3853 (2)0.0218 (5)
C50.28849 (14)0.42135 (19)0.4199 (3)0.0296 (5)
H50.32880.40690.33500.035*
C60.33676 (13)0.41179 (17)0.5894 (3)0.0233 (5)
H60.29640.40240.67570.028*
C70.43691 (12)0.51111 (16)0.7900 (2)0.0188 (4)
C80.38172 (13)0.74326 (18)0.6440 (3)0.0265 (5)
H8A0.41340.74960.54620.040*
H8B0.41950.74200.74400.040*
H8C0.34460.81030.64810.040*
C90.22227 (16)0.3268 (2)0.3955 (3)0.0395 (6)
H9A0.20210.32520.27710.047*
H9B0.24800.25030.42250.047*
C100.14949 (17)0.3420 (3)0.4977 (4)0.0529 (8)
H10A0.16850.34340.61530.079*
H10B0.11110.27690.47640.079*
H10C0.12150.41550.46770.079*
C110.39292 (15)0.30511 (19)0.5954 (3)0.0309 (5)
H11A0.35990.23500.57050.046*
H11B0.42110.29810.70610.046*
H11C0.43380.31370.51340.046*
C120.19862 (13)0.55613 (18)0.2308 (3)0.0264 (5)
C130.22078 (15)0.5074 (2)0.0822 (3)0.0363 (6)
H130.27070.46460.08150.044*
C140.17192 (17)0.5200 (3)0.0628 (3)0.0451 (7)
H140.18880.48600.16160.054*
C150.09955 (19)0.5806 (3)0.0673 (3)0.0482 (8)
C160.07687 (17)0.6306 (3)0.0789 (4)0.0531 (8)
H160.02710.67390.07810.064*
C170.12617 (15)0.6183 (2)0.2270 (3)0.0375 (6)
H170.10950.65310.32550.045*
C180.0446 (2)0.5926 (3)0.2266 (4)0.0746 (12)
H18A0.07570.62930.31160.112*
H18B0.00320.64090.20640.112*
H18C0.02590.51520.26460.112*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0239 (8)0.0327 (8)0.0157 (7)0.0019 (6)0.0042 (6)0.0032 (6)
O20.0230 (8)0.0367 (9)0.0174 (7)0.0017 (6)0.0054 (6)0.0045 (7)
C10.0233 (10)0.0190 (10)0.0151 (10)0.0021 (8)0.0044 (8)0.0008 (8)
C20.0244 (10)0.0193 (10)0.0154 (10)0.0017 (8)0.0038 (8)0.0007 (8)
C30.0256 (11)0.0241 (11)0.0221 (11)0.0034 (9)0.0042 (9)0.0029 (9)
C40.0216 (10)0.0230 (10)0.0199 (10)0.0038 (8)0.0044 (8)0.0042 (8)
C50.0380 (13)0.0240 (11)0.0245 (12)0.0038 (10)0.0119 (10)0.0007 (9)
C60.0280 (11)0.0192 (10)0.0214 (11)0.0022 (8)0.0077 (8)0.0014 (8)
C70.0230 (10)0.0143 (9)0.0183 (10)0.0002 (8)0.0038 (8)0.0007 (8)
C80.0319 (12)0.0206 (11)0.0263 (12)0.0001 (9)0.0033 (9)0.0013 (9)
C90.0514 (15)0.0252 (12)0.0379 (14)0.0123 (11)0.0234 (12)0.0060 (10)
C100.0462 (16)0.0547 (17)0.0531 (18)0.0244 (14)0.0270 (14)0.0263 (14)
C110.0401 (13)0.0215 (11)0.0294 (12)0.0016 (10)0.0077 (10)0.0003 (9)
C120.0293 (12)0.0235 (11)0.0246 (11)0.0097 (9)0.0094 (9)0.0076 (9)
C130.0360 (13)0.0472 (15)0.0244 (12)0.0151 (11)0.0060 (10)0.0032 (11)
C140.0464 (16)0.0629 (18)0.0241 (13)0.0255 (14)0.0100 (11)0.0075 (12)
C150.0627 (19)0.0496 (16)0.0288 (14)0.0275 (14)0.0196 (13)0.0142 (12)
C160.0407 (15)0.0444 (16)0.069 (2)0.0003 (12)0.0292 (14)0.0159 (15)
C170.0370 (13)0.0334 (13)0.0392 (14)0.0016 (10)0.0168 (11)0.0046 (11)
C180.084 (2)0.081 (2)0.0512 (19)0.037 (2)0.0441 (18)0.0289 (18)
Geometric parameters (Å, º) top
O1—C71.221 (2)C9—H9A0.9900
O2—C71.315 (2)C9—H9B0.9900
O2—H20.8400C10—H10A0.9800
C1—C71.504 (3)C10—H10B0.9800
C1—C21.531 (3)C10—H10C0.9800
C1—C61.533 (3)C11—H11A0.9800
C1—H11.0000C11—H11B0.9800
C2—C31.503 (3)C11—H11C0.9800
C2—C81.529 (3)C12—C171.377 (3)
C2—H2A1.0000C12—C131.399 (3)
C3—C41.336 (3)C13—C141.376 (3)
C3—H30.9500C13—H130.9500
C4—C121.488 (3)C14—C151.366 (4)
C4—C51.509 (3)C14—H140.9500
C5—C91.531 (3)C15—C161.391 (4)
C5—C61.534 (3)C15—C181.520 (3)
C5—H51.0000C16—C171.400 (3)
C6—C111.526 (3)C16—H160.9500
C6—H61.0000C17—H170.9500
C8—H8A0.9800C18—H18A0.9800
C8—H8B0.9800C18—H18B0.9800
C8—H8C0.9800C18—H18C0.9800
C9—C101.506 (4)
C7—O2—H2109.5C10—C9—H9A108.5
C7—C1—C2109.17 (16)C5—C9—H9A108.5
C7—C1—C6110.13 (16)C10—C9—H9B108.5
C2—C1—C6112.06 (16)C5—C9—H9B108.5
C7—C1—H1108.5H9A—C9—H9B107.5
C2—C1—H1108.5C9—C10—H10A109.5
C6—C1—H1108.5C9—C10—H10B109.5
C3—C2—C8110.39 (17)H10A—C10—H10B109.5
C3—C2—C1109.38 (16)C9—C10—H10C109.5
C8—C2—C1111.48 (16)H10A—C10—H10C109.5
C3—C2—H2A108.5H10B—C10—H10C109.5
C8—C2—H2A108.5C6—C11—H11A109.5
C1—C2—H2A108.5C6—C11—H11B109.5
C4—C3—C2125.09 (19)H11A—C11—H11B109.5
C4—C3—H3117.5C6—C11—H11C109.5
C2—C3—H3117.5H11A—C11—H11C109.5
C3—C4—C12120.19 (19)H11B—C11—H11C109.5
C3—C4—C5122.59 (18)C17—C12—C13117.6 (2)
C12—C4—C5117.18 (18)C17—C12—C4122.2 (2)
C4—C5—C9111.40 (19)C13—C12—C4120.2 (2)
C4—C5—C6113.25 (17)C14—C13—C12121.5 (3)
C9—C5—C6111.93 (18)C14—C13—H13119.2
C4—C5—H5106.6C12—C13—H13119.2
C9—C5—H5106.6C15—C14—C13121.2 (3)
C6—C5—H5106.6C15—C14—H14119.4
C11—C6—C1110.87 (17)C13—C14—H14119.4
C11—C6—C5110.55 (18)C14—C15—C16118.1 (2)
C1—C6—C5110.37 (16)C14—C15—C18121.3 (3)
C11—C6—H6108.3C16—C15—C18120.6 (3)
C1—C6—H6108.3C15—C16—C17121.1 (3)
C5—C6—H6108.3C15—C16—H16119.5
O1—C7—O2122.94 (18)C17—C16—H16119.5
O1—C7—C1122.33 (18)C12—C17—C16120.4 (3)
O2—C7—C1114.73 (17)C12—C17—H17119.8
C2—C8—H8A109.5C16—C17—H17119.8
C2—C8—H8B109.5C15—C18—H18A109.5
H8A—C8—H8B109.5C15—C18—H18B109.5
C2—C8—H8C109.5H18A—C18—H18B109.5
H8A—C8—H8C109.5C15—C18—H18C109.5
H8B—C8—H8C109.5H18A—C18—H18C109.5
C10—C9—C5115.0 (2)H18B—C18—H18C109.5
C3—C4—C12—C13133.7 (2)C4—C5—C6—C138.9 (3)
C3—C4—C12—C1745.6 (3)C9—C5—C6—C1165.82 (19)
C6—C1—C2—C8170.80 (17)C2—C1—C7—O165.4 (2)
C2—C1—C6—C11176.17 (17)C6—C1—C7—O158.0 (2)
C7—C1—C2—C3170.71 (16)C2—C1—C7—O2114.42 (19)
C7—C1—C6—C5177.26 (17)C6—C1—C7—O2122.14 (19)
C6—C1—C2—C348.4 (2)C4—C5—C9—C1056.7 (3)
C7—C1—C2—C866.9 (2)C6—C5—C9—C1071.2 (3)
C8—C2—C3—C4139.8 (2)C5—C4—C12—C17136.7 (2)
C1—C2—C3—C416.8 (3)C5—C4—C12—C1344.0 (3)
C2—C3—C4—C12173.91 (19)C17—C12—C13—C140.5 (3)
C2—C3—C4—C53.6 (3)C4—C12—C13—C14179.8 (2)
C3—C4—C5—C9135.2 (2)C12—C13—C14—C150.2 (4)
C12—C4—C5—C947.2 (3)C13—C14—C15—C160.8 (4)
C3—C4—C5—C67.9 (3)C13—C14—C15—C18178.7 (2)
C12—C4—C5—C6174.46 (18)C14—C15—C16—C170.8 (4)
C7—C1—C6—C1154.4 (2)C18—C15—C16—C17178.8 (3)
C2—C1—C6—C561.0 (2)C13—C12—C17—C160.5 (3)
C4—C5—C6—C11161.90 (19)C4—C12—C17—C16179.8 (2)
C9—C5—C6—C1171.2 (3)C15—C16—C17—C120.1 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.841.812.654 (2)178
C3—H3···Cg1ii0.953.234.069 (2)148
Symmetry codes: (i) x+1, y+1, z+2; (ii) x, y+3/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC18H24O2
Mr272.37
Crystal system, space groupMonoclinic, P21/c
Temperature (K)100
a, b, c (Å)16.2786 (14), 11.472 (1), 8.1035 (7)
β (°) 94.318 (5)
V3)1509.0 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.41 × 0.17 × 0.15
Data collection
DiffractometerBruker Kappa APEX II CCD
Absorption correctionMulti-scan
(SADABS; Bruker, 2005)
Tmin, Tmax0.600, 0.989
No. of measured, independent and
observed [I > 2σ(I)] reflections
19084, 2952, 2211
Rint0.054
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.058, 0.150, 1.03
No. of reflections2952
No. of parameters186
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.55, 0.46

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005) and SADABS (Bruker, 2005), SIR92 (Altomare et al., 1994), LS in TEXSAN (Molecular Structure Corporation, 1997) and SHELXL97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997) and PLATON (Spek, 2003).

Selected torsion angles (º) top
C3—C4—C12—C13133.7 (2)C2—C1—C6—C11176.17 (17)
C3—C4—C12—C1745.6 (3)C7—C1—C2—C3170.71 (16)
C6—C1—C2—C8170.80 (17)C7—C1—C6—C5177.26 (17)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.841.812.654 (2)178
C3—H3···Cg1ii0.953.234.069 (2)148
Symmetry codes: (i) x+1, y+1, z+2; (ii) x, y+3/2, z+1/2.
 

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