Download citation
Download citation
link to html
The ring system of the title compound, C13H18O3, was synthesized by addition of ethyl acryl­ate to the dien­amine of 2-octalone. The keto acid aggregates in the solid as acid-to-acid dimers [O...O = 2.663 (2) Å and O—H...O = 170 (3)°] whose centrosymmetric hydrogen bonds lie across the a edges and the center of the chosen cell. Three intermolecular C—H...O close contacts within 2.7 Å were found involving the ketone group.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102006893/fr1370sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102006893/fr1370Isup2.hkl
Contains datablock I

CCDC reference: 188613

Comment top

Of the five hydrogen-bonding modes known for crystalline keto carboxylic acids, only three involve the ketone function, while the remainder correspond to the common pairing and rare chain modes of simple acids (Leiserowitz, 1976). As part of our study of factors governing the choice of hydrogen-bonding mode, we have examined (±)-12-oxotricyclo[6.2.2.01,6]dodecane-10-carboxylic acid, (I), which belongs to the category of δ-keto acids, one generally rich in hydrogen-bonding types.

Fig. 1 presents a view of the asymmetric unit of (I), which was synthesized by addition of ethyl acrylate to the dienamine of 2-octalone (see Experimental). Compound (I) is a `Diels-Alder-type' product and the arrangement of reactants required for the observed stereochemistry does, indeed, appear to be the most favorable of all the candidate [4 + 2] electrocyclic processes. Moreover, a study by House et al. (1965) indicates that the cross-conjugated homoannular diene required for such a [4 + 2] addition is a significant component of the mixture of isomers present in this dienamine. However, we have no actual evidence as to whether the bridged portion of the molecule arises from such a [4 + 2] electrocyclic reaction or a polar stepwise one. Compound (I) has not previously been reported, but several studies have been carried out on addition of vinyl ketones to the dienamine involved in our synthesis and to closely analogous ones. These have concluded that both [4 + 2] electrocyclic and polar stepwise processes can operate, with the observed mix dependent on specific conditions of reactant, solvent, etc. (Hickmott & Simpson, 1992). Despite the alternative configurational options available at C6 and C10, compound (I) was the only crystalline material isolated from the reaction sequence involved, and whether the configurations in (I) are the result of kinetic or thermodynamic processes is unknown.

Simple bicyclo[2.2.2]octane systems are not entirely rigid, and the nominally parallel ethylene bridges are often significantly skewed, presumably to relieve eclipsing strain (Deutsch, 1972; Blackstock et al., 1987; Zimmerman et al., 1992). In (I), this bridged portion of the molecule displays a modest conformational twist, described by the torsion angles C1—C6—C7—C8 [-0.5 (2)°], C1—C10—C9—C8 [8.5 (2)°] and C1—C11—C12—C8 [4.2 (2)], which would all be 0° in the absence of any twist. The relatively small size of this twist is probably attributable in part to the lack of eclipsing strain in the ketone bridge and in part to restraint presented by the appended cyclohexane, which adopts the expected chair conformation. Full rotation is possible only about C10—C13, and the carboxyl is rotated so that its carbonyl lies on the same face of the molecule as the ketone, with an O2—C13—C10—C9 torsion angle of -37.8 (2)°. The intramolecular dihedral angle between the carboxyl and ketone planes is 58.58 (12)°.

Averaging of the C—O bond lengths and C—C—O angles by disorder is common in carboxylic acids, but is seen only in dimers (Leiserowitz, 1976), whose geometry can support the averaging mechanisms. In (I), these C—O bond lengths are 1.229 (2)/1.313 (2) Å, with C—C—O angles of 123.5 (2)/114.1 (2)°. In comparison, typical values cited for highly ordered dimeric carboxyls are 1.21/1.31 Å and 123/112° (Borthwick, 1980). The observed lengths and angles, therefore, appear to represent only a slight degree of carboxyl disordering, and we were unable to find any electron density representing the minority disorder species in electron-density difference maps.

The packing of the cell involves acid-to-acid dimers [O···O = 2.663 (2) Å and O—H···O = 170 (3)°], which pair centrosymmetrically across the a edges and the center of the chosen cell. Lying within the 2.7 Å range we usually employ for non-bonded C—H···O packing interactions (Steiner, 1997), were found three intermolecular close contacts to the ketone O: 2.61 Å to H7A [related through a center of symmetry on the b edge], and 2.70 Å to H9A and 2.68 Å to H10, both to a molecule screw-related in c. Using compiled data for a large number of such C—H···O contacts, Steiner & Desiraju (1998) have found significant statistical directionality even as far out as 3.0 Å, and conclude that these are legitimately viewed as `weak hydrogen bonds', with a greater contribution to packing forces than simple van der Waals attractions.

The solid-state (KBr) IR spectrum of (I) has CO stretching absorptions at 1722 and 1691 cm-1, for ketone and acid, respectively. In CHCl3 solution, these bands coalesce to a single broad absorption at 1720 cm-1, with a typical carboxyl-dilution shoulder at ca 1740 cm-1.

Experimental top

The pyrrolidine enamine of cyclohexanone was treated with methyl vinyl ketone, to generate the expected mixture of octalone dienamines, which was isolated and purified by distillation (Stork et al., 1963). This was treated with ethyl acrylate essentially as described by Szmuszkovicz (1963). The isolated alkylation product in that reference was an ester assigned a bicyclic structure; that assignment is now cast into doubt by our present results. In the present case, the ester product was isolated by distillation and saponified to yield (I), and material suitable for X-ray analysis (m.p. 416 K) was obtained from diethyl ether.

Refinement top

All H atoms were found in electron-density difference maps but were placed in calculated positions (0.98 Å for methine H atoms and 0.97 Å for methylene H atoms) and allowed to refine as riding models on their respective C atoms (C—H = 0.97 or 0.98 Å). The displacement parameterd were fixed at 120% of those of their respective C atoms. The carboxyl H atom was allowed to refine fully.

Computing details top

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. A view of the asymmetric unit of (I) with the atom-numbering scheme. Displacement ellipsoids are shown at the 20% probability level.
(±)-12-Oxotricyclo[6.2.2.01,6]dodecane-10-carboxylic acid top
Crystal data top
C13H18O3Dx = 1.242 Mg m3
Mr = 222.27Melting point: 416 K
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 12.832 (4) ÅCell parameters from 27 reflections
b = 7.961 (3) Åθ = 3.0–8.4°
c = 11.809 (4) ŵ = 0.09 mm1
β = 99.79 (2)°T = 296 K
V = 1188.8 (7) Å3Hexagonal rod, colourless
Z = 40.38 × 0.28 × 0.24 mm
F(000) = 480
Data collection top
Siemens P4
diffractometer
1539 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.034
Graphite monochromatorθmax = 25.0°, θmin = 3.0°
2θ/θ scansh = 1515
Absorption correction: numerical
(Sheldrick, 1997)
k = 91
Tmin = 0.96, Tmax = 0.97l = 114
2775 measured reflections3 standard reflections every 97 reflections
2083 independent reflections intensity decay: variation <1%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.114 w = 1/[σ2(Fo2) + (0.0429P)2 + 0.3022P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max < 0.001
2083 reflectionsΔρmax = 0.13 e Å3
150 parametersΔρmin = 0.12 e Å3
0 restraintsExtinction correction: SHELXTL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.026 (3)
Crystal data top
C13H18O3V = 1188.8 (7) Å3
Mr = 222.27Z = 4
Monoclinic, P21/cMo Kα radiation
a = 12.832 (4) ŵ = 0.09 mm1
b = 7.961 (3) ÅT = 296 K
c = 11.809 (4) Å0.38 × 0.28 × 0.24 mm
β = 99.79 (2)°
Data collection top
Siemens P4
diffractometer
1539 reflections with I > 2σ(I)
Absorption correction: numerical
(Sheldrick, 1997)
Rint = 0.034
Tmin = 0.96, Tmax = 0.973 standard reflections every 97 reflections
2775 measured reflections intensity decay: variation <1%
2083 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.114H atoms treated by a mixture of independent and constrained refinement
S = 1.04Δρmax = 0.13 e Å3
2083 reflectionsΔρmin = 0.12 e Å3
150 parameters
Special details top

Experimental. Crystal mounted on glass fiber using epoxy resin

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.12497 (14)0.4104 (3)1.09881 (14)0.0874 (6)
O20.38247 (10)0.07214 (18)1.02304 (11)0.0552 (4)
O30.44970 (11)0.08608 (18)0.86133 (12)0.0533 (4)
C10.28654 (13)0.3970 (2)0.87176 (14)0.0371 (4)
C20.39291 (14)0.4661 (2)0.84855 (17)0.0450 (5)
C30.39529 (17)0.6587 (3)0.84045 (19)0.0574 (6)
C40.30510 (19)0.7220 (3)0.7498 (2)0.0663 (6)
C50.19840 (18)0.6609 (3)0.77377 (19)0.0622 (6)
C60.19450 (14)0.4688 (2)0.78163 (16)0.0453 (5)
C70.08695 (15)0.4020 (3)0.80629 (18)0.0595 (6)
C80.10278 (14)0.2847 (3)0.91054 (18)0.0574 (6)
C90.17441 (15)0.1368 (3)0.88968 (19)0.0540 (5)
C100.27888 (13)0.2023 (2)0.85609 (15)0.0392 (4)
C110.26769 (14)0.4411 (3)0.99350 (15)0.0467 (5)
C120.16025 (16)0.3818 (3)1.01151 (17)0.0546 (6)
C130.37436 (13)0.1135 (2)0.92161 (15)0.0390 (4)
H30.503 (2)0.025 (4)0.905 (3)0.100 (9)*
H2A0.44860.42970.90970.054*
H2B0.40750.41880.77720.054*
H3A0.38920.70700.91440.069*
H3B0.46230.69430.82080.069*
H4A0.31530.68280.67470.080*
H4B0.30580.84390.74890.080*
H5A0.14300.69910.71290.075*
H5B0.18520.70920.84540.075*
H60.20360.42460.70650.054*
H7A0.04280.49590.82050.071*
H7B0.05090.34190.73950.071*
H80.03460.24390.92620.069*
H9A0.13780.06630.82860.065*
H9B0.19030.06930.95880.065*
H100.27640.17820.77430.047*
H11A0.32180.38861.04980.056*
H11B0.27280.56171.00450.056*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0752 (11)0.1378 (18)0.0559 (9)0.0190 (11)0.0309 (8)0.0022 (11)
O20.0485 (8)0.0684 (10)0.0497 (8)0.0191 (7)0.0116 (6)0.0152 (7)
O30.0483 (8)0.0601 (9)0.0542 (8)0.0208 (7)0.0165 (7)0.0105 (7)
C10.0340 (9)0.0402 (10)0.0363 (9)0.0062 (8)0.0037 (7)0.0036 (8)
C20.0423 (10)0.0423 (11)0.0499 (11)0.0035 (8)0.0068 (8)0.0003 (9)
C30.0649 (13)0.0434 (12)0.0643 (13)0.0040 (10)0.0121 (11)0.0012 (10)
C40.0899 (17)0.0404 (12)0.0681 (14)0.0077 (12)0.0116 (12)0.0075 (11)
C50.0707 (14)0.0526 (13)0.0594 (13)0.0253 (11)0.0000 (11)0.0041 (11)
C60.0438 (10)0.0508 (12)0.0394 (10)0.0156 (9)0.0023 (8)0.0009 (9)
C70.0376 (10)0.0816 (16)0.0560 (12)0.0178 (10)0.0015 (9)0.0020 (12)
C80.0298 (9)0.0814 (16)0.0623 (12)0.0042 (10)0.0114 (9)0.0073 (12)
C90.0392 (10)0.0577 (13)0.0631 (12)0.0068 (9)0.0025 (9)0.0034 (11)
C100.0367 (9)0.0405 (10)0.0393 (9)0.0041 (8)0.0032 (7)0.0018 (8)
C110.0473 (11)0.0524 (12)0.0396 (10)0.0118 (9)0.0052 (8)0.0031 (9)
C120.0497 (11)0.0722 (15)0.0442 (11)0.0208 (10)0.0146 (9)0.0084 (10)
C130.0390 (9)0.0327 (9)0.0457 (10)0.0035 (8)0.0080 (8)0.0005 (8)
Geometric parameters (Å, º) top
O1—C121.216 (2)O3—H30.92 (3)
O2—C131.229 (2)C2—H2A0.9700
O3—C131.313 (2)C2—H2B0.9700
C1—C111.538 (2)C3—H3A0.9700
C1—C21.539 (2)C3—H3B0.9700
C1—C61.558 (2)C4—H4A0.9700
C1—C101.562 (3)C4—H4B0.9700
C2—C31.537 (3)C5—H5A0.9700
C3—C41.522 (3)C5—H5B0.9700
C4—C51.524 (3)C6—H60.9800
C5—C61.533 (3)C7—H7A0.9700
C6—C71.552 (3)C7—H7B0.9700
C7—C81.531 (3)C8—H80.9800
C8—C121.505 (3)C9—H9A0.9700
C8—C91.539 (3)C9—H9B0.9700
C9—C101.552 (3)C10—H100.9800
C10—C131.509 (2)C11—H11A0.9700
C11—C121.506 (3)C11—H11B0.9700
C11—C1—C2111.71 (15)C2—C3—H3B109.5
C11—C1—C6109.47 (14)H3A—C3—H3B108.1
C2—C1—C6109.84 (15)C3—C4—H4A109.4
C11—C1—C10108.69 (15)C5—C4—H4A109.4
C2—C1—C10111.92 (14)C3—C4—H4B109.4
C6—C1—C10104.97 (14)C5—C4—H4B109.4
C3—C2—C1113.28 (16)H4A—C4—H4B108.0
C4—C3—C2110.69 (17)C4—C5—H5A109.3
C3—C4—C5111.30 (18)C6—C5—H5A109.3
C4—C5—C6111.68 (17)C4—C5—H5B109.3
C5—C6—C7113.10 (16)C6—C5—H5B109.3
C5—C6—C1112.26 (16)H5A—C5—H5B107.9
C7—C6—C1109.93 (15)C5—C6—H6107.1
C8—C7—C6111.06 (15)C7—C6—H6107.1
C12—C8—C7107.70 (19)C1—C6—H6107.1
C12—C8—C9107.11 (16)C8—C7—H7A109.4
C7—C8—C9109.82 (17)C6—C7—H7A109.4
C8—C9—C10110.45 (17)C8—C7—H7B109.4
C13—C10—C9111.90 (16)C6—C7—H7B109.4
C13—C10—C1112.02 (14)H7A—C7—H7B108.0
C9—C10—C1110.04 (15)C12—C8—H8110.7
C12—C11—C1110.70 (15)C7—C8—H8110.7
O1—C12—C8124.4 (2)C9—C8—H8110.7
O1—C12—C11122.9 (2)C8—C9—H9A109.6
C8—C12—C11112.72 (16)C10—C9—H9A109.6
O2—C13—O3122.39 (16)C8—C9—H9B109.6
O2—C13—C10123.50 (16)C10—C9—H9B109.6
O3—C13—C10114.10 (16)H9A—C9—H9B108.1
C13—O3—H3108.8 (18)C13—C10—H10107.5
C3—C2—H2A108.9C9—C10—H10107.5
C1—C2—H2A108.9C1—C10—H10107.5
C3—C2—H2B108.9C12—C11—H11A109.5
C1—C2—H2B108.9C1—C11—H11A109.5
H2A—C2—H2B107.7C12—C11—H11B109.5
C4—C3—H3A109.5C1—C11—H11B109.5
C2—C3—H3A109.5H11A—C11—H11B108.1
C4—C3—H3B109.5
C11—C1—C2—C368.9 (2)C8—C9—C10—C18.5 (2)
C6—C1—C2—C352.8 (2)C11—C1—C10—C1373.49 (18)
C10—C1—C2—C3169.00 (16)C2—C1—C10—C1350.4 (2)
C1—C2—C3—C455.5 (2)C6—C1—C10—C13169.46 (14)
C2—C3—C4—C556.1 (2)C11—C1—C10—C951.66 (19)
C3—C4—C5—C656.5 (2)C2—C1—C10—C9175.52 (14)
C4—C5—C6—C7179.85 (17)C6—C1—C10—C965.38 (18)
C4—C5—C6—C154.8 (2)C2—C1—C11—C12176.40 (15)
C11—C1—C6—C570.9 (2)C6—C1—C11—C1254.5 (2)
C2—C1—C6—C552.1 (2)C10—C1—C11—C1259.62 (19)
C10—C1—C6—C5172.58 (16)C7—C8—C12—O1118.8 (2)
C11—C1—C6—C755.9 (2)C9—C8—C12—O1123.2 (2)
C2—C1—C6—C7178.92 (16)C7—C8—C12—C1161.3 (2)
C10—C1—C6—C760.60 (19)C9—C8—C12—C1156.8 (2)
C5—C6—C7—C8126.85 (19)C1—C11—C12—O1175.8 (2)
C1—C6—C7—C80.5 (2)C1—C11—C12—C84.2 (2)
C6—C7—C8—C1258.2 (2)C9—C10—C13—O237.8 (2)
C6—C7—C8—C958.1 (2)C1—C10—C13—O286.3 (2)
C12—C8—C9—C1063.4 (2)C9—C10—C13—O3143.25 (17)
C7—C8—C9—C1053.3 (2)C1—C10—C13—O392.63 (19)
C8—C9—C10—C13133.72 (17)

Experimental details

Crystal data
Chemical formulaC13H18O3
Mr222.27
Crystal system, space groupMonoclinic, P21/c
Temperature (K)296
a, b, c (Å)12.832 (4), 7.961 (3), 11.809 (4)
β (°) 99.79 (2)
V3)1188.8 (7)
Z4
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.38 × 0.28 × 0.24
Data collection
DiffractometerSiemens P4
diffractometer
Absorption correctionNumerical
(Sheldrick, 1997)
Tmin, Tmax0.96, 0.97
No. of measured, independent and
observed [I > 2σ(I)] reflections
2775, 2083, 1539
Rint0.034
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.114, 1.04
No. of reflections2083
No. of parameters150
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.13, 0.12

Computer programs: XSCANS (Siemens, 1996), XSCANS, SHELXTL (Sheldrick, 1997), SHELXTL.

Selected geometric parameters (Å, º) top
O2—C131.229 (2)O3—C131.313 (2)
O2—C13—C10123.50 (16)O3—C13—C10114.10 (16)
 

Follow Acta Cryst. C
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds