The structure of the title compound, C9H12O4, contains two independent molecules in the asymmetric unit, with an unusually strong twist around the norbornane C2-C3 bond.
Supporting information
CCDC reference: 202312
Key indicators
- Single-crystal X-ray study
- T = 150 K
- Mean (C-C) = 0.002 Å
- R factor = 0.049
- wR factor = 0.123
- Data-to-parameter ratio = 13.9
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
Hydrogen was admitted, with stirring, to a mixture of (II) (0.66 g, 4 mmol), palladium on carbon (5% Pd, 100 mg) and acetic acid (10 ml). The catalyst was filtered off and the solvent removed using a rotary evaporator. The product was recrystallized from doubly-distilled water, giving colourless crystalline (I) in 88% yield (0.58 g, 3 mmol). Single crystals of (I) suitable for X-ray study were grown from ethyl acetate. The melting point of (I) coincided with that (433–434 K) quoted in the literature (Alder & Stein, 1933b).
All H atoms were refined in isotropic approximation; Csp3—H bond lengths were in the range 0.96 (2)–1.02 (2) Å.
Data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXTL.
bicyclo[2.2.1]heptane-
endo-
cis-2,3-dicarboxylic acid
top
Crystal data top
C9H12O4 | Dx = 1.409 Mg m−3 |
Mr = 184.19 | Melting point: 160–161° C K |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 20.737 (5) Å | Cell parameters from 489 reflections |
b = 9.310 (2) Å | θ = 7.5–20.7° |
c = 9.003 (2) Å | µ = 0.11 mm−1 |
β = 92.59 (1)° | T = 150 K |
V = 1736.4 (7) Å3 | Prism, colourless |
Z = 8 | 0.45 × 0.35 × 0.15 mm |
F(000) = 784 | |
Data collection top
SMART 1K CCD area-detector diffractometer | 3553 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.049 |
Graphite monochromator | θmax = 29.0°, θmin = 2.0° |
Detector resolution: 8 pixels mm-1 | h = −27→28 |
ω scan in 0.3° frames, 10 s/frame | k = −9→12 |
12920 measured reflections | l = −12→11 |
4594 independent reflections | |
Refinement top
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)] = 0.049 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.123 | All H-atom parameters refined |
S = 1.14 | w = 1/[σ2(Fo2) + (0.0419P)2 + 0.9532P] where P = (Fo2 + 2Fc2)/3 |
4594 reflections | (Δ/σ)max = 0.001 |
331 parameters | Δρmax = 0.32 e Å−3 |
0 restraints | Δρmin = −0.35 e Å−3 |
Crystal data top
C9H12O4 | V = 1736.4 (7) Å3 |
Mr = 184.19 | Z = 8 |
Monoclinic, P21/c | Mo Kα radiation |
a = 20.737 (5) Å | µ = 0.11 mm−1 |
b = 9.310 (2) Å | T = 150 K |
c = 9.003 (2) Å | 0.45 × 0.35 × 0.15 mm |
β = 92.59 (1)° | |
Data collection top
SMART 1K CCD area-detector diffractometer | 3553 reflections with I > 2σ(I) |
12920 measured reflections | Rint = 0.049 |
4594 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.049 | 0 restraints |
wR(F2) = 0.123 | All H-atom parameters refined |
S = 1.14 | Δρmax = 0.32 e Å−3 |
4594 reflections | Δρmin = −0.35 e Å−3 |
331 parameters | |
Special details top
Experimental. The data collection nominally covered more than a hemisphere of reciprocal space, by a combination of 4 sets of ω scans; each set at different ϕ and/or 2θ angles and each scan (10 sec exposure) covering 0.3° in ω. Crystal to detector distance 4.57 cm. |
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
C1 | 0.92500 (7) | 0.44919 (17) | 0.12981 (17) | 0.0184 (3) | |
H1 | 0.9377 (9) | 0.386 (2) | 0.047 (2) | 0.023 (5)* | |
C2 | 0.85440 (7) | 0.42098 (16) | 0.17647 (16) | 0.0155 (3) | |
H2 | 0.8272 (9) | 0.402 (2) | 0.085 (2) | 0.020 (5)* | |
C3 | 0.83551 (7) | 0.56831 (16) | 0.24618 (16) | 0.0162 (3) | |
H3 | 0.8049 (9) | 0.614 (2) | 0.176 (2) | 0.022 (5)* | |
C4 | 0.89891 (8) | 0.65397 (17) | 0.24804 (17) | 0.0177 (3) | |
H4 | 0.8930 (9) | 0.756 (2) | 0.262 (2) | 0.014 (4)* | |
C5 | 0.95055 (8) | 0.58492 (19) | 0.35414 (19) | 0.0218 (3) | |
H51 | 0.9334 (9) | 0.562 (2) | 0.453 (2) | 0.018 (4)* | |
H52 | 0.9874 (10) | 0.653 (2) | 0.370 (2) | 0.026 (5)* | |
C6 | 0.97156 (8) | 0.4490 (2) | 0.2676 (2) | 0.0248 (4) | |
H61 | 0.9688 (10) | 0.358 (2) | 0.327 (2) | 0.030 (5)* | |
H62 | 1.0158 (11) | 0.455 (2) | 0.238 (2) | 0.033 (6)* | |
C7 | 0.92227 (8) | 0.61056 (18) | 0.09455 (18) | 0.0210 (3) | |
H71 | 0.8903 (10) | 0.635 (2) | 0.013 (2) | 0.028 (5)* | |
H72 | 0.9656 (10) | 0.649 (2) | 0.077 (2) | 0.031 (5)* | |
C8 | 0.85239 (8) | 0.29325 (17) | 0.27827 (18) | 0.0199 (3) | |
O2 | 0.85288 (7) | 0.30107 (13) | 0.41299 (13) | 0.0279 (3) | |
O1 | 0.85298 (8) | 0.16430 (13) | 0.21490 (15) | 0.0336 (3) | |
H01 | 0.8542 (13) | 0.173 (3) | 0.117 (3) | 0.062 (8)* | |
C9 | 0.79841 (7) | 0.56304 (17) | 0.38589 (17) | 0.0181 (3) | |
O4 | 0.81585 (6) | 0.62250 (13) | 0.50227 (13) | 0.0235 (3) | |
O3 | 0.74262 (6) | 0.49528 (14) | 0.36656 (13) | 0.0254 (3) | |
H03 | 0.7213 (14) | 0.496 (3) | 0.459 (3) | 0.065 (8)* | |
C11 | 0.57692 (8) | 0.42913 (18) | 0.94997 (18) | 0.0209 (3) | |
H11 | 0.5326 (9) | 0.396 (2) | 0.967 (2) | 0.019 (5)* | |
C12 | 0.57733 (7) | 0.55274 (17) | 0.83730 (17) | 0.0177 (3) | |
H12 | 0.5492 (10) | 0.633 (2) | 0.873 (2) | 0.028 (5)* | |
C13 | 0.64839 (8) | 0.60889 (17) | 0.85192 (18) | 0.0187 (3) | |
H13 | 0.6499 (9) | 0.712 (2) | 0.873 (2) | 0.024 (5)* | |
C14 | 0.67587 (8) | 0.5250 (2) | 0.99153 (19) | 0.0245 (4) | |
H14 | 0.7123 (11) | 0.577 (2) | 1.044 (2) | 0.036 (6)* | |
C15 | 0.69095 (9) | 0.3695 (2) | 0.9469 (2) | 0.0294 (4) | |
H151 | 0.7228 (11) | 0.363 (2) | 0.865 (2) | 0.037 (6)* | |
H152 | 0.7107 (11) | 0.317 (2) | 1.037 (3) | 0.038 (6)* | |
C16 | 0.62300 (9) | 0.30823 (19) | 0.9041 (2) | 0.0255 (4) | |
H161 | 0.6173 (10) | 0.287 (2) | 0.795 (2) | 0.030 (5)* | |
H162 | 0.6143 (10) | 0.222 (2) | 0.959 (2) | 0.027 (5)* | |
C17 | 0.61513 (9) | 0.5013 (2) | 1.08008 (19) | 0.0259 (4) | |
H171 | 0.5943 (11) | 0.592 (3) | 1.116 (2) | 0.035 (6)* | |
H172 | 0.6235 (10) | 0.436 (2) | 1.163 (2) | 0.033 (6)* | |
C18 | 0.54746 (8) | 0.52313 (18) | 0.68477 (18) | 0.0207 (3) | |
O12 | 0.52033 (6) | 0.41016 (13) | 0.65219 (14) | 0.0267 (3) | |
O11 | 0.54823 (7) | 0.63511 (13) | 0.59527 (15) | 0.0283 (3) | |
H011 | 0.5244 (14) | 0.613 (3) | 0.507 (3) | 0.069 (9)* | |
C19 | 0.68963 (8) | 0.58406 (17) | 0.72095 (18) | 0.0202 (3) | |
O14 | 0.67573 (6) | 0.50462 (14) | 0.61675 (14) | 0.0277 (3) | |
O13 | 0.74477 (6) | 0.65464 (15) | 0.73455 (15) | 0.0302 (3) | |
H013 | 0.7706 (14) | 0.633 (3) | 0.657 (3) | 0.063 (8)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0183 (7) | 0.0197 (7) | 0.0174 (7) | 0.0016 (6) | 0.0032 (5) | −0.0008 (6) |
C2 | 0.0187 (7) | 0.0157 (7) | 0.0120 (6) | 0.0005 (6) | −0.0001 (5) | 0.0002 (5) |
C3 | 0.0168 (7) | 0.0161 (7) | 0.0155 (7) | 0.0016 (6) | 0.0000 (5) | −0.0005 (5) |
C4 | 0.0197 (7) | 0.0150 (7) | 0.0186 (7) | −0.0008 (6) | 0.0029 (6) | −0.0007 (6) |
C5 | 0.0181 (7) | 0.0257 (8) | 0.0214 (8) | −0.0004 (6) | −0.0020 (6) | −0.0031 (6) |
C6 | 0.0177 (8) | 0.0264 (9) | 0.0299 (9) | 0.0057 (7) | −0.0031 (6) | −0.0021 (7) |
C7 | 0.0236 (8) | 0.0207 (8) | 0.0192 (8) | −0.0021 (6) | 0.0065 (6) | 0.0019 (6) |
C8 | 0.0266 (8) | 0.0167 (7) | 0.0165 (7) | −0.0008 (6) | 0.0015 (6) | 0.0009 (6) |
O2 | 0.0460 (8) | 0.0241 (6) | 0.0139 (5) | 0.0007 (6) | 0.0038 (5) | 0.0037 (5) |
O1 | 0.0660 (10) | 0.0157 (6) | 0.0196 (6) | −0.0015 (6) | 0.0058 (6) | 0.0001 (5) |
C9 | 0.0173 (7) | 0.0171 (7) | 0.0200 (7) | 0.0005 (6) | 0.0020 (5) | −0.0019 (6) |
O4 | 0.0222 (6) | 0.0284 (6) | 0.0204 (6) | −0.0059 (5) | 0.0050 (4) | −0.0068 (5) |
O3 | 0.0203 (6) | 0.0340 (7) | 0.0224 (6) | −0.0086 (5) | 0.0050 (4) | −0.0076 (5) |
C11 | 0.0191 (8) | 0.0222 (8) | 0.0215 (8) | −0.0019 (6) | 0.0027 (6) | 0.0014 (6) |
C12 | 0.0165 (7) | 0.0183 (7) | 0.0184 (7) | 0.0010 (6) | 0.0022 (5) | −0.0005 (6) |
C13 | 0.0196 (7) | 0.0182 (7) | 0.0184 (7) | −0.0027 (6) | 0.0028 (6) | −0.0033 (6) |
C14 | 0.0225 (8) | 0.0287 (9) | 0.0220 (8) | −0.0024 (7) | −0.0033 (6) | −0.0002 (7) |
C15 | 0.0227 (8) | 0.0303 (10) | 0.0350 (10) | 0.0056 (7) | −0.0003 (7) | 0.0035 (8) |
C16 | 0.0270 (9) | 0.0210 (8) | 0.0286 (9) | 0.0020 (7) | 0.0012 (7) | 0.0018 (7) |
C17 | 0.0317 (9) | 0.0290 (9) | 0.0172 (8) | −0.0003 (8) | 0.0028 (6) | 0.0021 (7) |
C18 | 0.0183 (7) | 0.0213 (8) | 0.0224 (8) | −0.0004 (6) | 0.0008 (6) | 0.0014 (6) |
O12 | 0.0307 (6) | 0.0231 (6) | 0.0257 (6) | −0.0080 (5) | −0.0069 (5) | 0.0040 (5) |
O11 | 0.0359 (7) | 0.0216 (6) | 0.0264 (7) | −0.0067 (5) | −0.0091 (5) | 0.0063 (5) |
C19 | 0.0202 (7) | 0.0190 (7) | 0.0216 (8) | −0.0034 (6) | 0.0036 (6) | −0.0015 (6) |
O14 | 0.0255 (6) | 0.0327 (7) | 0.0254 (6) | −0.0106 (5) | 0.0080 (5) | −0.0114 (5) |
O13 | 0.0249 (6) | 0.0360 (7) | 0.0306 (7) | −0.0148 (6) | 0.0108 (5) | −0.0140 (6) |
Geometric parameters (Å, º) top
C1—C7 | 1.536 (2) | C11—C12 | 1.534 (2) |
C1—C6 | 1.537 (2) | C11—C17 | 1.539 (2) |
C1—C2 | 1.563 (2) | C11—C16 | 1.545 (2) |
C1—H1 | 0.99 (2) | C11—H11 | 0.988 (19) |
C2—C8 | 1.503 (2) | C12—C18 | 1.506 (2) |
C2—C3 | 1.566 (2) | C12—C13 | 1.563 (2) |
C2—H2 | 0.995 (19) | C12—H12 | 1.01 (2) |
C3—C9 | 1.505 (2) | C13—C19 | 1.505 (2) |
C3—C4 | 1.537 (2) | C13—C14 | 1.565 (2) |
C3—H3 | 0.98 (2) | C13—H13 | 0.98 (2) |
C4—C7 | 1.539 (2) | C14—C17 | 1.537 (3) |
C4—C5 | 1.543 (2) | C14—C15 | 1.538 (3) |
C4—H4 | 0.970 (19) | C14—H14 | 1.00 (2) |
C5—C6 | 1.559 (2) | C15—C16 | 1.552 (3) |
C5—H51 | 1.000 (19) | C15—H151 | 1.01 (2) |
C5—H52 | 1.00 (2) | C15—H152 | 1.02 (2) |
C6—H61 | 1.01 (2) | C16—H161 | 1.00 (2) |
C6—H62 | 0.97 (2) | C16—H162 | 0.96 (2) |
C7—H71 | 0.99 (2) | C17—H171 | 1.01 (2) |
C7—H72 | 0.99 (2) | C17—H172 | 0.97 (2) |
C8—O2 | 1.215 (2) | C18—O12 | 1.222 (2) |
C8—O1 | 1.329 (2) | C18—O11 | 1.318 (2) |
O1—H01 | 0.88 (3) | O11—H011 | 0.94 (3) |
C9—O4 | 1.2251 (19) | C19—O14 | 1.219 (2) |
C9—O3 | 1.3222 (19) | C19—O13 | 1.3196 (19) |
O3—H03 | 0.96 (3) | O13—H013 | 0.92 (3) |
| | | |
C7—C1—C6 | 100.61 (13) | C12—C11—C17 | 99.09 (13) |
C7—C1—C2 | 101.16 (12) | C12—C11—C16 | 110.36 (14) |
C6—C1—C2 | 110.15 (13) | C17—C11—C16 | 102.59 (14) |
C7—C1—H1 | 115.5 (12) | C12—C11—H11 | 111.9 (11) |
C6—C1—H1 | 115.2 (11) | C17—C11—H11 | 118.0 (11) |
C2—C1—H1 | 112.7 (11) | C16—C11—H11 | 113.7 (11) |
C8—C2—C1 | 110.42 (13) | C18—C12—C11 | 116.81 (14) |
C8—C2—C3 | 115.75 (13) | C18—C12—C13 | 119.03 (13) |
C1—C2—C3 | 102.41 (12) | C11—C12—C13 | 103.21 (12) |
C8—C2—H2 | 109.4 (11) | C18—C12—H12 | 101.9 (11) |
C1—C2—H2 | 108.0 (11) | C11—C12—H12 | 108.8 (12) |
C3—C2—H2 | 110.4 (11) | C13—C12—H12 | 106.5 (12) |
C9—C3—C4 | 118.51 (13) | C19—C13—C12 | 116.71 (13) |
C9—C3—C2 | 116.95 (13) | C19—C13—C14 | 110.69 (14) |
C4—C3—C2 | 103.27 (12) | C12—C13—C14 | 102.03 (13) |
C9—C3—H3 | 102.5 (12) | C19—C13—H13 | 106.6 (12) |
C4—C3—H3 | 108.0 (12) | C12—C13—H13 | 111.5 (11) |
C2—C3—H3 | 106.9 (12) | C14—C13—H13 | 109.2 (11) |
C3—C4—C7 | 99.07 (12) | C17—C14—C15 | 100.43 (14) |
C3—C4—C5 | 111.10 (13) | C17—C14—C13 | 102.20 (14) |
C7—C4—C5 | 102.05 (13) | C15—C14—C13 | 109.31 (14) |
C3—C4—H4 | 113.5 (11) | C17—C14—H14 | 116.5 (13) |
C7—C4—H4 | 115.1 (11) | C15—C14—H14 | 114.8 (13) |
C5—C4—H4 | 114.5 (10) | C13—C14—H14 | 112.3 (13) |
C4—C5—C6 | 103.35 (13) | C14—C15—C16 | 102.57 (14) |
C4—C5—H51 | 112.2 (11) | C14—C15—H151 | 112.9 (13) |
C6—C5—H51 | 113.1 (11) | C16—C15—H151 | 114.5 (13) |
C4—C5—H52 | 109.2 (12) | C14—C15—H152 | 108.7 (13) |
C6—C5—H52 | 111.2 (12) | C16—C15—H152 | 110.5 (13) |
H51—C5—H52 | 107.8 (15) | H151—C15—H152 | 107.6 (18) |
C1—C6—C5 | 102.86 (13) | C11—C16—C15 | 103.38 (14) |
C1—C6—H61 | 112.2 (12) | C11—C16—H161 | 110.9 (12) |
C5—C6—H61 | 113.5 (12) | C15—C16—H161 | 112.4 (12) |
C1—C6—H62 | 110.0 (13) | C11—C16—H162 | 109.5 (13) |
C5—C6—H62 | 112.2 (13) | C15—C16—H162 | 111.5 (12) |
H61—C6—H62 | 106.1 (18) | H161—C16—H162 | 109.1 (17) |
C1—C7—C4 | 94.67 (12) | C14—C17—C11 | 94.23 (13) |
C1—C7—H71 | 113.4 (12) | C14—C17—H171 | 114.7 (13) |
C4—C7—H71 | 112.0 (12) | C11—C17—H171 | 113.4 (12) |
C1—C7—H72 | 111.4 (13) | C14—C17—H172 | 111.6 (13) |
C4—C7—H72 | 112.1 (12) | C11—C17—H172 | 112.5 (13) |
H71—C7—H72 | 112.2 (17) | H171—C17—H172 | 109.8 (18) |
O2—C8—O1 | 118.87 (15) | O12—C18—O11 | 123.51 (15) |
O2—C8—C2 | 124.21 (14) | O12—C18—C12 | 122.83 (15) |
O1—C8—C2 | 116.85 (14) | O11—C18—C12 | 113.37 (14) |
C8—O1—H01 | 110.1 (19) | C18—O11—H011 | 109.0 (19) |
O4—C9—O3 | 123.42 (14) | O14—C19—O13 | 123.19 (15) |
O4—C9—C3 | 123.91 (14) | O14—C19—C13 | 124.95 (14) |
O3—C9—C3 | 112.52 (13) | O13—C19—C13 | 111.81 (14) |
C9—O3—H03 | 108.3 (17) | C19—O13—H013 | 110.5 (18) |
| | | |
O2—C8—C2—C3 | −18.6 (2) | O12—C18—C12—C13 | 129.44 (17) |
C8—C2—C3—C9 | −18.4 (2) | C18—C12—C13—C19 | −19.7 (2) |
C2—C3—C9—O4 | 124.25 (17) | C12—C13—C19—O14 | −12.6 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H01···O2i | 0.88 (3) | 1.85 (3) | 2.7371 (19) | 177 (3) |
O3—H03···O14 | 0.96 (3) | 1.74 (3) | 2.6996 (17) | 174 (3) |
O11—H011···O12ii | 0.94 (3) | 1.69 (3) | 2.6222 (18) | 175 (3) |
O13—H013···O4 | 0.92 (3) | 1.72 (3) | 2.6294 (18) | 170 (3) |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | C9H12O4 |
Mr | 184.19 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 150 |
a, b, c (Å) | 20.737 (5), 9.310 (2), 9.003 (2) |
β (°) | 92.59 (1) |
V (Å3) | 1736.4 (7) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.45 × 0.35 × 0.15 |
|
Data collection |
Diffractometer | SMART 1K CCD area-detector diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12920, 4594, 3553 |
Rint | 0.049 |
(sin θ/λ)max (Å−1) | 0.682 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.123, 1.14 |
No. of reflections | 4594 |
No. of parameters | 331 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.32, −0.35 |
Selected geometric parameters (Å, º) topC1—C7 | 1.536 (2) | C11—C12 | 1.534 (2) |
C1—C6 | 1.537 (2) | C11—C17 | 1.539 (2) |
C1—C2 | 1.563 (2) | C11—C16 | 1.545 (2) |
C2—C8 | 1.503 (2) | C12—C18 | 1.506 (2) |
C2—C3 | 1.566 (2) | C12—C13 | 1.563 (2) |
C3—C9 | 1.505 (2) | C13—C19 | 1.505 (2) |
C3—C4 | 1.537 (2) | C13—C14 | 1.565 (2) |
C4—C7 | 1.539 (2) | C14—C17 | 1.537 (3) |
C4—C5 | 1.543 (2) | C14—C15 | 1.538 (3) |
C5—C6 | 1.559 (2) | C15—C16 | 1.552 (3) |
C8—O2 | 1.215 (2) | C18—O12 | 1.222 (2) |
C8—O1 | 1.329 (2) | C18—O11 | 1.318 (2) |
C9—O4 | 1.2251 (19) | C19—O14 | 1.219 (2) |
C9—O3 | 1.3222 (19) | C19—O13 | 1.3196 (19) |
| | | |
C7—C1—C6 | 100.61 (13) | C12—C11—C17 | 99.09 (13) |
C7—C1—C2 | 101.16 (12) | C12—C11—C16 | 110.36 (14) |
C6—C1—C2 | 110.15 (13) | C17—C11—C16 | 102.59 (14) |
C8—C2—C1 | 110.42 (13) | C18—C12—C11 | 116.81 (14) |
C8—C2—C3 | 115.75 (13) | C18—C12—C13 | 119.03 (13) |
C1—C2—C3 | 102.41 (12) | C11—C12—C13 | 103.21 (12) |
C9—C3—C4 | 118.51 (13) | C19—C13—C12 | 116.71 (13) |
C9—C3—C2 | 116.95 (13) | C19—C13—C14 | 110.69 (14) |
C4—C3—C2 | 103.27 (12) | C12—C13—C14 | 102.03 (13) |
C3—C4—C7 | 99.07 (12) | C17—C14—C15 | 100.43 (14) |
C3—C4—C5 | 111.10 (13) | C17—C14—C13 | 102.20 (14) |
C7—C4—C5 | 102.05 (13) | C15—C14—C13 | 109.31 (14) |
C4—C5—C6 | 103.35 (13) | C14—C15—C16 | 102.57 (14) |
C1—C6—C5 | 102.86 (13) | C11—C16—C15 | 103.38 (14) |
C1—C7—C4 | 94.67 (12) | C14—C17—C11 | 94.23 (13) |
| | | |
O2—C8—C2—C3 | −18.6 (2) | O12—C18—C12—C13 | 129.44 (17) |
C8—C2—C3—C9 | −18.4 (2) | C18—C12—C13—C19 | −19.7 (2) |
C2—C3—C9—O4 | 124.25 (17) | C12—C13—C19—O14 | −12.6 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H01···O2i | 0.88 (3) | 1.85 (3) | 2.7371 (19) | 177 (3) |
O3—H03···O14 | 0.96 (3) | 1.74 (3) | 2.6996 (17) | 174 (3) |
O11—H011···O12ii | 0.94 (3) | 1.69 (3) | 2.6222 (18) | 175 (3) |
O13—H013···O4 | 0.92 (3) | 1.72 (3) | 2.6294 (18) | 170 (3) |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1. |
The title compound, (I), alternatively called bicyclo[2.2.1]heptane-endo-cis-2,3-dicarboxylic acid, was studied as part of a series of small-molecule models of organic polymers influencing the crystallization of inorganic salts, particularly CaCO3 (Megson, 1997; Feast et al., 2002).
Compound (I) was prepared following the usual route through `kinetic' (at moderate temperature) Diels–Alder addition of cyclopentadiene to maleic anhydride, hydrolysis of the anhydride into 2-norbornene-endo-cis-5,6-dicarboxylic acid, (II), and hydrogenation of the C═C bond of the latter (Diels & Alder, 1928; Alder & Stein, 1933a,b). The only previous structural characterization of (I) was in the form of a copper complex of its monoanion (Geraghty et al., 1999). However, the precision of this structure is too low (R = 0.18) to permit any meaningful comparison with the present one.
The asymmetric unit of (I) comprises two molecules, A and B (Fig. 1). Both show large torsion angles (HO2)C—C2—C3—C(O2H) of −18.4 (2) and −19.7 (2)°. Obviously, this distortion can be attributed to the steric repulsion between cis-carboxylic acid groups. However, the corresponding torsion angles are much smaller in some closely related molecules, where the steric overcrowding must be comparable, viz. 6.2° in (II) (Bolte et al., 2000), 5.2° in its potassium salt (Cser & Sasvari, 1976), 3.6 (2)° in the endo–cis isomer of (I) (Batsanov & Hesselink, 2002b), 4.7 (2), 0.6 (2) and 6.3 (2)° in the three independent molecules of the endo–cis isomer of (II) (Batsanov & Hesselink, 2002a), 12.2 and 11.5° in the isostructural Mn and Co complexes, containing anions of (II) as monodentate ligands (Hartung et al., 1993), and 4.5° in the Mn complex with a bidentate dianion of (II), coordinated via both carboxylate groups (Devereux et al., 1995). A possible explanation is a peculiar orientation of the carboxylic acid groups in (I). In both independent molecules, one of the carboxyl C═O bonds is almost eclipsed with the norbornane C2—C3 bond. Thus, a carbonyl O atom of one carboxylic acid group forms a short intramolecular contact with the C atom of the other carboxylic acid group, viz. O2···C9 = 2.694 (2) Å and O14···C18 = 2.762 (2) Å, much shorter than the normal van der Waals O···C contact distance of 3.24 Å (Rowland & Taylor, 1996). The conformation of (II) is somewhat similar, but the corresponding O···C contact is much longer, 2.92 Å. In other analogues (see above), carboxylic acid groups are inclined with respect to the C1/C2/C3/C4 plane in the same direction, in a `propeller' conformation.
Molecules A and B are linked by a pair of hydrogen bonds, as shown in Fig. 1. The other carboxylic acid group of molecule B forms a similar pair of hydrogen bonds with its inversion equivalent, thus forming a A···B···Bi···Ai tetramer (Fig. 2). The remaining carboxylic acid group of molecule A adopts a less common anti conformation [the O2═C8—O1—H01 torsion angle is 178 (3)°], and forms with its equivalents (related by the c-glide plane) an infinite chain of hydrogen bonds –H01···O2═C8—O1—H01···O2═C8–, running parallel to the z axis. The hydrogen bonds of the latter type link the tetramers into a layer, parallel to the crystallographic (100) plane and roughly perpendicular to the longest dimension of the tetramer itself.