Acta Cryst. (2009). E65, o1217 [ doi:10.1107/S1600536809016468 ]
The title compound, C9H4F6O2, contains two molecules in the asymmetric unit, one of which exhibits disorder in both of its trifluoromethyl groups. The dihedral angles between the benzene ring and the carboxyl group are 71.5 (2) and 99.3 (2)° in the two independent molecules. The compound exhibits a catemeric structure resulting from intermolecular O-H
O hydrogen bonding between the carboxyl groups.
The title compound was prepared following the literature methods (Dmowski & Piasecka-Macieiewska, 1998) with a slight modification. The compound crystallized from the oily reaction mixture that remained after acidification of the potassium benzoate salt with concentrated HCl, extraction of the organic components with toluene, drying of the organic fraction with magnesium sulfate and concentration by rotary evaporation.
H atoms were placed in geometrically idealized positions with C—H = 0.93 Å and O—H = 0.82 Å and constrained to ride on the parent atom with Uiso(H) = 1.2 Ueq(C) or 1.5 Ueq(O). The trifluoromethyl groups belonging to C17 and C18 were modeled with a two-site disorder of the F atoms with refined site occupancy factors of 0.569 (5):0.431 (5) and 0.689 (5):0.311 (5), respectively.
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
![[Figure 1]](./bi2369fig1thm.gif)
| Fig. 1. The two molecules in the asymmetric unit with displacement ellipsoids shown at 50% probability for non-H atoms. For the disordered CF3 groups, both disorder components are shown. |
![[Figure 2]](./bi2369fig2thm.gif)
| Fig. 2. Ball and stick representation featuring the catemeric structure formed through O—H···O hydrogen bonding. H atoms not involved in H-bonding and the CF3 groups have been omitted for clarity. |
| C9H4F6O2 | F000 = 1024 |
| Mr = 258.12 | Dx = 1.738 Mg m−3 |
| Monoclinic, P21/c | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -P 2ybc | Cell parameters from 6970 reflections |
| a = 10.873 (2) Å | θ = 2.3–28.0º |
| b = 15.755 (3) Å | µ = 0.20 mm−1 |
| c = 11.561 (2) Å | T = 296 K |
| β = 94.961 (2)º | Block, colorless |
| V = 1973.0 (6) Å3 | 0.39 × 0.31 × 0.26 mm |
| Z = 8 |
| Bruker APEXII CCD diffractometer | 3438 independent reflections |
| Radiation source: fine-focus sealed tube | 2889 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.021 |
| T = 296 K | θmax = 25.0º |
| φ and ω scans | θmin = 2.2º |
| Absorption correction: multi-scan (SADABS; Bruker, 2008) | h = −12→12 |
| Tmin = 0.834, Tmax = 0.951 | k = −18→18 |
| 12904 measured reflections | l = −13→11 |
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
| R[F2 > 2σ(F2)] = 0.039 | H-atom parameters constrained |
| wR(F2) = 0.112 | w = 1/[σ2(Fo2) + (0.058P)2 + 0.5224P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.02 | (Δ/σ)max < 0.001 |
| 3438 reflections | Δρmax = 0.21 e Å−3 |
| 331 parameters | Δρmin = −0.23 e Å−3 |
| Primary atom site location: structure-invariant direct methods | Extinction correction: none |
| C9H4F6O2 | V = 1973.0 (6) Å3 |
| Mr = 258.12 | Z = 8 |
| Monoclinic, P21/c | Mo Kα |
| a = 10.873 (2) Å | µ = 0.20 mm−1 |
| b = 15.755 (3) Å | T = 296 K |
| c = 11.561 (2) Å | 0.39 × 0.31 × 0.26 mm |
| β = 94.961 (2)º |
| Bruker APEXII CCD diffractometer | 3438 independent reflections |
| Absorption correction: multi-scan (SADABS; Bruker, 2008) | 2889 reflections with I > 2σ(I) |
| Tmin = 0.834, Tmax = 0.951 | Rint = 0.021 |
| 12904 measured reflections |
| R[F2 > 2σ(F2)] = 0.039 | 331 parameters |
| wR(F2) = 0.112 | H-atom parameters constrained |
| S = 1.02 | Δρmax = 0.21 e Å−3 |
| 3438 reflections | Δρmin = −0.23 e Å−3 |
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. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| C1 | 0.25273 (16) | 0.14562 (11) | 0.00186 (14) | 0.0532 (4) | |
| C2 | 0.34011 (15) | 0.08652 (10) | 0.07069 (14) | 0.0490 (4) | |
| C3 | 0.43893 (16) | 0.11687 (12) | 0.14433 (16) | 0.0564 (4) | |
| C4 | 0.51596 (17) | 0.06028 (14) | 0.20807 (17) | 0.0666 (5) | |
| H4A | 0.5807 | 0.0808 | 0.2581 | 0.080* | |
| C5 | 0.49740 (19) | −0.02557 (14) | 0.19783 (18) | 0.0689 (5) | |
| H5A | 0.5498 | −0.0629 | 0.2405 | 0.083* | |
| C6 | 0.40178 (18) | −0.05640 (12) | 0.12489 (16) | 0.0614 (5) | |
| H6A | 0.3900 | −0.1147 | 0.1175 | 0.074* | |
| C7 | 0.32257 (15) | −0.00131 (10) | 0.06209 (14) | 0.0508 (4) | |
| C8 | 0.46743 (19) | 0.20978 (14) | 0.1562 (2) | 0.0756 (6) | |
| F1 | 0.5244 (2) | 0.22865 (11) | 0.25885 (18) | 0.1361 (7) | |
| F2 | 0.53907 (15) | 0.23619 (9) | 0.07602 (19) | 0.1232 (7) | |
| F3 | 0.36850 (12) | 0.25931 (8) | 0.14440 (14) | 0.0893 (4) | |
| C9 | 0.21830 (18) | −0.03876 (12) | −0.01534 (17) | 0.0632 (5) | |
| F4 | 0.11518 (12) | −0.04286 (10) | 0.03733 (13) | 0.0975 (4) | |
| F5 | 0.19338 (14) | 0.00483 (8) | −0.11254 (11) | 0.0911 (4) | |
| F6 | 0.24344 (13) | −0.11707 (8) | −0.04877 (12) | 0.0906 (4) | |
| C10 | 0.10257 (17) | 0.15284 (11) | 0.30263 (15) | 0.0545 (4) | |
| C11 | 0.07034 (16) | 0.13002 (10) | 0.42282 (14) | 0.0514 (4) | |
| C12 | −0.04150 (17) | 0.15569 (11) | 0.46310 (15) | 0.0561 (4) | |
| C13 | −0.0643 (2) | 0.14110 (13) | 0.57757 (18) | 0.0711 (5) | |
| H13A | −0.1380 | 0.1593 | 0.6045 | 0.085* | |
| C14 | 0.0220 (2) | 0.09977 (15) | 0.65140 (18) | 0.0801 (6) | |
| H14A | 0.0066 | 0.0906 | 0.7283 | 0.096* | |
| C15 | 0.1301 (2) | 0.07212 (14) | 0.61252 (17) | 0.0730 (6) | |
| H15A | 0.1869 | 0.0430 | 0.6626 | 0.088* | |
| C16 | 0.15558 (18) | 0.08709 (12) | 0.49899 (16) | 0.0603 (5) | |
| O1 | 0.14736 (11) | 0.15753 (8) | 0.02411 (10) | 0.0606 (3) | |
| O2 | 0.30404 (14) | 0.18036 (9) | −0.08444 (12) | 0.0751 (4) | |
| H2A | 0.2549 | 0.2129 | −0.1192 | 0.113* | |
| O3 | 0.05615 (13) | 0.10397 (9) | 0.22093 (11) | 0.0684 (4) | |
| H3A | 0.0818 | 0.1182 | 0.1592 | 0.103* | |
| O4 | 0.16936 (19) | 0.21110 (11) | 0.28586 (13) | 0.0999 (6) | |
| C17 | −0.13950 (10) | 0.19782 (8) | 0.38373 (10) | 0.0726 (5) | |
| F7A | −0.09321 (12) | 0.25255 (8) | 0.31618 (10) | 0.1010 (13) | 0.569 (5) |
| F8A | −0.19164 (10) | 0.13805 (10) | 0.31178 (10) | 0.0901 (11) | 0.569 (5) |
| F9A | −0.22489 (10) | 0.23045 (8) | 0.43893 (12) | 0.139 (2) | 0.569 (5) |
| F7B | −0.17175 (10) | 0.16347 (9) | 0.28614 (11) | 0.144 (3) | 0.431 (5) |
| F9B | −0.10986 (11) | 0.28028 (10) | 0.35381 (9) | 0.1164 (19) | 0.431 (5) |
| F8B | −0.24254 (11) | 0.21614 (8) | 0.43317 (12) | 0.0970 (19) | 0.431 (5) |
| C18 | 0.27540 (10) | 0.05569 (8) | 0.46034 (11) | 0.0751 (6) | |
| F10A | 0.26369 (10) | 0.01894 (8) | 0.35789 (13) | 0.0877 (11) | 0.689 (5) |
| F11A | 0.36230 (10) | 0.11205 (10) | 0.46284 (11) | 0.1163 (14) | 0.689 (5) |
| F12A | 0.32020 (9) | −0.01015 (9) | 0.52898 (13) | 0.1142 (11) | 0.689 (5) |
| F10B | 0.33236 (9) | 0.12165 (10) | 0.40107 (11) | 0.108 (2) | 0.311 (5) |
| F12B | 0.35672 (10) | 0.03614 (8) | 0.54011 (13) | 0.125 (3) | 0.311 (5) |
| F11B | 0.26173 (10) | 0.00490 (9) | 0.37781 (12) | 0.154 (5) | 0.311 (5) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| C1 | 0.0618 (10) | 0.0542 (9) | 0.0442 (9) | 0.0104 (7) | 0.0085 (7) | 0.0040 (7) |
| C2 | 0.0497 (8) | 0.0552 (9) | 0.0428 (8) | 0.0073 (7) | 0.0077 (7) | 0.0041 (7) |
| C3 | 0.0508 (9) | 0.0623 (10) | 0.0566 (10) | 0.0011 (8) | 0.0089 (8) | −0.0018 (8) |
| C4 | 0.0507 (10) | 0.0864 (14) | 0.0607 (11) | 0.0064 (9) | −0.0062 (8) | −0.0020 (10) |
| C5 | 0.0631 (11) | 0.0776 (13) | 0.0641 (12) | 0.0199 (10) | −0.0061 (9) | 0.0105 (10) |
| C6 | 0.0689 (11) | 0.0567 (10) | 0.0582 (11) | 0.0113 (8) | 0.0025 (9) | 0.0077 (8) |
| C7 | 0.0535 (9) | 0.0551 (9) | 0.0436 (9) | 0.0056 (7) | 0.0044 (7) | 0.0031 (7) |
| C8 | 0.0608 (11) | 0.0702 (12) | 0.0965 (16) | −0.0044 (10) | 0.0112 (11) | −0.0113 (11) |
| F1 | 0.1536 (16) | 0.0987 (11) | 0.1447 (15) | −0.0163 (10) | −0.0518 (13) | −0.0361 (10) |
| F2 | 0.1085 (11) | 0.0773 (9) | 0.1956 (19) | −0.0172 (8) | 0.0813 (12) | −0.0035 (10) |
| F3 | 0.0828 (8) | 0.0627 (7) | 0.1245 (12) | 0.0037 (6) | 0.0221 (8) | −0.0124 (7) |
| C9 | 0.0672 (11) | 0.0597 (11) | 0.0615 (11) | 0.0030 (9) | −0.0013 (9) | 0.0003 (9) |
| F4 | 0.0628 (7) | 0.1270 (12) | 0.1024 (10) | −0.0164 (7) | 0.0050 (7) | −0.0162 (9) |
| F5 | 0.1201 (11) | 0.0832 (8) | 0.0628 (7) | −0.0013 (7) | −0.0338 (7) | 0.0035 (6) |
| F6 | 0.1079 (10) | 0.0632 (7) | 0.0972 (10) | 0.0013 (6) | −0.0118 (8) | −0.0186 (6) |
| C10 | 0.0609 (10) | 0.0574 (10) | 0.0454 (9) | −0.0107 (8) | 0.0059 (7) | −0.0075 (7) |
| C11 | 0.0640 (10) | 0.0495 (9) | 0.0408 (8) | −0.0136 (7) | 0.0046 (7) | −0.0079 (7) |
| C12 | 0.0679 (11) | 0.0526 (9) | 0.0486 (9) | −0.0112 (8) | 0.0089 (8) | −0.0117 (7) |
| C13 | 0.0839 (13) | 0.0731 (12) | 0.0591 (12) | −0.0128 (10) | 0.0231 (10) | −0.0126 (10) |
| C14 | 0.1122 (18) | 0.0860 (15) | 0.0440 (10) | −0.0135 (13) | 0.0171 (11) | 0.0010 (10) |
| C15 | 0.0927 (15) | 0.0781 (13) | 0.0473 (10) | −0.0043 (11) | 0.0009 (10) | 0.0031 (9) |
| C16 | 0.0698 (11) | 0.0606 (10) | 0.0499 (10) | −0.0094 (9) | 0.0017 (8) | −0.0042 (8) |
| O1 | 0.0575 (7) | 0.0753 (8) | 0.0490 (7) | 0.0156 (6) | 0.0041 (5) | 0.0077 (6) |
| O2 | 0.0858 (9) | 0.0756 (9) | 0.0677 (8) | 0.0301 (7) | 0.0294 (7) | 0.0303 (7) |
| O3 | 0.0850 (9) | 0.0783 (9) | 0.0420 (6) | −0.0259 (7) | 0.0064 (6) | −0.0103 (6) |
| O4 | 0.1505 (15) | 0.0963 (11) | 0.0575 (9) | −0.0706 (11) | 0.0357 (9) | −0.0223 (8) |
| C17 | 0.0723 (13) | 0.0783 (14) | 0.0675 (13) | 0.0023 (11) | 0.0087 (10) | −0.0092 (11) |
| F7A | 0.115 (2) | 0.088 (2) | 0.099 (2) | 0.0095 (16) | 0.0008 (17) | 0.0347 (18) |
| F8A | 0.0718 (17) | 0.0977 (19) | 0.095 (2) | −0.0026 (14) | −0.0251 (14) | −0.0169 (16) |
| F9A | 0.153 (4) | 0.144 (3) | 0.121 (4) | 0.087 (3) | 0.022 (3) | −0.030 (3) |
| F7B | 0.156 (5) | 0.187 (5) | 0.079 (3) | 0.090 (4) | −0.040 (3) | −0.064 (3) |
| F9B | 0.100 (3) | 0.097 (3) | 0.151 (4) | 0.009 (2) | 0.005 (3) | 0.039 (3) |
| F8B | 0.055 (2) | 0.146 (4) | 0.092 (4) | 0.006 (3) | 0.018 (2) | 0.007 (3) |
| C18 | 0.0736 (13) | 0.0807 (15) | 0.0699 (14) | −0.0014 (11) | 0.0001 (11) | −0.0030 (11) |
| F10A | 0.082 (2) | 0.116 (2) | 0.0655 (15) | 0.0210 (16) | 0.0119 (13) | −0.0152 (16) |
| F11A | 0.0730 (14) | 0.115 (2) | 0.161 (3) | −0.0229 (14) | 0.0114 (17) | −0.033 (2) |
| F12A | 0.1041 (18) | 0.130 (2) | 0.107 (2) | 0.0381 (17) | −0.0002 (15) | 0.0232 (16) |
| F10B | 0.076 (3) | 0.109 (4) | 0.146 (6) | 0.006 (3) | 0.039 (3) | 0.029 (4) |
| F12B | 0.084 (3) | 0.204 (9) | 0.081 (4) | 0.039 (5) | −0.020 (3) | 0.023 (4) |
| F11B | 0.099 (7) | 0.145 (7) | 0.222 (11) | −0.022 (5) | 0.038 (6) | −0.109 (7) |
| C1—O1 | 1.210 (2) | C11—C12 | 1.399 (3) |
| C1—O2 | 1.305 (2) | C12—C13 | 1.387 (3) |
| C1—C2 | 1.507 (2) | C12—C17 | 1.500 (2) |
| C2—C3 | 1.396 (2) | C13—C14 | 1.376 (3) |
| C2—C7 | 1.399 (2) | C13—H13A | 0.930 |
| C3—C4 | 1.390 (3) | C14—C15 | 1.365 (3) |
| C3—C8 | 1.500 (3) | C14—H14A | 0.930 |
| C4—C5 | 1.371 (3) | C15—C16 | 1.385 (3) |
| C4—H4A | 0.930 | C15—H15A | 0.930 |
| C5—C6 | 1.370 (3) | C16—C18 | 1.498 (2) |
| C5—H5A | 0.930 | O2—H2A | 0.820 |
| C6—C7 | 1.383 (2) | O3—H3A | 0.820 |
| C6—H6A | 0.930 | C17—F7B | 1.2729 (11) |
| C7—C9 | 1.503 (3) | C17—F9A | 1.2791 (11) |
| C8—F1 | 1.324 (3) | C17—F7A | 1.2941 (11) |
| C8—F3 | 1.326 (3) | C17—F8B | 1.3326 (12) |
| C8—F2 | 1.328 (3) | C17—F8A | 1.3485 (12) |
| C9—F4 | 1.323 (2) | C17—F9B | 1.3895 (12) |
| C9—F5 | 1.325 (2) | C18—F11B | 1.2443 (10) |
| C9—F6 | 1.328 (2) | C18—F12B | 1.2593 (11) |
| C10—O4 | 1.197 (2) | C18—F11A | 1.2952 (11) |
| C10—O3 | 1.287 (2) | C18—F10A | 1.3146 (11) |
| C10—C11 | 1.506 (2) | C18—F12A | 1.3697 (11) |
| C11—C16 | 1.397 (3) | C18—F10B | 1.4165 (12) |
| O1—C1—O2 | 124.93 (16) | C13—C12—C17 | 118.76 (16) |
| O1—C1—C2 | 123.28 (15) | C11—C12—C17 | 121.09 (14) |
| O2—C1—C2 | 111.78 (14) | C14—C13—C12 | 120.1 (2) |
| C3—C2—C7 | 118.36 (15) | C14—C13—H13A | 119.9 |
| C3—C2—C1 | 121.80 (15) | C12—C13—H13A | 119.9 |
| C7—C2—C1 | 119.84 (15) | C15—C14—C13 | 120.45 (19) |
| C4—C3—C2 | 120.00 (17) | C15—C14—H14A | 119.8 |
| C4—C3—C8 | 117.85 (18) | C13—C14—H14A | 119.8 |
| C2—C3—C8 | 122.14 (17) | C14—C15—C16 | 120.4 (2) |
| C5—C4—C3 | 120.63 (18) | C14—C15—H15A | 119.8 |
| C5—C4—H4A | 119.7 | C16—C15—H15A | 119.8 |
| C3—C4—H4A | 119.7 | C15—C16—C11 | 120.24 (19) |
| C6—C5—C4 | 120.08 (17) | C15—C16—C18 | 118.50 (17) |
| C6—C5—H5A | 120.0 | C11—C16—C18 | 121.25 (15) |
| C4—C5—H5A | 120.0 | C1—O2—H2A | 109.5 |
| C5—C6—C7 | 120.36 (18) | C10—O3—H3A | 109.5 |
| C5—C6—H6A | 119.8 | F9A—C17—F7A | 111.7 |
| C7—C6—H6A | 119.8 | F7B—C17—F8B | 107.2 |
| C6—C7—C2 | 120.55 (16) | F9A—C17—F8A | 107.7 |
| C6—C7—C9 | 118.00 (16) | F7A—C17—F8A | 104.9 |
| C2—C7—C9 | 121.45 (15) | F7B—C17—F9B | 103.2 |
| F1—C8—F3 | 105.80 (19) | F8B—C17—F9B | 97.2 |
| F1—C8—F2 | 107.3 (2) | F7B—C17—C12 | 118.73 (8) |
| F3—C8—F2 | 105.3 (2) | F9A—C17—C12 | 112.38 (8) |
| F1—C8—C3 | 112.2 (2) | F7A—C17—C12 | 111.79 (8) |
| F3—C8—C3 | 113.92 (17) | F8B—C17—C12 | 114.37 (8) |
| F2—C8—C3 | 111.77 (18) | F8A—C17—C12 | 107.87 (8) |
| F4—C9—F5 | 107.23 (17) | F9B—C17—C12 | 113.47 (8) |
| F4—C9—F6 | 107.01 (17) | F11B—C18—F12B | 115.7 |
| F5—C9—F6 | 105.48 (16) | F11A—C18—F10A | 109.6 |
| F4—C9—C7 | 111.76 (16) | F11A—C18—F12A | 106.5 |
| F5—C9—C7 | 112.95 (16) | F10A—C18—F12A | 101.0 |
| F6—C9—C7 | 111.98 (16) | F11B—C18—F10B | 97.4 |
| O4—C10—O3 | 123.01 (17) | F12B—C18—F10B | 103.0 |
| O4—C10—C11 | 121.71 (15) | F11B—C18—C16 | 113.07 (8) |
| O3—C10—C11 | 115.25 (15) | F12B—C18—C16 | 115.85 (8) |
| C16—C11—C12 | 118.60 (16) | F11A—C18—C16 | 114.75 (8) |
| C16—C11—C10 | 120.19 (16) | F10A—C18—C16 | 113.29 (8) |
| C12—C11—C10 | 121.10 (16) | F12A—C18—C16 | 110.63 (9) |
| C13—C12—C11 | 120.14 (18) | F10B—C18—C16 | 109.27 (9) |
| C7—C2—C1—O1 | 71.5 (2) | C12—C11—C10—O4 | 99.3 (2) |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O2—H2A···O4i | 0.82 | 1.82 | 2.6340 (19) | 169 |
| O3—H3A···O1 | 0.82 | 1.88 | 2.6951 (18) | 176 |
| Symmetry codes: (i) x, −y+1/2, z−1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O2—H2A···O4i | 0.82 | 1.82 | 2.6340 (19) | 169 |
| O3—H3A···O1 | 0.82 | 1.88 | 2.6951 (18) | 176 |
| Symmetry codes: (i) x, −y+1/2, z−1/2. |
The authors thank Saint Mary's University for providing funding in the form of initial operating funds (JDM) and student funding through the Summer Employment Experience Program (JMT).
Bruker (2008). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
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The title molecule crystallizes in a catemer motif, a relatively rare form compared to the typical dimeric motif exhibited by benzoic acids resulting from intermolecular hydrogen bonding between the carboxylic acid groups (Moorthy et al., 2002). The sterically bulky o-CF3 groups result in the carboxylic acid fragments being twisted with respect to the aryl ring. This results in dihedral angles between the aryl ring and carboxylic acid fragments of C7—C2—C1—O1 = 71.5 (2)° and C12—C11—C10—O4 = 99.3 (2)°.