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accessEthyl 2-(2,3,4,5,6-Pentabromophenyl)acetate
aAlbemarle Process Development Center, Albemarle Corporation, PO Box 341, Baton Rouge, LA 70821, USA, and bDepartment of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804, USA
*Correspondence e-mail: ffroncz@lsu.edu
The title compound PBPEA, C10H7Br5O2, has its ethyl acetate portion nearly orthogonal to the benzene ring, with a C—C—C—C torsion angle of 88.3 (5)°. The packing involves an intermolecular contact with a Br⋯Br distance of 3.491 (1) Å, having C—Br⋯Br angles of 173.4 (2) and 106.0 (2)°. The crystal studied was an inversion twin.
Related literature
For synthetic procedures, see: Holmes & Lightner (1995![[Holmes, D. L. & Lightner, D. A. (1995). Tetrahedron, 51, 1607-1622.]](../../../../../../logos/arrows/e_arr.gif "Holmes, D. L. & Lightner, D. A. (1995). Tetrahedron, 51, 1607-1622.")
); Adams & Thal (1941). For a description of the Cambridge Structural Database, see: Allen (2002). For related structures, see: Eriksson & Hu (2002a,b); Eriksson et al. (1999); Köppen et al. (2007); Krigbaum & Wildman (1971); Mrse et al. (2000); Pedireddi et al. (1994); Williams et al. (1985).
![[Scheme 1]](jj2038scheme1.gif)
Experimental
Crystal data
|
Data collection: COLLECT (Nonius, 2000); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
Supporting information
contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810025626/jj2038sup1.cif
Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810025626/jj2038Isup2.hkl
Preparation of PBBN (9263–183):(Fig. 3) To a 3-neck, 100-ml RBF, fitted with a nitrogen inlet, thermocouple and septum, was charged the starting PBBB (5 g, 8.84 mmol) in DMSO (50 ml). To this slurry was added the sodium cyanide (0.44 g, 8.98 mmol) in one portion at room temperature and the reaction mixture immediately became mint in color. This color quickly dissipated and became brown. The reaction was allowed to heat for one hour, with vigorous stirring, at 80 °C under an inert atmosphere. Upon conclusion, the contents were filtered hot to remove an insoluble material (1.01 g) and the resulting brown filtrate was treated with water to precipitate the PBBN product. The light brown solids (fluffy) were collected via suction filtration. Drying overnight afforded a dark brown solid. Solids were rinsed with IPA and filtered to provide 2.58 g PBBN material (light brown in color and free flowing) upon drying (~57% yield), mp = 178.6 & 179.5 °C. Purity of the crude PBBN was found to be ~70% (trimethylbenzene as internal standard) and was used without further purification. The trace unreacted sodium cyanide was destroyed by bleach solution in the aqueous DMSO solution.
Preparation of PBPEA (9263–189): (Fig. 3) To a 3-neck, 100-ml RBF, fitted with a reflux condenser, thermocouple, and nitrogen inlet was charged absolute ethanol (30 g). Concentrated sulfuric acid (30 g) as added slowly as to minimize exotherm. When heating subsided, the starting nitrile, PBBN (1.0 g), was added in one portion. The temperature was set to ~96 °C, and the contents were allowed to reflux for 7 h. After heating for ~15 minutes, the reaction turned dark brown in color with no visible evidence of insoluble PBBN. After 2 h. heating, reflux had stabilized. Gradually, the temperature dropped to ~88 °C. The reactor was cooled, and the contents were poured into ice water. Immediately, a grey-brown solid precipitate was formed and subsequently collected via suction filtration. Air-drying overnight provided 1.65 grams crude material. The solids were slurried in acetone and filtered to collect 0.46 grams (42.2% yield) brown solid on drying. Crude NMR revealed desired ethyl ester as the major component. 1H NMR: (400 MHz, DMSO-d6): δ = 4.32 (singlet, benzylic –CH2–, 2H), 4.17–4.12 (quartet, ester methylene, 2H), 1.22–1.19 (triplet, ester methyl, 3H). (Impurities consist of the acetic acid derivative, along with the amide intermediate.) Recrystallization from acetone / IPA afforded the title ester compound obtained in pure form as spear-like needles, mp (DSC-melt) = 142.9–145.8 °C.
H atoms on C were placed in idealized positions with C—H distances 0.98–0.99 Å and thereafter treated as riding. A torsional parameter was refined for the methyl group. Uiso for H were assigned as 1.2 times Ueq of the attached atoms (1.5 for methyl). The Flack (1983) parameter refined to a value of 0.467 (13), indicating a nearly perfect Friedel pairs were kept separate in the refinement.
In an effort to prepare a series of proposed pentabromophenyl-substituted compounds necessary as analytical standards, the title ethyl ester derivative rendered itself to be an important intermediate and was synthesized via PBBN as an intermediate. This PBBN nitrile precursor was prepared by known procedures (Holmes & Lightner, 1995) from hexabromotoluene, henceforth referred to as pentabromobenzyl bromide, PBBB. Subsequent conversion of the resulting pentabromobenzyl nitrile intermediate to PBPEA was completed with ethanol in sulfuric acid. (Adams & Thal, 1941). The nature of such sterically hindered and electronically deprived pentabromo-compounds has provided a unique opportunity to examine the reactivity and resulting isolation / purification tendencies associated with these systems.
The ethyl acetate portion of the molecule (Fig. 1) is extended, with torsion angles C1—C7—C8—O1 174.8 (3)°, C7—C8—O1—C9 179.3 (3)°, C8—O1—C9—C10 - 165.1 (3)°, and it is nearly orthogonal to the phenyl ring, with C2—C1—C7—C8 torsion angle 88.3 (5)°. The C—Br distances are in the range 1.876 (4)–1.896 (4) Å, with mean value 1.887 Å. This value compares favorably with the mean value of 1.880 Å in decabromodiphenylethane (Köppen et al., 2007), the only ordered entry in the CSD (version 5.31, Nov. 2009; Allen 2002) with Br5Ph on an sp3 C atom. The structure of pentabromotoluene has also been reported (Krigbaum & Wildman, 1971), but it has the methyl group statistically disordered, sharing all six sites with Br. Structures of several pentabromophenyl have also been reported (Eriksson & Hu, 2002a,b; Eriksson et al., 1999; Mrse et al., 2000; Williams et al., 1985), and the geometries of their Br5Ph groups are similar.
Packing of compounds containing Br5Ph groups usually involves intermolecular Br···Br contacts, and one such interaction exists in the structure of the title compound, as illustrated in Fig. 2. The contact is between glide-related molecules, and has Br3···Br5 distance 3.491 (1) Å. The angular disposition of the contact is termed type II by Pedireddi et al. (1994), having one C–Br···Br angle near linear and the other nearly orthogonal. In this case, the angle about Br5 is 173.4 (2)°, and the angle about Br3 is 106.0 (2)°. Also, both O atoms make intermolecular contacts with Br, O1···Br4(1 + x, 1 - y, 1/2 + z) 3.184 (3) Å; O2···Br2 (x - 1/2, 3/2 - y, 1/2 + z) 3.123 (3) Å.
For synthetic procedures, see: Holmes & Lightner (1995); Adams & Thal (1941). For a description of the Cambridge Structural Database, see: Allen (2002). For related structures, see: Eriksson & Hu (2002a,b); Eriksson et al. (1999); Köppen et al. (2007); Krigbaum & Wildman (1971); Mrse et al. (2000); Pedireddi et al. (1994); Williams et al. (1985).
Data collection: COLLECT (Nonius, 2000); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
![[Figure 1]](./jj2038fig1thm.gif) | Fig. 1. Ellipsoids at the 50% probability level, with H atoms having arbitrary radius. |
![[Figure 2]](./jj2038fig2thm.gif) | Fig. 2. The intermolecular Br···Br contact. H atoms are omitted. |
![[Figure 3]](./jj2038fig3thm.gif) | Fig. 3. Preparation of the title compound. |
| C10H7Br5O2 | F(000) = 1032 |
| Mr = 558.71 | Dx = 2.704 Mg m−3 |
| Monoclinic, Cc | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: C -2yc | Cell parameters from 2027 reflections |
| a = 4.6136 (10) Å | θ = 2.5–30.0° |
| b = 22.548 (5) Å | µ = 14.63 mm−1 |
| c = 13.195 (2) Å | T = 90 K |
| β = 90.993 (11)° | Needle fragment, light brown |
| V = 1372.4 (5) Å3 | 0.25 × 0.12 × 0.12 mm |
| Z = 4 |
| Nonius KappaCCD diffractometer with Oxford Cryostream | 3863 independent reflections |
| Radiation source: fine-focus sealed tube | 3676 reflections with I > 2σ(I) |
| Graphite monochromator | Rint = 0.013 |
| ω and φ scans | θmax = 30.0°, θmin = 3.0° |
| Absorption correction: multi-scan (SCALEPACK; Otwinowski & Minor, 1997) | h = −6→6 |
| Tmin = 0.121, Tmax = 0.273 | k = −31→31 |
| 10525 measured reflections | l = −18→18 |
| Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
| Least-squares matrix: full | H-atom parameters constrained |
| R[F2 > 2σ(F2)] = 0.025 | w = 1/[σ2(Fo2) + (0.0154P)2 + 2.9894P] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.053 | (Δ/σ)max = 0.002 |
| S = 1.17 | Δρmax = 0.65 e Å−3 |
| 3863 reflections | Δρmin = −0.66 e Å−3 |
| 157 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| 2 restraints | Extinction coefficient: 0.00100 (7) |
| Primary atom site location: structure-invariant direct methods | Absolute structure: Flack (1983), 1842 Friedel pairs |
| Secondary atom site location: difference Fourier map | Absolute structure parameter: 0.467 (13) |
| C10H7Br5O2 | V = 1372.4 (5) Å3 |
| Mr = 558.71 | Z = 4 |
| Monoclinic, Cc | Mo Kα radiation |
| a = 4.6136 (10) Å | µ = 14.63 mm−1 |
| b = 22.548 (5) Å | T = 90 K |
| c = 13.195 (2) Å | 0.25 × 0.12 × 0.12 mm |
| β = 90.993 (11)° |
| Nonius KappaCCD diffractometer with Oxford Cryostream | 3863 independent reflections |
| Absorption correction: multi-scan (SCALEPACK; Otwinowski & Minor, 1997) | 3676 reflections with I > 2σ(I) |
| Tmin = 0.121, Tmax = 0.273 | Rint = 0.013 |
| 10525 measured reflections |
| R[F2 > 2σ(F2)] = 0.025 | H-atom parameters constrained |
| wR(F2) = 0.053 | Δρmax = 0.65 e Å−3 |
| S = 1.17 | Δρmin = −0.66 e Å−3 |
| 3863 reflections | Absolute structure: Flack (1983), 1842 Friedel pairs |
| 157 parameters | Absolute structure parameter: 0.467 (13) |
| 2 restraints |
Experimental. PBBN: 1H NMR: (400MHz, DMSO-d6): δ = 4.46 (singlet, benzylic –CH2–, 2H); 13C NMR: (125MHz, DMSO-d6): δ = 134.06, 130.18, 129.66, 127.90, 116.37, 31.29. PBPEA: 1H NMR: (400 MHz, CDCl3): δ = 4.36 (singlet, benzylic –CH2–, 2H), 4.26–4.20 (quartet, ester methylene, 2H), 1.32–1.28 (triplet, ester methyl 2H), 4.26–4.20 (quartet, ester methylene, 2H), 1.32–1.28 (triplet, ester methyl, 3H). 13C NMR: (100 MHz, CDCl3): δ = 168.79, 137.56, 129.37, 129.1, 128.55, 61.98, 47.94, 14.60. |
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 | ||
| Br1 | 0.88580 (8) | 0.721320 (18) | 0.44969 (3) | 0.01668 (9) | |
| Br2 | 0.57652 (8) | 0.735821 (17) | 0.22457 (3) | 0.01500 (9) | |
| Br3 | 0.16294 (9) | 0.628526 (18) | 0.13378 (3) | 0.01501 (9) | |
| Br4 | 0.06205 (8) | 0.507432 (18) | 0.26957 (3) | 0.01482 (9) | |
| Br5 | 0.36995 (8) | 0.495585 (18) | 0.49436 (3) | 0.01383 (9) | |
| O1 | 0.7331 (6) | 0.61466 (13) | 0.7294 (2) | 0.0136 (6) | |
| O2 | 0.3795 (6) | 0.65392 (14) | 0.6300 (2) | 0.0162 (6) | |
| C1 | 0.6196 (9) | 0.60801 (18) | 0.4523 (3) | 0.0113 (7) | |
| C2 | 0.6548 (8) | 0.65956 (18) | 0.3941 (3) | 0.0115 (8) | |
| C3 | 0.5193 (9) | 0.66594 (17) | 0.3000 (3) | 0.0096 (7) | |
| C4 | 0.3429 (8) | 0.62048 (18) | 0.2616 (3) | 0.0103 (7) | |
| C5 | 0.2983 (8) | 0.56956 (18) | 0.3187 (3) | 0.0110 (8) | |
| C6 | 0.4373 (8) | 0.56364 (18) | 0.4137 (3) | 0.0118 (8) | |
| C7 | 0.7750 (9) | 0.60088 (18) | 0.5534 (3) | 0.0122 (8) | |
| H7A | 0.9647 | 0.6213 | 0.5510 | 0.015* | |
| H7B | 0.8118 | 0.5582 | 0.5660 | 0.015* | |
| C8 | 0.6017 (8) | 0.62599 (17) | 0.6398 (3) | 0.0101 (7) | |
| C9 | 0.5844 (9) | 0.6377 (2) | 0.8175 (3) | 0.0148 (8) | |
| H9A | 0.4116 | 0.6132 | 0.8316 | 0.018* | |
| H9B | 0.5200 | 0.6790 | 0.8046 | 0.018* | |
| C10 | 0.7928 (10) | 0.6360 (2) | 0.9071 (3) | 0.0170 (9) | |
| H10A | 0.8614 | 0.5953 | 0.9176 | 0.026* | |
| H10B | 0.6938 | 0.6497 | 0.9679 | 0.026* | |
| H10C | 0.9583 | 0.6620 | 0.8939 | 0.026* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Br1 | 0.0201 (2) | 0.01398 (19) | 0.0157 (2) | −0.00486 (17) | −0.00499 (16) | 0.00049 (16) |
| Br2 | 0.0221 (2) | 0.01098 (19) | 0.01185 (18) | −0.00063 (16) | −0.00041 (15) | 0.00243 (15) |
| Br3 | 0.0200 (2) | 0.01540 (18) | 0.00946 (16) | 0.00203 (16) | −0.00374 (14) | −0.00085 (16) |
| Br4 | 0.01717 (19) | 0.0141 (2) | 0.0131 (2) | −0.00421 (16) | −0.00080 (16) | −0.00249 (16) |
| Br5 | 0.01896 (19) | 0.01114 (19) | 0.0114 (2) | −0.00113 (16) | 0.00103 (16) | 0.00194 (15) |
| O1 | 0.0148 (13) | 0.0184 (15) | 0.0076 (12) | 0.0050 (11) | −0.0008 (11) | −0.0002 (11) |
| O2 | 0.0156 (14) | 0.0184 (15) | 0.0144 (13) | 0.0054 (12) | −0.0028 (11) | −0.0036 (12) |
| C1 | 0.0129 (17) | 0.0116 (19) | 0.0095 (17) | 0.0013 (14) | 0.0024 (15) | 0.0005 (14) |
| C2 | 0.0104 (18) | 0.0118 (19) | 0.0125 (18) | −0.0011 (14) | 0.0040 (15) | −0.0021 (14) |
| C3 | 0.0133 (17) | 0.0070 (18) | 0.0086 (16) | 0.0010 (14) | 0.0003 (14) | 0.0017 (13) |
| C4 | 0.0103 (17) | 0.0134 (19) | 0.0072 (16) | 0.0023 (14) | −0.0022 (14) | −0.0004 (14) |
| C5 | 0.0112 (18) | 0.0114 (19) | 0.0105 (18) | −0.0019 (14) | −0.0001 (14) | −0.0039 (14) |
| C6 | 0.0149 (19) | 0.0101 (19) | 0.0106 (18) | 0.0026 (15) | 0.0040 (15) | 0.0014 (14) |
| C7 | 0.0127 (18) | 0.0109 (18) | 0.0129 (19) | −0.0013 (14) | −0.0018 (15) | 0.0000 (15) |
| C8 | 0.0121 (18) | 0.0098 (17) | 0.0081 (16) | −0.0021 (14) | −0.0031 (14) | −0.0023 (14) |
| C9 | 0.015 (2) | 0.019 (2) | 0.0101 (18) | 0.0031 (16) | −0.0008 (15) | −0.0034 (16) |
| C10 | 0.016 (2) | 0.022 (2) | 0.0139 (19) | 0.0032 (17) | −0.0003 (16) | −0.0005 (16) |
| Br1—C2 | 1.894 (4) | C3—C4 | 1.398 (6) |
| Br2—C3 | 1.885 (4) | C4—C5 | 1.391 (6) |
| Br3—C4 | 1.876 (4) | C5—C6 | 1.404 (5) |
| Br4—C5 | 1.883 (4) | C7—C8 | 1.514 (5) |
| Br5—C6 | 1.896 (4) | C7—H7A | 0.9900 |
| O1—C8 | 1.344 (5) | C7—H7B | 0.9900 |
| O1—C9 | 1.456 (5) | C9—C10 | 1.511 (6) |
| O2—C8 | 1.208 (5) | C9—H9A | 0.9900 |
| C1—C6 | 1.397 (6) | C9—H9B | 0.9900 |
| C1—C2 | 1.404 (5) | C10—H10A | 0.9800 |
| C1—C7 | 1.512 (5) | C10—H10B | 0.9800 |
| C2—C3 | 1.388 (6) | C10—H10C | 0.9800 |
| C8—O1—C9 | 115.0 (3) | C1—C7—H7A | 109.2 |
| C6—C1—C2 | 117.9 (4) | C8—C7—H7A | 109.2 |
| C6—C1—C7 | 121.2 (4) | C1—C7—H7B | 109.2 |
| C2—C1—C7 | 120.9 (4) | C8—C7—H7B | 109.2 |
| C3—C2—C1 | 121.4 (4) | H7A—C7—H7B | 107.9 |
| C3—C2—Br1 | 120.8 (3) | O2—C8—O1 | 124.2 (4) |
| C1—C2—Br1 | 117.8 (3) | O2—C8—C7 | 124.9 (4) |
| C2—C3—C4 | 119.9 (4) | O1—C8—C7 | 110.8 (3) |
| C2—C3—Br2 | 119.6 (3) | O1—C9—C10 | 108.3 (3) |
| C4—C3—Br2 | 120.5 (3) | O1—C9—H9A | 110.0 |
| C5—C4—C3 | 120.0 (3) | C10—C9—H9A | 110.0 |
| C5—C4—Br3 | 120.0 (3) | O1—C9—H9B | 110.0 |
| C3—C4—Br3 | 120.0 (3) | C10—C9—H9B | 110.0 |
| C4—C5—C6 | 119.5 (4) | H9A—C9—H9B | 108.4 |
| C4—C5—Br4 | 121.2 (3) | C9—C10—H10A | 109.5 |
| C6—C5—Br4 | 119.3 (3) | C9—C10—H10B | 109.5 |
| C1—C6—C5 | 121.3 (4) | H10A—C10—H10B | 109.5 |
| C1—C6—Br5 | 118.6 (3) | C9—C10—H10C | 109.5 |
| C5—C6—Br5 | 120.1 (3) | H10A—C10—H10C | 109.5 |
| C1—C7—C8 | 112.1 (3) | H10B—C10—H10C | 109.5 |
| C6—C1—C2—C3 | −1.6 (6) | C2—C1—C6—C5 | 1.5 (6) |
| C7—C1—C2—C3 | 178.3 (4) | C7—C1—C6—C5 | −178.5 (4) |
| C6—C1—C2—Br1 | 176.8 (3) | C2—C1—C6—Br5 | −176.6 (3) |
| C7—C1—C2—Br1 | −3.3 (5) | C7—C1—C6—Br5 | 3.5 (5) |
| C1—C2—C3—C4 | 0.2 (6) | C4—C5—C6—C1 | 0.1 (6) |
| Br1—C2—C3—C4 | −178.1 (3) | Br4—C5—C6—C1 | 178.6 (3) |
| C1—C2—C3—Br2 | −179.5 (3) | C4—C5—C6—Br5 | 178.1 (3) |
| Br1—C2—C3—Br2 | 2.2 (5) | Br4—C5—C6—Br5 | −3.4 (4) |
| C2—C3—C4—C5 | 1.5 (6) | C6—C1—C7—C8 | −91.8 (5) |
| Br2—C3—C4—C5 | −178.9 (3) | C2—C1—C7—C8 | 88.3 (5) |
| C2—C3—C4—Br3 | −179.3 (3) | C9—O1—C8—O2 | 1.2 (6) |
| Br2—C3—C4—Br3 | 0.4 (5) | C9—O1—C8—C7 | 179.3 (3) |
| C3—C4—C5—C6 | −1.6 (6) | C1—C7—C8—O2 | −7.1 (6) |
| Br3—C4—C5—C6 | 179.1 (3) | C1—C7—C8—O1 | 174.8 (3) |
| C3—C4—C5—Br4 | 180.0 (3) | C8—O1—C9—C10 | −165.1 (3) |
| Br3—C4—C5—Br4 | 0.7 (5) |
Experimental details
| Crystal data | |
| Chemical formula | C10H7Br5O2 |
| Mr | 558.71 |
| Crystal system, space group | Monoclinic, Cc |
| Temperature (K) | 90 |
| a, b, c (Å) | 4.6136 (10), 22.548 (5), 13.195 (2) |
| β (°) | 90.993 (11) |
| V (Å3) | 1372.4 (5) |
| Z | 4 |
| Radiation type | Mo Kα |
| µ (mm−1) | 14.63 |
| Crystal size (mm) | 0.25 × 0.12 × 0.12 |
| Data collection | |
| Diffractometer | Nonius KappaCCD diffractometer with Oxford Cryostream |
| Absorption correction | Multi-scan (SCALEPACK; Otwinowski & Minor, 1997) |
| Tmin, Tmax | 0.121, 0.273 |
| No. of measured, independent and observed [I > 2σ(I)] reflections | 10525, 3863, 3676 |
| Rint | 0.013 |
| (sin θ/λ)max (Å−1) | 0.703 |
| Refinement | |
| R[F2 > 2σ(F2)], wR(F2), S | 0.025, 0.053, 1.17 |
| No. of reflections | 3863 |
| No. of parameters | 157 |
| No. of restraints | 2 |
| H-atom treatment | H-atom parameters constrained |
| Δρmax, Δρmin (e Å−3) | 0.65, −0.66 |
| Absolute structure | Flack (1983), 1842 Friedel pairs |
| Absolute structure parameter | 0.467 (13) |
Computer programs: COLLECT (Nonius, 2000), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997).
Acknowledgements
The purchase of the diffractometer was made possible by grant No. LEQSF(1999–2000)-ENH-TR-13, administered by the Louisiana Board of Regents.
References
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In an effort to prepare a series of proposed pentabromophenyl-substituted compounds necessary as analytical standards, the title ethyl ester derivative rendered itself to be an important intermediate and was synthesized via PBBN as an intermediate. This PBBN nitrile precursor was prepared by known procedures (Holmes & Lightner, 1995) from hexabromotoluene, henceforth referred to as pentabromobenzyl bromide, PBBB. Subsequent conversion of the resulting pentabromobenzyl nitrile intermediate to PBPEA was completed with ethanol in sulfuric acid. (Adams & Thal, 1941). The nature of such sterically hindered and electronically deprived pentabromo-compounds has provided a unique opportunity to examine the reactivity and resulting isolation / purification tendencies associated with these systems.
The ethyl acetate portion of the molecule (Fig. 1) is extended, with torsion angles C1—C7—C8—O1 174.8 (3)°, C7—C8—O1—C9 179.3 (3)°, C8—O1—C9—C10 - 165.1 (3)°, and it is nearly orthogonal to the phenyl ring, with C2—C1—C7—C8 torsion angle 88.3 (5)°. The C—Br distances are in the range 1.876 (4)–1.896 (4) Å, with mean value 1.887 Å. This value compares favorably with the mean value of 1.880 Å in decabromodiphenylethane (Köppen et al., 2007), the only ordered entry in the CSD (version 5.31, Nov. 2009; Allen 2002) with Br5Ph on an sp3 C atom. The structure of pentabromotoluene has also been reported (Krigbaum & Wildman, 1971), but it has the methyl group statistically disordered, sharing all six sites with Br. Structures of several pentabromophenyl ethers have also been reported (Eriksson & Hu, 2002a,b; Eriksson et al., 1999; Mrse et al., 2000; Williams et al., 1985), and the geometries of their Br5Ph groups are similar.
Packing of compounds containing Br5Ph groups usually involves intermolecular Br···Br contacts, and one such interaction exists in the structure of the title compound, as illustrated in Fig. 2. The contact is between glide-related molecules, and has Br3···Br5 distance 3.491 (1) Å. The angular disposition of the contact is termed type II by Pedireddi et al. (1994), having one C–Br···Br angle near linear and the other nearly orthogonal. In this case, the angle about Br5 is 173.4 (2)°, and the angle about Br3 is 106.0 (2)°. Also, both O atoms make intermolecular contacts with Br, O1···Br4(1 + x, 1 - y, 1/2 + z) 3.184 (3) Å; O2···Br2 (x - 1/2, 3/2 - y, 1/2 + z) 3.123 (3) Å.