organic compounds
1-Bromo-2,3,6-trichloro-4,5-dimethoxybenzene
aCollege of Pharmaceutical Sciences, Southwest University, Chong Qing 400716, People's Republic of China, bUniversity of Kentucky, Department of Chemistry, Lexington, KY 40506-0055, USA, and cThe University of Iowa, Department of Occupational and Environmental Health, 100 Oakdale Campus, 124 IREH, Iowa City, IA 52242-5000, USA
*Correspondence e-mail: hans-joachim-lehmler@uiowa.edu
The halogen atoms of the title compound, C8H6BrCl3O2, are located within the plane of the benzene ring [r.m.s. deviation = 0.036 (11) Å]. The two methoxy groups are twisted out of this plane, with dihedral angles of 84.7 (3) and 68.5 (3)°, and point in opposite directions. The structure is disordered by a non-crystallographic twofold rotation which superimposes Cl and Br at two of the halogen sites. The refined occupancies for the major and minor components are 0.517 (2) and 0.483 (2).
Related literature
For similar structures of halogenated methoxy benzenes, see: Iimura et al. (1984); Rissanen et al. (1987, 1988a,b); Song et al. (2008, 2010); Telu et al. (2008); Weller & Gerstner (1995); Wieczorek (1980). For background to halogenated methoxy benzenes, see: Brownlee et al. (1993); Curtis et al. (1972); Pereira et al. (2000); Vlachos et al. (2007); Zhang et al. (2006).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2006); cell SAINT (Bruker, 2006); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 and local procedures.
Supporting information
https://doi.org/10.1107/S1600536810002977/om2317sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810002977/om2317Isup2.hkl
This title compound was synthesized by chlorination of 1-bromo-3,4-dimethoxy-benzene with HCl/H2O2 as described previosuly (Song et al., 2008). Crystals suitable for X-ray diffraction were grown by slow evaporation of a
of the title compound in CHCl3.H atoms were found in difference Fourier maps and subsequently placed in idealized positions with constrained C-H distances of 0.98 Å and Uiso(H) values set to 1.5Ueq of the attached C atom. The structure is disordered by a non-crystallographic 2-fold rotation about an axis that bisects the midpoints of bonds C1—C2 and C4—C5. This disorder superimposes Cl and Br at the halogen sites bonded to C4 and C5. The refined occupancies for the major and minor components are 0.517 (2) and 0.483 (2). To ensure a physically/chemically sensible model in spite of the disorder, the bond distances for C—Cl were restrained to a refined variable, 1.713 (8). The C—Br bond distance was restrained to the same variable, but multiplied by 1.096, which is the ratio of C—Br:C—Cl for this type of bond. Six restraints in total were required. In addition, the displacement parameters of the superimposed atoms were constrained to be the same.
Chlorinated methoxy benzenes are a group of persistent organic pollutants that are associated with off-flavors in water, fish, chicken and wine (Brownlee et al.,1993; Curtis et al., 1972; Pereira et al., 2000; Vlachos et al., 2007; Zhang et al., 2006). Their biological properties depend, at least in part, on the conformation of the methoxy group relative to the aromatic ring system. The two methoxy groups of the title compound are twisted out of the plane of the benzene ring system due to the bulky ortho chlorine substituents and point in opposite directions. The respective dihedral angles were calculated between the plane of the benzene ring (C1 through C6) and the methoxy group and are 84.7 (3)° (atoms C1,O1,C7) and 68.5 (3)° (atoms C2,O2,C8), respectively. These dihedral angles are in agreement with the dihedral angels observed for other chlorinated methoxy benzenes with two ortho substituents (Iimura et al.,1984; Rissanen et al., 1987; Rissanen et al., 1988b; Telu et al., 2008; Weller & Gerstner, 1995; Wieczorek, 1980). In contrast, the methoxy group of structurally related compound with no or one substituent ortho to the methoxy group typically lie within the plane of the benzene ring system (Rissanen et al., 1988a; Song et al., 2010).
For similar structures of halogenated methoxy benzenes, see: Iimura et al. (1984); Rissanen et al. (1987, 1988a,b); Rissanen et al. (1988a,b); Song et al. (2008, 2010); Telu et al. (2008); Weller & Gerstner (1995); Wieczorek (1980). For background to halogenated methoxy benzenes, see: Brownlee et al. (1993); Curtis et al. (1972); Pereira et al. (2000); Vlachos et al. (2007); Zhang et al. (2006).
Data collection: APEX2 (Bruker, 2006); cell
SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELX97 (Sheldrick, 2008) and local procedures.Fig. 1. View of the title compound showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. |
C8H6BrCl3O2 | Z = 2 |
Mr = 320.39 | F(000) = 312 |
Triclinic, P1 | Dx = 1.994 Mg m−3 |
Hall symbol: -P 1 | Cu Kα radiation, λ = 1.54178 Å |
a = 7.7885 (7) Å | Cell parameters from 5684 reflections |
b = 8.8600 (7) Å | θ = 5.5–66.1° |
c = 9.1523 (8) Å | µ = 11.94 mm−1 |
α = 62.256 (3)° | T = 90 K |
β = 75.358 (4)° | Irregular plate, colourless |
γ = 75.133 (4)° | 0.20 × 0.15 × 0.07 mm |
V = 533.64 (8) Å3 |
Bruker X8 Proteum diffractometer | 1828 independent reflections |
Radiation source: fine-focus rotating anode | 1720 reflections with I > 2σ(I) |
Graded multilayer optics monochromator | Rint = 0.038 |
Detector resolution: 18 pixels mm-1 | θmax = 67.4°, θmin = 5.5° |
φ and ω scans | h = −9→7 |
Absorption correction: multi-scan (SADABS; Bruker, 2006) | k = −10→10 |
Tmin = 0.193, Tmax = 0.434 | l = −10→10 |
6588 measured reflections |
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)] = 0.038 | H-atom parameters constrained |
wR(F2) = 0.103 | w = 1/[σ2(Fo2) + (0.0466P)2 + 0.726P] where P = (Fo2 + 2Fc2)/3 |
S = 1.12 | (Δ/σ)max = 0.004 |
1828 reflections | Δρmax = 0.35 e Å−3 |
138 parameters | Δρmin = −0.52 e Å−3 |
6 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0232 (18) |
C8H6BrCl3O2 | γ = 75.133 (4)° |
Mr = 320.39 | V = 533.64 (8) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.7885 (7) Å | Cu Kα radiation |
b = 8.8600 (7) Å | µ = 11.94 mm−1 |
c = 9.1523 (8) Å | T = 90 K |
α = 62.256 (3)° | 0.20 × 0.15 × 0.07 mm |
β = 75.358 (4)° |
Bruker X8 Proteum diffractometer | 1828 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2006) | 1720 reflections with I > 2σ(I) |
Tmin = 0.193, Tmax = 0.434 | Rint = 0.038 |
6588 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | 6 restraints |
wR(F2) = 0.103 | H-atom parameters constrained |
S = 1.12 | Δρmax = 0.35 e Å−3 |
1828 reflections | Δρmin = −0.52 e Å−3 |
138 parameters |
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 > 2σ(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 | 0.2391 (4) | 0.6704 (4) | 0.7165 (4) | 0.0318 (6) | |
C2 | 0.2512 (4) | 0.7913 (5) | 0.7681 (4) | 0.0360 (7) | |
C3 | 0.2598 (4) | 0.9603 (4) | 0.6519 (4) | 0.0356 (7) | |
C4 | 0.2536 (4) | 1.0107 (4) | 0.4851 (4) | 0.0366 (7) | |
C5 | 0.2393 (4) | 0.8899 (4) | 0.4345 (4) | 0.0350 (7) | |
C6 | 0.2314 (4) | 0.7212 (4) | 0.5504 (4) | 0.0329 (7) | |
O1 | 0.2295 (3) | 0.5051 (3) | 0.8291 (3) | 0.0418 (6) | |
C7 | 0.3984 (6) | 0.3991 (5) | 0.8622 (6) | 0.0592 (11) | |
H7A | 0.4694 | 0.3956 | 0.7585 | 0.089* | |
H7B | 0.3800 | 0.2818 | 0.9444 | 0.089* | |
H7C | 0.4627 | 0.4464 | 0.9066 | 0.089* | |
O2 | 0.2646 (3) | 0.7442 (4) | 0.9285 (3) | 0.0486 (6) | |
C8 | 0.1070 (5) | 0.6975 (6) | 1.0458 (5) | 0.0558 (10) | |
H8A | 0.0096 | 0.7968 | 1.0188 | 0.084* | |
H8B | 0.1309 | 0.6619 | 1.1584 | 0.084* | |
H8C | 0.0717 | 0.6014 | 1.0412 | 0.084* | |
Cl1 | 0.27710 (13) | 1.10613 (13) | 0.71869 (14) | 0.0567 (3) | |
Cl2 | 0.265 (3) | 1.2206 (17) | 0.326 (2) | 0.0539 (7) | 0.483 (3) |
Br3 | 0.2388 (9) | 0.9427 (6) | 0.2147 (7) | 0.0495 (7) | 0.483 (3) |
Br2 | 0.2599 (11) | 1.2383 (6) | 0.3376 (8) | 0.0539 (7) | 0.517 (3) |
Cl3 | 0.228 (2) | 0.9701 (14) | 0.2211 (15) | 0.0495 (7) | 0.517 (3) |
Cl4 | 0.20968 (13) | 0.56783 (11) | 0.49546 (11) | 0.0485 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0236 (14) | 0.0338 (16) | 0.0354 (16) | −0.0092 (12) | −0.0006 (11) | −0.0123 (13) |
C2 | 0.0257 (15) | 0.0442 (18) | 0.0406 (17) | −0.0106 (13) | 0.0000 (12) | −0.0203 (15) |
C3 | 0.0255 (15) | 0.0388 (17) | 0.0513 (19) | −0.0071 (12) | −0.0013 (13) | −0.0280 (15) |
C4 | 0.0242 (15) | 0.0279 (15) | 0.0501 (19) | −0.0039 (12) | 0.0005 (13) | −0.0136 (14) |
C5 | 0.0269 (15) | 0.0348 (16) | 0.0392 (16) | −0.0046 (12) | −0.0039 (12) | −0.0133 (14) |
C6 | 0.0291 (15) | 0.0323 (16) | 0.0387 (16) | −0.0080 (12) | −0.0021 (12) | −0.0163 (13) |
O1 | 0.0424 (13) | 0.0343 (12) | 0.0402 (12) | −0.0132 (10) | −0.0033 (10) | −0.0072 (10) |
C7 | 0.054 (2) | 0.040 (2) | 0.060 (2) | 0.0007 (17) | −0.0095 (19) | −0.0062 (18) |
O2 | 0.0456 (14) | 0.0687 (17) | 0.0418 (13) | −0.0189 (12) | −0.0064 (10) | −0.0275 (13) |
C8 | 0.050 (2) | 0.076 (3) | 0.0380 (19) | −0.009 (2) | −0.0024 (16) | −0.0245 (19) |
Cl1 | 0.0559 (6) | 0.0536 (6) | 0.0797 (7) | −0.0177 (4) | 0.0007 (5) | −0.0454 (5) |
Cl2 | 0.0526 (6) | 0.0296 (11) | 0.0692 (11) | −0.0075 (10) | −0.0009 (7) | −0.0165 (7) |
Br3 | 0.0579 (9) | 0.0403 (16) | 0.0456 (6) | −0.0037 (12) | −0.0149 (5) | −0.0133 (8) |
Br2 | 0.0526 (6) | 0.0296 (11) | 0.0692 (11) | −0.0075 (10) | −0.0009 (7) | −0.0165 (7) |
Cl3 | 0.0579 (9) | 0.0403 (16) | 0.0456 (6) | −0.0037 (12) | −0.0149 (5) | −0.0133 (8) |
Cl4 | 0.0670 (6) | 0.0407 (5) | 0.0471 (5) | −0.0185 (4) | −0.0078 (4) | −0.0221 (4) |
C1—O1 | 1.351 (4) | C5—Cl3 | 1.758 (12) |
C1—C6 | 1.383 (5) | C5—Br3 | 1.842 (6) |
C1—C2 | 1.388 (5) | C6—Cl4 | 1.710 (3) |
C2—O2 | 1.350 (4) | O1—C7 | 1.417 (5) |
C2—C3 | 1.382 (5) | C7—H7A | 0.9800 |
C3—C4 | 1.387 (5) | C7—H7B | 0.9800 |
C3—Cl1 | 1.711 (3) | C7—H7C | 0.9800 |
C4—C5 | 1.386 (5) | O2—C8 | 1.418 (5) |
C4—Cl2 | 1.756 (15) | C8—H8A | 0.9800 |
C4—Br2 | 1.837 (6) | C8—H8B | 0.9800 |
C5—C6 | 1.379 (5) | C8—H8C | 0.9800 |
O1—C1—C6 | 120.3 (3) | C4—C5—Br3 | 122.6 (3) |
O1—C1—C2 | 120.0 (3) | C5—C6—C1 | 120.8 (3) |
C6—C1—C2 | 119.7 (3) | C5—C6—Cl4 | 121.6 (3) |
O2—C2—C3 | 119.5 (3) | C1—C6—Cl4 | 117.6 (2) |
O2—C2—C1 | 120.9 (3) | C1—O1—C7 | 114.5 (3) |
C3—C2—C1 | 119.5 (3) | O1—C7—H7A | 109.5 |
C2—C3—C4 | 120.7 (3) | O1—C7—H7B | 109.5 |
C2—C3—Cl1 | 118.5 (3) | H7A—C7—H7B | 109.5 |
C4—C3—Cl1 | 120.8 (3) | O1—C7—H7C | 109.5 |
C5—C4—C3 | 119.5 (3) | H7A—C7—H7C | 109.5 |
C5—C4—Cl2 | 115.5 (6) | H7B—C7—H7C | 109.5 |
C3—C4—Cl2 | 125.0 (7) | C2—O2—C8 | 115.4 (3) |
C5—C4—Br2 | 121.8 (3) | O2—C8—H8A | 109.5 |
C3—C4—Br2 | 118.7 (3) | O2—C8—H8B | 109.5 |
C6—C5—C4 | 119.7 (3) | H8A—C8—H8B | 109.5 |
C6—C5—Cl3 | 125.0 (5) | O2—C8—H8C | 109.5 |
C4—C5—Cl3 | 115.3 (4) | H8A—C8—H8C | 109.5 |
C6—C5—Br3 | 117.6 (3) | H8B—C8—H8C | 109.5 |
O1—C1—C2—O2 | 4.0 (5) | Br2—C4—C5—Cl3 | 0.1 (7) |
C6—C1—C2—O2 | −177.9 (3) | C3—C4—C5—Br3 | −177.6 (3) |
O1—C1—C2—C3 | −179.6 (3) | Cl2—C4—C5—Br3 | 1.8 (9) |
C6—C1—C2—C3 | −1.5 (5) | Br2—C4—C5—Br3 | 3.7 (5) |
O2—C2—C3—C4 | 177.4 (3) | C4—C5—C6—C1 | −0.6 (5) |
C1—C2—C3—C4 | 1.0 (5) | Cl3—C5—C6—C1 | −179.2 (7) |
O2—C2—C3—Cl1 | −2.9 (4) | Br3—C5—C6—C1 | 177.2 (3) |
C1—C2—C3—Cl1 | −179.3 (2) | C4—C5—C6—Cl4 | 178.8 (2) |
C2—C3—C4—C5 | −0.3 (5) | Cl3—C5—C6—Cl4 | 0.2 (8) |
Cl1—C3—C4—C5 | −179.9 (2) | Br3—C5—C6—Cl4 | −3.4 (4) |
C2—C3—C4—Cl2 | −179.6 (9) | O1—C1—C6—C5 | 179.4 (3) |
Cl1—C3—C4—Cl2 | 0.7 (10) | C2—C1—C6—C5 | 1.3 (5) |
C2—C3—C4—Br2 | 178.5 (4) | O1—C1—C6—Cl4 | 0.0 (4) |
Cl1—C3—C4—Br2 | −1.2 (5) | C2—C1—C6—Cl4 | −178.1 (2) |
C3—C4—C5—C6 | 0.0 (5) | C6—C1—O1—C7 | 96.2 (4) |
Cl2—C4—C5—C6 | 179.4 (8) | C2—C1—O1—C7 | −85.7 (4) |
Br2—C4—C5—C6 | −178.7 (4) | C3—C2—O2—C8 | 113.2 (4) |
C3—C4—C5—Cl3 | 178.8 (6) | C1—C2—O2—C8 | −70.5 (4) |
Cl2—C4—C5—Cl3 | −1.8 (10) |
Experimental details
Crystal data | |
Chemical formula | C8H6BrCl3O2 |
Mr | 320.39 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 90 |
a, b, c (Å) | 7.7885 (7), 8.8600 (7), 9.1523 (8) |
α, β, γ (°) | 62.256 (3), 75.358 (4), 75.133 (4) |
V (Å3) | 533.64 (8) |
Z | 2 |
Radiation type | Cu Kα |
µ (mm−1) | 11.94 |
Crystal size (mm) | 0.20 × 0.15 × 0.07 |
Data collection | |
Diffractometer | Bruker X8 Proteum diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2006) |
Tmin, Tmax | 0.193, 0.434 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6588, 1828, 1720 |
Rint | 0.038 |
(sin θ/λ)max (Å−1) | 0.599 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.103, 1.12 |
No. of reflections | 1828 |
No. of parameters | 138 |
No. of restraints | 6 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.35, −0.52 |
Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP in SHELXTL (Sheldrick, 2008), SHELX97 (Sheldrick, 2008) and local procedures.
Acknowledgements
This research was supported by grants ES05605, ES012475, ES013661 from the National Institute of Environmental Health Sciences, NIH (HJL) and NSFC grant No. 20907037 from the National Science Fund of China (YS).
References
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Chlorinated methoxy benzenes are a group of persistent organic pollutants that are associated with off-flavors in water, fish, chicken and wine (Brownlee et al.,1993; Curtis et al., 1972; Pereira et al., 2000; Vlachos et al., 2007; Zhang et al., 2006). Their biological properties depend, at least in part, on the conformation of the methoxy group relative to the aromatic ring system. The two methoxy groups of the title compound are twisted out of the plane of the benzene ring system due to the bulky ortho chlorine substituents and point in opposite directions. The respective dihedral angles were calculated between the plane of the benzene ring (C1 through C6) and the methoxy group and are 84.7 (3)° (atoms C1,O1,C7) and 68.5 (3)° (atoms C2,O2,C8), respectively. These dihedral angles are in agreement with the dihedral angels observed for other chlorinated methoxy benzenes with two ortho substituents (Iimura et al.,1984; Rissanen et al., 1987; Rissanen et al., 1988b; Telu et al., 2008; Weller & Gerstner, 1995; Wieczorek, 1980). In contrast, the methoxy group of structurally related compound with no or one substituent ortho to the methoxy group typically lie within the plane of the benzene ring system (Rissanen et al., 1988a; Song et al., 2010).