1-Bromo-2,3,6-trichloro-4,5-dimethoxy­benzene

Abstract

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

• C₈H₆BrCl₃O₂

• M _r = 320.39

• Triclinic,

• a = 7.7885 (7) Å

• b = 8.8600 (7) Å

• c = 9.1523 (8) Å

• α = 62.256 (3)°

• β = 75.358 (4)°

• γ = 75.133 (4)°

• V = 533.64 (8) ų

• Z = 2

• Cu Kα radiation

• μ = 11.94 mm⁻¹

• T = 90 K

• 0.20 × 0.15 × 0.07 mm

Data collection

• Bruker X8 Proteum diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2006 ▶) T _min = 0.193, T _max = 0.434

• 6588 measured reflections

• 1828 independent reflections

• 1720 reflections with I > 2σ(I)

• R _int = 0.038

Refinement

• R[F ² > 2σ(F ²)] = 0.038

• wR(F ²) = 0.103

• S = 1.12

• 1828 reflections

• 138 parameters

• 6 restraints

• H-atom parameters constrained

• Δρ_max = 0.35 e Å⁻³

• Δρ_min = −0.52 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: 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.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

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).

Experimental

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 saturated solution of the title compound in CHCl₃.

Refinement

H atoms were found in difference Fourier maps and subsequently placed in idealized positions with constrained C-H distances of 0.98 Å and U_iso(H) values set to 1.5U_eq 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.

Figures

Fig. 1.

View of the title compound showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Crystal data

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

Data collection

Bruker X8 Proteum diffractometer	1828 independent reflections
Radiation source: fine-focus rotating anode	1720 reflections with I > 2σ(I)
graded multilayer optics	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

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)

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	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)

Atomic displacement parameters (Ų)

	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)

Geometric parameters (Å, °)

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)