1,4-Dibromo-2,5-dimeth­oxy­benzene

Abstract

The asymmetric unit of the title compound, C₈H₈Br₂O₂, contains one half-mol­ecule, the complete mol­ecule being generated by inversion symmetry.

Related literature

For standard bond lengths, see: Allen et al. (1987 ▶). For the synthetic procedure, see: Lopez-Alvarado et al. (2002 ▶). For potential uses of compounds derived from the title compound, see: Chen et al. (2006 ▶).

Experimental

Crystal data

• C₈H₈Br₂O₂

• M _r = 295.94

• Monoclinic,

• a = 6.573 (1) Å

• b = 8.438 (2) Å

• c = 8.756 (2) Å

• β = 90.14 (3)°

• V = 485.6 (2) ų

• Z = 2

• Mo Kα radiation

• μ = 8.30 mm⁻¹

• T = 298 K

• 0.20 × 0.10 × 0.10 mm

Data collection

• Enraf–Nonius CAD-4 diffractometer

• Absorption correction: ψ scan (North et al., 1968 ▶) T _min = 0.288, T _max = 0.491

• 1761 measured reflections

• 884 independent reflections

• 622 reflections with I > 2σ(I)

• R _int = 0.112

• 3 standard reflections every 200 reflections intensity decay: 1%

Refinement

• R[F ² > 2σ(F ²)] = 0.044

• wR(F ²) = 0.102

• S = 1.01

• 884 reflections

• 55 parameters

• H-atom parameters constrained

• Δρ_max = 0.58 e Å⁻³

• Δρ_min = −0.41 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1985 ▶); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

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

supplementary crystallographic information

Comment

The title compound, 1,4-dibromo-2,5-dimethoxybenzene is an important intermediate in the synthesis of 4-(2',5'-dimethoxy-4'-acetylthiophenyl)phenyl-nonafluorobiphenyl, which can be used as molecular switch, transistor and in the manufacture of memory devices (Chen et al., 2006). We report here the crystal structure of the title compound, (I).

The molecular structure of (I) is shown in Fig. 1. Bond lengths and angles are within normal ranges (Allen et al., 1987).

The benzene ring is planar and it's center respresents a crystallographic center of inversion. So only half of the molecule was observed in the asymmetric unit. No hydrogen bond interactions were observed in the crystal structure.

Experimental

The title compound, (I) was synthesized according to a literature method reported before (Lopez-Alvarado et al., 2002). Single crystals were obtained by slow evaporation of a methanolic (25 ml) solution of the compound (0.30 g, 1.0 mmol) at room temperature for about 15 d.

Refinement

H atoms were positioned geometrically, with C—H = 0.93 Å for aromatic H and 0.96 Å for methyl H, and constrained to ride on their parent atoms, with U_iso(H) = xU_eq(C/O), where x = 1.2 for aromatic H and x = 1.5 for other H.

Figures

Fig. 1.

Molecular structure of the title compound showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level.

Fig. 2.

Molecular packing of the title compound.

Crystal data

C8H8Br2O2	F(000) = 284
Mr = 295.94	Dx = 2.024 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 6.573 (1) Å	θ = 9–13°
b = 8.438 (2) Å	µ = 8.30 mm−1
c = 8.756 (2) Å	T = 298 K
β = 90.14 (3)°	Block, colourless
V = 485.6 (2) Å3	0.20 × 0.10 × 0.10 mm
Z = 2

Data collection

Enraf–Nonius CAD-4 diffractometer	622 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.112
graphite	θmax = 25.3°, θmin = 3.4°
ω/2θ scans	h = −7→7
Absorption correction: ψ scan (North et al., 1968)	k = −10→0
Tmin = 0.288, Tmax = 0.491	l = −10→10
1761 measured reflections	3 standard reflections every 200 reflections
884 independent reflections	intensity decay: 1%

Refinement

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.102	H-atom parameters constrained
S = 1.01	w = 1/[σ2(Fo2) + (0.03P)2 + 0.0P] where P = (Fo2 + 2Fc2)/3
884 reflections	(Δ/σ)max < 0.001
55 parameters	Δρmax = 0.58 e Å−3
0 restraints	Δρmin = −0.41 e Å−3

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 > 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.

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

	x	y	z	Uiso*/Ueq
Br	0.26386 (11)	0.73471 (7)	0.78061 (8)	0.0598 (3)
O	−0.1091 (7)	0.5578 (5)	0.7000 (5)	0.0551 (11)
C1	−0.0605 (9)	0.5256 (6)	0.8479 (6)	0.0394 (13)
C2	0.1090 (9)	0.5986 (5)	0.9077 (7)	0.0400 (13)
C3	0.1721 (9)	0.5752 (5)	1.0558 (7)	0.0433 (14)
H3A	0.2881	0.6260	1.0922	0.052*
C4	−0.2593 (11)	0.4649 (8)	0.6294 (8)	0.0649 (19)
H4A	−0.2775	0.4993	0.5257	0.097*
H4B	−0.3852	0.4761	0.6837	0.097*
H4C	−0.2181	0.3558	0.6304	0.097*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Br	0.0762 (5)	0.0516 (4)	0.0517 (5)	−0.0207 (3)	0.0162 (3)	0.0026 (3)
O	0.065 (3)	0.055 (2)	0.045 (3)	−0.011 (2)	−0.004 (2)	0.0031 (19)
C1	0.049 (3)	0.036 (3)	0.033 (3)	0.002 (3)	0.007 (3)	−0.003 (2)
C2	0.047 (3)	0.031 (3)	0.042 (4)	−0.004 (3)	0.009 (3)	−0.002 (2)
C3	0.049 (3)	0.034 (3)	0.046 (4)	−0.006 (3)	0.007 (3)	−0.003 (2)
C4	0.070 (5)	0.078 (4)	0.047 (5)	−0.004 (4)	−0.014 (4)	0.009 (4)

Geometric parameters (Å, °)

Br—C2	1.897 (5)	C3—C1i	1.405 (7)
O—C1	1.361 (7)	C3—H3A	0.9300
O—C4	1.403 (8)	C4—H4A	0.9600
C1—C2	1.375 (8)	C4—H4B	0.9600
C1—C3i	1.405 (7)	C4—H4C	0.9600
C2—C3	1.375 (8)
C1—O—C4	118.1 (5)	C2—C3—H3A	120.1
O—C1—C2	117.4 (5)	C1i—C3—H3A	120.1
O—C1—C3i	124.8 (5)	O—C4—H4A	109.5
C2—C1—C3i	117.8 (5)	O—C4—H4B	109.5
C1—C2—C3	122.5 (5)	H4A—C4—H4B	109.5
C1—C2—Br	118.9 (4)	O—C4—H4C	109.5
C3—C2—Br	118.6 (4)	H4A—C4—H4C	109.5
C2—C3—C1i	119.7 (5)	H4B—C4—H4C	109.5
C4—O—C1—C2	169.3 (5)	O—C1—C2—Br	−1.0 (6)
C4—O—C1—C3i	−11.4 (8)	C3i—C1—C2—Br	179.7 (4)
O—C1—C2—C3	179.8 (5)	C1—C2—C3—C1i	−0.5 (8)
C3i—C1—C2—C3	0.5 (8)	Br—C2—C3—C1i	−179.7 (4)

Symmetry codes: (i) −x, −y+1, −z+2.