1,4-Di­bromo-2,5-dibut­­oxy­benzene

The asymmetric unit of the title compound, C₁₄H₂₀Br₂O₂, contains one half-mol­ecule located on an inversion centre. The mol­ecule is essentially planar, with a maximum deviation from the best plane of the non-H atoms of 0.054 (2) Å for the O atoms. The but­oxy group adopts a fully extended all-trans conformation. In the crystal, mol­ecules are connected via C—Br⋯O halogen bonds [Br⋯O = 3.2393 (19) Å] into a two-dimensional corrugated network in the bc plane.

Related literature

For related structures, see: Choi et al. (2010); Fun et al. (2010); Li et al. (2008). For applications of dialk­oxy­benzenes, see: Brandon et al. (1997); Huang et al. (2007); Lightowler & Hird (2005); Promarak & Ruchirawat (2007). For the synthetic procedure, see: Lopez-Alvarado et al. (2002).

Experimental

Crystal data

• C₁₄H₂₀Br₂O₂

• M_r = 380.10

• Monoclinic, P 2₁ /c

• a = 8.3685 (4) Å

• b = 12.6395 (5) Å

• c = 7.1083 (3) Å

• β = 96.461 (5)°

• V = 747.10 (6) ų

• Z = 2

• Cu Kα radiation

• μ = 6.82 mm⁻¹

• T = 150 K

• 0.07 × 0.06 × 0.01 mm

Data collection

• Oxford Diffraction Gemini diffractometer

• Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) T_min = 0.647, T_max = 0.935

• 5426 measured reflections

• 1442 independent reflections

• 1303 reflections with I > 2σ(I)

• R_int = 0.029

Refinement

• R[F² > 2σ(F²)] = 0.030

• wR(F²) = 0.081

• S = 1.07

• 1442 reflections

• 83 parameters

• H-atom parameters constrained

• Δρ_max = 0.73 e Å⁻³

• Δρ_min = −0.38 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006); 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, PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Supporting information

S1. Comment

Dialkoxy-substituted benzenes such as the title compound (I) are very useful intermediates to synthesize soluble poly(p-phenylene) (Huang et al., 2007; Lightowler & Hird, 2005), thiophene–phenylene co-oligomers (Promarak & Ruchirawat, 2007) and poly(phenylene vinylene) (Brandon et al., 1997), which have wide range of applications in semiconductor and electronics industries.

The title compound is similar to its analog, 1,4-dibromo-2,5-bis(hexyloxy)-benzene (II) (Li et al., 2008). The alkyl chains are nearly coplanar with the benzene ring, with C4—O1—C3—C2 torsion angles of 3.3 (4)°, which is similar to II. However, the title compound is stabilized by intermolecular Br···O interactions [3.2393 (19) Å], which has shorter distance, compared to Br···Br interactions (3.410 Å) found in II. The intermolecular Br···O interaction is shorter than the sum of the Van der Waals radii of the relevant atoms (3.37 Å) and those found in other compound [3.301 (4) Å] (Fun et al. 2010).

In the crystal, nearly linear halogen bond C1–Br1···O1(-x, 1/2 + y, 1/2 - z) [<C1-Br···O159.96 (9)°] link the molecules into a two-dimensional corrugated network along bc plane (Figure 2).

Related literature

For related structures, see: Choi et al. (2010); Fun et al. (2010); Li et al. (2008). For applications of dialkoxybenzenes, see: Brandon et al. (1997); Huang et al. (2007); Lightowler & Hird (2005); Promarak & Ruchirawat (2007). For the synthetic procedure, see: Lopez-Alvarado et al. (2002).

S2. Experimental

The compound was prepared according to previously published work with a slight modification (Lopez-Alvarado et al., 2002). To 1,4-bis(butoxy)benzene (5.00 g, 22.5 mmol) was added dropwise Br₂ (7. 55 g, 47.25 mmol) in glacial acetic acid. The mixture was stirred at room temperature for two hours followed by heating under reflux for another two hours. The mixture was left to cool to room temperature and water was then added to precipitate the product. The product was filtered, washed with excess water and 1.0 M sodium bicarbonate solution. Slow recrystallization of the product from methanol–ethyl acetate mixture afforded crystals suitable for single X-ray diffraction (yield: 82%).

S3. Refinement

The hydrogen atom positions were calculated geometrically and refined in a riding model approximation with C–H bond lengths in the range 0.93–0.97 Å and U_iso(H) = 1.2U_eq(C) for aromatic and CH₂ group, and U_iso(H) = 1.5U_eq(C) for methyl group.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); 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 (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Figures

	Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level. Symmetry code for atoms with the A label: -x, 1 - y, 1 - z.
	Fig. 2. Crystal packing of the title compound showing intermolecular halogen bonds C1–Br1···O1 [-x,1/2 + y,1/2 - z] resulting in the formation of two-dimensional network along bc plane.

1,4-Dibromo-2,5-dibutoxybenzene

Crystal data

C14H20Br2O2	F(000) = 380
Mr = 380.10	Dx = 1.690 Mg m^−3
Monoclinic, P21/c	Melting point = 343–345 K
Hall symbol: -P 2ybc	Cu Kα radiation, λ = 1.54178 Å
a = 8.3685 (4) Å	Cell parameters from 2679 reflections
b = 12.6395 (5) Å	θ = 3–71°
c = 7.1083 (3) Å	µ = 6.82 mm^−1
β = 96.461 (5)°	T = 150 K
V = 747.10 (6) Å^3	Plate, colourless
Z = 2	0.07 × 0.06 × 0.01 mm

Data collection

Oxford Diffraction Gemini diffractometer	1442 independent reflections
Radiation source: fine-focus sealed tube	1303 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
ω scans	θmax = 71.6°, θmin = 5.3°
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	h = −8→10
Tmin = 0.647, Tmax = 0.935	k = −15→15
5426 measured reflections	l = −8→6

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.081	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0507P)^2 + 0.4756P] where P = (Fo^2 + 2Fc^2)/3
1442 reflections	(Δ/σ)max < 0.001
83 parameters	Δρmax = 0.73 e Å^−3
0 restraints	Δρmin = −0.38 e Å^−3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems open-flow nitrogen cryostat (Cosier & Glazer 1986) with a nominal stability of 0.1 K.

Cosier, J. & Glazer, A.M., (1986)., J. Appl. Cryst. 105 107.

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
Br1	−0.15758 (3)	1.17923 (2)	0.20385 (4)	0.01819 (14)
O1	0.2931 (2)	0.90585 (15)	0.4561 (3)	0.0186 (4)
C1	−0.0674 (3)	1.0747 (2)	0.3762 (4)	0.0165 (6)
C2	0.0787 (3)	1.0299 (2)	0.3466 (4)	0.0170 (6)
H2	0.1301	1.0506	0.2431	0.020*
C3	0.1490 (3)	0.9538 (2)	0.4722 (4)	0.0160 (5)
C4	0.3733 (4)	0.9319 (2)	0.2931 (4)	0.0188 (6)
H4A	0.4017	1.0064	0.2949	0.023*
H4B	0.3034	0.9175	0.1776	0.023*
C5	0.5229 (3)	0.8644 (2)	0.3018 (4)	0.0199 (6)
H5A	0.4923	0.7904	0.2966	0.024*
H5B	0.5883	0.8766	0.4213	0.024*
C6	0.6222 (3)	0.8887 (2)	0.1394 (4)	0.0202 (6)
H6A	0.5590	0.8727	0.0198	0.024*
H6B	0.6483	0.9635	0.1403	0.024*
C7	0.7771 (4)	0.8243 (2)	0.1556 (5)	0.0249 (7)
H7A	0.8411	0.8413	0.2724	0.037*
H7B	0.8363	0.8409	0.0513	0.037*
H7C	0.7516	0.7503	0.1535	0.037*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0183 (2)	0.01468 (19)	0.0219 (2)	0.00149 (10)	0.00335 (13)	0.00358 (10)
O1	0.0161 (10)	0.0183 (9)	0.0223 (10)	0.0030 (8)	0.0061 (8)	0.0029 (8)
C1	0.0200 (15)	0.0114 (12)	0.0174 (13)	0.0022 (10)	−0.0003 (10)	0.0031 (10)
C2	0.0185 (14)	0.0134 (12)	0.0200 (14)	−0.0002 (10)	0.0063 (11)	0.0002 (10)
C3	0.0149 (13)	0.0127 (12)	0.0202 (14)	0.0005 (10)	0.0012 (10)	−0.0017 (10)
C4	0.0209 (15)	0.0175 (13)	0.0188 (14)	−0.0002 (11)	0.0062 (11)	0.0010 (11)
C5	0.0193 (14)	0.0162 (13)	0.0243 (15)	0.0012 (11)	0.0036 (11)	0.0024 (11)
C6	0.0161 (14)	0.0181 (13)	0.0269 (15)	0.0005 (11)	0.0049 (11)	0.0008 (11)
C7	0.0216 (16)	0.0241 (16)	0.0305 (18)	0.0036 (12)	0.0085 (13)	−0.0015 (12)

Geometric parameters (Å, º)

Br1—C1	1.900 (3)	C5—C6	1.527 (4)
O1—C3	1.366 (3)	C5—H5A	0.9700
O1—C4	1.441 (3)	C5—H5B	0.9700
C1—C2	1.384 (4)	C6—C7	1.523 (4)
C1—C3^i	1.386 (4)	C6—H6A	0.9700
C2—C3	1.397 (4)	C6—H6B	0.9700
C2—H2	0.9300	C7—H7A	0.9600
C4—C5	1.511 (4)	C7—H7B	0.9600
C4—H4A	0.9700	C7—H7C	0.9600
C4—H4B	0.9700
C3—O1—C4	117.5 (2)	C4—C5—H5A	109.2
C2—C1—C3^i	122.2 (3)	C6—C5—H5A	109.2
C2—C1—Br1	118.7 (2)	C4—C5—H5B	109.2
C3^i—C1—Br1	119.1 (2)	C6—C5—H5B	109.2
C1—C2—C3	120.0 (3)	H5A—C5—H5B	107.9
C1—C2—H2	120.0	C7—C6—C5	111.5 (2)
C3—C2—H2	120.0	C7—C6—H6A	109.3
O1—C3—C1^i	117.8 (2)	C5—C6—H6A	109.3
O1—C3—C2	124.3 (3)	C7—C6—H6B	109.3
C1^i—C3—C2	117.8 (3)	C5—C6—H6B	109.3
O1—C4—C5	107.3 (2)	H6A—C6—H6B	108.0
O1—C4—H4A	110.3	C6—C7—H7A	109.5
C5—C4—H4A	110.3	C6—C7—H7B	109.5
O1—C4—H4B	110.3	H7A—C7—H7B	109.5
C5—C4—H4B	110.3	C6—C7—H7C	109.5
H4A—C4—H4B	108.5	H7A—C7—H7C	109.5
C4—C5—C6	112.0 (2)	H7B—C7—H7C	109.5

Symmetry code: (i) −x, −y+2, −z+1.