meso-Di­methyl 2,5-di­bromo­hexa­ne­dioate

The title compound, C₈H₁₂Br₂O₄, lies about a crystallographic center of inversion at the midpoint of the central C—C bond. The latter is also repsonsible for the observation of the meso form. There are no intra­molecular hydrogen bonds, but mol­ecules are connected by inter­molecular C—H⋯O inter­actions, forming a three-dimensional network.

Related literature

The title compound is an important intermediate in organic synthesis. For the synthetic procedure, see: McDonald & Reitz (1972). For bond-length data, see: Allen et al. (1987).

Experimental

Crystal data

• C₈H₁₂Br₂O₄

• M_r = 331.98

• Monoclinic, P 2₁ /c

• a = 4.5580 (9) Å

• b = 12.134 (2) Å

• c = 10.554 (2) Å

• β = 90.36 (3)°

• V = 583.7 (2) ų

• Z = 2

• Mo Kα radiation

• μ = 6.93 mm⁻¹

• T = 293 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 = 0.338, T_max = 0.544

• 1428 measured reflections

• 1271 independent reflections

• 639 reflections with I > 2σ(I)

• R_int = 0.071

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

Refinement

• R[F² > 2σ(F²)] = 0.040

• wR(F²) = 0.072

• S = 1.00

• 1271 reflections

• 64 parameters

• 3 restraints

• H-atom parameters constrained

• Δρ_max = 0.33 e Å⁻³

• Δρ_min = −0.37 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3A⋯O2^i	0.98	2.59	3.33 (1)	132
Symmetry code: (i) x+1, y, z.

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.

Supporting information

S1. Comment

The tittle compound, meso-2,5-dibromo-hexanedioic acid dimethyl ester is an important intermediate for the synthesis of dimethyl cyclobut-1-ene-1,2-dicarboxylate. We herein report 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 central C4—C4A bond of the title compound, C₈H₁₂Br₂O₄, represents a crystallographic center of inversion. The latter is also repsonsible for the observation of the meso form. There are no intramolecular hydrogen bonds, but molecules of the title compound are connected by C—H···O intermolecular interactions to form a three dimensional network (Table 1).

Related literature

The title compound is an important organic synthesis intermediate. For the synthetic procedure, see: McDonald & Reitz (1972). For bond-length data, see: Allen et al. (1987).

S2. Experimental

The title compound, (I) was prepared by a method reported in literature (McDonald & Reitz, 1972). Single crystals were obtained by dissolving (I) (0.5 g, 1.5 mmol) in ethanol (25 ml) and evaporating the solvent slowly at room temperature for about 3 d.

S3. Refinement

H atoms were positioned geometrically, with C—H = 0.96 Å for alkyl H, and constrained to ride on their parent atoms, with U_iso(H) = 1.5U_eq(C).

Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1985); cell refinement: CAD-4 Software (Enraf–Nonius, 1985); 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 (Sheldrick, 2008).

Figures

	Fig. 1. Molecular structure of the title compound showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level. Atoms labeled with the suffixes A are generated by the symmetry operation (1/2 - x, 3/2 - y, 1 - z). Hydrogen bonds are shown as dashed lines.
	Fig. 2. Packing diagram for (I). C—H···O hydrogen bonds are shown as dashed lines.

meso-Dimethyl 2,5-dibromohexanedioate

Crystal data

C8H12Br2O4	F(000) = 324
Mr = 331.98	Dx = 1.889 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 4.5580 (9) Å	θ = 9–13°
b = 12.134 (2) Å	µ = 6.93 mm^−1
c = 10.554 (2) Å	T = 293 K
β = 90.36 (3)°	Block, colourless
V = 583.7 (2) Å^3	0.20 × 0.10 × 0.10 mm
Z = 2

Data collection

Enraf–Nonius CAD-4 diffractometer	639 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.071
Graphite monochromator	θmax = 27.1°, θmin = 2.6°
ω/2θ scans	h = 0→5
Absorption correction: ψ scan (North et al., 1968)	k = −15→0
Tmin = 0.338, Tmax = 0.544	l = −13→13
1428 measured reflections	3 standard reflections every 200 reflections
1271 independent reflections	intensity decay: 1%

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.072	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.022P)^2] where P = (Fo^2 + 2Fc^2)/3
1271 reflections	(Δ/σ)max < 0.001
64 parameters	Δρmax = 0.33 e Å^−3
3 restraints	Δρmin = −0.37 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	0.23822 (12)	0.64074 (4)	0.70596 (6)	0.0813 (2)
O1	0.3762 (8)	0.4221 (3)	0.8857 (4)	0.0888 (12)
O2	0.0821 (9)	0.3620 (3)	0.7400 (4)	0.0980 (12)
C1	0.2255 (11)	0.3583 (4)	0.9715 (5)	0.0872 (17)
H1A	0.3263	0.3595	1.0516	0.131*
H1B	0.2144	0.2839	0.9409	0.131*
H1C	0.0310	0.3872	0.9817	0.131*
C2	0.2723 (12)	0.4259 (4)	0.7836 (5)	0.0572 (12)
C3	0.4550 (10)	0.4973 (3)	0.6885 (4)	0.0477 (11)
H3A	0.6595	0.5044	0.7166	0.057*
C4	0.4369 (9)	0.4614 (3)	0.5570 (4)	0.0475 (11)
H4A	0.2315	0.4476	0.5384	0.057*
H4B	0.5370	0.3911	0.5517	0.057*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br	0.0997 (4)	0.0232 (2)	0.1214 (5)	0.0072 (3)	0.0337 (3)	−0.0032 (4)
O1	0.111 (3)	0.058 (2)	0.098 (3)	0.002 (2)	0.007 (2)	0.035 (2)
O2	0.119 (3)	0.063 (3)	0.112 (3)	−0.028 (3)	0.023 (2)	0.020 (3)
C1	0.123 (5)	0.061 (4)	0.078 (3)	0.014 (4)	0.029 (3)	0.022 (3)
C2	0.062 (3)	0.040 (3)	0.070 (3)	0.006 (3)	0.022 (2)	0.025 (3)
C3	0.070 (3)	0.029 (2)	0.043 (2)	−0.002 (2)	−0.0005 (19)	−0.0068 (19)
C4	0.063 (3)	0.029 (2)	0.050 (3)	−0.004 (2)	−0.006 (2)	0.007 (2)

Geometric parameters (Å, º)

Br—C3	2.011 (4)	C2—C3	1.569 (6)
O1—C2	1.175 (5)	C3—C4	1.456 (5)
O1—C1	1.378 (5)	C3—H3A	0.9800
O2—C2	1.249 (6)	C4—C4^i	1.632 (7)
C1—H1A	0.9600	C4—H4A	0.9700
C1—H1B	0.9600	C4—H4B	0.9700
C1—H1C	0.9600
C2—O1—C1	115.1 (5)	C4—C3—Br	108.7 (3)
O1—C1—H1A	109.5	C2—C3—Br	99.0 (3)
O1—C1—H1B	109.5	C4—C3—H3A	111.3
H1A—C1—H1B	109.5	C2—C3—H3A	111.3
O1—C1—H1C	109.5	Br—C3—H3A	111.3
H1A—C1—H1C	109.5	C3—C4—C4^i	120.9 (4)
H1B—C1—H1C	109.5	C3—C4—H4A	107.1
O1—C2—O2	126.0 (5)	C4^i—C4—H4A	107.1
O1—C2—C3	113.3 (5)	C3—C4—H4B	107.1
O2—C2—C3	118.5 (5)	C4^i—C4—H4B	107.1
C4—C3—C2	114.7 (4)	H4A—C4—H4B	106.8
C1—O1—C2—O2	−15.8 (8)	O1—C2—C3—Br	−95.3 (4)
C1—O1—C2—C3	−178.7 (4)	O2—C2—C3—Br	100.4 (4)
O1—C2—C3—C4	149.2 (4)	C2—C3—C4—C4^i	168.8 (4)
O2—C2—C3—C4	−15.1 (6)	Br—C3—C4—C4^i	59.1 (5)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3A···O2^ii	0.98	2.59	3.33 (1)	132

Symmetry code: (ii) x+1, y, z.