2,5-Dibromo­terephthalic acid dihydrate

Abstract

The asymmetric unit of the title compound, C₈H₄Br₂O₄·2H₂O, contains one half-mol­ecule of 2,5-dibromo­terephthalic acid (DBTA) and one water mol­ecule. The DBTA mol­ecule is centrosymmetric. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules, forming a three-dimensional framework.

Related literature

For general background, see: Yao & Tour (1999 ▶). For a related structure, see: Singh & Bedi (1957 ▶).

Experimental

Crystal data

• C₈H₄Br₂O₄·2H₂O

• M _r = 359.94

• Monoclinic,

• a = 10.670 (2) Å

• b = 7.413 (1) Å

• c = 7.074 (1) Å

• β = 92.74 (3)°

• V = 558.89 (15) ų

• Z = 2

• Mo Kα radiation

• μ = 7.26 mm⁻¹

• T = 293 (2) K

• 0.10 × 0.10 × 0.08 mm

Data collection

• Enraf–Nonius CAD-4 diffractometer

• Absorption correction: ψ scan (North et al., 1968 ▶) T _min = 0.530, T _max = 0.594 (expected range = 0.499–0.559)

• 1003 measured reflections

• 1003 independent reflections

• 763 reflections with I > 2σ(I)

• 3 standard reflections every 200 reflections intensity decay: none

Refinement

• R[F ² > 2σ(F ²)] = 0.048

• wR(F ²) = 0.117

• S = 1.05

• 1003 reflections

• 67 parameters

• 21 restraints

• H-atom parameters constrained

• Δρ_max = 0.55 e Å⁻³

• Δρ_min = −0.70 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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
OW—HWA⋯O1i	0.85	2.11	2.903 (9)	155
OW—HWB⋯O1ii	0.85	2.22	2.944 (9)	142
O2—H2A⋯OW	0.82	1.75	2.566 (8)	177

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

Comment

2,5-Dibromoterephthalic acid (DBTA) is an important intermediate in the preparation of flame-retardant polymers (Yao et al., 1999). We report herein the crystal structure of the title compound (I).

The asymmetric unit of I (Fig. 1), contains one half of a molecule of 2,5-dibromoterephthalic acid (DBTA), which is related to the other half by a center of symmetry, and one water molecule. Three neighbouring DBTA molecules are linked through one water molecule by intermolecular O—H···O hydrogen bonds, to form a three dimensional framework.

Experimental

The title compound was prepared according to the method described by Singh & Bedi (1957). Crystals of (I) suitable for X-ray analysis were obtained by dissolving DBTA (2.0 g) in water (80 ml) and evaporating slowly at room temperature for about 15 d.

Refinement

Anisotropic parameters of the C atoms in the phenyl ring were restrained to have equal components and approximately isotropic behavior. H atoms were positioned geometrically, with O—H = 0.82 (for OH) and 0.85 (for H₂O) and C—H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, 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.

The molecular structure of (I), showing the atom labelling scheme. Anisotropic displacement parameters are shown at the 50% probability level.

Crystal data

C8H4Br2O4·2H2O	F000 = 348
Mr = 359.94	Dx = 2.139 Mg m−3
Monoclinic, P21/c	Mo Kα radiation λ = 0.71073 Å
a = 10.670 (2) Å	Cell parameters from 25 reflections
b = 7.413 (1) Å	θ = 10–13º
c = 7.074 (1) Å	µ = 7.26 mm−1
β = 92.74 (3)º	T = 293 (2) K
V = 558.89 (15) Å3	Block, colorless
Z = 2	0.10 × 0.10 × 0.08 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	Rint = 0.0000
Radiation source: fine-focus sealed tube	θmax = 25.2º
Monochromator: graphite	θmin = 1.9º
T = 293(2) K	h = −12→12
ω/2θ scans	k = 0→8
Absorption correction: ψ scan(North et al., 1968)	l = 0→8
Tmin = 0.530, Tmax = 0.594	3 standard reflections
1003 measured reflections	every 200 reflections
1003 independent reflections	intensity decay: none
763 reflections with I > 2σ(I)

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)] = 0.048	H-atom parameters constrained
wR(F2) = 0.117	w = 1/[σ2(Fo2) + (0.06P)2 + 1.5P] where P = (Fo2 + 2Fc2)/3
S = 1.05	(Δ/σ)max < 0.001
1003 reflections	Δρmax = 0.55 e Å−3
67 parameters	Δρmin = −0.70 e Å−3
21 restraints	Extinction correction: none
Primary atom site location: structure-invariant direct methods

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	0.31754 (7)	0.35260 (9)	0.52687 (10)	0.0366 (3)
OW	−0.0069 (5)	−0.2828 (11)	0.7105 (11)	0.093 (3)
HWA	−0.0608	−0.2028	0.6780	0.111*
HWB	−0.0299	−0.3786	0.7651	0.111*
O1	0.1532 (5)	0.0220 (6)	0.5124 (8)	0.0495 (14)
O2	0.2259 (5)	−0.2252 (7)	0.6570 (9)	0.0554 (15)
H2A	0.1515	−0.2402	0.6767	0.083*
C1	0.5431 (6)	0.1725 (10)	0.4729 (9)	0.034
H1A	0.5725	0.2885	0.4518	0.040*
C2	0.4182 (6)	0.1457 (8)	0.5085 (9)	0.0276 (13)
C3	0.3736 (6)	−0.0245 (8)	0.5317 (8)	0.0255 (13)
C4	0.2396 (6)	−0.0748 (9)	0.5662 (9)	0.0314 (15)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Br	0.0487 (4)	0.0111 (4)	0.0496 (5)	0.0050 (3)	−0.0007 (3)	0.0002 (3)
OW	0.030 (3)	0.111 (6)	0.139 (7)	0.008 (3)	0.013 (3)	0.073 (5)
O1	0.045 (3)	0.016 (3)	0.087 (4)	−0.004 (2)	−0.002 (3)	0.015 (3)
O2	0.051 (3)	0.028 (3)	0.087 (4)	−0.006 (3)	−0.004 (3)	0.029 (3)
C1	0.034	0.034	0.034	0.000	0.002	0.000
C2	0.043 (3)	0.009 (3)	0.030 (3)	0.002 (3)	−0.009 (3)	0.000 (3)
C3	0.038 (3)	0.013 (3)	0.025 (3)	−0.002 (3)	−0.003 (2)	−0.004 (3)
C4	0.035 (3)	0.022 (3)	0.038 (4)	0.003 (3)	0.004 (3)	0.005 (3)

Geometric parameters (Å, °)

Br—C2	1.880 (6)	C1—C2	1.383 (8)
OW—HWA	0.8500	C1—C3i	1.413 (9)
OW—HWB	0.8500	C1—H1A	0.9300
O1—C4	1.215 (8)	C2—C3	1.361 (8)
O2—C4	1.299 (8)	C3—C1i	1.413 (9)
O2—H2A	0.8200	C3—C4	1.508 (9)
HWA—OW—HWB	120.0	C1—C2—Br	117.0 (5)
C4—O2—H2A	109.5	C2—C3—C1i	119.5 (6)
C2—C1—C3i	120.4 (6)	C2—C3—C4	126.0 (6)
C2—C1—H1A	119.8	C1i—C3—C4	114.5 (5)
C3i—C1—H1A	119.8	O1—C4—O2	124.1 (6)
C3—C2—C1	120.1 (6)	O1—C4—C3	121.0 (6)
C3—C2—Br	122.9 (5)	O2—C4—C3	115.0 (6)
C3i—C1—C2—C3	−2.7 (10)	Br—C2—C3—C4	2.8 (9)
C3i—C1—C2—Br	176.2 (5)	C2—C3—C4—O1	26.1 (10)
C1—C2—C3—C1i	2.7 (10)	C1i—C3—C4—O1	−154.9 (6)
Br—C2—C3—C1i	−176.2 (5)	C2—C3—C4—O2	−153.4 (7)
C1—C2—C3—C4	−178.3 (6)	C1i—C3—C4—O2	25.6 (8)

Symmetry codes: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
OW—HWA···O1ii	0.85	2.11	2.903 (9)	155
OW—HWB···O1iii	0.85	2.22	2.944 (9)	142
O2—H2A···OW	0.82	1.75	2.566 (8)	177

Symmetry codes: (ii) −x, −y, −z+1; (iii) −x, y−1/2, −z+3/2.