rac-2,3-Di­bromo­succinic acid

rac-2,3-Di­bromo­succinic acid, C₄H₄Br₂O₄, is the product of the electrophilic addition of bromine to maleic acid. Whereas the carboxyl groups and the bromo ligands are in a gauche arrangement with respect to each other, the tertiary H atoms attached to the central C atoms are in a trans arrangement. The hydroxyl groups form hydrogen bonds with the carbonyl O atoms of neighbouring mol­ecules.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

rac-Dibromosuccinic acid

Crystal data

C4H4Br2O4	F(000) = 520
Mr = 275.89	Dx = 2.462 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.725 (4) Å	Cell parameters from 512 reflections
b = 6.167 (1) Å	θ = 1–20°
c = 10.228 (2) Å	µ = 10.84 mm^−1
β = 111.98 (1)°	T = 173 K
V = 744.3 (3) Å^3	Block, colourless
Z = 4	0.30 × 0.20 × 0.15 mm

Data collection

Siemens CCD three-circle diffractometer	1517 independent reflections
Radiation source: fine-focus sealed tube	1356 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.073
ω scans	θmax = 26.4°, θmin = 3.7°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −15→15
Tmin = 0.090, Tmax = 0.193	k = −7→7
12264 measured reflections	l = −12→12

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.031	H-atom parameters constrained
wR(F^2) = 0.081	w = 1/[σ^2(Fo^2) + (0.0464P)^2 + 0.0831P] where P = (Fo^2 + 2Fc^2)/3
S = 1.12	(Δ/σ)max = 0.001
1517 reflections	Δρmax = 1.16 e Å^−3
94 parameters	Δρmin = −0.72 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0049 (8)

Special details

Experimental. Coverage of the unique set is 100% complete to at least 26.5° in θ. Crystal decay was monitored by repeating the initial frames at the end of data collection and analyzing the duplicate reflections.

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
C1	0.1415 (3)	0.6347 (5)	0.3116 (3)	0.0143 (6)
O11	0.0819 (2)	0.7357 (4)	0.2070 (2)	0.0184 (5)
O12	0.1182 (2)	0.6008 (4)	0.4248 (2)	0.0179 (5)
H12	0.0562	0.6602	0.4147	0.021*
C2	0.2521 (3)	0.5281 (5)	0.3219 (3)	0.0151 (7)
H2	0.2609	0.3866	0.3726	0.018*
Br2	0.37350 (3)	0.72428 (6)	0.43050 (4)	0.02705 (17)
C3	0.2551 (3)	0.4903 (5)	0.1764 (3)	0.0151 (7)
H3	0.2596	0.6327	0.1320	0.018*
Br3	0.38534 (3)	0.31078 (7)	0.18868 (4)	0.02555 (17)
C4	0.1500 (3)	0.3680 (5)	0.0830 (3)	0.0137 (7)
O41	0.0902 (2)	0.2691 (4)	0.1308 (2)	0.0194 (5)
O42	0.1328 (2)	0.3889 (4)	−0.0520 (2)	0.0183 (5)
H42	0.0743	0.3197	−0.1006	0.022*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0092 (16)	0.0152 (14)	0.0161 (16)	−0.0031 (13)	0.0021 (13)	−0.0023 (12)
O11	0.0120 (13)	0.0243 (12)	0.0149 (11)	0.0031 (10)	0.0005 (10)	0.0022 (9)
O12	0.0128 (13)	0.0236 (12)	0.0193 (12)	0.0056 (10)	0.0084 (10)	0.0029 (9)
C2	0.0076 (16)	0.0218 (16)	0.0142 (15)	−0.0011 (13)	0.0022 (13)	−0.0014 (12)
Br2	0.0105 (2)	0.0422 (3)	0.0257 (2)	−0.00744 (16)	0.00359 (17)	−0.01437 (16)
C3	0.0074 (16)	0.0220 (17)	0.0162 (15)	0.0036 (13)	0.0047 (13)	0.0017 (12)
Br3	0.0101 (2)	0.0407 (3)	0.0236 (2)	0.00869 (14)	0.00387 (17)	−0.00464 (14)
C4	0.0059 (16)	0.0169 (15)	0.0172 (15)	0.0048 (12)	0.0030 (13)	−0.0007 (12)
O41	0.0114 (13)	0.0262 (13)	0.0205 (12)	−0.0059 (10)	0.0057 (11)	−0.0022 (10)
O42	0.0143 (13)	0.0240 (12)	0.0125 (11)	−0.0026 (10)	0.0001 (10)	−0.0008 (9)

Geometric parameters (Å, º)

C1—O11	1.225 (4)	C3—C4	1.521 (4)
C1—O12	1.315 (4)	C3—Br3	1.957 (3)
C1—C2	1.520 (4)	C3—H3	1.0000
O12—H12	0.8400	C4—O41	1.212 (4)
C2—C3	1.522 (4)	C4—O42	1.321 (4)
C2—Br2	1.950 (3)	O42—H42	0.8400
C2—H2	1.0000
O11—C1—O12	125.4 (3)	C4—C3—C2	110.6 (3)
O11—C1—C2	122.3 (3)	C4—C3—Br3	106.5 (2)
O12—C1—C2	112.2 (3)	C2—C3—Br3	110.8 (2)
C1—O12—H12	109.5	C4—C3—H3	109.6
C1—C2—C3	111.1 (2)	C2—C3—H3	109.6
C1—C2—Br2	106.7 (2)	Br3—C3—H3	109.6
C3—C2—Br2	110.3 (2)	O41—C4—O42	125.9 (3)
C1—C2—H2	109.6	O41—C4—C3	122.3 (3)
C3—C2—H2	109.6	O42—C4—C3	111.8 (3)
Br2—C2—H2	109.6	C4—O42—H42	109.5
O11—C1—C2—C3	−21.2 (4)	C1—C2—C3—Br3	−170.5 (2)
O12—C1—C2—C3	157.4 (3)	Br2—C2—C3—Br3	71.4 (2)
O11—C1—C2—Br2	99.1 (3)	C2—C3—C4—O41	−17.5 (4)
O12—C1—C2—Br2	−82.3 (3)	Br3—C3—C4—O41	103.0 (3)
C1—C2—C3—C4	−52.7 (4)	C2—C3—C4—O42	161.1 (3)
Br2—C2—C3—C4	−170.8 (2)	Br3—C3—C4—O42	−78.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O12—H12···O41^i	0.84	1.87	2.702 (3)	172
O42—H42···O11^ii	0.84	1.91	2.706 (3)	159

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