(RS)-2,3-Dibromo­succinic acid

Crystals of the title compound, C₄H₄Br₂O₄, were grown from an aqueous solution. The structure features centrosymmetric mol­ecules, each of which forms hydrogen bonds with two adjacent acid mol­ecules, yielding long chains.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.013 Å
• R factor = 0.045
• wR factor = 0.102
• Data-to-parameter ratio = 18.1

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for    C1     -   C2      ..      10.18 su

Alert level C
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT230_ALERT_2_C Hirshfeld Test Diff for    Br1    -   C2      ..       5.07 su
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         C2
PLAT341_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...         13
PLAT360_ALERT_2_C Short  C(sp3)-C(sp3) Bond  C2     -   C2_a   ...       1.40 Ang.
PLAT431_ALERT_2_C Short Inter HL..A Contact  Br1    ..  O2      ..       3.25 Ang.

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   5 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion


checkCIF publication errors

Alert level A
PUBL022_ALERT_1_A There is a mismatched ~ on line 117
              Crystals of (R,S)-2,3-dibromosuccinic acid, C~4#H~4~Br~2~O~4~, were grown from
              If you require a ~ then it should be escaped
              with a \, i.e. \~
              Otherwise there must be a matching closing ~, e.g. C~2~H~4~

   1 ALERT level A = Data missing that is essential or data in wrong format
   0 ALERT level G = General alerts. Data that may be required is missing

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S1. Comment

Some time ago, the structure of racemic 2,3-dibromosuccinic acid, which had been obtained by an electrophilic reaction between maleic acid and bromine, was determined (Bolte & Degen, 2000). The structure features a complex pattern of hydrogen bonds between carboxy groups of adjacent acid molecules. Inspired by the fact that the melting points of the racemic and the meso compounds are extremely different (racemate: 444 K; meso compound: 528 K), we expected very different hydrogen-bonding patterns in the two phases and decided therefore to determine the structure of the meso compound. From a reaction between bromine and fumaric acid, we obtained single crystals of the meso compound, (I), whose structure is described here. The molecule lies about an inversion centre located at the mid-point of the C2—C2ⁱ bond [symmetry code: (i) 1/2 − x, 1/2 − y, 1 − z). The geometry of the molecule is essentially the same as in the structure of pyridone.(R,S)-2,3-dibromosuccinic acid (1:1) (Aakeröy et al., 2000). In the crystal structure, the carboxy groups link pairs of molecules, forming an inversion-related closed hydrogen-bonding loop and infinite chains along the a axis (Fig 2).

S2. Experimental

An aqueous solution (2.5 ml) with the respective concentrations 0.69 mol l⁻¹ of fumaric acid, 2.1 mol l⁻¹ of KBr and 1.9 mol l⁻¹ of Br₂ was placed in a boiling water bath. To avoid precipitation of KBr, the volume of the solution was kept constant by addition of deionized water. After 10 min, crystals of (I) were vacuum-filtered and placed in a heated cabinet at 373 K for one hour.

S3. Refinement

The H atoms were located in a difference Fourier map and were refined using a riding model, with C—H = 0.96 Å and U_iso(H) = 1.2U_eq(C), and with O—H = 0.82 Å and U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: DIRAX/LSQ (Duisenberg et al., 2003); data reduction: EVALCCD (Duisenberg, 1992); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: maXus (Mackay et al., 1999).

Figures

	Fig. 1. : The (R,S)-2,3-dibromosuccinic acid molecule. Displacement ellipsoids are drawn at the 50% probability level [symmetry code: (i) 1/2 − x, 1/2 − y, 1 − z].
	Fig. 2. : The chains formed by hydrogen bonds in (I). Hydrogen bonds are indicated by dashed lines.

(I)

Crystal data

C4H4Br2O4	Z = 4
Mr = 275.89	Dx = 2.477 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 37 reflections
a = 14.244 (1) Å	θ = 4.3–21.0°
b = 5.1664 (6) Å	µ = 10.91 mm^−1
c = 11.3736 (8) Å	T = 298 K
β = 117.684 (9)°	Cube, colourless
V = 741.17 (13) Å^3	0.33 × 0.30 × 0.27 mm

Data collection

Bruker–Nonius KappaCCD diffractometer	679 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.039
ϕ scans	θmax = 27.5°, θmin = 4.5°
Absorption correction: numerical HABITUS (Herrendorf & Bärnighausen, 1997)	h = −15→18
Tmin = 0.091, Tmax = 0.137	k = −6→6
5265 measured reflections	l = −14→14
849 independent reflections

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.102	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0299P)^2 + 8.0961P] where P = (Fo^2 + 2Fc^2)/3
849 reflections	(Δ/σ)max < 0.001
47 parameters	Δρmax = 1.14 e Å^−3
0 restraints	Δρmin = −0.73 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
Br1	0.15304 (5)	0.36080 (15)	0.28052 (6)	0.0568 (3)
O1	0.0918 (5)	−0.1270 (12)	0.4481 (7)	0.0808 (17)
H1	0.0395	−0.1590	0.4580	0.121*
O2	0.0784 (4)	0.2541 (10)	0.5270 (5)	0.0636 (13)
C1	0.1201 (5)	0.0978 (18)	0.4820 (8)	0.065 (2)
C2	0.2153 (7)	0.1680 (17)	0.4492 (8)	0.080 (2)
H2	0.2491	0.0147	0.4392	0.096*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0415 (3)	0.0827 (5)	0.0441 (4)	0.0038 (3)	0.0182 (3)	0.0114 (3)
O1	0.077 (4)	0.073 (4)	0.130 (5)	0.002 (3)	0.079 (4)	0.007 (3)
O2	0.052 (3)	0.057 (3)	0.074 (3)	−0.021 (2)	0.023 (2)	−0.004 (3)
C1	0.035 (3)	0.083 (6)	0.084 (5)	0.003 (4)	0.033 (3)	0.025 (4)
C2	0.089 (6)	0.074 (6)	0.069 (5)	0.016 (4)	0.030 (4)	−0.003 (4)

Geometric parameters (Å, º)

Br1—C2	1.969 (8)	C1—C2	1.605 (11)
O1—C1	1.229 (10)	C2—C2^i	1.403 (16)
O1—H1	0.8200	C2—H2	0.9600
O2—C1	1.244 (9)
C1—O1—H1	109.5	C2^i—C2—Br1	108.9 (8)
O1—C1—O2	126.1 (6)	C1—C2—Br1	107.1 (5)
O1—C1—C2	109.2 (7)	C2^i—C2—H2	113.1
O2—C1—C2	124.5 (7)	C1—C2—H2	111.5
C2^i—C2—C1	107.1 (9)	Br1—C2—H2	108.9

Symmetry code: (i) −x+1/2, −y+1/2, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2^ii	0.82	1.83	2.650 (7)	175

Symmetry code: (ii) −x, −y, −z+1.