Redetermination of racemic tartaric acid monohydrate

The structure of the title compound, 2,3-di­hydroxy­succinic acid mono­hydrate, C₄H₆O₆·H₂O, (I), was first determined (to R = 0.22) and reported by Parry [Acta Cryst. (1951), 4, 131-138]. We present here a redetermination with significantly improved accuracy. In the centrosymmetric crystals (space group P, Z = 2), the enantiomeric mol­ecules with both D- and L-configurations co-exist. An extensive intermolecular hydrogen-bond system involves hydrogen bonds formed by carboxyl and hydroxyl groups of the tartaric acid mol­ecule, as well as the crystalline water mol­ecule.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.040
• wR factor = 0.114
• Data-to-parameter ratio = 11.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

NO COMMENT

S2. Experimental

Single crystals of racemic tartaric acid monohydrate (Parry, 1951) were obtained from an aqueous solution containing L-camphoramic acid and D,L-tartaric acid in a 1:1 molar ratio when we tried to separate the racemic acid by L-camphoramic acid.

S3. Refinement

H atoms were located from a difference Fourier map. They were included in the final cycles of least-squares refinement with fixed coordinates and U_iso (0.08 Ų).

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1992a); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1992b); program(s) used to solve structure: SHELXS93 (Sheldrick, 1993); program(s) used to refine structure: SHELXL93 (Sheldrick, 1993); molecular graphics: XP (Siemens, 1994).

Figures

Fig. 1. View of the crystal packing of the title compound with 50% probability displacement ellipsoids, with dashed lines showing the hydrogen-bond network. H atoms have been omitted for clarity.

2,3-Dihydroxysuccinic acid monohydrate

Crystal data

C4H6O6·H2O	Z = 2
Mr = 168.10	F(000) = 176
Triclinic, P1	Dx = 1.699 Mg m^−3
a = 4.869 (5) Å	Mo Kα radiation, λ = 0.71069 Å
b = 8.052 (5) Å	Cell parameters from 16 reflections
c = 9.153 (5) Å	θ = 4.7–9.9°
α = 109.260 (5)°	µ = 0.17 mm^−1
β = 99.862 (5)°	T = 293 K
γ = 96.108 (5)°	Prism, colourless
V = 328.6 (4) Å^3	0.70 × 0.60 × 0.40 mm

Data collection

Rigaku AFC-7S diffractometer	1040 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.000
Graphite monochromator	θmax = 25.0°, θmin = 2.9°
ω–2θ scans	h = −5→5
Absorption correction: ψ scan (North et al., 1968)	k = 0→9
Tmin = 0.888, Tmax = 0.934	l = −10→9
1145 measured reflections	3 standard reflections every 150 reflections
1145 independent reflections	intensity decay: 1.4%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.040	H-atom parameters not refined
wR(F^2) = 0.114	w = 1/[σ^2(Fo^2) + (0.073P)^2 + 0.1479P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
1145 reflections	Δρmax = 0.34 e Å^−3
102 parameters	Δρmin = −0.16 e Å^−3
0 restraints	Extinction correction: SHELXL93 (Sheldrick, 1993), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.64 (7)

Special details

Experimental. Data collection were performed with a scan width of Δω = (1.63 + 0.35 tan θ)^o and a scan rate of less than 16°min^-1 in ω.

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 on F² for ALL reflections except for 1 with very negative F²

or flagged by the user for potential systematic errors. Weighted R-factors

wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating_refine_ls_R_factor_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
O1	0.2091 (3)	0.4357 (2)	0.3708 (2)	0.0406 (4)
O2	−0.0110 (3)	0.2696 (2)	0.4835 (2)	0.0403 (5)
O3	0.4040 (3)	0.1621 (2)	0.19547 (15)	0.0307 (4)
O4	−0.1667 (3)	−0.0229 (2)	0.14076 (15)	0.0340 (4)
O5	0.1126 (3)	−0.2886 (2)	0.0393 (2)	0.0430 (5)
O6	0.3946 (3)	−0.2208 (2)	0.2797 (2)	0.0378 (4)
OW	0.6175 (3)	0.5052 (2)	0.1831 (2)	0.0450 (5)
C1	0.1529 (4)	0.2952 (2)	0.3925 (2)	0.0268 (4)
C2	0.2829 (3)	0.1338 (2)	0.3169 (2)	0.0260 (5)
C3	0.0594 (4)	−0.0375 (2)	0.2524 (2)	0.0272 (5)
C4	0.1918 (4)	−0.1979 (2)	0.1776 (2)	0.0287 (5)
H2	−0.0691	0.3666	0.5268	0.080*
H2C	0.4305	0.1231	0.3964	0.080*
H3	0.5380	0.1021	0.1814	0.080*
H3C	−0.0136	−0.0532	0.3395	0.080*
H4	−0.1660	−0.0954	0.0391	0.080*
H6	0.4477	−0.3273	0.2410	0.080*
H1W	0.7133	0.4556	0.0990	0.080*
H2W	0.5156	0.4088	0.2015	0.080*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0561 (9)	0.0253 (7)	0.0478 (9)	0.0146 (6)	0.0253 (7)	0.0135 (6)
O2	0.0543 (9)	0.0266 (7)	0.0416 (8)	0.0103 (6)	0.0268 (7)	0.0051 (6)
O3	0.0352 (7)	0.0278 (7)	0.0337 (7)	0.0128 (5)	0.0151 (5)	0.0108 (5)
O4	0.0334 (7)	0.0343 (7)	0.0291 (7)	0.0128 (5)	0.0047 (5)	0.0034 (5)
O5	0.0548 (9)	0.0314 (8)	0.0342 (8)	0.0158 (6)	0.0069 (6)	−0.0007 (6)
O6	0.0482 (8)	0.0288 (7)	0.0372 (8)	0.0177 (6)	0.0089 (6)	0.0099 (6)
OW	0.0588 (9)	0.0295 (8)	0.0555 (10)	0.0183 (6)	0.0282 (7)	0.0156 (7)
C1	0.0308 (9)	0.0229 (9)	0.0232 (8)	0.0054 (7)	0.0046 (7)	0.0039 (7)
C2	0.0306 (9)	0.0234 (9)	0.0239 (8)	0.0077 (7)	0.0060 (7)	0.0071 (7)
C3	0.0321 (9)	0.0236 (9)	0.0269 (9)	0.0080 (7)	0.0091 (7)	0.0079 (7)
C4	0.0343 (9)	0.0206 (8)	0.0326 (10)	0.0052 (7)	0.0119 (7)	0.0089 (7)

Geometric parameters (Å, º)

O1—C1	1.223 (2)	O6—H6	0.8980
O2—C1	1.296 (2)	OW—H1W	0.9641
O2—H2	0.8536	OW—H2W	0.9535
O3—C2	1.413 (2)	C1—C2	1.516 (2)
O3—H3	0.8545	C2—C3	1.536 (3)
O4—C3	1.411 (2)	C2—H2C	0.964
O4—H4	0.9217	C3—C4	1.516 (2)
O5—C4	1.203 (2)	C3—H3C	0.965
O6—C4	1.311 (2)
C1—O2—H2	109.1	C1—C2—H2C	108.6
C2—O3—H3	109.5	C3—C2—H2C	108.7
C3—O4—H4	111.4	O4—C3—C4	110.43 (14)
C4—O6—H6	111.9	O4—C3—C2	110.15 (14)
H1W—OW—H2W	108.2	C4—C3—C2	110.20 (15)
O1—C1—O2	124.9 (2)	O4—C3—H3C	108.6
O1—C1—C2	121.6 (2)	C4—C3—H3C	108.8
O2—C1—C2	113.54 (15)	C2—C3—H3C	108.7
O3—C2—C1	108.47 (14)	O5—C4—O6	126.4 (2)
O3—C2—C3	111.51 (14)	O5—C4—C3	121.3 (2)
C1—C2—C3	110.67 (15)	O6—C4—C3	112.24 (15)
O3—C2—H2C	108.8

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1^i	0.854	1.828	2.680 (2)	175.0
O3—H3···O4^ii	0.854	1.861	2.714 (3)	176.4
O6—H6···OW^iii	0.898	1.643	2.526 (2)	167.0
OW—H2W···O3	0.954	1.983	2.891 (2)	158.5
OW—H1W···O5^iv	0.964	1.902	2.824 (2)	159.2

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