Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102006650/bk1636sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102006650/bk1636Isup2.hkl | |
Portable Document Format (PDF) file https://doi.org/10.1107/S0108270102006650/bk1636sup3.pdf |
CCDC reference: 188617
Compound (I) (Sigma, St. Louis, MO) was recrystallized from absolute ethanol by slow evaporation followed by vacuum drying at 373 K for 12 h. The X-ray powder diffraction patterns (D5000, Bruker AXS Inc., Madison, WI) of the recrystallized material, as well as the commercial bulk material, matched the pattern found in the ICDD for (I) (listed as DL-tartaric acid; Organic Databook 1989). The theoretically generated X-ray powder diffraction pattern (Materials Studio 2.0, Powder Diffraction Module, Accelrys, Princeton, NJ) from the structure reported here corresponded with the experimentally determined pattern of the commercial bulk sample, verifying the identity of the single-crystal form (pattern available in supplementary material). The true density of the commercial bulk sample was determined by helium pycnometry (MPY-2, Quantachrome, Boynton Beach, FL).
All H atoms were refined with isotropic displacement parameters [C—H = 0.88 (2)–0.93 (1) Å].
Data collection: CAD-4 Operations Manual (Enraf-Nonius, 1977); cell refinement: CAD-4 Operations Manual; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
C4H6O6 | F(000) = 156 |
Mr = 150.09 | Dx = 1.796 Mg m−3 Dm = 1.786 Mg m−3 Dm measured by He Pycnometry |
Triclinic, P1 | Melting point: 479 K |
a = 6.580 (1) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 9.186 (1) Å | Cell parameters from 50 reflections |
c = 4.8966 (7) Å | θ = 13.9–17.4° |
α = 91.52 (1)° | µ = 0.18 mm−1 |
β = 103.52 (1)° | T = 293 K |
γ = 74.78 (1)° | Prism, colorless |
V = 277.50 (7) Å3 | 0.31 × 0.21 × 0.17 mm |
Z = 2 |
Enraf-Nonius CAD-4 diffractometer | Rint = 0.015 |
Radiation source: fine-focus sealed tube | θmax = 30.0°, θmin = 2.0° |
Graphite monochromator | h = −9→9 |
θ–2θ scans | k = −12→12 |
3193 measured reflections | l = −6→6 |
1598 independent reflections | 4 standard reflections every 120 min |
1363 reflections with I > 2σ(I) | intensity decay: <2% |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.033 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.101 | All H-atom parameters refined |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0537P)2 + 0.0695P] where P = (Fo2 + 2Fc2)/3 |
1598 reflections | (Δ/σ)max = 0.012 |
115 parameters | Δρmax = 0.46 e Å−3 |
0 restraints | Δρmin = −0.19 e Å−3 |
C4H6O6 | γ = 74.78 (1)° |
Mr = 150.09 | V = 277.50 (7) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.580 (1) Å | Mo Kα radiation |
b = 9.186 (1) Å | µ = 0.18 mm−1 |
c = 4.8966 (7) Å | T = 293 K |
α = 91.52 (1)° | 0.31 × 0.21 × 0.17 mm |
β = 103.52 (1)° |
Enraf-Nonius CAD-4 diffractometer | Rint = 0.015 |
3193 measured reflections | 4 standard reflections every 120 min |
1598 independent reflections | intensity decay: <2% |
1363 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.033 | 0 restraints |
wR(F2) = 0.101 | All H-atom parameters refined |
S = 1.06 | Δρmax = 0.46 e Å−3 |
1598 reflections | Δρmin = −0.19 e Å−3 |
115 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.89078 (16) | 0.39473 (10) | 0.1805 (2) | 0.0213 (2) | |
O1 | 0.74120 (13) | 0.48288 (10) | 0.29074 (19) | 0.0331 (2) | |
H1 | 0.804 (4) | 0.529 (3) | 0.434 (5) | 0.082 (7)* | |
O2 | 1.08426 (12) | 0.38222 (9) | 0.25797 (16) | 0.0276 (2) | |
C2 | 0.79394 (15) | 0.30530 (11) | −0.05750 (19) | 0.0202 (2) | |
H2 | 0.687 (2) | 0.3739 (15) | −0.186 (3) | 0.024 (3)* | |
O5 | 0.94702 (12) | 0.22956 (9) | −0.20703 (15) | 0.02443 (18) | |
H5 | 1.050 (3) | 0.163 (2) | −0.091 (4) | 0.053 (5)* | |
C3 | 0.69085 (16) | 0.19626 (11) | 0.06351 (19) | 0.0205 (2) | |
H3 | 0.573 (2) | 0.2528 (16) | 0.129 (3) | 0.024 (3)* | |
O6 | 0.84217 (14) | 0.09436 (9) | 0.26827 (16) | 0.0283 (2) | |
H6 | 0.872 (3) | 0.140 (2) | 0.429 (4) | 0.056 (5)* | |
C4 | 0.60465 (15) | 0.10406 (11) | −0.17674 (19) | 0.0202 (2) | |
O3 | 0.67218 (12) | −0.03252 (8) | −0.18357 (15) | 0.02461 (19) | |
O4 | 0.45352 (14) | 0.18895 (9) | −0.37348 (17) | 0.0316 (2) | |
H4 | 0.409 (3) | 0.132 (2) | −0.510 (4) | 0.061 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0248 (5) | 0.0174 (4) | 0.0193 (4) | −0.0066 (3) | −0.0005 (3) | −0.0034 (3) |
O1 | 0.0270 (4) | 0.0324 (4) | 0.0369 (5) | −0.0080 (3) | 0.0036 (3) | −0.0202 (3) |
O2 | 0.0249 (4) | 0.0289 (4) | 0.0261 (4) | −0.0086 (3) | −0.0005 (3) | −0.0087 (3) |
C2 | 0.0222 (4) | 0.0187 (4) | 0.0172 (4) | −0.0060 (3) | −0.0004 (3) | −0.0043 (3) |
O5 | 0.0267 (4) | 0.0262 (4) | 0.0181 (3) | −0.0054 (3) | 0.0032 (3) | −0.0049 (3) |
C3 | 0.0231 (4) | 0.0196 (4) | 0.0171 (4) | −0.0066 (3) | 0.0008 (3) | −0.0052 (3) |
O6 | 0.0377 (4) | 0.0242 (4) | 0.0170 (3) | −0.0070 (3) | −0.0036 (3) | −0.0020 (3) |
C4 | 0.0200 (4) | 0.0222 (4) | 0.0185 (4) | −0.0081 (3) | 0.0024 (3) | −0.0052 (3) |
O3 | 0.0275 (4) | 0.0206 (3) | 0.0226 (4) | −0.0066 (3) | 0.0001 (3) | −0.0061 (3) |
O4 | 0.0339 (4) | 0.0234 (4) | 0.0268 (4) | −0.0046 (3) | −0.0099 (3) | −0.0065 (3) |
C1—O1 | 1.312 (1) | C3—C4 | 1.520 (1) |
C1—O2 | 1.216 (1) | C3—H3 | 0.93 (1) |
C1—C2 | 1.522 (1) | C3—O6 | 1.402 (1) |
O1—H1 | 0.88 (2) | O6—H6 | 0.88 (2) |
C2—C3 | 1.546 (1) | C4—O3 | 1.219 (1) |
C2—H2 | 0.93 (1) | C4—O4 | 1.308 (1) |
C2—O5 | 1.409 (1) | O4—H4 | 0.88 (2) |
O5—H5 | 0.88 (2) | ||
O2—C1—O1 | 125.3 (1) | O6—C3—C4 | 107.3 (1) |
O2—C1—C2 | 122.9 (1) | O6—C3—C2 | 112.3 (1) |
O1—C1—C2 | 111.8 (1) | C4—C3—C2 | 107.6 (1) |
C1—O1—H1 | 109 (2) | O6—C3—H3 | 113 (1) |
O5—C2—C1 | 112.2 (1) | C4—C3—H3 | 108 (1) |
O5—C2—C3 | 112.3 (1) | C2—C3—H3 | 109 (1) |
C1—C2—C3 | 108.9 (1) | C3—O6—H6 | 111 (1) |
O5—C2—H2 | 106 (1) | O3—C4—O4 | 124.8 (1) |
C1—C2—H2 | 108 (1) | O3—C4—C3 | 123.3 (1) |
C3—C2—H2 | 110 (1) | O4—C4—C3 | 112.0 (1) |
C2—O5—H5 | 108 (1) | C4—O4—H4 | 110 (1) |
O2—C1—C2—O5 | −10.8 (1) | O5—C2—C3—C4 | −52.7 (1) |
O1—C1—C2—O5 | 170.3 (1) | C1—C2—C3—C4 | −177.6 (1) |
O2—C1—C2—C3 | 114.2 (1) | O6—C3—C4—O3 | −4.1 (1) |
O1—C1—C2—C3 | −64.8 (1) | C2—C3—C4—O3 | 117.0 (1) |
O5—C2—C3—O6 | 65.2 (1) | O6—C3—C4—O4 | 176.8 (1) |
C1—C2—C3—O6 | −59.7 (1) | C2—C3—C4—O4 | −62.1 (1) |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4···O3i | 0.88 (2) | 1.78 (2) | 2.660 (1) | 173 (2) |
O1—H1···O2ii | 0.88 (2) | 1.80 (2) | 2.675 (1) | 175 (2) |
O6—H6···O5iii | 0.88 (2) | 1.96 (2) | 2.841 (1) | 177 (2) |
O5—H5···O3iv | 0.88 (2) | 2.09 (2) | 2.962 (1) | 170 (2) |
O5—H5···O6iv | 0.88 (2) | 2.48 (2) | 2.975 (1) | 116 (1) |
Symmetry codes: (i) −x+1, −y, −z−1; (ii) −x+2, −y+1, −z+1; (iii) x, y, z+1; (iv) −x+2, −y, −z. |
Experimental details
Crystal data | |
Chemical formula | C4H6O6 |
Mr | 150.09 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.580 (1), 9.186 (1), 4.8966 (7) |
α, β, γ (°) | 91.52 (1), 103.52 (1), 74.78 (1) |
V (Å3) | 277.50 (7) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.18 |
Crystal size (mm) | 0.31 × 0.21 × 0.17 |
Data collection | |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3193, 1598, 1363 |
Rint | 0.015 |
(sin θ/λ)max (Å−1) | 0.703 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.101, 1.06 |
No. of reflections | 1598 |
No. of parameters | 115 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.46, −0.19 |
Computer programs: CAD-4 Operations Manual (Enraf-Nonius, 1977), CAD-4 Operations Manual, MolEN (Fair, 1990), SHELXTL (Sheldrick, 1997), SHELXTL.
C1—O1 | 1.312 (1) | C3—C4 | 1.520 (1) |
C1—O2 | 1.216 (1) | C3—O6 | 1.402 (1) |
C1—C2 | 1.522 (1) | C4—O3 | 1.219 (1) |
C2—C3 | 1.546 (1) | C4—O4 | 1.308 (1) |
C2—O5 | 1.409 (1) | ||
O2—C1—O1 | 125.3 (1) | O6—C3—C4 | 107.3 (1) |
O2—C1—C2 | 122.9 (1) | O6—C3—C2 | 112.3 (1) |
O1—C1—C2 | 111.8 (1) | C4—C3—C2 | 107.6 (1) |
O5—C2—C1 | 112.2 (1) | O3—C4—O4 | 124.8 (1) |
O5—C2—C3 | 112.3 (1) | O3—C4—C3 | 123.3 (1) |
C1—C2—C3 | 108.9 (1) | O4—C4—C3 | 112.0 (1) |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4···O3i | 0.88 (2) | 1.78 (2) | 2.660 (1) | 173 (2) |
O1—H1···O2ii | 0.88 (2) | 1.80 (2) | 2.675 (1) | 175 (2) |
O6—H6···O5iii | 0.88 (2) | 1.96 (2) | 2.841 (1) | 177 (2) |
O5—H5···O3iv | 0.88 (2) | 2.09 (2) | 2.962 (1) | 170 (2) |
O5—H5···O6iv | 0.88 (2) | 2.48 (2) | 2.975 (1) | 116 (1) |
Symmetry codes: (i) −x+1, −y, −z−1; (ii) −x+2, −y+1, −z+1; (iii) x, y, z+1; (iv) −x+2, −y, −z. |
Tartaric acid is an important additive in foods and pharmaceuticals. The structures of its various forms are of historical interest dating back to the work of Pasteur (1848, 1850). The study of the molecular packing and hydrogen bonding in tartaric acid and its derivatives is relevant to the development of approaches for crystal engineering (Aakeröy et al., 1992; Rychlewska & Warzajtis 2000). Furthermore, tartaric acid has often been cited as a case satisfying Wallach's rule [see references in Brock et al. (1991)], which states that racemic crystals tend to be denser than their chiral counterparts (Wallach 1895). The structure of the title compound, (I) (also known as DL-tartaric or racemic acid), has not been reported previously, although the structures of the homochiral [(+)-L-tartaric acid or (2R,3R)-(+)-tartaric acid, (II)] and meso forms have been determined (Stern & Beevers 1950; Okaya et al., 1966; Bootsma & Schoone 1967). Anhydrous (I) can be recrystallized from water above 346 K; however, the crystals obtained were of poor quality for structure determination (Parry, 1951). Consequently, Parry (1951) reported the structure of the hydrate. Very early reports of the structure of (I) were incomplete (Astbury, 1923; Gerstäker et al., 1927). An appropriate comparison of the crystallographic features of the homochiral and heterochiral crystal forms requires the structures of both anhydrous forms. As part of our investigation of the molecular basis for differences between the near-IR spectra of (I) and (II) (Patel et al., 2000), we have isolated a single-crystal of (I) from absolute ethanol and determined its crystal structure. We report here the crystal structure of (I) and also compare its hydrogen-bonding features to those of (II).
The refined molecule and labeling scheme for (I) are shown in Fig. 1. The structure is characterized by five hydrogen bonds (Table 2). Unique to the structure of (I), relative to (II), is the hydrogen-bonding pattern associated with the carboxylic acid groups and the formation of centrosymmetric dimers in the former (Fig. 2). Graph-set analysis (Bernstein et al., 1995) of the hydrogen bonds reveals four separate centrosymmetric rings between adjacent enantiomers formed by four of the hydrogen-bond motifs. The fifth motif is a helical C(5) chain formed between molecules of like chirality, propagating along the c axis. A combination of the two unique motifs associated with the carboxylic acid dimers (O4—H4···O3 and O1—H1···O2) forms a chain of rings, C22(14)[R22(8)R22(8)]. These twisted chains are crosslinked into sheets by the C(5) motif. Rings R22(12) and R22(10) result from O5—H5···O3 and O5—H5···O6 hydrogen bonds, respectively. Other binary graph sets form a variety of ladder and rail configurations with rings. The angle between the two planes formed by the carboxyl groups was 55.9 (1)°. Carbonyl–carbonyl interactions of the antiparallel motif (Allen et al., 1998) exist between C4—O3 carbonyl groups on adjacent molecules [O3···C4i = 3.009 (1) Å; symmetry code: (i) 1 - x, -y, -z] and similarly for C1—O2 carbonyl groups [O2···C1ii = 3.068 (1) Å; symmetry code: (ii) 2 - x, 1 - y, -z].
In constrast, for (II), carboxyl O atoms form hydrogen bonds with alcohol OH groups in addition to acidic OH groups on translationally related molecules in a head-to-tail arrangement along the a axis (Okaya et al., 1966). Carboxylic acid dimers are not present despite their propensity to form (Leiserowitz, 1976). Both (I) and (II) contain binary graph-set R21(5), formed among two α-hydroxyl groups and a carboxyl O atom. However, (II) features C(7) and C22(7) chains that form a ring R33(12) (Rychlewska et al., 1999; Rychlewska & Warzajtis, 2000). This feature links together three molecules and results in a more diffuse network in (II) than in (I). The impact of dimer formation and the altered hydrogen-bonding scheme in (I) is readily observed when comparing the splitting and shifting patterns of the 13C CP/MAS solid-state NMR and Raman spectra of the two forms (Patel et al., 2000). There are other short O···O contacts [O4···O2iii = 2.858 (1) Å, O4···O1iv = 3.007 (1) Å and O6···O6v = 2.930 (2) Å; symmetry codes: (iii) -1 + x, y, -1 + z; (iv) 1 - x, 1 - y, -z; (v) 2 - x, -y, 1 - z] that are not hydrogen-bonding contacts, as the associated H atoms are involved in hydrogen bonds with other O atoms.
The calculated value of Δ% (Brock et al., 1991), a measure of the extent to which the racemate is denser than the homochiral form, was 2.2 for the tartaric acid pair. This value appears in the upper quartile for a wide range of structures examined by Brock et al. (1991) and is greater than the mean for pairs of chiral and racemic structures examined (0.92). The formation of dimers likely contributes to tighter packing in (I), as evidenced by its higher calculated density [1.796 versus 1.757 Mg m-3 for (II)]. Thus, the crystal pair reasonably satisfies Wallach's rule, provided the inherent bias in comparing resolvable racemic/chiral pairs is recognized (Brock et al., 1991).