Structure determination of tartaric acid with the Bruker SMART X2S benchtop crystallographic system

A crystal of tartaric acid with the dimensions of 0.40 mm x 0.50 mm x 0.61 mm mounted on a Mitegen Micromount was automatically centered on a Bruker SMART X2S benchtop crystallographic system. Intensity measurements were performed using a monochromated (Doubly Curved Silicon Crystal) Mo-K_α-radiation (0.71073 Å) from a sealed MicroFocus tube. Generator settings were 50 kV, 1 mA. Data collection temperature was 23°C.
Data were acquired using three sets of Omega scans at different Phi settings. The frame width was 0.5°.

The detailed data collection strategy was as follows:
Detector distance: 40 mm
Detector swing angle (fixed 2 Theta): -20°.

Run	Omega (start)	Omega (end)	Phi	Frames
1	-20.0	-200.0	0.0	360
2	-20.0	-140.0	120.0	240
3	-20.0	-80.0	240.0	120

APEX2 software was used for preliminary determination of the unit cell. Determination of integral intensities and unit cell refinement were performed using SAINT. The integration of the data yielded a total of 1811 reflections to a maximum θ angle of 25.10° (0.84 Å resolution).
The constants for the monoclinic unit cell are a = 6.2293(13) Å, b = 6.0267(11) Å, c = 7.7476(15) Å, β = 100.074(6)°, V = 286.38(10) ų.
Data were corrected for absorption effects with SADABS using the multiscan technique. The ratio of minimum to maximum apparent transmission is 89.6:100. The average residual for symmetry equivalent reflections is R_int = 2.38% and R_σ = 2.70%. XPREP determined the space group to be P 1 21 1, with Z = 2 for the formula unit, C₄H₆O₆.
The structure was solved with XS and subsequent structure refinements were performed with XL. The final anisotropic full-matrix least-squares refinement on F_o² with 95 variables converged at R₁ = 2.49% for the observed data and wR₂ = 6.45% for all data. The goodness-of-fit was 1.140. The largest peak on the final difference electron density synthesis was 0.13 e^-/ų and the deepest hole was -0.15 e^-/ų with an RMS deviation of 0.05 e^-/ų. On the basis of the final model, the calculated density is 1.741 g/cm³ and F(000) = 156.

APEX2 Version 2.2 (Bruker AXS Inc., 2007)
SAINT Version 7.34a (Bruker AXS Inc., 2007)
SADABS Version 2007/2 (Sheldrick, Bruker AXS Inc.)
XPREP Version 2005/2 (Sheldrick, Bruker AXS Inc.)
XS Version 2008/1 (George M. Sheldrick, Acta Cryst. (2008). A64, 112-122)
XL Version 2008/1 (George M. Sheldrick, Acta Cryst. (2008). A64, 112-122)

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Table 1. Crystal data and structure refinement for tartaric acid.

Identification code	tartaric acid
Empirical formula	C4 H6 O6
Formula weight	150.09
Temperature	296(2) K
Wavelength	0.71073 Å
Crystal system	Monoclinic
Space group	P 1 21 1
Unit cell dimensions	a = 6.2293(13) Å	α = 90°
	b = 6.0267(11) Å	β = 100.074(6)°
	c = 7.7476(15) Å	γ = 90°
Volume	286.38(10) Å^3
Z	2
Density (calculated)	1.741 Mg/cm^3
Absorption coefficient	0.171 mm^-1
F(000)	156
Crystal size	0.40 x 0.50 x 0.61 mm^3
Index ranges	-7<=h<=7, -7<=k<=7, -9<=l<=8
Reflections collected	1811
Independent reflections	998 [R(int) = 0.0238]
Absorption correction	Multiscan
Max. and min. transmission	0.9348 and 0.9029
Refinement method	Full-matrix least-squares on F^2
Data / restraints / parameters	998 / 1 / 95
Goodness-of-fit on F^2	1.140
Final R indices [I>2sigma(I)]	R1 = 0.0249, wR2 = 0.0643
R indices (all data)	R1 = 0.0253, wR2 = 0.0645
Absolute structure parameter	0.4(11)
Largest diff. peak and hole	0.127 and -0.150

R_int = Σ|F_o² - F_o²(mean)| / Σ[F_o²]
R₁ = Σ||F_o| - |F_c|| / Σ|F_o|
GOOF = S = {Σ[w(F_o² - F_c²)²] / (n - p)}^1/2
wR₂ = {Σ[w(F_o² - F_c²)²] / Σ[w(F_o²)²]}^1/2
w = 1 / [σ(F_o²) + (aP)² + bP] where P is [2F_c² + Max(F_o², 0)] / 3

Table 2. Atomic coordinates (x10⁴) and equivalent isotropic displacement parameters (Ųx10³) for tartaric acid.

U(eq) is defined as one third of the trace of the orthogonalized U^ij tensor.

	x	y	z	U(eq)
O2	1500(2)	4954(2)	5211(1)	42(1)
O3	3200(2)	1691(2)	5772(1)	37(1)
O1	5216(2)	553(2)	710(1)	32(1)
O6	1995(2)	953(2)	-1086(1)	31(1)
O5	-101(2)	1219(2)	1622(1)	29(1)
O4	2663(2)	5065(2)	1934(1)	24(1)
C4	2498(2)	3399(3)	4788(2)	23(1)
C2	2176(2)	1041(3)	2058(2)	21(1)
C1	3093(2)	823(2)	364(2)	21(1)
C3	3187(2)	3159(3)	2996(2)	20(1)

Table 3. Bond lengths (Å) and angles (°) for tartaric acid.

O2-C4	1.202(2)
O3-C4	1.309(2)
O1-C1	1.3128(18)
O6-C1	1.2112(18)
O5-C2	1.4030(17)
O4-C3	1.4177(18)
C4-C3	1.5299(18)
C2-C1	1.5260(17)
C2-C3	1.547(2)
O2-C4-O3	126.19(13)
O2-C4-C3	124.17(14)
O3-C4-C3	109.63(12)
O5-C2-C1	108.33(11)
O5-C2-C3	111.16(12)
C1-C2-C3	107.01(11)
O6-C1-O1	125.67(12)
O6-C1-C2	123.80(12)
O1-C1-C2	110.49(11)
O4-C3-C4	112.19(12)
O4-C3-C2	111.24(10)
C4-C3-C2	110.41(12)

Table 4. Anisotropic displacement parameters (Ųx10³) for tartaric acid.

The anisotropic displacement factor exponent takes the form: -2π²[ h² a^*2 U¹¹ + ... + 2 h k a^* b^* U¹² ]

	U^11	U^22	U^33	U^23	U^13	U^12
O2	55(1)	44(1)	30(1)	-3(1)	21(1)	16(1)
O3	49(1)	48(1)	18(1)	9(1)	15(1)	16(1)
O1	29(1)	47(1)	24(1)	-5(1)	13(1)	5(1)
O6	35(1)	42(1)	16(1)	-3(1)	8(1)	-6(1)
O5	23(1)	43(1)	24(1)	-1(1)	10(1)	-7(1)
O4	25(1)	27(1)	21(1)	3(1)	8(1)	-1(1)
C4	22(1)	32(1)	16(1)	-2(1)	6(1)	-1(1)
C2	25(1)	24(1)	16(1)	1(1)	8(1)	-1(1)
C1	28(1)	17(1)	19(1)	-3(1)	10(1)	-4(1)
C3	20(1)	26(1)	15(1)	2(1)	6(1)	1(1)

Table 5. Hydrogen coordinates (x10⁴) and isotropic displacement parameters (Ųx10³) for tartaric acid.

	x	y	z	U(eq)
H3	2660	1714	6664	56
H1	5697	522	-209	49
H5	-646	940	2487	44
H4	1338	5129	1609	36
H2	2573	-261	2803	25
H3A	4775	2984	3196	24