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Crystals of the title complex, C
3H
7NO
2·C
8H
8O
3·0.5H
2O, were obtained from an aqueous solution containing racemic mandelic acid and (
S)-alanine. The unit cell includes two independent molecular complexes and one water molecule. The structure formed by (
R)-mandelic acid and (
S)-alanine in a 1:1 molar ratio shows the successful optical separation of racemic mandelic acid. Strong hydrogen bonding, with a rather short O
O separation of 2.494 (3) Å, is observed between the carboxyl and carboxylate groups. A structural comparison suggests that the strong hydrogen bonding affects the neighbouring covalent bond.
Supporting information
CCDC reference: 197339
Racemic mandelic acid (Mass?, 10 mmol) and (S)-alanine (Mass?, 10 mmol) were
dissolved in turn in hot water (10 ml) with continuous stirring. The solution
was kept at room temperature and powder crystals were obtained from the
solution after 2 d. These powder crystals were separated from the solution and
dried in vacuo at 333 K. The C, H and N content was analyzed using an
Eager 200 elemental analysis instrument. Analysis calculated for
C22H32N2O11: C 52.75, H 6.44, N 5.59%; found: C 52.80, H 6.40, N
5.60%. The specific optical rotation [α]D of -78.8° (H2O, c = 0.19) was
determined using a Wzz-1 s instrument for the powder crystal sample.
Recrystallization was performed from an aqueous solution at room temperature
and well shaped single crystals of complex (I) were obtained after one week. A
small amount of (I) was dissolved in water and the pH of the solution was
adjusted to 2 with dilute HCl; the solution was then kept in a refrigerator.
Colourless crystals of a different shape were obtained. The specific optical
rotation [α]D of -153.9° (H2O, c = 0.35) agrees well with that of
(R)-mandelic acid (Swinney et al., 1999), showing that the
complex crystals do not include (S)-mandelic acid. This is not clear - was the
crystal used here from the first batch, or the pH2 batch?
The H atoms were placed in calculated positions with C—H = 0.93–0.98 Å,
O—H = 0.82 Å and N—H = 0.89 Å, guided by difference Fourier maps. The
H atoms were included in the final cycles of the refinement in the riding
mode, with Uiso(H) = 1.2Ueq of carrier atoms, except for the
H atoms of the water molecules, which had fixed positional parameters and
Uiso(H) = 0.08 Å2. A torsional parameter was refined for each
CH3, NH3 and OH group. The absolute configuration was assigned based on
that of the starting reagent, (S)-alanine, but could not be determined
directly from the X-ray data. Friedel pairs were averaged.
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1992); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1985); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994).
(
R)-mandelic acid (S)-alanine hemihydrate
top
Crystal data top
C3H7NO2·C8H8O3·0.5H2O | Z = 2 |
Mr = 250.25 | F(000) = 266 |
Triclinic, P1 | Dx = 1.348 Mg m−3 |
a = 6.0193 (11) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 8.2285 (10) Å | Cell parameters from 20 reflections |
c = 12.5811 (11) Å | θ = 4.9–9.8° |
α = 82.545 (9)° | µ = 0.11 mm−1 |
β = 86.000 (14)° | T = 298 K |
γ = 89.752 (13)° | Prism, colourless |
V = 616.36 (15) Å3 | 0.60 × 0.55 × 0.30 mm |
Data collection top
Rigaku AFC-7S diffractometer | Rint = 0.016 |
Radiation source: fine-focus sealed tube | θmax = 26.0°, θmin = 2.5° |
Graphite monochromator | h = 0→7 |
ω/2θ scans | k = −10→10 |
2617 measured reflections | l = −15→15 |
2436 independent reflections | 3 standard reflections every 150 reflections |
2011 reflections with I > 2σ(I) | intensity decay: 0.3% |
Refinement top
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)] = 0.030 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.084 | H-atom parameters constrained |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0474P)2 + 0.0307P] where P = (Fo2 + 2Fc2)/3 |
2436 reflections | (Δ/σ)max = 0.010 |
324 parameters | Δρmax = 0.14 e Å−3 |
3 restraints | Δρmin = −0.15 e Å−3 |
Crystal data top
C3H7NO2·C8H8O3·0.5H2O | γ = 89.752 (13)° |
Mr = 250.25 | V = 616.36 (15) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.0193 (11) Å | Mo Kα radiation |
b = 8.2285 (10) Å | µ = 0.11 mm−1 |
c = 12.5811 (11) Å | T = 298 K |
α = 82.545 (9)° | 0.60 × 0.55 × 0.30 mm |
β = 86.000 (14)° | |
Data collection top
Rigaku AFC-7S diffractometer | Rint = 0.016 |
2617 measured reflections | 3 standard reflections every 150 reflections |
2436 independent reflections | intensity decay: 0.3% |
2011 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.030 | 3 restraints |
wR(F2) = 0.084 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.14 e Å−3 |
2436 reflections | Δρmin = −0.15 e Å−3 |
324 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.2598 (3) | 0.7048 (2) | 0.33142 (17) | 0.0506 (5) | |
H1 | 0.2590 | 0.6043 | 0.3422 | 0.061* | |
O2 | −0.0021 (3) | 0.6777 (2) | 0.46728 (16) | 0.0484 (5) | |
O3 | −0.0541 (3) | 0.9997 (2) | 0.45949 (16) | 0.0471 (5) | |
H3 | −0.1249 | 0.9225 | 0.4933 | 0.057* | |
C1 | 0.1100 (4) | 0.7614 (3) | 0.39579 (19) | 0.0352 (5) | |
C2 | 0.0752 (4) | 0.9446 (3) | 0.3734 (2) | 0.0374 (5) | |
H2 | 0.2212 | 0.9985 | 0.3676 | 0.045* | |
C3 | −0.0296 (4) | 0.9859 (3) | 0.2672 (2) | 0.0375 (5) | |
C4 | −0.2352 (5) | 0.9231 (4) | 0.2519 (3) | 0.0506 (7) | |
H4 | −0.3097 | 0.8542 | 0.3074 | 0.061* | |
C5 | −0.3323 (6) | 0.9608 (5) | 0.1555 (3) | 0.0671 (9) | |
H5 | −0.4703 | 0.9168 | 0.1457 | 0.080* | |
C6 | −0.2221 (7) | 1.0646 (5) | 0.0738 (3) | 0.0752 (11) | |
H6 | −0.2871 | 1.0910 | 0.0089 | 0.090* | |
C7 | −0.0199 (7) | 1.1286 (5) | 0.0872 (3) | 0.0672 (10) | |
H7 | 0.0526 | 1.1985 | 0.0316 | 0.081* | |
C8 | 0.0787 (5) | 1.0899 (4) | 0.1837 (2) | 0.0507 (7) | |
H8 | 0.2175 | 1.1335 | 0.1926 | 0.061* | |
O4 | 0.4347 (3) | 0.1919 (2) | 0.46812 (17) | 0.0486 (5) | |
O5 | 0.2715 (3) | 0.4006 (2) | 0.37551 (17) | 0.0470 (5) | |
N1 | 0.8234 (3) | 0.3378 (2) | 0.46222 (17) | 0.0381 (5) | |
H9A | 0.8157 | 0.2294 | 0.4646 | 0.046* | |
H9B | 0.7920 | 0.3652 | 0.5277 | 0.046* | |
H9C | 0.9603 | 0.3721 | 0.4386 | 0.046* | |
C9 | 0.4379 (4) | 0.3278 (3) | 0.4153 (2) | 0.0332 (5) | |
C10 | 0.6606 (4) | 0.4159 (3) | 0.3883 (2) | 0.0330 (5) | |
H10 | 0.6424 | 0.5308 | 0.3999 | 0.040* | |
C11 | 0.7425 (5) | 0.4094 (5) | 0.2723 (2) | 0.0573 (8) | |
H11A | 0.8923 | 0.4507 | 0.2604 | 0.069* | |
H11B | 0.6480 | 0.4753 | 0.2258 | 0.069* | |
H11C | 0.7392 | 0.2981 | 0.2572 | 0.069* | |
O6 | 0.8102 (3) | 0.2952 (2) | 0.80887 (17) | 0.0486 (5) | |
H12 | 0.7981 | 0.2058 | 0.7875 | 0.058* | |
O7 | 1.0561 (4) | 0.3416 (2) | 0.66728 (16) | 0.0517 (5) | |
O8 | 1.1004 (4) | 0.6560 (3) | 0.68694 (18) | 0.0604 (6) | |
H14 | 1.0358 | 0.6632 | 0.6313 | 0.073* | |
C12 | 0.9498 (4) | 0.3873 (3) | 0.7430 (2) | 0.0378 (5) | |
C13 | 0.9705 (5) | 0.5607 (3) | 0.7703 (2) | 0.0426 (6) | |
H13 | 0.8216 | 0.6087 | 0.7767 | 0.051* | |
C14 | 1.0802 (4) | 0.5645 (3) | 0.8747 (2) | 0.0400 (6) | |
C15 | 1.2837 (5) | 0.4886 (4) | 0.8900 (2) | 0.0492 (7) | |
H15 | 1.3505 | 0.4317 | 0.8372 | 0.059* | |
C16 | 1.3867 (6) | 0.4976 (5) | 0.9834 (3) | 0.0629 (9) | |
H16 | 1.5228 | 0.4462 | 0.9938 | 0.075* | |
C17 | 1.2874 (6) | 0.5832 (5) | 1.0619 (3) | 0.0656 (9) | |
H17 | 1.3576 | 0.5892 | 1.1248 | 0.079* | |
C18 | 1.0902 (6) | 0.6577 (4) | 1.0475 (3) | 0.0607 (8) | |
H18 | 1.0256 | 0.7158 | 1.1003 | 0.073* | |
C19 | 0.9831 (5) | 0.6482 (4) | 0.9544 (2) | 0.0492 (7) | |
H19 | 0.8456 | 0.6982 | 0.9455 | 0.059* | |
O9 | 0.7927 (3) | 0.0223 (3) | 0.7333 (2) | 0.0570 (6) | |
O10 | 0.6338 (3) | −0.1422 (2) | 0.63425 (17) | 0.0487 (5) | |
N2 | 0.2377 (3) | −0.0029 (3) | 0.65009 (17) | 0.0353 (4) | |
H20A | 0.2414 | −0.1112 | 0.6507 | 0.042* | |
H20B | 0.2683 | 0.0458 | 0.5833 | 0.042* | |
H20C | 0.1028 | 0.0267 | 0.6739 | 0.042* | |
C20 | 0.6294 (4) | −0.0320 (3) | 0.6924 (2) | 0.0358 (5) | |
C21 | 0.4047 (4) | 0.0467 (3) | 0.7204 (2) | 0.0330 (5) | |
H21 | 0.4221 | 0.1661 | 0.7070 | 0.040* | |
C22 | 0.3296 (5) | −0.0014 (5) | 0.8374 (2) | 0.0570 (8) | |
H22A | 0.4285 | 0.0461 | 0.8816 | 0.068* | |
H22B | 0.3316 | −0.1186 | 0.8539 | 0.068* | |
H22C | 0.1812 | 0.0377 | 0.8510 | 0.068* | |
O11 | 0.5440 (4) | 0.5155 (3) | 0.6117 (2) | 0.0666 (6) | |
H1W | 0.5723 | 0.6281 | 0.6007 | 0.080* | |
H2W | 0.4091 | 0.4977 | 0.6379 | 0.080* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0498 (11) | 0.0432 (10) | 0.0552 (12) | 0.0078 (9) | 0.0110 (9) | −0.0012 (9) |
O2 | 0.0568 (11) | 0.0405 (10) | 0.0450 (10) | −0.0023 (9) | 0.0087 (9) | −0.0016 (8) |
O3 | 0.0586 (12) | 0.0393 (10) | 0.0428 (10) | 0.0012 (9) | 0.0066 (9) | −0.0082 (8) |
C1 | 0.0317 (12) | 0.0403 (13) | 0.0337 (12) | −0.0012 (10) | −0.0061 (10) | −0.0029 (10) |
C2 | 0.0357 (12) | 0.0390 (13) | 0.0374 (13) | −0.0019 (10) | −0.0005 (10) | −0.0057 (10) |
C3 | 0.0420 (13) | 0.0301 (12) | 0.0400 (13) | 0.0055 (10) | 0.0004 (10) | −0.0045 (10) |
C4 | 0.0433 (15) | 0.0535 (17) | 0.0545 (16) | −0.0008 (12) | −0.0072 (12) | −0.0033 (13) |
C5 | 0.058 (2) | 0.071 (2) | 0.077 (2) | 0.0111 (17) | −0.0285 (18) | −0.0156 (19) |
C6 | 0.093 (3) | 0.083 (3) | 0.052 (2) | 0.021 (2) | −0.0273 (19) | −0.0078 (19) |
C7 | 0.091 (3) | 0.068 (2) | 0.0380 (16) | 0.013 (2) | 0.0077 (17) | 0.0015 (15) |
C8 | 0.0506 (16) | 0.0519 (16) | 0.0473 (16) | 0.0033 (13) | 0.0071 (13) | −0.0033 (13) |
O4 | 0.0438 (10) | 0.0371 (10) | 0.0616 (12) | −0.0090 (8) | −0.0032 (9) | 0.0062 (9) |
O5 | 0.0278 (9) | 0.0433 (10) | 0.0699 (13) | 0.0023 (7) | −0.0065 (8) | −0.0057 (9) |
N1 | 0.0329 (10) | 0.0358 (11) | 0.0450 (12) | −0.0042 (8) | −0.0095 (9) | 0.0003 (9) |
C9 | 0.0294 (11) | 0.0325 (12) | 0.0389 (12) | 0.0011 (9) | −0.0005 (10) | −0.0111 (10) |
C10 | 0.0292 (11) | 0.0281 (11) | 0.0412 (13) | 0.0011 (9) | −0.0032 (10) | −0.0023 (10) |
C11 | 0.0402 (15) | 0.084 (2) | 0.0416 (15) | 0.0056 (15) | 0.0030 (12) | 0.0097 (15) |
O6 | 0.0479 (11) | 0.0449 (11) | 0.0533 (11) | −0.0076 (9) | 0.0048 (9) | −0.0123 (9) |
O7 | 0.0602 (12) | 0.0465 (11) | 0.0476 (11) | 0.0052 (9) | 0.0049 (10) | −0.0080 (9) |
O8 | 0.0847 (16) | 0.0488 (12) | 0.0470 (11) | −0.0188 (11) | −0.0228 (11) | 0.0071 (10) |
C12 | 0.0376 (13) | 0.0410 (13) | 0.0362 (13) | 0.0050 (11) | −0.0082 (11) | −0.0078 (11) |
C13 | 0.0425 (14) | 0.0413 (14) | 0.0455 (14) | 0.0045 (11) | −0.0107 (11) | −0.0078 (11) |
C14 | 0.0417 (14) | 0.0395 (13) | 0.0397 (13) | −0.0044 (11) | −0.0048 (11) | −0.0072 (11) |
C15 | 0.0448 (15) | 0.0571 (17) | 0.0479 (15) | 0.0038 (13) | −0.0069 (12) | −0.0137 (13) |
C16 | 0.0544 (18) | 0.078 (2) | 0.0586 (19) | 0.0046 (16) | −0.0235 (15) | −0.0058 (17) |
C17 | 0.080 (2) | 0.079 (2) | 0.0415 (16) | −0.009 (2) | −0.0163 (16) | −0.0124 (16) |
C18 | 0.077 (2) | 0.065 (2) | 0.0405 (15) | −0.0046 (17) | 0.0051 (15) | −0.0155 (14) |
C19 | 0.0482 (15) | 0.0492 (16) | 0.0509 (16) | −0.0010 (12) | 0.0044 (13) | −0.0127 (13) |
O9 | 0.0251 (9) | 0.0560 (12) | 0.0964 (16) | 0.0001 (8) | −0.0083 (9) | −0.0324 (12) |
O10 | 0.0364 (9) | 0.0440 (10) | 0.0701 (13) | 0.0042 (8) | −0.0001 (9) | −0.0256 (9) |
N2 | 0.0285 (10) | 0.0371 (10) | 0.0406 (11) | 0.0024 (8) | −0.0045 (8) | −0.0051 (9) |
C20 | 0.0279 (11) | 0.0334 (12) | 0.0459 (14) | −0.0005 (9) | −0.0007 (10) | −0.0057 (11) |
C21 | 0.0271 (11) | 0.0333 (12) | 0.0396 (13) | −0.0012 (9) | −0.0014 (9) | −0.0092 (10) |
C22 | 0.0412 (15) | 0.089 (2) | 0.0413 (15) | −0.0060 (15) | 0.0000 (12) | −0.0130 (16) |
O11 | 0.0722 (15) | 0.0612 (14) | 0.0682 (14) | 0.0127 (12) | 0.0043 (12) | −0.0197 (11) |
Geometric parameters (Å, º) top
O1—C1 | 1.296 (3) | O6—H12 | 0.8200 |
O1—H1 | 0.8200 | O7—C12 | 1.210 (3) |
O2—C1 | 1.223 (3) | O8—C13 | 1.416 (4) |
O3—C2 | 1.412 (3) | O8—H14 | 0.8200 |
O3—H3 | 0.8200 | C12—C13 | 1.518 (4) |
C1—C2 | 1.514 (4) | C13—C14 | 1.515 (4) |
C2—C3 | 1.515 (4) | C13—H13 | 0.9800 |
C2—H2 | 0.9800 | C14—C19 | 1.384 (4) |
C3—C4 | 1.378 (4) | C14—C15 | 1.386 (4) |
C3—C8 | 1.392 (4) | C15—C16 | 1.376 (4) |
C4—C5 | 1.382 (5) | C15—H15 | 0.9300 |
C4—H4 | 0.9300 | C16—C17 | 1.387 (5) |
C5—C6 | 1.381 (6) | C16—H16 | 0.9300 |
C5—H5 | 0.9300 | C17—C18 | 1.346 (5) |
C6—C7 | 1.358 (6) | C17—H17 | 0.9300 |
C6—H6 | 0.9300 | C18—C19 | 1.387 (5) |
C7—C8 | 1.388 (5) | C18—H18 | 0.9300 |
C7—H7 | 0.9300 | C19—H19 | 0.9300 |
C8—H8 | 0.9300 | O9—C20 | 1.252 (3) |
O4—C9 | 1.224 (3) | O10—C20 | 1.235 (3) |
O5—C9 | 1.264 (3) | N2—C21 | 1.476 (3) |
N1—C10 | 1.485 (3) | N2—H20A | 0.8900 |
N1—H9A | 0.8900 | N2—H20B | 0.8900 |
N1—H9B | 0.8900 | N2—H20C | 0.8900 |
N1—H9C | 0.8900 | C20—C21 | 1.536 (3) |
C9—C10 | 1.523 (3) | C21—C22 | 1.512 (4) |
C10—C11 | 1.515 (4) | C21—H21 | 0.9800 |
C10—H10 | 0.9800 | C22—H22A | 0.9600 |
C11—H11A | 0.9600 | C22—H22B | 0.9600 |
C11—H11B | 0.9600 | C22—H22C | 0.9600 |
C11—H11C | 0.9600 | O11—H1W | 0.934 |
O6—C12 | 1.309 (3) | O11—H2W | 0.861 |
| | | |
C1—O1—H1 | 109.5 | C13—O8—H14 | 109.5 |
C2—O3—H3 | 109.5 | O7—C12—O6 | 124.5 (3) |
O2—C1—O1 | 124.8 (3) | O7—C12—C13 | 121.7 (2) |
O2—C1—C2 | 121.0 (2) | O6—C12—C13 | 113.8 (2) |
O1—C1—C2 | 114.2 (2) | O8—C13—C14 | 108.5 (2) |
O3—C2—C1 | 110.0 (2) | O8—C13—C12 | 109.3 (2) |
O3—C2—C3 | 112.3 (2) | C14—C13—C12 | 111.8 (2) |
C1—C2—C3 | 109.8 (2) | O8—C13—H13 | 109.0 |
O3—C2—H2 | 108.2 | C14—C13—H13 | 109.0 |
C1—C2—H2 | 108.2 | C12—C13—H13 | 109.0 |
C3—C2—H2 | 108.2 | C19—C14—C15 | 119.2 (3) |
C4—C3—C8 | 118.7 (3) | C19—C14—C13 | 120.6 (2) |
C4—C3—C2 | 120.7 (2) | C15—C14—C13 | 120.2 (2) |
C8—C3—C2 | 120.6 (2) | C16—C15—C14 | 120.0 (3) |
C3—C4—C5 | 121.0 (3) | C16—C15—H15 | 120.0 |
C3—C4—H4 | 119.5 | C14—C15—H15 | 120.0 |
C5—C4—H4 | 119.5 | C15—C16—C17 | 120.0 (3) |
C6—C5—C4 | 119.2 (3) | C15—C16—H16 | 120.0 |
C6—C5—H5 | 120.4 | C17—C16—H16 | 120.0 |
C4—C5—H5 | 120.4 | C18—C17—C16 | 120.4 (3) |
C7—C6—C5 | 120.8 (3) | C18—C17—H17 | 119.8 |
C7—C6—H6 | 119.6 | C16—C17—H17 | 119.8 |
C5—C6—H6 | 119.6 | C17—C18—C19 | 120.3 (3) |
C6—C7—C8 | 120.1 (3) | C17—C18—H18 | 119.9 |
C6—C7—H7 | 120.0 | C19—C18—H18 | 119.9 |
C8—C7—H7 | 120.0 | C14—C19—C18 | 120.2 (3) |
C7—C8—C3 | 120.1 (3) | C14—C19—H19 | 119.9 |
C7—C8—H8 | 119.9 | C18—C19—H19 | 119.9 |
C3—C8—H8 | 119.9 | C21—N2—H20A | 109.5 |
C10—N1—H9A | 109.5 | C21—N2—H20B | 109.5 |
C10—N1—H9B | 109.5 | H20A—N2—H20B | 109.5 |
H9A—N1—H9B | 109.5 | C21—N2—H20C | 109.5 |
C10—N1—H9C | 109.5 | H20A—N2—H20C | 109.5 |
H9A—N1—H9C | 109.5 | H20B—N2—H20C | 109.5 |
H9B—N1—H9C | 109.5 | O10—C20—O9 | 126.1 (2) |
O4—C9—O5 | 125.5 (2) | O10—C20—C21 | 118.6 (2) |
O4—C9—C10 | 118.7 (2) | O9—C20—C21 | 115.2 (2) |
O5—C9—C10 | 115.7 (2) | N2—C21—C22 | 110.8 (2) |
N1—C10—C11 | 110.7 (2) | N2—C21—C20 | 109.28 (19) |
N1—C10—C9 | 108.32 (19) | C22—C21—C20 | 110.9 (2) |
C11—C10—C9 | 111.3 (2) | N2—C21—H21 | 108.6 |
N1—C10—H10 | 108.8 | C22—C21—H21 | 108.6 |
C11—C10—H10 | 108.8 | C20—C21—H21 | 108.6 |
C9—C10—H10 | 108.8 | C21—C22—H22A | 109.5 |
C10—C11—H11A | 109.5 | C21—C22—H22B | 109.5 |
C10—C11—H11B | 109.5 | H22A—C22—H22B | 109.5 |
H11A—C11—H11B | 109.5 | C21—C22—H22C | 109.5 |
C10—C11—H11C | 109.5 | H22A—C22—H22C | 109.5 |
H11A—C11—H11C | 109.5 | H22B—C22—H22C | 109.5 |
H11B—C11—H11C | 109.5 | H1W—O11—H2W | 109.5 |
C12—O6—H12 | 109.5 | | |
| | | |
O2—C1—C2—O3 | 14.3 (3) | O6—C12—C13—O8 | −172.1 (2) |
O1—C1—C2—O3 | −167.8 (2) | O7—C12—C13—C14 | −111.7 (3) |
O2—C1—C2—C3 | −109.7 (3) | O6—C12—C13—C14 | 67.7 (3) |
O1—C1—C2—C3 | 68.2 (3) | O8—C13—C14—C19 | 109.9 (3) |
O3—C2—C3—C4 | −61.9 (3) | C12—C13—C14—C19 | −129.4 (3) |
C1—C2—C3—C4 | 60.7 (3) | O8—C13—C14—C15 | −67.8 (3) |
O3—C2—C3—C8 | 117.2 (3) | C12—C13—C14—C15 | 52.9 (3) |
C1—C2—C3—C8 | −120.1 (3) | C19—C14—C15—C16 | −0.2 (4) |
C8—C3—C4—C5 | 0.6 (4) | C13—C14—C15—C16 | 177.6 (3) |
C2—C3—C4—C5 | 179.7 (3) | C14—C15—C16—C17 | −0.3 (5) |
C3—C4—C5—C6 | −0.7 (5) | C15—C16—C17—C18 | 0.1 (6) |
C4—C5—C6—C7 | 0.4 (6) | C16—C17—C18—C19 | 0.6 (6) |
C5—C6—C7—C8 | 0.1 (6) | C15—C14—C19—C18 | 0.9 (4) |
C6—C7—C8—C3 | −0.2 (5) | C13—C14—C19—C18 | −176.8 (3) |
C4—C3—C8—C7 | −0.1 (4) | C17—C18—C19—C14 | −1.2 (5) |
C2—C3—C8—C7 | −179.2 (3) | O10—C20—C21—N2 | −12.6 (3) |
O4—C9—C10—N1 | −17.9 (3) | O9—C20—C21—N2 | 168.3 (2) |
O5—C9—C10—N1 | 165.6 (2) | O10—C20—C21—C22 | 109.8 (3) |
O4—C9—C10—C11 | 104.0 (3) | O9—C20—C21—C22 | −69.2 (3) |
O5—C9—C10—C11 | −72.5 (3) | O3—C2—C1—O2 | 14.3 (3) |
O7—C12—C13—O8 | 8.5 (3) | O8—C13—C12—O7 | 8.5 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O5 | 0.82 | 1.68 | 2.494 (3) | 174 |
O11—H1W···O10i | 0.93 | 2.03 | 2.924 (3) | 160 |
O11—H2W···O7ii | 0.86 | 2.47 | 3.263 (3) | 154 |
O11—H2W···O8ii | 0.86 | 2.36 | 3.045 (4) | 137 |
O3—H3···O2 | 0.82 | 2.20 | 2.656 (3) | 115 |
O3—H3···O10iii | 0.82 | 2.22 | 2.916 (3) | 142 |
N1—H9A···O3iv | 0.89 | 2.05 | 2.879 (3) | 155 |
N1—H9C···O5v | 0.89 | 1.99 | 2.861 (3) | 168 |
N1—H9B···O7 | 0.89 | 2.44 | 3.024 (3) | 124 |
N1—H9B···O11 | 0.89 | 2.23 | 2.959 (3) | 139 |
O6—H12···O9 | 0.82 | 1.74 | 2.554 (3) | 175 |
O8—H14···O2v | 0.82 | 2.08 | 2.856 (3) | 158 |
N2—H20A···O8vi | 0.89 | 2.08 | 2.899 (3) | 152 |
N2—H20B···O4 | 0.89 | 1.98 | 2.811 (3) | 156 |
N2—H20C···O9ii | 0.89 | 1.96 | 2.824 (3) | 163 |
Symmetry codes: (i) x, y+1, z; (ii) x−1, y, z; (iii) x−1, y+1, z; (iv) x+1, y−1, z; (v) x+1, y, z; (vi) x−1, y−1, z. |
Experimental details
Crystal data |
Chemical formula | C3H7NO2·C8H8O3·0.5H2O |
Mr | 250.25 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 298 |
a, b, c (Å) | 6.0193 (11), 8.2285 (10), 12.5811 (11) |
α, β, γ (°) | 82.545 (9), 86.000 (14), 89.752 (13) |
V (Å3) | 616.36 (15) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.60 × 0.55 × 0.30 |
|
Data collection |
Diffractometer | Rigaku AFC-7S diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2617, 2436, 2011 |
Rint | 0.016 |
(sin θ/λ)max (Å−1) | 0.617 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.030, 0.084, 1.04 |
No. of reflections | 2436 |
No. of parameters | 324 |
No. of restraints | 3 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.14, −0.15 |
Selected geometric parameters (Å, º) topO1—C1 | 1.296 (3) | O6—C12 | 1.309 (3) |
O2—C1 | 1.223 (3) | O7—C12 | 1.210 (3) |
O4—C9 | 1.224 (3) | O9—C20 | 1.252 (3) |
O5—C9 | 1.264 (3) | O10—C20 | 1.235 (3) |
| | | |
O2—C1—O1 | 124.8 (3) | O7—C12—O6 | 124.5 (3) |
O4—C9—O5 | 125.5 (2) | O10—C20—O9 | 126.1 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O5 | 0.82 | 1.68 | 2.494 (3) | 174 |
O11—H1W···O10i | 0.93 | 2.03 | 2.924 (3) | 160 |
O11—H2W···O7ii | 0.86 | 2.47 | 3.263 (3) | 154 |
O11—H2W···O8ii | 0.86 | 2.36 | 3.045 (4) | 137 |
O3—H3···O2 | 0.82 | 2.20 | 2.656 (3) | 115 |
O3—H3···O10iii | 0.82 | 2.22 | 2.916 (3) | 142 |
N1—H9A···O3iv | 0.89 | 2.05 | 2.879 (3) | 155 |
N1—H9C···O5v | 0.89 | 1.99 | 2.861 (3) | 168 |
N1—H9B···O7 | 0.89 | 2.44 | 3.024 (3) | 124 |
N1—H9B···O11 | 0.89 | 2.23 | 2.959 (3) | 139 |
O6—H12···O9 | 0.82 | 1.74 | 2.554 (3) | 175 |
O8—H14···O2v | 0.82 | 2.08 | 2.856 (3) | 158 |
N2—H20A···O8vi | 0.89 | 2.08 | 2.899 (3) | 152 |
N2—H20B···O4 | 0.89 | 1.98 | 2.811 (3) | 156 |
N2—H20C···O9ii | 0.89 | 1.96 | 2.824 (3) | 163 |
Symmetry codes: (i) x, y+1, z; (ii) x−1, y, z; (iii) x−1, y+1, z; (iv) x+1, y−1, z; (v) x+1, y, z; (vi) x−1, y−1, z. |
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Optical resolution of racemic mandelic acid has been performed using some chiral separating reagents, such as S-2-benzylaminobutanol (Kozma et al., 2000) and (1R,3S)-camphoramic acid (Hu et al., 2001). Recently, we separated racemic mandelic acid using (S)-alanine as the separating reagent. The crystal structure of the title complex, (I), shows this successful optical resolution. \sch
The structure of (I) is shown in Fig. 1. The structure has two independent (R)-mandelic acid molecules, two independent (S)-alanine molecules and one water molecule in the unit cell.
Both (R)-mandelic acid molecules have almost identical structures. The C—O(hydroxy) is syn to the C═O bond of the carboxyl group, with an O(H)—C—C═O torsion angle of 14.3 (3)° (in the C1-mandelic acid molecule) and 8.5 (3)° (in the C12 mandelic acid molecule). This is in agreement with data for (R)-mandelic acid reported previously by Wei & Ward (1977).
An intramolecular hydrogen bond (O3—H3···O2) between the hydroxy and carboxyl groups is observed in the C1-mandelic acid but not in the C12-mandelic acid, the hydroxy group (O8—H14) in the C12-mandelic acid forming an intermolecular hydrogen bond to a carboxyl group from the neighbouring mandelic acid, as shown in Fig. 1. This is the most distinct structural difference between the two mandelic acid molecules in (I).
Both (S)-alanine molecules display the normal inner salt structure (Destro et al., 1988). The difference of 0.017 (4) Å in the C—O bond distances observed in the C20-alanine agrees well with the difference of 0.016 (2) Å determined by neutron diffraction (Lehmann et al., 1972), but is significantly smaller than the difference of 0.040 (4) Å between C—O bond distances in the C9-alanine in (I). This may result from the strong hydrogen bonding, discussed below.
An extensive hydrogen-bond network exists in the crystal structure of (I), with all O and N atoms involved in the network. A stronger hydrogen bond with a rather short O1···O5 separation of 2.494 (3) Å is observed between the carboxyl group of the C1-mandelic acid and the carboxylate group of the C9-alanine, which is comparable with the value of 2.501 (2) Å found between mandelic acid and mandelate (Larsen & Lopez de Diego, 1993).
Several structures of compounds containing mandelic acid, mandelate or alanine have been reported to date, all with the carboxylate group involved in the hydrogen bonding (Larsen & Lopez de Diego, 1993; Lopez de Diego, 1995; Okamura et al., 1997). A structural comparison reveals that the shorter the donor···acceptor separation in the hydrogen bond, the larger the difference between the C—O bond distances in the carboxylate group. For example, the shorter O···O separation of 2.501 (2) Å in the hydrogen bond corresponds to the larger difference of 0.040 (2) Å between C—O bond distances in the carboxylate (Larsen & Lopez de Diego, 1993), whereas the longer (normal) N···O separation of 2.813 (1) Å in the hydrogen bond corresponds to the smaller difference of 0.016 (2) Å between C—O bond distances in the carboxylate (Lehmann et al., 1972). This conclusion also agrees well with the present work; the larger difference of 0.040 (4) Å between the O5—C9 and O4—C9 bonds corresponds to the shorter O1···O5 separation of 2.494 (3) Å, and the smaller difference of 0.017 (4) Å between the O9—C20 and O10—C20 bonds corresponds to the longer O6···O9 separation of 2.554 (3) Å. These facts may suggest the effect of the strong hydrogen bond on the neighbouring covalent bond (Larsen & Lopez de Diego, 1993).
Several bifurcated hydrogen bonds are observed in the structure of (I). The O3—H3 hydroxy group, in addition to being the acceptor linking to an amine group from the adjacent alanine, acts as a bifurcated hydrogen-bond donor, intramolecularly to the C1═O2 group and intermolecularly to a C20—O10 carboxyl group from an adjacent alanine. The other hydroxy group, O8—H14, is involved in a similar hydrogen-bonding network. In addition to being the donor linking to the C1—O2 carboxyl group from a neighbouring mandelic acid, the O8—H14 group also acts as a bifurcated hydrogen-bond acceptor, intermolecularly to both the adjacent N2-amine group and the solvate water. The water molecule also acts as both acceptor and donor, with both H atoms involved in the hydrogen bonding. It is notable that, of the carboxyl groups involved in the stronger hydrogen bonds, O1—H1 and O6—H12 serve only as donors.