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In the title compound, C3H8NO2+·C2HO4, the alanine mol­ecule exists in the protonated cationic form and the oxalic acid mol­ecule in the mono-ionized state. The alanine mol­ecules dimerize across inversion centres through head-to-tail N—H...O hydrogen bonds. The semi-oxalate ions aggregate into hydrogen-bonded strings along the shortest cell axis. The crystal structure is also characterized by the presence of a C—H...O hydrogen bond and a short C...O contact between amino acids.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801010558/cf6092sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801010558/cf6092Isup2.hkl
Contains datablock I

CCDC reference: 170883

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.044
  • wR factor = 0.126
  • Data-to-parameter ratio = 12.4

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
PLAT_369 Alert C Long C(sp2)-C(sp2) Bond C(4) - C(5) = 1.54 Ang.
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

X-ray crystallographic investigations of the complexes of amino acids with carboxylic acids are expected to throw light on the nature of intermolecular interactions and biomolecular aggregation patterns that might have occurred in prebiotic polymerization (Vijayan, 1988; Prasad & Vijayan, 1993). Recently, an accurate determination of the crystal structures of DL-alanine (Subha Nandhini et al., 2001b) was carried out in our laboratory. The present study reports the crystal structure of the title salt, (I), a complex of DL-alanine with oxalic acid.

Fig. 1 shows the molecular numbering scheme. The amino acid molecule exists in the cationic form with a neutral carboxylic acid group and a protonated amino group. The oxalic acid molecule exists in the mono-ionized state. In the asymmetric unit, the DL-alaninium cation and the semi-oxalate anion are linked to each other through a N—H···O hydrogen bond. The conformation of the DL-alaninium ions in the present structure is significantly different from the values observed for DL-alanine. The N atom deviates by 0.148 (4) Å from the carboxylate plane and the methyl C atom deviates by 1.063 (5) Å in the opposite direction. The corresponding values observed in DL-alanine are 0.392 (5) and 1.356 (4) Å, respectively. The conformation of the semi-oxalate ion remains essentially planar as observed in the crystal structures of other complexes of amino acids with oxalic acid.

In the crystal structure of (I), the alanine molecules dimerize across inversion centres through head-to-tail N - H···O hydrogen bonds, as observed in many other amino acid racemates (Soman & Vijayan, 1989). The hydrogen-bonded alanine dimers form columns along the b axis and each such column is connected to others through semi-oxalate ions (Fig. 2). The semi-oxalate ions aggregate into hydrogen-bonded strings along the shortest cell axis, generated by translation as observed in glycinium oxalate (Subha Nandhini et al., 2001a) and L-alaninium oxalate (Subha Nandhini et al., 2001c). The crystal structure is also characterized by the presence of a C—H···O hydrogen bond and a short C···O contact [C1···O2(-x + 2,-y + 1,-z + 1) = 2.987 (6) Å] between amino acids. While the aggregation pattern of the semi-oxalate ions is identical in the crystal structures of oxalic acid complexes of glycine, L-alanine and the title compound, (I), the aggregation of amino acid molecules shows no common pattern.

Experimental top

Crystals of (I) were grown from a saturated aqueous solution containing DL-alanine and oxalic acid in a 1:1 stoichiometric ratio.

Refinement top

H atoms were placed in calculated positions and were allowed to ride on their parent atoms with HFIX instructions using SHELXL97 defaults (Sheldrick, 1997).

Computing details top

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) with atom-numbering scheme and 50% probability displacement ellipsoids.
[Figure 2] Fig. 2. Packing diagram of the molecules of (I) in the unit cell viewed down the b axis.
DL-alaninium oxalate top
Crystal data top
C3H8NO2+·C2HO4F(000) = 376
Mr = 179.13Dx = 1.499 Mg m3
Dm = 1.50 Mg m3
Dm measured by floatation in a mixture of xylene and bromoform
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 5.662 (2) ÅCell parameters from 25 reflections
b = 7.342 (2) Åθ = 6–14°
c = 19.157 (6) ŵ = 0.14 mm1
β = 94.48 (3)°T = 293 K
V = 793.9 (4) Å3Needle, colourless
Z = 40.48 × 0.32 × 0.22 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1103 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.011
Graphite monochromatorθmax = 24.9°, θmin = 2.1°
ω–2θ scansh = 06
Absorption correction: ψ scan
(North et al., 1968)
k = 08
Tmin = 0.89, Tmax = 0.97l = 2222
1542 measured reflections2 standard reflections every 60 min
1390 independent reflections intensity decay: 0.1%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044H-atom parameters constrained
wR(F2) = 0.126 w = 1/[σ2(Fo2) + (0.0529P)2 + 0.5084P]
where P = (Fo2 + 2Fc2)/3
S = 1.12(Δ/σ)max < 0.001
1390 reflectionsΔρmax = 0.29 e Å3
112 parametersΔρmin = 0.21 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.016 (4)
Crystal data top
C3H8NO2+·C2HO4V = 793.9 (4) Å3
Mr = 179.13Z = 4
Monoclinic, P21/nMo Kα radiation
a = 5.662 (2) ŵ = 0.14 mm1
b = 7.342 (2) ÅT = 293 K
c = 19.157 (6) Å0.48 × 0.32 × 0.22 mm
β = 94.48 (3)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1103 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.011
Tmin = 0.89, Tmax = 0.972 standard reflections every 60 min
1542 measured reflections intensity decay: 0.1%
1390 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.126H-atom parameters constrained
S = 1.12Δρmax = 0.29 e Å3
1390 reflectionsΔρmin = 0.21 e Å3
112 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
xyzUiso*/Ueq
O10.8597 (4)0.7994 (3)0.47437 (10)0.0640 (6)
H10.88720.76380.43530.096*
O20.7452 (3)0.5134 (2)0.48762 (8)0.0440 (5)
O30.0945 (3)0.7374 (3)0.81048 (8)0.0468 (5)
H30.03840.72290.79100.070*
O40.2081 (3)0.6750 (4)0.70572 (9)0.0749 (8)
O50.5443 (3)0.7832 (2)0.85896 (7)0.0424 (5)
O60.6636 (3)0.7056 (3)0.75614 (8)0.0479 (5)
N10.6243 (3)0.5701 (3)0.61814 (9)0.0395 (5)
H1A0.71350.47080.61610.059*
H1B0.48200.54900.59660.059*
H1C0.60900.59830.66270.059*
C10.7808 (4)0.6655 (4)0.50960 (12)0.0391 (6)
C20.7377 (5)0.7225 (3)0.58355 (12)0.0441 (6)
H20.89160.74620.60900.053*
C30.5910 (7)0.8905 (4)0.58644 (16)0.0766 (10)
H3A0.56980.91970.63440.115*
H3B0.43920.87010.56170.115*
H3C0.66950.98970.56510.115*
C40.5086 (3)0.7357 (3)0.79733 (10)0.0312 (5)
C50.2518 (3)0.7132 (3)0.76556 (10)0.0335 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0888 (16)0.0609 (12)0.0469 (11)0.0031 (11)0.0358 (11)0.0044 (9)
O20.0367 (9)0.0617 (12)0.0341 (9)0.0010 (8)0.0068 (7)0.0080 (8)
O30.0200 (8)0.0839 (13)0.0371 (9)0.0035 (8)0.0072 (6)0.0130 (8)
O40.0291 (9)0.158 (2)0.0372 (10)0.0009 (11)0.0007 (7)0.0360 (12)
O50.0285 (8)0.0726 (12)0.0267 (8)0.0081 (8)0.0053 (6)0.0110 (7)
O60.0208 (7)0.0938 (14)0.0298 (8)0.0022 (8)0.0064 (6)0.0134 (8)
N10.0435 (11)0.0528 (12)0.0228 (9)0.0063 (9)0.0063 (7)0.0019 (8)
C10.0324 (12)0.0545 (15)0.0312 (11)0.0059 (11)0.0068 (9)0.0023 (11)
C20.0462 (13)0.0568 (15)0.0298 (11)0.0030 (11)0.0072 (10)0.0041 (11)
C30.121 (3)0.0573 (19)0.0565 (18)0.0166 (18)0.0382 (19)0.0017 (14)
C40.0215 (10)0.0473 (13)0.0255 (10)0.0026 (9)0.0049 (8)0.0038 (9)
C50.0215 (10)0.0499 (13)0.0293 (11)0.0014 (9)0.0043 (8)0.0082 (9)
Geometric parameters (Å, º) top
O1—C11.290 (3)N1—H1B0.890
O1—H10.820N1—H1C0.890
O2—C11.205 (3)C1—C21.516 (3)
O3—C51.298 (2)C2—C31.491 (4)
O3—H30.820C2—H20.980
O4—C51.187 (3)C3—H3A0.960
O5—C41.233 (2)C3—H3B0.960
O6—C41.245 (2)C3—H3C0.960
N1—C21.472 (3)C4—C51.541 (3)
N1—H1A0.890
C1—O1—H1109.5C3—C2—H2108.2
C5—O3—H3109.5C1—C2—H2108.2
C2—N1—H1A109.5C2—C3—H3A109.5
C2—N1—H1B109.5C2—C3—H3B109.5
H1A—N1—H1B109.5H3A—C3—H3B109.5
C2—N1—H1C109.5C2—C3—H3C109.5
H1A—N1—H1C109.5H3A—C3—H3C109.5
H1B—N1—H1C109.5H3B—C3—H3C109.5
O2—C1—O1125.3 (2)O5—C4—O6125.93 (19)
O2—C1—C2123.3 (2)O5—C4—C5119.18 (17)
O1—C1—C2111.4 (2)O6—C4—C5114.88 (17)
N1—C2—C3110.3 (2)O4—C5—O3124.8 (2)
N1—C2—C1108.5 (2)O4—C5—C4121.69 (18)
C3—C2—C1113.3 (2)O3—C5—C4113.49 (17)
N1—C2—H2108.2
O2—C1—C2—N16.2 (3)O5—C4—C5—O4176.9 (3)
O1—C1—C2—N1174.0 (2)O6—C4—C5—O42.1 (4)
O2—C1—C2—C3129.1 (3)O5—C4—C5—O34.0 (3)
O1—C1—C2—C351.0 (3)O6—C4—C5—O3177.1 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O5i0.821.802.591 (2)161
O3—H3···O6ii0.821.772.587 (2)174
N1—H1A···O5iii0.891.982.834 (3)161
N1—H1B···O2iv0.892.032.863 (3)154
N1—H1C···O60.891.962.818 (2)162
C2—H2···O4v0.982.533.423 (3)152
Symmetry codes: (i) x+1/2, y+3/2, z1/2; (ii) x1, y, z; (iii) x+3/2, y1/2, z+3/2; (iv) x+1, y+1, z+1; (v) x+1, y, z.

Experimental details

Crystal data
Chemical formulaC3H8NO2+·C2HO4
Mr179.13
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)5.662 (2), 7.342 (2), 19.157 (6)
β (°) 94.48 (3)
V3)793.9 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.14
Crystal size (mm)0.48 × 0.32 × 0.22
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.89, 0.97
No. of measured, independent and
observed [I > 2σ(I)] reflections
1542, 1390, 1103
Rint0.011
(sin θ/λ)max1)0.593
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.126, 1.12
No. of reflections1390
No. of parameters112
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.29, 0.21

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1999), SHELXL97.

Selected torsion angles (º) top
O2—C1—C2—N16.2 (3)O2—C1—C2—C3129.1 (3)
O1—C1—C2—N1174.0 (2)O1—C1—C2—C351.0 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O5i0.821.802.591 (2)160.6
O3—H3···O6ii0.821.772.587 (2)174.0
N1—H1A···O5iii0.891.982.834 (3)161.1
N1—H1B···O2iv0.892.032.863 (3)154.2
N1—H1C···O60.891.962.818 (2)162.0
C2—H2···O4v0.982.533.423 (3)151.6
Symmetry codes: (i) x+1/2, y+3/2, z1/2; (ii) x1, y, z; (iii) x+3/2, y1/2, z+3/2; (iv) x+1, y+1, z+1; (v) x+1, y, z.
 

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