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In the title compound, C2H6NO2+·C2HO4-, the glycine mol­ecule exists in the cationic form and the oxalic acid mol­ecule in the mono-ionized state. The mol­ecules aggregate into alternate columns of glycinium and semi-oxalate ions. The structure is stabilized by an extensive network of hydrogen bonds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100015456/vj1115sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100015456/vj1115Isup2.hkl
Contains datablock I

CCDC reference: 158278

Comment top

Structural data on the complexes of amino acids with carboxylic acids seem to be very limited. Single crystal X-ray investigations on such complexes are expected to throw light on the geometrical features of biomolecular interactions and aggregation patterns that might well have occurred in prebiotic polymerization (Vijayan, 1988; Prasad & Vijayan, 1993). The present study reports the crystal structure of a complex of glycine, the simplest of amino acids commonly found in proteins, with oxalic acid, (I). \sch

The glycine molecule exists in the cationic form with a positively charged amino group and an uncharged carboxylic group. The oxalic acid molecule exists in a mono ionized state in the crystals. The crystal structure of the complex is illustrated in Figure 2 and the hydrogen bonds that stabilize it are listed in Table 1. The glycine molecules form columns around 21 screw axes parallel to b. The molecules in each column are interconnected by a hydrogen bond between the amino and carboxyl groups of adjacent molecules, in a head-to-tail arrangement. Semi-oxalate ions also form columns parallel to b. The adjacent molecules are related by a cell translation and interconnected by a O—H···O hydrogen bond. Each such column and its equivalent generated by a centre of inversion connect two glycine columns giving rise to a double layer parallel to (102). In each layer, the unlike molecules are connected through an O—H···O hydrogen bond between the carboxyl group of the amino acid and the carboxylate group of the semi-oxalate ion, and their symmetry equivalents. The double layer is further stabilized by hydrogen bonds of the amino group of glycine with the semi-oxalate ion. The double layers are held together by possible C—H···O and van der Waals interactions. The mode of aggregation in the structure is different from those observed so far in amino acid- oxalic acid complexes (Bakke & Mostad, 1980; Prabu et al., 1996; Chandra et al., 1998; Krishnakumar et al., 1999).

Experimental top

Colourless single crystals of the above complex were grown as transparent plates, from a saturated aqueous solution containing glycine and oxalic acid in stoichiometric ratio, 1:1 proportion. The density was determined by the flotation method using a liquid mixture of carbon tetrachloride and xylene.

Refinement top

All the H atoms were located from a difference Fourier map and refined isotropically.

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, 1990); 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 molecule viewed down the b axis.
Glycinium oxalate top
Crystal data top
C2H6NO2+·C2HO4F(000) = 344
Mr = 165.11Dx = 1.658 Mg m3
Dm = 1.66 Mg m3
Dm measured by flotation method
Monoclinic, P21/cCu Kα radiation, λ = 1.54180 Å
a = 10.5807 (15) ÅCell parameters from 25 reflections
b = 5.650 (2) Åθ = 16–29°
c = 12.093 (3) ŵ = 1.43 mm1
β = 113.83 (1)°T = 293 K
V = 661.3 (3) Å3Plates, colourless
Z = 40.45 × 0.32 × 0.22 mm
Data collection top
Enraf-Nonius CAD4
diffractometer
1183 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.013
Graphite monochromatorθmax = 70.0°, θmin = 4.6°
ω–2θ scansh = 012
Absorption correction: ψ scan
(North et al., 1968)
k = 06
Tmin = 0.555, Tmax = 0.730l = 1413
1280 measured reflections2 standard reflections every 200 reflections
1212 independent reflections intensity decay: 0.1%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: located
R[F2 > 2σ(F2)] = 0.036All H-atom parameters refined
wR(F2) = 0.106Calculated w = 1/[σ2(Fo2) + (0.058P)2 + 0.2023P]
where P = (Fo2 + 2Fc2)/3
S = 1.21(Δ/σ)max < 0.001
1212 reflectionsΔρmax = 0.28 e Å3
129 parametersΔρmin = 0.21 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.069 (4)
Crystal data top
C2H6NO2+·C2HO4V = 661.3 (3) Å3
Mr = 165.11Z = 4
Monoclinic, P21/cCu Kα radiation
a = 10.5807 (15) ŵ = 1.43 mm1
b = 5.650 (2) ÅT = 293 K
c = 12.093 (3) Å0.45 × 0.32 × 0.22 mm
β = 113.83 (1)°
Data collection top
Enraf-Nonius CAD4
diffractometer
1183 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.013
Tmin = 0.555, Tmax = 0.7302 standard reflections every 200 reflections
1280 measured reflections intensity decay: 0.1%
1212 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0360 restraints
wR(F2) = 0.106All H-atom parameters refined
S = 1.21Δρmax = 0.28 e Å3
1212 reflectionsΔρmin = 0.21 e Å3
129 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
N10.27816 (15)0.2485 (3)0.79503 (13)0.0355 (4)
O10.60285 (13)0.1930 (2)0.54347 (12)0.0468 (4)
O20.50188 (13)0.5083 (2)0.65663 (11)0.0418 (4)
O30.09956 (12)0.0715 (2)0.58171 (12)0.0378 (4)
O40.11644 (11)0.2165 (2)0.66801 (10)0.0343 (3)
O50.20401 (11)0.49360 (19)0.55030 (12)0.0396 (4)
O60.00490 (11)0.65912 (17)0.62212 (10)0.0320 (3)
C10.49894 (15)0.3073 (3)0.62413 (13)0.0301 (4)
C20.36952 (16)0.1594 (3)0.67389 (14)0.0319 (4)
C30.00764 (15)0.2399 (2)0.62010 (12)0.0249 (4)
C40.07662 (15)0.4867 (2)0.59528 (12)0.0247 (4)
H10.671 (3)0.289 (5)0.510 (3)0.076 (8)*
H20.320 (2)0.174 (4)0.6224 (18)0.046 (5)*
H30.390 (2)0.006 (4)0.6808 (17)0.035 (5)*
H40.261 (2)0.407 (5)0.797 (2)0.058 (6)*
H50.313 (3)0.217 (4)0.851 (2)0.066 (7)*
H60.191 (2)0.174 (4)0.8206 (19)0.047 (5)*
H70.060 (2)0.071 (5)0.597 (2)0.062 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0241 (8)0.0347 (8)0.0426 (8)0.0004 (6)0.0081 (6)0.0036 (6)
O10.0292 (7)0.0396 (7)0.0549 (8)0.0067 (5)0.0005 (6)0.0092 (6)
O20.0315 (7)0.0369 (7)0.0507 (7)0.0057 (5)0.0102 (5)0.0073 (5)
O30.0294 (7)0.0187 (6)0.0606 (8)0.0004 (4)0.0132 (5)0.0001 (5)
O40.0251 (7)0.0285 (6)0.0442 (6)0.0043 (4)0.0088 (5)0.0028 (4)
O50.0220 (7)0.0272 (6)0.0613 (8)0.0036 (4)0.0083 (5)0.0031 (5)
O60.0270 (6)0.0187 (6)0.0472 (6)0.0012 (4)0.0117 (5)0.0004 (4)
C10.0249 (8)0.0315 (8)0.0341 (7)0.0021 (6)0.0121 (6)0.0003 (6)
C20.0249 (8)0.0323 (9)0.0384 (8)0.0034 (6)0.0127 (7)0.0013 (6)
C30.0258 (9)0.0195 (8)0.0292 (7)0.0012 (5)0.0109 (6)0.0018 (5)
C40.0247 (9)0.0206 (7)0.0281 (7)0.0008 (5)0.0098 (6)0.0011 (5)
Geometric parameters (Å, º) top
N1—C21.480 (2)O3—H70.89 (3)
N1—H40.91 (3)O4—C31.2092 (19)
N1—H50.90 (3)O5—C41.234 (2)
N1—H60.94 (2)O6—C41.2540 (18)
O1—C11.308 (2)C1—C21.506 (2)
O1—H10.86 (3)C2—H20.96 (2)
O2—C11.207 (2)C2—H30.90 (2)
O3—C31.3047 (19)C3—C41.546 (2)
C2—N1—H4113.8 (15)N1—C2—H2107.8 (13)
C2—N1—H5111.7 (16)C1—C2—H2109.7 (12)
H4—N1—H5108 (2)N1—C2—H3108.6 (12)
C2—N1—H6109.4 (13)C1—C2—H3110.8 (12)
H4—N1—H6106 (2)H2—C2—H3110.6 (17)
H5—N1—H6108 (2)O4—C3—O3126.84 (13)
C1—O1—H1110 (2)O4—C3—C4121.87 (13)
C3—O3—H7111.5 (16)O3—C3—C4111.29 (12)
O2—C1—O1125.66 (15)O5—C4—O6127.17 (13)
O2—C1—C2122.07 (14)O5—C4—C3117.42 (13)
O1—C1—C2112.26 (14)O6—C4—C3115.41 (12)
N1—C2—C1109.37 (13)
O2—C1—C2—N124.7 (2)O3—C3—C4—O53.57 (18)
O1—C1—C2—N1155.86 (14)O4—C3—C4—O63.73 (19)
O4—C3—C4—O5177.25 (13)O3—C3—C4—O6175.44 (12)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O5i0.86 (3)1.73 (3)2.593 (2)174 (3)
N1—H4···O4ii0.91 (3)2.25 (3)3.082 (2)152 (2)
N1—H5···O2iii0.90 (3)2.26 (3)2.949 (2)133 (2)
N1—H5···O5iv0.90 (3)2.51 (2)3.172 (2)130 (2)
N1—H6···O6v0.94 (2)1.81 (2)2.698 (2)156 (2)
O3—H7···O6vi0.89 (3)1.65 (3)2.540 (2)177 (2)
C2—H2···O50.96 (2)2.53 (2)3.314 (2)139 (2)
Symmetry codes: (i) x1, y+1, z+1; (ii) x, y+1/2, z+3/2; (iii) x1, y1/2, z+3/2; (iv) x, y+1/2, z+1/2; (v) x, y1/2, z+3/2; (vi) x, y1, z.

Experimental details

Crystal data
Chemical formulaC2H6NO2+·C2HO4
Mr165.11
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)10.5807 (15), 5.650 (2), 12.093 (3)
β (°) 113.83 (1)
V3)661.3 (3)
Z4
Radiation typeCu Kα
µ (mm1)1.43
Crystal size (mm)0.45 × 0.32 × 0.22
Data collection
DiffractometerEnraf-Nonius CAD4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.555, 0.730
No. of measured, independent and
observed [I > 2σ(I)] reflections
1280, 1212, 1183
Rint0.013
(sin θ/λ)max1)0.610
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.106, 1.21
No. of reflections1212
No. of parameters129
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.28, 0.21

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1999), SHELXL97.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O5i0.86 (3)1.73 (3)2.593 (2)174 (3)
N1—H4···O4ii0.91 (3)2.25 (3)3.082 (2)152 (2)
N1—H5···O2iii0.90 (3)2.26 (3)2.949 (2)133 (2)
N1—H5···O5iv0.90 (3)2.51 (2)3.172 (2)130 (2)
N1—H6···O6v0.94 (2)1.81 (2)2.698 (2)156 (2)
O3—H7···O6vi0.89 (3)1.65 (3)2.540 (2)177 (2)
C2—H2···O50.96 (2)2.53 (2)3.314 (2)139 (2)
Symmetry codes: (i) x1, y+1, z+1; (ii) x, y+1/2, z+3/2; (iii) x1, y1/2, z+3/2; (iv) x, y+1/2, z+1/2; (v) x, y1/2, z+3/2; (vi) x, y1, z.
 

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