(±)-3-Carb­oxy-2-(imidazol-3-ium-1-yl)­propanoate

Reeb, S.A.; Shields, M.C.; Wheeler, K.A.

doi:10.1107/S1600536809018510

organic compounds

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Volume 65| Part 6| June 2009| Page o1424

doi:10.1107/S1600536809018510

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(±)-3-Carboxy-2-(imidazol-3-ium-1-yl)propanoate

Sarah A. Reeb,^a Marlesa C. Shields ^a and Kraig A. Wheeler ^a ^*

^aEastern Illinois University, Department of Chemistry, 600 Lincoln Avenue, Charleston, IL 61920-3099, USA
^*Correspondence e-mail: kawheeler@eiu.edu

(Received 8 May 2009; accepted 15 May 2009; online 29 May 2009)

The title compound, C₇H₈N₂O₄, crystallizes as a zwitterion, with molecules organized into molecular sheets via carboxyl–carboxylate and N⁺—H⋯carboxylate contacts. These sheets are constructed from translationally related molecules that further link to neighboring motifs via π-stacking [centroid–centroid distance 3.504 (3) Å] and weak C—H⋯O contacts.

Related literature

For related compounds, see: Centnerzwer (1899 ); Pasteur (1853 ); Wheeler et al. (2008 ). For a description of the Cambridge Structural Database, see: Allen (2002 ).

Experimental

Crystal data

C₇H₈N₂O₄
M_r = 184.15
Monoclinic, P 2₁ /c
a = 7.6328 (7) Å
b = 7.4701 (7) Å
c = 13.7616 (12) Å
β = 96.752 (1)°
V = 779.21 (12) Å³
Z = 4
Mo Kα radiation
μ = 0.13 mm⁻¹
T = 296 K
0.38 × 0.28 × 0.18 mm

Data collection

Bruker P4 CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.952, T_max = 0.977
4668 measured reflections
1540 independent reflections
1254 reflections with I > 2σ(I)
R_int = 0.021

Refinement

R[F² > 2σ(F²)] = 0.042
wR(F²) = 0.115
S = 1.06
1540 reflections
126 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H1⋯O2ⁱ	0.95 (3)	1.62 (3)	2.5440 (18)	163 (3)
N2—H3⋯O1ⁱⁱ	0.89 (3)	1.85 (3)	2.732 (2)	170 (2)
C7—H7⋯O1ⁱⁱⁱ	0.93	2.42	3.333 (2)	168
C5—H5⋯O4^iv	0.93	2.57	3.260 (3)	131
Symmetry codes: (i) x-1, y, z; (ii) x, y-1, z; (iii) $[-x+2, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iv) $[x, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT and XPREP (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001 ); software used to prepare material for publication: X-SEED.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809018510/hk2685sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809018510/hk2685Isup2.hkl

checkCIF report

Comment top

Our recent reinvestigation of Pasteur's 1853 quasiracemates (Pasteur, 1853; Wheeler et al., 2008) has motivated us to explore other examples of these unusual materials of historical and supramolecular importance. In 1899, Centnerzwer reported that mixtures of (+)-chlorosuccinic acid and (-)-bromosuccinic acid formed a binary compound that also exhibited quasiracemic behavior (Centnerzwer, 1899). Our initial attempts to grow crystals of this quasiracemic phase were unsuccessful. This result was somewhat anticipated given that Centnerzwer's melting point phase diagrams showed the crystal stabilities of the homochiral phases more stable than the quasiracemate. We then turned our attention to investigating the effects of co-crystalline additives to crystal growth of this quasiracemate and the corresponding racemic and homochiral compounds. During the course of these co-crystal screening investigations, we observed the formation of crystals of the title compound from slow evaporation of a methanol:CH₂Cl₂ (1:1) solution of (±)-2-chlorosuccinic acid and imidazole.

The title compound, (I), formed from the substitution reaction of imidazole and 2-chlorosuccinic acid, crystallizes in space group P2₁/c as the imidazolium carboxylate zwitterion (Fig. 1). Inspection of the molecular structure reveals a resonance stabilized imidazolium ring with (N1—C7) - (N2—C7) = +0.038 Å. A search of the Cambridge Structural Database (CSD, Version 5.30 with August 2008 and February 2009 updates; Allen, 2002) for other N-alkylimidazolium fragments uncovered 44 organic structures. This collection shows similar bonding patterns to (I) with a concentration of Δ(N—C) values near 0.00, +0.01, and +0.03 Å.

The crystal structure of (I) is organized by a complex blend of strong and weak intermolecular contacts (Table 1). Neighboring molecules are linked by carboxyl···carboxylate interactions to give a catemeric motif that propagates along the a-axis (Fig. 2). This motif is extended by N2⁺—H···carboxylate contacts to produce a molecular sheet in the ab plane. The participation of the imidazolium N⁺—H group in hydrogen bonding is also a common feature in the 44 structures retrieved from the CSD. Each of these structures show N⁺—H···A contacts with a diverse set of acceptors [A = oxygen(52), nitrogen(3), halogen(15), or π(2); 72 contacts]. Interestingly, each molecular sheet in (I) consists of translationally related molecules with imidazolium groups exposed on one side of the motif and carboxyl O4 atoms on the other side. The crystal structure of (I) is characterized by the stacking of these molecular sheets with adjacent motifs related by inversion symmetry and linked by either interdigitated imadazolium···imidazolium stacks [3.504 (3) Å] or weak C5—H5···O4 interactions (Fig. 3).

Related literature top

For related structures, see: Centnerzwer (1899); Pasteur (1853); Wheeler et al. (2008). For the Cambridge Structural Database, see: Allen (2002).

Experimental top

Single crystals of the title compound were prepared by slow evaporation at room temperature of a methanol:CH₂Cl₂ (1:1) solution of (±)-2-chlorosuccinic acid and imidazole (1:1).

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008) and XPREP (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: X-SEED (Barbour, 2001).

Figures top

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A partial packing diagram of the title compound, showing molecular sheets constructed from carboxyl···carboxylate and N—H···O contacts [symmetry codes: (i) 1 + x, y, z, (ii) x, 1 + y, z; (iii) x - 1, y, z].
	Fig. 3. Projection showing alignment of molecular sheets with imidazolium π stacking and C—H···O interactions [symmetry codes: i) x, y - 1, z, (ii) x, 3/2 - y, 1/2 + z; (iii) x - 3, 3/2 - y, z - 1/2].
	Fig. 4. The tautomeric forms of the title compound.

(±)-3-Carboxy-2-(imidazol-3-ium-1-yl)propanoate top

Crystal data top

C₇H₈N₂O₄	F(000) = 384
M_r = 184.15	D_x = 1.570 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1902 reflections
a = 7.6328 (7) Å	θ = 6.0–54.6°
b = 7.4701 (7) Å	µ = 0.13 mm⁻¹
c = 13.7616 (12) Å	T = 296 K
β = 96.752 (1)°	Transparent prism, colourless
V = 779.21 (12) Å³	0.38 × 0.28 × 0.18 mm
Z = 4

Data collection top

Bruker P4 CCD diffractometer	1540 independent reflections
Radiation source: fine-focus sealed tube	1254 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.021
ϕ and ω scans	θ_max = 26.0°, θ_min = 2.7°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −9→9
T_min = 0.952, T_max = 0.977	k = −9→8
4668 measured reflections	l = −16→16

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)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.115	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ²(F_o²) + (0.0548P)² + 0.3288P] where P = (F_o² + 2F_c²)/3
1540 reflections	(Δ/σ)_max < 0.001
126 parameters	Δρ_max = 0.24 e Å⁻³
0 restraints	Δρ_min = −0.26 e Å⁻³

Crystal data top

C₇H₈N₂O₄	V = 779.21 (12) Å³
M_r = 184.15	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 7.6328 (7) Å	µ = 0.13 mm⁻¹
b = 7.4701 (7) Å	T = 296 K
c = 13.7616 (12) Å	0.38 × 0.28 × 0.18 mm
β = 96.752 (1)°

Data collection top

Bruker P4 CCD diffractometer	1540 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	1254 reflections with I > 2σ(I)
T_min = 0.952, T_max = 0.977	R_int = 0.021
4668 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.042	0 restraints
wR(F²) = 0.115	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	Δρ_max = 0.24 e Å⁻³
1540 reflections	Δρ_min = −0.26 e Å⁻³
126 parameters

Special details top

Experimental. The instrument used for data collection was a Bruker P4 with a APEXII CCD detector upgrade.

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	U_iso*/U_eq
O1	1.00100 (17)	1.13604 (17)	0.63749 (11)	0.0446 (4)
O2	1.09600 (17)	0.86066 (19)	0.61600 (13)	0.0558 (5)
O3	0.42339 (18)	0.9309 (2)	0.62306 (10)	0.0475 (4)
O4	0.4539 (2)	0.8529 (3)	0.77836 (13)	0.0813 (7)
N1	0.77182 (17)	0.72061 (19)	0.57875 (10)	0.0293 (3)
N2	0.8241 (2)	0.4386 (2)	0.57164 (14)	0.0448 (4)
C1	0.9788 (2)	0.9740 (2)	0.62128 (12)	0.0296 (4)
C2	0.7853 (2)	0.9081 (2)	0.61136 (12)	0.0290 (4)
H2	0.7163	0.9819	0.5619	0.035*
C3	0.7111 (2)	0.9343 (3)	0.70828 (13)	0.0367 (4)
H3A	0.7738	0.8551	0.7563	0.044*
H3B	0.7355	1.0561	0.7301	0.044*
C4	0.5163 (2)	0.9005 (3)	0.70683 (14)	0.0378 (4)
C5	0.7043 (2)	0.6631 (3)	0.48706 (14)	0.0391 (5)
H5	0.6466	0.7330	0.4373	0.047*
C6	0.7375 (3)	0.4871 (3)	0.48305 (16)	0.0474 (5)
H6	0.7071	0.4121	0.4298	0.057*
C7	0.8438 (2)	0.5806 (2)	0.62777 (15)	0.0400 (5)
H7	0.8993	0.5830	0.6917	0.048*
H1	0.301 (5)	0.920 (4)	0.630 (2)	0.098 (10)*
H3	0.870 (3)	0.333 (4)	0.5910 (17)	0.061 (7)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0352 (7)	0.0277 (7)	0.0694 (10)	−0.0049 (5)	−0.0004 (6)	−0.0018 (6)
O2	0.0231 (7)	0.0362 (8)	0.1069 (13)	0.0015 (6)	0.0032 (7)	−0.0128 (8)
O3	0.0277 (7)	0.0630 (10)	0.0517 (9)	−0.0032 (6)	0.0042 (6)	0.0051 (7)
O4	0.0476 (10)	0.1370 (19)	0.0607 (11)	−0.0101 (11)	0.0125 (8)	0.0310 (11)
N1	0.0244 (7)	0.0263 (8)	0.0370 (8)	−0.0015 (5)	0.0021 (6)	−0.0016 (6)
N2	0.0378 (9)	0.0255 (9)	0.0715 (12)	0.0012 (7)	0.0078 (8)	0.0026 (8)
C1	0.0255 (8)	0.0299 (9)	0.0330 (9)	−0.0015 (7)	0.0021 (6)	−0.0006 (7)
C2	0.0249 (8)	0.0259 (9)	0.0356 (9)	0.0001 (6)	0.0006 (6)	−0.0008 (7)
C3	0.0290 (9)	0.0422 (11)	0.0387 (10)	0.0019 (8)	0.0028 (7)	−0.0039 (8)
C4	0.0308 (9)	0.0384 (10)	0.0449 (11)	0.0021 (7)	0.0078 (8)	0.0001 (8)
C5	0.0409 (10)	0.0372 (11)	0.0383 (10)	−0.0025 (8)	0.0007 (8)	−0.0041 (8)
C6	0.0541 (13)	0.0360 (11)	0.0527 (13)	−0.0051 (9)	0.0079 (10)	−0.0120 (9)
C7	0.0374 (10)	0.0317 (10)	0.0492 (11)	−0.0007 (8)	−0.0023 (8)	0.0039 (8)

Geometric parameters (Å, º) top

O1—C1	1.239 (2)	C1—C2	1.548 (2)
O2—C1	1.240 (2)	C2—C3	1.522 (2)
O3—C4	1.300 (2)	C2—H2	0.9800
O3—H1	0.95 (3)	C3—C4	1.506 (3)
O4—C4	1.197 (2)	C3—H3A	0.9700
N1—C7	1.328 (2)	C3—H3B	0.9700
N1—C5	1.374 (2)	C5—C6	1.341 (3)
N1—C2	1.471 (2)	C5—H5	0.9300
N2—C7	1.310 (3)	C6—H6	0.9300
N2—C6	1.366 (3)	C7—H7	0.9300
N2—H3	0.89 (3)

C4—O3—H1	110 (2)	C4—C3—H3A	108.3
C7—N1—C5	107.96 (15)	C2—C3—H3A	108.3
C7—N1—C2	125.82 (15)	C4—C3—H3B	108.3
C5—N1—C2	125.65 (15)	C2—C3—H3B	108.3
C7—N2—C6	108.73 (17)	H3A—C3—H3B	107.4
C7—N2—H3	121.9 (16)	O4—C4—O3	123.55 (18)
C6—N2—H3	129.2 (16)	O4—C4—C3	121.78 (18)
O1—C1—O2	126.38 (16)	O3—C4—C3	114.66 (16)
O1—C1—C2	115.82 (15)	C6—C5—N1	106.96 (18)
O2—C1—C2	117.74 (15)	C6—C5—H5	126.5
N1—C2—C3	111.71 (14)	N1—C5—H5	126.5
N1—C2—C1	111.19 (13)	C5—C6—N2	107.30 (18)
C3—C2—C1	109.36 (13)	C5—C6—H6	126.3
N1—C2—H2	108.2	N2—C6—H6	126.3
C3—C2—H2	108.2	N2—C7—N1	109.04 (17)
C1—C2—H2	108.2	N2—C7—H7	125.5
C4—C3—C2	115.82 (15)	N1—C7—H7	125.5

C7—N1—C2—C3	−59.2 (2)	C2—C3—C4—O4	152.5 (2)
C5—N1—C2—C3	130.59 (17)	C2—C3—C4—O3	−28.9 (2)
C7—N1—C2—C1	63.3 (2)	C7—N1—C5—C6	0.1 (2)
C5—N1—C2—C1	−106.93 (18)	C2—N1—C5—C6	171.80 (16)
O1—C1—C2—N1	172.03 (15)	N1—C5—C6—N2	0.1 (2)
O2—C1—C2—N1	−10.5 (2)	C7—N2—C6—C5	−0.3 (2)
O1—C1—C2—C3	−64.1 (2)	C6—N2—C7—N1	0.3 (2)
O2—C1—C2—C3	113.28 (18)	C5—N1—C7—N2	−0.3 (2)
N1—C2—C3—C4	−64.66 (19)	C2—N1—C7—N2	−171.95 (16)
C1—C2—C3—C4	171.82 (15)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1···O2ⁱ	0.95 (3)	1.62 (3)	2.5440 (18)	163 (3)
N2—H3···O1ⁱⁱ	0.89 (3)	1.85 (3)	2.732 (2)	170 (2)
C7—H7···O1ⁱⁱⁱ	0.93	2.42	3.333 (2)	168
C5—H5···O4^iv	0.93	2.57	3.260 (3)	131

Symmetry codes: (i) x−1, y, z; (ii) x, y−1, z; (iii) −x+2, y−1/2, −z+3/2; (iv) x, −y+3/2, z−1/2.

Experimental details

Crystal data
Chemical formula	C₇H₈N₂O₄
M_r	184.15
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	7.6328 (7), 7.4701 (7), 13.7616 (12)
β (°)	96.752 (1)
V (Å³)	779.21 (12)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.13
Crystal size (mm)	0.38 × 0.28 × 0.18

Data collection
Diffractometer	Bruker P4 CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2008)
T_min, T_max	0.952, 0.977
No. of measured, independent and observed [I > 2σ(I)] reflections	4668, 1540, 1254
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.042, 0.115, 1.06
No. of reflections	1540
No. of parameters	126
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.24, −0.26

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008) and XPREP (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1···O2ⁱ	0.95 (3)	1.62 (3)	2.5440 (18)	163 (3)
N2—H3···O1ⁱⁱ	0.89 (3)	1.85 (3)	2.732 (2)	170 (2)
C7—H7···O1ⁱⁱⁱ	0.93	2.42	3.333 (2)	168.2
C5—H5···O4^iv	0.93	2.57	3.260 (3)	131.4

Symmetry codes: (i) x−1, y, z; (ii) x, y−1, z; (iii) −x+2, y−1/2, −z+3/2; (iv) x, −y+3/2, z−1/2.

Acknowledgements

Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund Type B, the National Science Foundation (grant No. 0722547) and Eastern Illinois University for support of this crystallographic investigation.

References

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