3-Carboxypyridinium hydrogen oxalate

In the title compound, C₆H₆NO₂⁺·C₂HO₄⁻, the cations and anions are situated on a mirror plane. The crystal structure involves two-dimensional lamellar sheets formed by cations and anions linked through N—H...O and O—H...O hydrogen bonds. These sheets are separated by a distance of 3.024 (1) Å.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.038
• wR factor = 0.108
• Data-to-parameter ratio = 10.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.74
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       3.08
PLAT355_ALERT_3_C Long    O-H Bond (0.82A)   O1B    -   H1B    ...       1.03 Ang.
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C11    -   C12    ...       1.55 Ang.
PLAT432_ALERT_2_C Short Inter X...Y Contact  O11    ..  C2      ..       2.97 Ang.
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          1
              C6 H6 N O2

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   4 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXTL/PC (Bruker, 2000); program(s) used to refine structure: SHELXTL/PC; molecular graphics: Mercury (Macrae et al., 2006) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXTL/PC.

3-carboxypyridinium oxalate

Crystal data

C6H6NO2^+·C2HO4^−	F(000) = 220
Mr = 213.15	Dx = 1.612 Mg m^−3 Dm = 1.59 (2) Mg m^−3 Dm measured by flotation using a mixture of xylene and bromoform
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 25 reflections
a = 8.438 (6) Å	θ = 9.2–13.8°
b = 6.048 (2) Å	µ = 0.14 mm^−1
c = 8.774 (5) Å	T = 293 K
β = 101.29 (3)°	Plate, colourless
V = 439.1 (4) Å^3	0.23 × 0.21 × 0.14 mm
Z = 2

Data collection

Enraf–Nonius MACH3 sealed-tube diffractometer	865 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.024
Graphite monochromator	θmax = 27.0°, θmin = 2.4°
ω–2θ scans	h = 0→10
Absorption correction: ψ scan (North et al., 1968)	k = −1→7
Tmin = 0.960, Tmax = 0.978	l = −11→10
1304 measured reflections	3 standard reflections every 60 min
1046 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.108	w = 1/[σ^2(Fo^2) + (0.0663P)^2 + 0.0801P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max < 0.001
1046 reflections	Δρmax = 0.25 e Å^−3
101 parameters	Δρmin = −0.26 e Å^−3
0 restraints	Extinction correction: SHELXTL/PC, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.029 (8)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
N1	0.69232 (17)	0.7500	−0.12209 (18)	0.0302 (4)
C2	0.5436 (2)	0.7500	−0.0884 (2)	0.0291 (4)
H2	0.5313	0.7500	0.0147	0.035*
C3	0.4096 (2)	0.7500	−0.20650 (19)	0.0261 (4)
C31	0.2441 (2)	0.7500	−0.1678 (2)	0.0277 (4)
O1A	0.12231 (15)	0.7500	−0.26787 (15)	0.0356 (4)
O1B	0.24874 (15)	0.7500	−0.01840 (15)	0.0391 (4)
C4	0.4309 (2)	0.7500	−0.3602 (2)	0.0345 (5)
H4	0.3418	0.7500	−0.4416	0.041*
C5	0.5860 (2)	0.7500	−0.3904 (2)	0.0387 (5)
H5	0.6019	0.7500	−0.4924	0.046*
C6	0.7164 (2)	0.7500	−0.2685 (2)	0.0346 (5)
H6	0.8209	0.7500	−0.2877	0.042*
H1	0.784 (4)	0.7500	−0.034 (3)	0.054 (7)*
H1B	0.135 (4)	0.7500	0.008 (4)	0.084 (10)*
C11	0.8674 (2)	0.7500	0.30634 (19)	0.0288 (4)
C12	1.0166 (2)	0.7500	0.2283 (2)	0.0297 (4)
O11	0.72923 (15)	0.7500	0.23662 (15)	0.0371 (4)
O12	0.90199 (17)	0.7500	0.45935 (15)	0.0443 (4)
O13	0.98505 (16)	0.7500	0.08098 (15)	0.0379 (4)
O14	1.14877 (16)	0.7500	0.31554 (15)	0.0451 (4)
H12	1.006 (4)	0.7500	0.495 (3)	0.056 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0160 (7)	0.0464 (9)	0.0280 (7)	0.000	0.0034 (6)	0.000
C2	0.0202 (8)	0.0424 (10)	0.0249 (8)	0.000	0.0050 (7)	0.000
C3	0.0176 (8)	0.0361 (9)	0.0248 (8)	0.000	0.0048 (7)	0.000
C31	0.0193 (8)	0.0395 (10)	0.0250 (8)	0.000	0.0059 (6)	0.000
O1A	0.0173 (6)	0.0611 (9)	0.0276 (6)	0.000	0.0021 (5)	0.000
O1B	0.0200 (6)	0.0739 (11)	0.0252 (7)	0.000	0.0089 (5)	0.000
C4	0.0219 (9)	0.0553 (12)	0.0260 (9)	0.000	0.0043 (7)	0.000
C5	0.0275 (10)	0.0650 (13)	0.0263 (9)	0.000	0.0119 (7)	0.000
C6	0.0208 (9)	0.0501 (11)	0.0359 (10)	0.000	0.0128 (7)	0.000
C11	0.0227 (8)	0.0421 (10)	0.0222 (8)	0.000	0.0058 (6)	0.000
C12	0.0211 (8)	0.0438 (10)	0.0253 (8)	0.000	0.0069 (6)	0.000
O11	0.0206 (6)	0.0613 (9)	0.0285 (7)	0.000	0.0031 (5)	0.000
O12	0.0233 (7)	0.0889 (12)	0.0214 (6)	0.000	0.0060 (5)	0.000
O13	0.0218 (6)	0.0711 (10)	0.0221 (6)	0.000	0.0072 (5)	0.000
O14	0.0196 (7)	0.0846 (11)	0.0301 (7)	0.000	0.0027 (5)	0.000

Geometric parameters (Å, º)

N1—C6	1.339 (2)	C4—H4	0.9300
N1—C2	1.344 (2)	C5—C6	1.376 (3)
N1—H1	0.98 (3)	C5—H5	0.9300
C2—C3	1.376 (2)	C6—H6	0.9300
C2—H2	0.9300	C11—O11	1.206 (2)
C3—C4	1.395 (2)	C11—O12	1.317 (2)
C3—C31	1.500 (2)	C11—C12	1.547 (2)
C31—O1A	1.214 (2)	C12—O14	1.223 (2)
C31—O1B	1.304 (2)	C12—O13	1.268 (2)
O1B—H1B	1.03 (4)	O12—H12	0.87 (3)
C4—C5	1.385 (3)
C6—N1—C2	122.30 (15)	C3—C4—H4	120.3
C6—N1—H1	120.9 (17)	C6—C5—C4	119.51 (17)
C2—N1—H1	116.8 (17)	C6—C5—H5	120.2
N1—C2—C3	119.94 (16)	C4—C5—H5	120.2
N1—C2—H2	120.0	N1—C6—C5	119.83 (16)
C3—C2—H2	120.0	N1—C6—H6	120.1
C2—C3—C4	119.05 (16)	C5—C6—H6	120.1
C2—C3—C31	119.59 (15)	O11—C11—O12	121.12 (17)
C4—C3—C31	121.37 (15)	O11—C11—C12	124.43 (16)
O1A—C31—O1B	125.58 (17)	O12—C11—C12	114.46 (15)
O1A—C31—C3	122.01 (16)	O14—C12—O13	128.46 (17)
O1B—C31—C3	112.41 (14)	O14—C12—C11	116.40 (16)
C31—O1B—H1B	112.1 (18)	O13—C12—C11	115.14 (16)
C5—C4—C3	119.37 (17)	C11—O12—H12	111.7 (19)
C5—C4—H4	120.3
C6—N1—C2—C3	0.0	C31—C3—C4—C5	180.0
N1—C2—C3—C4	0.0	C3—C4—C5—C6	0.0
N1—C2—C3—C31	180.0	C2—N1—C6—C5	0.0
C2—C3—C31—O1A	180.0	C4—C5—C6—N1	0.0
C4—C3—C31—O1A	0.0	O11—C11—C12—O14	180.0
C2—C3—C31—O1B	0.0	O12—C11—C12—O14	0.0
C4—C3—C31—O1B	180.0	O11—C11—C12—O13	0.0
C2—C3—C4—C5	0.0	O12—C11—C12—O13	180.0

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O13	0.98 (3)	1.79 (3)	2.748 (2)	163 (3)
O1B—H1B···O13^i	1.03 (4)	1.53 (4)	2.5438 (18)	168 (3)
O12—H12···O1A^ii	0.87 (3)	2.12 (3)	2.7280 (18)	126 (2)
O12—H12···O14	0.87 (3)	2.16 (3)	2.6376 (19)	114 (2)

Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z+1.