Pyridine-2,4-dicarboxylic acid N-oxide

The title compound, C₇H₅NO₅, was obtained as recta­ngular prism-like crystals by the hydro­ponic method. It displays a planar one-dimensional chain structure stabilized via inter- and intra­molecular O—H...O hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.035
• wR factor = 0.096
• Data-to-parameter ratio = 13.3

checkCIF/PLATON results

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Alert level C
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.29
PLAT432_ALERT_2_C Short Inter X...Y Contact  O1     ..  C6      ..       3.00 Ang.
PLAT432_ALERT_2_C Short Inter X...Y Contact  O5     ..  C1      ..       3.01 Ang.

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
   3 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
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The structure of the title compound, (I) reveals a virtually planar molecule with r.m.s. of 0.0061 Å. All bond distances and angles are normal and the structure is stabilized by inter- and intramolecular hydrogen bonds. The molecules are linked in one-dimensional zigzag chains via intermolecular carboxylic hydrogen bonds (Figure 2; Table 2) between O4 and O3. On the other hand, there is a weaker but prominent intermolecular hydrogen bond between H5A and O5 which provides inter chain stabilization, yielding a planar two-dimensional arrangement. Furthermore, the structure displays a strong, almost ideal intramolecular carboxylic hydrogen bond (Figure 1; Table 2) between O2 and O1 (Dideberg & Dupont, 1975; Rychlewska & Gdaniec, 1977; Steiner et al., 2000). The carboxyl C—O and C═O bonds are normal (Table 1), while the N—O distance of 1.324 (1) Å is slightly elongated compared to the average value of 1.304 Å in pyridine N-oxides (Allen et al., 1992). The carboxylic hydrogen bonds display O—H···O angles around 160° (Table 2) due to stereochemical restriction of the C—O—H angle.

Related literature

For related literature, see: Allen et al. (1992); Dideberg & Dupont (1975); Li et al. (1987); Rychlewska & Gdaniec (1977); Steiner et al. (2000).

S2. Experimental

Glacial acetic acid (30 ml) and cold hydrogen peroxide (15 ml) were shaken in a round-bottomed flask, followed by the addition of pyridine-2,4- dicarboxylic acid monohydrate (2 g; 11 mmol), and the mixture was heated (Li et al., 1987). After the excess acetic acid and water were removed under reduced pressure, the title compound was obtained as a white powder (0.95 g, yield 48%). Slow evaporation at room temperature, following dissolution of the white powder (0.2 g, 1 mmol) in a mixture of boiling mixture of methanol (10 ml) and dichloromethane(15 ml) and careful filtration, yielded colorless crystals after 4 days.

S3. Refinement

The C-bound H atoms were included in the riding model approximation with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C) and the O2-bound H atom was included in the riding model approximation with O—H = 0.82 Å. The O4-bound H atom was located from a difference Fourier map and refined isotropically.

Computing details

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear (Rigaku, 2000); data reduction: CrystalClear (Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL (Bruker, 1997).

Figures

	Fig. 1. ORTEP drawing (at 50% probability) of (I); hydrogen atoms at arbitrary size.
	Fig. 2. Illustration of the hydrogen bonding in the one-dimensional chain.

Pyridine-2,4-dicarboxylic acid N-oxide

Crystal data

C7H5NO5	F(000) = 376
Mr = 183.12	Dx = 1.709 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1853 reflections
a = 7.323 (3) Å	θ = 2.8–27.5°
b = 6.985 (3) Å	µ = 0.15 mm^−1
c = 13.982 (6) Å	T = 293 K
β = 95.614 (4)°	Prism, colorless
V = 711.8 (5) Å^3	0.45 × 0.40 × 0.25 mm
Z = 4

Data collection

Bruker P4 diffractometer	1619 independent reflections
Radiation source: fine-focus sealed tube	1472 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.011
Detector resolution: 0 pixels mm^-1	θmax = 27.5°, θmin = 3.0°
CCD_Profile_fitting scans	h = −4→9
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000)	k = −9→9
Tmin = 0.920, Tmax = 0.963	l = −18→18
4998 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.096	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0503P)^2 + 0.2243P] where P = (Fo^2 + 2Fc^2)/3
1619 reflections	(Δ/σ)max < 0.001
122 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.19 e Å^−3

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	0.48719 (13)	0.26168 (14)	0.73729 (7)	0.0278 (2)
O1	0.41895 (14)	0.39139 (13)	0.79298 (7)	0.0398 (3)
O2	0.31826 (15)	0.13474 (15)	0.89520 (7)	0.0448 (3)
H2B	0.3347	0.2406	0.8721	0.067*
O3	0.40768 (15)	−0.16328 (14)	0.86771 (7)	0.0426 (3)
O4	0.79194 (13)	−0.07382 (13)	0.48418 (6)	0.0353 (2)
H4B	0.838 (2)	−0.169 (3)	0.4549 (13)	0.052 (5)*
O5	0.72985 (14)	−0.31254 (13)	0.58244 (7)	0.0405 (3)
C1	0.48397 (15)	0.07171 (16)	0.75937 (8)	0.0257 (2)
C2	0.56127 (15)	−0.05789 (16)	0.70098 (8)	0.0257 (2)
H2A	0.5580	−0.1878	0.7152	0.031*
C3	0.64396 (14)	0.00290 (16)	0.62119 (7)	0.0245 (2)
C4	0.64456 (16)	0.19734 (17)	0.60040 (8)	0.0291 (3)
H4A	0.6993	0.2416	0.5473	0.035*
C5	0.56388 (17)	0.32411 (17)	0.65864 (9)	0.0315 (3)
H5A	0.5619	0.4540	0.6439	0.038*
C6	0.39838 (16)	0.00556 (18)	0.84741 (8)	0.0317 (3)
C7	0.72671 (15)	−0.14509 (16)	0.56115 (8)	0.0261 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0339 (5)	0.0248 (5)	0.0261 (5)	0.0013 (4)	0.0099 (4)	−0.0030 (4)
O1	0.0562 (6)	0.0290 (5)	0.0371 (5)	0.0081 (4)	0.0188 (4)	−0.0071 (4)
O2	0.0598 (6)	0.0413 (5)	0.0384 (5)	0.0010 (4)	0.0303 (5)	−0.0032 (4)
O3	0.0616 (6)	0.0355 (5)	0.0346 (5)	−0.0033 (4)	0.0248 (4)	0.0067 (4)
O4	0.0485 (5)	0.0322 (5)	0.0288 (4)	0.0024 (4)	0.0213 (4)	−0.0002 (3)
O5	0.0585 (6)	0.0273 (5)	0.0391 (5)	0.0033 (4)	0.0216 (4)	0.0014 (4)
C1	0.0301 (5)	0.0257 (6)	0.0226 (5)	−0.0022 (4)	0.0089 (4)	0.0003 (4)
C2	0.0322 (6)	0.0227 (5)	0.0234 (5)	−0.0017 (4)	0.0085 (4)	0.0003 (4)
C3	0.0265 (5)	0.0269 (6)	0.0210 (5)	−0.0006 (4)	0.0069 (4)	−0.0007 (4)
C4	0.0349 (6)	0.0289 (6)	0.0250 (5)	−0.0037 (5)	0.0114 (4)	0.0027 (4)
C5	0.0425 (6)	0.0230 (5)	0.0305 (6)	−0.0019 (5)	0.0111 (5)	0.0033 (4)
C6	0.0372 (6)	0.0346 (6)	0.0256 (5)	−0.0040 (5)	0.0142 (5)	−0.0010 (5)
C7	0.0286 (5)	0.0275 (5)	0.0232 (5)	−0.0009 (4)	0.0080 (4)	−0.0011 (4)

Geometric parameters (Å, º)

N1—O1	1.3240 (13)	C1—C2	1.3773 (15)
N1—C5	1.3549 (15)	C1—C6	1.5076 (15)
N1—C1	1.3630 (16)	C2—C3	1.3869 (15)
O2—C6	1.2968 (15)	C2—H2A	0.9300
O2—H2B	0.8200	C3—C4	1.3890 (17)
O3—C6	1.2134 (17)	C3—C7	1.4967 (15)
O4—C7	1.3170 (14)	C4—C5	1.3750 (17)
O4—H4B	0.866 (19)	C4—H4A	0.9300
O5—C7	1.2066 (15)	C5—H5A	0.9300
O1—N1—C5	117.86 (10)	C4—C3—C7	123.24 (10)
O1—N1—C1	121.14 (9)	C5—C4—C3	119.69 (10)
C5—N1—C1	120.99 (10)	C5—C4—H4A	120.2
C6—O2—H2B	109.5	C3—C4—H4A	120.2
C7—O4—H4B	106.4 (12)	N1—C5—C4	120.65 (11)
N1—C1—C2	119.24 (10)	N1—C5—H5A	119.7
N1—C1—C6	120.07 (10)	C4—C5—H5A	119.7
C2—C1—C6	120.69 (10)	O3—C6—O2	125.01 (11)
C1—C2—C3	120.84 (10)	O3—C6—C1	118.07 (11)
C1—C2—H2A	119.6	O2—C6—C1	116.92 (11)
C3—C2—H2A	119.6	O5—C7—O4	124.64 (11)
C2—C3—C4	118.58 (10)	O5—C7—C3	122.00 (10)
C2—C3—C7	118.19 (10)	O4—C7—C3	113.35 (10)
O1—N1—C1—C2	−178.11 (10)	C1—N1—C5—C4	−1.63 (18)
C5—N1—C1—C2	0.49 (17)	C3—C4—C5—N1	1.41 (19)
O1—N1—C1—C6	1.23 (17)	N1—C1—C6—O3	−175.79 (12)
C5—N1—C1—C6	179.83 (11)	C2—C1—C6—O3	3.54 (18)
N1—C1—C2—C3	0.86 (17)	N1—C1—C6—O2	4.94 (17)
C6—C1—C2—C3	−178.47 (11)	C2—C1—C6—O2	−175.74 (11)
C1—C2—C3—C4	−1.06 (17)	C2—C3—C7—O5	−3.10 (17)
C1—C2—C3—C7	179.52 (10)	C4—C3—C7—O5	177.50 (12)
C2—C3—C4—C5	−0.07 (17)	C2—C3—C7—O4	176.24 (10)
C7—C3—C4—C5	179.32 (11)	C4—C3—C7—O4	−3.16 (16)
O1—N1—C5—C4	177.01 (11)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2B···O1	0.82	1.69	2.4508 (15)	154
O4—H4B···O3^i	0.866 (19)	1.80 (2)	2.6481 (14)	165.6 (18)

Symmetry code: (i) x+1/2, −y−1/2, z−1/2.