5,6-Dimethyl-pyrazine-2,3-dicarb-oxy-lic acid.

The asymmetric unit of the title compound, C(8)H(8)N(2)O(4), consists of one complete mol-ecule and a second mol-ecule generated by the application of twofold axis. The mean planes of the two carboxyl groups attached to the pyrazine ring at neighboring positions are twisted by 10.8 (1) and 87.9 (1)° in the complete molecule and 43.0 (1)° in the symmetry-generated molecule. The crystal packing features O-H⋯N hydrogen bonds, which link the mol-ecules into layers along [101].

Related literature

For the synthesis of the title compound, see Tsuda & Fujishima (1981 ▶). For the structure of the hydrate of the title compound, see Vishweshwar et al. (2001 ▶, 2004 ▶). For a related compound containing pyrazine-2,3-dicarb­oxy­lic acid, see: Alborés & Rentschler (2009 ▶).

Experimental

Crystal data

C8H8N2O4

M = 196.16

Monoclinic,

a = 15.873 (3) Å

b = 14.057 (3) Å

c = 11.991 (2) Å

β = 109.21 (3)°

V = 2526.6 (9) Å3

Z = 12

Mo Kα radiation

μ = 0.13 mm−1

T = 293 K

0.30 × 0.25 × 0.20 mm

Data collection

Rigaku SCX-mini diffractometer

10832 measured reflections

2230 independent reflections

1937 reflections with I > 2σ(I)

R int = 0.043

Refinement

R[F 2 > 2σ(F 2)] = 0.049

wR(F 2) = 0.133

S = 1.07

2230 reflections

196 parameters

H-atom parameters constrained

Δρmax = 0.63 e Å−3

Δρmin = −0.39 e Å−3

Data collection: PROCESS-AUTO (Rigaku, 1998 ▶); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2002 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811052366/jj2111sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811052366/jj2111Isup2.hkl

Supplementary material file. DOI: 10.1107/S1600536811052366/jj2111Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C8H8N2O4	F(000) = 1224
Mr = 196.16	Dx = 1.547 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 10631 reflections
a = 15.873 (3) Å	θ = 3.4–27.8°
b = 14.057 (3) Å	µ = 0.13 mm−1
c = 11.991 (2) Å	T = 293 K
β = 109.21 (3)°	Block, colourless
V = 2526.6 (9) Å3	0.30 × 0.25 × 0.20 mm
Z = 12

Rigaku SCX-mini diffractometer	1937 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.043
graphite	θmax = 25.0°, θmin = 3.4°
ω scans	h = −18→18
10832 measured reflections	k = −16→16
2230 independent reflections	l = −14→14

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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.133	H-atom parameters constrained
S = 1.07	w = 1/[σ2(Fo2) + (0.0617P)2 + 3.0039P] where P = (Fo2 + 2Fc2)/3
2230 reflections	(Δ/σ)max < 0.001
196 parameters	Δρmax = 0.63 e Å−3
0 restraints	Δρmin = −0.39 e Å−3

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.

	x	y	z	Uiso*/Ueq
O1	0.28005 (14)	0.38972 (11)	0.78999 (16)	0.0595 (6)
H1	0.2587	0.3468	0.7428	0.089*
O2	0.17345 (15)	0.47314 (13)	0.66739 (18)	0.0745 (7)
O3	0.20112 (11)	0.67092 (14)	0.57803 (14)	0.0482 (5)
H3	0.1591	0.6847	0.5190	0.072*
O4	0.09881 (12)	0.67291 (15)	0.66709 (16)	0.0567 (5)
O5	0.40546 (13)	0.35937 (12)	0.02848 (13)	0.0474 (5)
H5	0.3815	0.4101	0.0026	0.071*
O6	0.40159 (11)	0.41517 (11)	0.20060 (15)	0.0439 (4)
N1	0.34098 (12)	0.54156 (12)	0.92729 (14)	0.0318 (4)
N2	0.28289 (12)	0.72021 (12)	0.84036 (15)	0.0325 (4)
N3	0.43566 (12)	0.18493 (12)	0.14017 (14)	0.0311 (4)
C1	0.23855 (16)	0.46795 (15)	0.75119 (19)	0.0362 (5)
C2	0.27656 (14)	0.55308 (14)	0.82342 (17)	0.0291 (5)
C3	0.37616 (14)	0.61868 (15)	0.98780 (18)	0.0325 (5)
C4	0.44770 (18)	0.60708 (18)	1.1037 (2)	0.0491 (7)
H4A	0.4231	0.6160	1.1662	0.074*
H4B	0.4936	0.6534	1.1110	0.074*
H4C	0.4726	0.5444	1.1090	0.074*
C5	0.17291 (15)	0.66150 (14)	0.66717 (19)	0.0324 (5)
C6	0.24752 (13)	0.64193 (14)	0.78045 (17)	0.0276 (5)
C7	0.34688 (14)	0.70945 (15)	0.94401 (18)	0.0315 (5)
C8	0.38542 (18)	0.79617 (17)	1.0119 (2)	0.0489 (7)
H8A	0.4458	0.8040	1.0132	0.073*
H8B	0.3846	0.7900	1.0913	0.073*
H8C	0.3508	0.8506	0.9752	0.073*
C9	0.42126 (14)	0.35590 (15)	0.14246 (18)	0.0316 (5)
C10	0.46645 (14)	0.26613 (14)	0.19620 (17)	0.0286 (5)
C11	0.46841 (15)	0.10400 (15)	0.19300 (18)	0.0315 (5)
C12	0.43794 (18)	0.01403 (16)	0.1277 (2)	0.0462 (6)
H12A	0.3870	0.0264	0.0593	0.069*
H12B	0.4220	−0.0306	0.1780	0.069*
H12C	0.4851	−0.0120	0.1036	0.069*

	U11	U22	U33	U12	U13	U23
O1	0.0717 (13)	0.0232 (8)	0.0508 (11)	0.0069 (8)	−0.0244 (9)	−0.0016 (7)
O2	0.0871 (15)	0.0368 (10)	0.0546 (12)	0.0090 (10)	−0.0375 (11)	−0.0110 (9)
O3	0.0448 (10)	0.0646 (12)	0.0236 (8)	0.0094 (9)	−0.0042 (7)	0.0075 (8)
O4	0.0354 (10)	0.0753 (14)	0.0467 (11)	0.0054 (9)	−0.0037 (8)	0.0138 (9)
O5	0.0688 (12)	0.0361 (9)	0.0240 (8)	0.0145 (9)	−0.0028 (8)	0.0065 (7)
O6	0.0525 (11)	0.0343 (9)	0.0447 (10)	0.0100 (8)	0.0157 (8)	0.0008 (7)
N1	0.0353 (10)	0.0277 (9)	0.0221 (9)	−0.0014 (8)	−0.0044 (8)	0.0045 (7)
N2	0.0346 (10)	0.0269 (9)	0.0257 (9)	−0.0005 (8)	−0.0040 (8)	0.0010 (7)
N3	0.0375 (10)	0.0278 (9)	0.0201 (9)	−0.0013 (8)	−0.0014 (7)	−0.0005 (7)
C1	0.0447 (13)	0.0259 (11)	0.0258 (11)	−0.0001 (10)	−0.0049 (10)	0.0017 (9)
C2	0.0313 (11)	0.0263 (11)	0.0223 (10)	−0.0008 (9)	−0.0011 (8)	0.0021 (8)
C3	0.0344 (12)	0.0310 (11)	0.0232 (11)	−0.0061 (9)	−0.0027 (9)	0.0032 (8)
C4	0.0528 (16)	0.0414 (13)	0.0319 (13)	−0.0110 (12)	−0.0148 (11)	0.0073 (10)
C5	0.0341 (13)	0.0226 (11)	0.0295 (12)	0.0000 (9)	−0.0042 (9)	0.0024 (8)
C6	0.0291 (11)	0.0241 (10)	0.0226 (10)	−0.0021 (9)	−0.0011 (8)	−0.0004 (8)
C7	0.0340 (12)	0.0298 (11)	0.0229 (11)	−0.0052 (9)	−0.0012 (9)	0.0002 (8)
C8	0.0577 (16)	0.0324 (13)	0.0369 (14)	−0.0090 (11)	−0.0111 (12)	−0.0027 (10)
C9	0.0312 (11)	0.0287 (11)	0.0275 (11)	−0.0012 (9)	−0.0006 (9)	0.0019 (9)
C10	0.0339 (11)	0.0263 (11)	0.0210 (10)	−0.0003 (9)	0.0026 (8)	−0.0011 (8)
C11	0.0392 (12)	0.0260 (11)	0.0239 (11)	−0.0021 (9)	0.0027 (9)	−0.0010 (8)
C12	0.0618 (16)	0.0295 (12)	0.0338 (13)	−0.0040 (11)	−0.0025 (11)	−0.0054 (10)

O1—C1	1.288 (3)	C3—C7	1.400 (3)
O1—H1	0.8200	C3—C4	1.487 (3)
O2—C1	1.183 (3)	C4—H4A	0.9600
O3—C5	1.294 (3)	C4—H4B	0.9600
O3—H3	0.8200	C4—H4C	0.9600
O4—C5	1.187 (3)	C5—C6	1.505 (3)
O5—C9	1.307 (3)	C7—C8	1.482 (3)
O5—H5	0.8200	C8—H8A	0.9600
O6—C9	1.192 (3)	C8—H8B	0.9600
N1—C3	1.322 (3)	C8—H8C	0.9600
N1—C2	1.336 (3)	C9—C10	1.489 (3)
N2—C7	1.330 (3)	C10—C10i	1.377 (4)
N2—C6	1.333 (3)	C11—C11i	1.405 (4)
N3—C11	1.323 (3)	C11—C12	1.482 (3)
N3—C10	1.333 (3)	C12—H12A	0.9600
C1—C2	1.484 (3)	C12—H12B	0.9600
C2—C6	1.372 (3)	C12—H12C	0.9600
C1—O1—H1	109.5	C2—C6—C5	124.95 (18)
C5—O3—H3	109.5	N2—C7—C3	120.76 (18)
C9—O5—H5	109.5	N2—C7—C8	118.06 (19)
C3—N1—C2	117.91 (17)	C3—C7—C8	121.17 (19)
C7—N2—C6	117.82 (18)	C7—C8—H8A	109.5
C11—N3—C10	118.29 (17)	C7—C8—H8B	109.5
O2—C1—O1	124.0 (2)	H8A—C8—H8B	109.5
O2—C1—C2	121.3 (2)	C7—C8—H8C	109.5
O1—C1—C2	114.60 (18)	H8A—C8—H8C	109.5
N1—C2—C6	121.33 (18)	H8B—C8—H8C	109.5
N1—C2—C1	119.07 (18)	O6—C9—O5	126.0 (2)
C6—C2—C1	119.54 (18)	O6—C9—C10	121.38 (19)
N1—C3—C7	120.89 (18)	O5—C9—C10	112.56 (19)
N1—C3—C4	118.57 (19)	N3—C10—C10i	120.98 (11)
C7—C3—C4	120.54 (19)	N3—C10—C9	117.57 (18)
C3—C4—H4A	109.5	C10i—C10—C9	121.30 (11)
C3—C4—H4B	109.5	N3—C11—C11i	120.57 (11)
H4A—C4—H4B	109.5	N3—C11—C12	118.19 (19)
C3—C4—H4C	109.5	C11i—C11—C12	121.23 (13)
H4A—C4—H4C	109.5	C11—C12—H12A	109.5
H4B—C4—H4C	109.5	C11—C12—H12B	109.5
O4—C5—O3	126.7 (2)	H12A—C12—H12B	109.5
O4—C5—C6	120.7 (2)	C11—C12—H12C	109.5
O3—C5—C6	112.4 (2)	H12A—C12—H12C	109.5
N2—C6—C2	121.28 (18)	H12B—C12—H12C	109.5
N2—C6—C5	113.73 (17)
C3—N1—C2—C6	0.0 (3)	O4—C5—C6—C2	93.3 (3)
C3—N1—C2—C1	177.4 (2)	O3—C5—C6—C2	−91.5 (3)
O2—C1—C2—N1	169.2 (3)	C6—N2—C7—C3	0.4 (3)
O1—C1—C2—N1	−8.3 (3)	C6—N2—C7—C8	−179.0 (2)
O2—C1—C2—C6	−13.3 (4)	N1—C3—C7—N2	0.0 (3)
O1—C1—C2—C6	169.1 (2)	C4—C3—C7—N2	−180.0 (2)
C2—N1—C3—C7	−0.2 (3)	N1—C3—C7—C8	179.4 (2)
C2—N1—C3—C4	179.8 (2)	C4—C3—C7—C8	−0.6 (4)
C7—N2—C6—C2	−0.6 (3)	C11—N3—C10—C10i	3.0 (4)
C7—N2—C6—C5	177.3 (2)	C11—N3—C10—C9	−172.7 (2)
N1—C2—C6—N2	0.5 (3)	O6—C9—C10—N3	134.4 (2)
C1—C2—C6—N2	−177.0 (2)	O5—C9—C10—N3	−44.4 (3)
N1—C2—C6—C5	−177.3 (2)	O6—C9—C10—C10i	−41.3 (4)
C1—C2—C6—C5	5.3 (3)	O5—C9—C10—C10i	140.0 (3)
O4—C5—C6—N2	−84.5 (3)	C10—N3—C11—C11i	2.3 (4)
O3—C5—C6—N2	90.6 (2)	C10—N3—C11—C12	−176.5 (2)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N2ii	0.82 (1)	2.04	2.845 (2)	167.
O3—H3···N3iii	0.82 (1)	2.00	2.803 (2)	165.
O5—H5···N1iv	0.82 (1)	2.06	2.874 (2)	169.

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N2i	0.82 (1)	2.04	2.845 (2)	167
O3—H3⋯N3ii	0.82 (1)	2.00	2.803 (2)	165
O5—H5⋯N1iii	0.82 (1)	2.06	2.874 (2)	169

Symmetry codes: (i) ; (ii) ; (iii) .