1,4-Dihydroxy-quinoxaline-2,3(1H,4H)-dione.

The asymmetric unit of the title compound, C(8)H(6)N(2)O(4), contains one half-mol-ecule; a twofold rotation axis bisects the molecule. The quinoxaline ring is planar, which can be attributed to electron delocalization. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into R(2) (2)(10) motifs, leading to layers, which inter-act via phen-yl-phenyl inter-actions (C⋯C distances in the range 3.238-3.521 Å).

Related literature

For general background, see: Zarranz et al. (2004 ▶); Chowdhury et al. (2004 ▶); Monge et al. (1995 ▶); Fuchs et al. (2001 ▶); Dance (1996 ▶); Bernstein et al. (1995 ▶). For related literature, see: Elina & Tsyrul’nikova (1963 ▶); Akkurt et al. (2004 ▶); Mustaphi et al. (2001 ▶); Oxtoby et al. (2005 ▶); Ley & Seng (1975 ▶); For bond-length data, see: Allen et al. (1987 ▶);

Experimental

Crystal data

C8H6N2O4

M = 194.15

Orthorhombic,

a = 4.2562 (6) Å

b = 17.630 (3) Å

c = 10.4775 (17) Å

V = 786.2 (2) Å3

Z = 4

Mo Kα radiation

μ = 0.14 mm−1

T = 294 (2) K

0.50 × 0.20 × 0.10 mm

Data collection

Nicolet P3 diffractometer

Absorption correction: none

1004 measured reflections

529 independent reflections

437 reflections with I > 2σ(I)

R int = 0.022

3 standard reflections every 50 reflections intensity decay: 2%

Refinement

R[F 2 > 2σ(F 2)] = 0.034

wR(F 2) = 0.071

S = 1.07

529 reflections

69 parameters

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.12 e Å−3

Δρmin = −0.15 e Å−3

Data collection: P3/PC Data Collection Software (Siemens, 1991 ▶); cell refinement: P3/PC Data Collection Software; data reduction: SHELXTL-Plus (Sheldrick, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL-Plus; software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003 ▶).

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808003784/hk2425sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808003784/hk2425Isup2.hkl

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

C8H6N2O4	F000 = 400
Mr = 194.15	Dx = 1.640 Mg m−3
Orthorhombic, C2221	Mo Kα radiation λ = 0.71073 Å
Hall symbol: C 2c 2	Cell parameters from 20 reflections
a = 4.2562 (6) Å	θ = 14–16º
b = 17.630 (3) Å	µ = 0.14 mm−1
c = 10.4775 (17) Å	T = 294 (2) K
V = 786.2 (2) Å3	Plates, colourless
Z = 4	0.50 × 0.20 × 0.10 mm

Nicolet P3 diffractometer	Rint = 0.022
Radiation source: fine-focus sealed tube	θmax = 27.0º
Monochromator: graphite	θmin = 2.3º
T = 294(2) K	h = 0→5
Wyckoff scan	k = 0→22
Absorption correction: none	l = −13→13
1004 measured reflections	3 standard reflections
529 independent reflections	every 50 reflections
437 reflections with I > 2σ(I)	intensity decay: 2%

Refinement on F2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.034	w = 1/[σ2(Fo2) + (0.0208P)2 + 0.4073P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.071	(Δ/σ)max < 0.001
S = 1.07	Δρmax = 0.12 e Å−3
529 reflections	Δρmin = −0.15 e Å−3
69 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.013 (2)
Secondary atom site location: difference Fourier map

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
N1	0.2116 (4)	0.41727 (11)	0.15388 (16)	0.0350 (5)
C1	0.1130 (6)	0.48556 (11)	0.1948 (2)	0.0364 (6)
O1	0.4527 (4)	0.41624 (10)	0.06569 (15)	0.0456 (5)
H1	0.357 (7)	0.4338 (15)	−0.012 (3)	0.072 (10)*
C2	0.1068 (5)	0.34702 (11)	0.2004 (2)	0.0332 (5)
O2	0.1965 (5)	0.54622 (9)	0.14878 (15)	0.0531 (6)
C3	0.2131 (7)	0.27901 (13)	0.1487 (2)	0.0456 (7)
H3	0.3541	0.2788	0.0808	0.055*
C4	0.1046 (7)	0.21177 (13)	0.2002 (2)	0.0557 (8)
H4	0.1745	0.1659	0.1669	0.067*

	U11	U22	U33	U12	U13	U23
N1	0.0369 (10)	0.0401 (9)	0.0279 (8)	0.0022 (10)	0.0011 (9)	−0.0011 (8)
C1	0.0452 (15)	0.0371 (12)	0.0269 (10)	−0.0036 (11)	−0.0014 (13)	−0.0019 (9)
O1	0.0416 (9)	0.0631 (10)	0.0320 (8)	0.0113 (10)	0.0045 (9)	0.0052 (9)
C2	0.0354 (14)	0.0334 (10)	0.0309 (10)	0.0004 (10)	−0.0096 (12)	−0.0007 (8)
O2	0.0823 (16)	0.0374 (8)	0.0397 (9)	−0.0123 (10)	0.0136 (13)	0.0017 (7)
C3	0.0519 (16)	0.0435 (13)	0.0415 (13)	0.0099 (13)	−0.0118 (16)	−0.0077 (10)
C4	0.072 (2)	0.0336 (11)	0.0615 (16)	0.0086 (13)	−0.0242 (18)	−0.0079 (11)

N1—C1	1.345 (3)	C2—C2i	1.381 (4)
N1—O1	1.381 (2)	C2—C3	1.391 (3)
N1—C2	1.404 (3)	C3—C4	1.382 (3)
C1—O2	1.226 (3)	C3—H3	0.9300
C1—C1i	1.503 (4)	C4—C4i	1.372 (6)
O1—H1	0.96 (3)	C4—H4	0.9300
C1—N1—O1	117.21 (19)	C2i—C2—N1	118.08 (11)
C1—N1—C2	125.42 (18)	C3—C2—N1	121.5 (2)
O1—N1—C2	117.18 (18)	C4—C3—C2	118.6 (2)
O2—C1—N1	124.4 (2)	C4—C3—H3	120.7
O2—C1—C1i	119.22 (14)	C2—C3—H3	120.7
N1—C1—C1i	116.41 (12)	C4i—C4—C3	120.93 (16)
N1—O1—H1	104.2 (17)	C4i—C4—H4	119.5
C2i—C2—C3	120.47 (15)	C3—C4—H4	119.5
O1—N1—C1—O2	8.8 (3)	C1—N1—C2—C3	177.4 (2)
C2—N1—C1—O2	−176.4 (2)	O1—N1—C2—C3	−7.8 (3)
O1—N1—C1—C1i	−170.8 (2)	C2i—C2—C3—C4	−1.1 (4)
C2—N1—C1—C1i	4.1 (4)	N1—C2—C3—C4	178.9 (2)
C1—N1—C2—C2i	−2.5 (4)	C2—C3—C4—C4i	0.3 (5)
O1—N1—C2—C2i	172.3 (2)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2ii	0.96 (3)	1.63 (3)	2.584 (2)	174 (3)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O2i	0.96 (3)	1.63 (3)	2.584 (2)	174 (3)

Symmetry code: (i) .