Piperazine-2,3,5,6-tetraone

The molecule of the title compound, C4H2N2O4, is located around an inversion center and the four O atoms are in the 2,3,5,6-positions of the piperazine ring. In the crystal, bifurcated N—H⋯O hydrogen bonds link the molecules into a corrugated layer parallel to (101).

The molecule of the title compound, C 4 H 2 N 2 O 4 , is located around an inversion center and the four O atoms are in the 2,3,5,6-positions of the piperazine ring. In the crystal, bifurcated N-HÁ Á ÁO hydrogen bonds link the molecules into a corrugated layer parallel to (101).
tetraone derivatives, we report here the structure of the title compound.
The molecule of the title compound is located around inversion center and the four O atoms are in the 2,3,5,6 position on the piperazine ring ( Fig. 1). The molecule is planar with rms deviation of 0.013Å. The bond distances and angles are similar to those found in related piperazine derivatives (Sletten et al., 1970;Sarangarajan et al., 2005;Sletten et al., 1980;Ongania et al., 1985).
The N-H donor and the C-O acceptor groups participate in the hydrogen bonding forming corrugated layers parallel to the (1 0 1) plane through bifurcated N-H···O hydrogen bonds (Table 1, Fig. 2).

Experimental
For the preparation of the title compound,the 2-mercaptopyrazine (10 mmol,1.1200 g) was dissolved in ethanol (50 ml) at 358 K and a solution of 30% H 2 0 2 (10 ml) was added. The resulting solution was stirred at 358 K for 4 h, then concentrating at 388 K,until 3 ml solution remained. Colourless-block crystal suitable for X-ray diffraction were obtained by slow evaporation at room temperature after several days in 55% yield.

Refinement
H atom attached to N atom was positioned geometrically and treated as riding on the parent atom with N-H= 0.86 Å and U iso (H)=1.2U eq (N). Fig. 1

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )