Benzene-1,2,4,5-tetrol

Determination of the structure of benzene-1,2,4,5-tetrol

At 120 K the structure was found to crystallize in the triclinic space group P1 with the asymmetric unit containing four independent molecules of benzene-1,2,4,5-tetrol labelled A, B,C and D (Figs. 1,2a).Each symmetry unique molecule forms �-� stacks on itself, i.e. molecule A forms a stack consisting entirely of molecule A (Fig. 2b).This gives four unique �-� stacking interactions with centroid-to-distances of 3.7474 (11) A ˚, while the perpendicular centroid-to-plane distances are 3.4457 (7) A ˚(molecule A), 3.5166 (8) A ˚(molecule B), 3.5653 (8) A ˚(molecule C), and 3.5653 (8) A ˚(molecule D).Intermolecular hydrogen bonding is observed between each pair of molecules, where each hydroxy group can act as a hydrogen-bond donor and acceptor (Table 1).This creates an extended hydrogen-bond network, which can be described as a series of rings consisting of three molecules -the edges of two molecules make up the perimeter of the ring, and a single hydroxy group of a third molecule links the first two molecules into a continuous ring.There are two data reports IUCrData (2024).9, x240612

Figure 1
The asymmetric unit of the title compound showing the atom labelling with 50% probability displacement ellipsoids.Unlabelled atoms are related to labelled atoms by the symmetry operations  unique rings comprised of molecules A, B, and C, and of molecules C, B, and D, both of which exhibit an R 2 2 (14) graphset motif, and the remaining hydrogen-bonded rings are symmetry-related.All of the hydrogen bonds in the structure can thus be accounted for.

Synthesis and crystallization
Following a literature procedure (Weider et al., 1985), 2,5dihydroxy-1,4-benzoquinone (2.428 g, 17.3 mmol) was mixed with conc.hydrochloric acid (54 ml) under an inert atmosphere and stirred for 30 min to form a gold-coloured suspension.Addition of tin metal powder (2.1885 g, 18.4 mmol) caused vigorous effervescence and a grey suspension.The mixture was stirred for 10 min until cessation of bubbling then heated to 100 � C for 1 h, during which time the mixture became dark and bubbled vigorously.The mixture was allowed to cool briefly, then hot filtered under reduced pressure to give a yellow filtrate.The filtrate was cooled on ice for 30 min to give white crystals of benzene-1,2,4,5-tetrol (0.786 g, 5.54 mmol, 32%).The crude product was dissolved in a minimum of hot tetrahydrofuran, filtered, then cooled on ice.The resulting white crystals were collected via filtration then washed with ice-cold THF and dried in a vacuum to give benzene-1,2,4,5-tetrol (0.735 g, 5.17 mmol, 30%).IR (ATR) � max /cm

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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.All hydrogen atoms were observed in the electron difference map.All hydroxy hydrogen atoms were refined with their O-H distances restrained to a target distance of 0.84 %A (DFIX).All other hydrogen atoms were geometrically placed and refined with a riding model.

Figure 2 (
Figure 2 (a) View of unit cell along the crystallographic a-axis.Dashed lines represent hydrogen bonding between molecules.R 2 2 (14) rings are indicated with purple and green polygons; hydrogen bonds not lying on the indicated rings form the same class of ring with molecules not rendered in this diagram.(b) View approximately along the (001) axis, showing how molecules form �-� stacks.Some molecules have been removed for clarity.

Table 2
Experimental details.