2,5-Dichloro-3,6-diisopropylcyclohexa-2,5-diene-1,4-dione

The molecule of the title compound, C12H14Cl2O2, lies about an inversion center. The six-membered ring is almost planar, with the largest deviation from the least-squares plane being 0.014 (4) Å. The molecular conformation is stabilized by a weak intramolecular C—H⋯O hydrogen bond. In the crystal, molecules are packed into stacks along the c-axis direction, with an intercentroid separation of 4.811 (2) Å. Neighboring molecules within the stack are related by the c-glide plane.


supplementary materials
In the title molecule, the six-membered ring and attached oxygen and clorine atoms bound to every vertex of this carbon hexagon, share a same plane with the largest deviation being 0.053 (4) Å for C3. The two isopropyl groups extend from the plane, one above and one below the plane, as shown in Fig. 1. The C1═O1 bond has a lengths of 1.221 (4) Å, typical of Csp 2 ═ O double bonds (Allen et al., 1987). The C3-O2 bond, however, is a Csp 2 -O single bond with the lengths of 1.346 (5) Å, which is slightly shorter than the value expected for enol ester systems [1.354 (16) Å (Allen et al.,1987). The carbon-carbon bonds in the six-membered ring can also be divided into two groups: the C2═C3 bond is a typical double bond with the length of 1.343 (5) Å, whereas the C1-C2 and C1-C3 i bonds with the lengths of 1.463 (5) Å and 1.480 (6) Å, reaspectively, are obviously the Csp 2 -Csp 2 single bonds.
In the crystal, the molecules of the title compound are packed into stacks along the c direction with intercentroid separation of 4.811 (2) Å. Neighboring molecules within the stack are related by the c glide plane.

Experimental
Potassium hydroxide (5.0 g) was added to a solution containing chloranil (5.0 g) in 2-propanol (100 ml). The resulting mixture was stirred under reflux for 1 h, and then the red reaction solution was cooled to 283 K. The precipitated yellow solid was collected and recrystallized in ethanol.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms with C-H = 0.98 Å and U iso (H)= 1.2U eq (C) for tertiary hydrogen and with C-H = 0.96 Å and U iso (H)= 1.5U eq (C) for methyl group.

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: WinGX (Farrugia, 1999).  Molecular structure with atom labelling scheme and thermal ellipsoids drawn at the 30% probability level (symmetry code (i): 1 -x,1 -y,1 -z).  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.41 e Å −3 Δρ min = −0.24 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'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 s.u.'s 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 R-factors(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.