5-Chloro-8-hydroxy-6-methyl-1,4-naphthoquinone

The molecule of the title compound, C11H7ClO3, is planar, with a maximum deviation of 0.0383 (10) Å from the naphthoquinone plane. An intramolecular O—H⋯O hydrogen bond generates an S(6) ring motif. The crystal packing is stabilized by intermolecular C—H⋯O hydrogen bonds. Short intramolecular Cl⋯O [2.8234 (8) Å] and O⋯O [2.5530 (11) Å], and intermolecular Cl⋯Cl [3.2777 (3) Å] contacts further stabilize the crystal structure.

An intramolecular O-H···O hydrogen bond generates an S(6) ring motif (Bernstein et al., 1995). The crystal packing is stabilized by intermolecular C-H···O hydrogen bonds (

Experimental
The title compound was prepared from the Friedel-Crafts acylation of 4-chloro-3-methylphenol with maleic anhydride (Musgrave & Skoyles, 2001). Repeated Soxhlet extraction of the crude Friedel-Crafts product with n-hexane, and silica gel column chromatography purification [chloroform and n-hexane (1:9)] of the n-hexane extract afforded the title compound.
Finally, slow evaporation of a n-hexane solution at 305 K gave single crystals of the title compound.

Refinement
H atoms were positioned geometrically [C-H = 0.93 (aromatic) or 0.96Å (methyl)] and refined using a riding model, with U iso (H) = 1.2U eq (aromatic C) and 1.5U eq (methyl C). A rotating-group model was used for the methyl groups. The O bound hydrogen atom was located from the Fourier map and and refined isotropically with U iso (H) = 1.5U eq (C). Fig. 1

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All e.s. 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.