3,3-Dimethyl-2-benzofuran-1(3H)-one

In the title compound, C10H10O2, all the non-H atoms except the methyl C atoms lie on a crystallographic mirror plane. In the crystal, C—H⋯O hydrogen bonds link the molecules into zigzag chains running parallel to [100]. Weak π–π stacking interactions between the benzene rings [centroid–centroid distance = 3.9817 (5) Å] link the chains in the [010] direction.

In the title compound, C 10 H 10 O 2 , all the non-H atoms except the methyl C atoms lie on a crystallographic mirror plane. In the crystal, C-HÁ Á ÁO hydrogen bonds link the molecules into zigzag chains running parallel to [100]. Weakstacking interactions between the benzene rings [centroid-centroid distance = 3.9817 (5) Å ] link the chains in the [010] direction.
MSS thanks the University of Mysore for research facilities. RJB wishes to acknowledge the NSF-MRI program (grant CHE-0619278) for funds to purchase the diffractometer.

Structure Reports Online
In the title molecule (I), (Fig. 1), a mirror plane passes through the remaining atoms of the molecule, except the atoms of two methyl groups which are mirror images of each other.

Experimental
The title compound was obtained as a gift sample from R. L. Fine Chemicals, Bengaluru, India. Colourless prisms of (I) were grown from toluene solution by slow evaporation (m.p.: 337-340 K).

Refinement
All H atoms were added in calculated positions and refined as riding with C-H distances of 0.93 and 0.96 Å. The isotropic atomic displacement parameters of H atoms were fixed to 1.2 or 1.5 ×U eq of the parent atom.

Special details
Experimental. Absorption correction: XABS2 (Parkin et al., 1995); cubic fit to sinθ/λ -24 parameters Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.