3-(2,4-Dichlorophenyl)-5-methyl-1,2,4-oxadiazole

In the title compound, C9H6Cl2N2O, the dihedral angle between the oxadiazole and benzene rings is 1.7 (2)°. In the crystal, the molecules are linked into chains along the b axis by short intermolecular Cl⋯O contacts [3.019 (3) Å].

In the title compound, C 9 H 6 Cl 2 N 2 O, the dihedral angle between the oxadiazole and benzene rings is 1.7 (2) . In the crystal, the molecules are linked into chains along the b axis by short intermolecular ClÁ Á ÁO contacts [3.019 (3) Å ].

Comment
Heterocyclic compounds are important in recent years due to pharmacological activities. Nitrogen, oxygen containing fiveand six-membered heterocyclic compounds have enormous significance in the field of medicinal chemistry. Oxadiazoles play a very vital role in the preparation of various biologically active drugs with anti-inflammatory (Andersen et al., 1994), anti-cancer (Showell et al., 1991), anti-HIV (Watjen et al., 1989), anti-diabetic and anti-microbial (Swain et al., 1991) properties. The results of biological studies showed that oxadiazole derivatives are molecules with maximum anti-inflammatory, analgesic and minimum ulcerogenic and lipid per-oxidation (Clitherow et al., 1996) properties.

Experimental
The title compound was prepared by heating a solution of 2,4-dichloro-N'-hydroxy-benzamidine (1 g, 0.0042 mol) and acetyl chloride (0.38 g, 0.004 mol) in pyridine (30 ml) at 387 K for 1.5 h and the contents were concentrated under vacuum.

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 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq