3-Chloro-4-methylquinolin-2(1H)-one

The title compound, C10H8ClNO, is almost planar (r.m.s. deviation for the 13 non-H atoms = 0.023 Å). In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) rings. Weak aromatic π–π stacking interactions [centroid–centroid distance = 3.7622 (12) Å] also occur.

In the title compound ( Fig. 1), the quinoline ring (N1/C1-C9) is essentially planar with a maximum deviation of 0.012 (2) Å at atom C1. The bond lengths (Allen et al., 1987) and angles are within normal ranges are comparable to the related structure (Vasuki et al., 2001).

Experimental
This compound was prepared according to the reported method (Hodgkinson & Staskun, 1969). Colorless needles of the title compound were grown from a mixed solution of EtOH/DMF (V/V = 2/1) by slow evaporation at room temperature.

Refinement
Atom H1 was located from the difference map and was fixed at their found positions with U iso (H) = 1.2 U eq (N) [N-H = 0.9256 Å]. The remaining H atoms were positioned geometrically and refined using a riding model with U iso (H) = 1.2 or 1.5U eq (C) (C-H = 0.93 and 0.96 Å). A rotating group model was applied to the methyl group.

Computing details
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009   The crystal packing of the title compound, viewed along the b axis. H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.21 e Å −3 Extinction correction: SHELXTL (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0031 (9) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'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 e.s.d.'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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl1