The title molecule, C 9 H 6 ClNO 2 , is almost planar, with an r.m.s. deviation of the fitted non-hydrogen atoms of 0.0922 (19) Å . In the crystal, molecules are connected through methyl-C-HÁ Á ÁO(carbonyl) interactions into supramolecular helical chains along the b axis. Inter-chain -interactions lead to layers parallel to the ab plane [centroid-centroid distances = 3.4861 (13) to 3.9767 (12) Å ]. The crystal studied was a non-merohedral twin with a ratio of the twin components of 0.8612 (12) The title compound (Fig. 1) was synthesized by the alkylation method (Kharbach et al., 2015) under phase-transfer catalysis conditions (Bouhfid et al., 2005). The crystal studied was a non-merohedral twin with a ratio of the twin components of 0.8612 (12): 0.1388 (12).The title molecule, C 9 H 6 ClNO 2 , is almost planar, with an r.m.s. deviation of 0.0922 (19) Å . In the crystal, molecules are connected through methyl--carbonyl C-HÁ Á ÁO interactions (Table 1) into infinite chains along the b axis. The packing (Fig. 2) is also influenced by inter-chain -interactions, which form layers parallel to the ab plane [centroid-centroid distances = 3.4861 (13) to 3.9767 (12) Å ].