Carbon­yl–carbonyl, carbon­yl–π and carbon­yl–halogen dipolar inter­actions as the directing motifs of the supra­molecular structure of ethyl 6‐chloro‐2‐oxo‐2 H ‐chromene‐3‐carboxyl­ate and ethyl 6‐bromo‐2‐oxo‐2 H ‐chromene‐3‐carboxyl­ate

The title compounds, C 12 H 9 ClO 4 , (I), and C 12 H 9 BrO 4 , (II), are isomorphous and crystallize in the monoclinic space group P 2 1 / c . Both compounds present an anti conformation between the 3‐carb­oxy and the lactone carbonyl groups. Both carbonyl groups are out of the plane defined by the remaining chromene atoms, by 8.37 (6) and 17.57 (6)° for (I), and by 9.07 (8) and 18.96 (18)° for (II), owing to their involvement in inter­molecular inter­actions. In both compounds, layers of centrosymmetric hydrogen‐bonded dimers are developed in the [ 22] plane through C—H⋯O inter­actions, involving both carbonyl groups as acceptors. Two families of dimers stack through C=O⋯C=O, C=O⋯π and C— X ⋯C=O ( X = Cl and Br) dipolar inter­actions, as well as a C—H⋯π inter­action, developing the three‐dimensional structure along the c axis.