Crystal structures of three 1-[4-(4-bromo-but-oxy)-phen-yl] chalcone derivatives: (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-phenyl-prop-2-en-1-one, (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(4-meth-oxy-phen-yl)prop-2-en-1-one and (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one.

The crystal structures of three chalcones with a bromo-substituted but-oxy side chain, viz. (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-phenyl-prop-2-en-1-one, C(19)H(19)BrO(2), (I), (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(4-meth-oxy-phen-yl)prop-2-en-1-one, C(20)H(21)BrO(3), (II), and (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one, C(21)H(23)BrO(4), (III), are reported. In all mol-ecules, the conformation of the keto group with respect to the olefinic bond is s-cis. Mol-ecules of (I) and (II) are nearly planar, while mol-ecule (III) is not planar. In the crystal of compounds (I) and (II), mol-ecules are linked into chains parallel to the c axis by C-H⋯π inter-actions. In the crystal of compound (III), mol-ecules are linked by a pairs of C-H⋯O hydrogen bonds, forming inversion dimers. Weak C-Br⋯π inter-actions are also observed in (III).