An additional methyl­ene group driving the conformation and assembly of two aryl­sulfonamide para-alk­oxy­chalcone hybrids

The structures of two aryl­sulfonamide para-alk­oxy­chalcones, namely, N-{4-[(E)-3-(4-methoxy­phenyl)prop-2-en­oyl]phenyl}benzene­sulfon­amide, C₂₂H₁₉NO₄S, (I), and N-{4-[(E)-3-(4-ethoxy­phenyl)prop-2-en­oyl]phenyl}benzene­sulfon­amide, C₂₃H₂₁NO₄S, (II), reveal the effect of the inclusion of one -CH₂- group between the CH₃ branch and the alk­oxy O atom on the conformation and crystal structure. Although the mol­ecular conformations and one-dimensional chain motifs are the same in both structures, their crystallographic symmetry, number of independent mol­ecules and crystal packing are different. The crystal packing of (I) is stabilized by weak C-H...[pi] and [pi]-[pi] inter­actions, while only C-H...[pi] contacts occur in the structure of (II). The role of the additional methyl­ene group in the crystal packing can also be seen in the fact that the alk­oxy O atom is an acceptor in non­classical hydrogen bonds only in the para-eth­oxy analogue, (II). The remarkable similarity between the crystal packing features of (I) and (II) lies in the formation of N-H...O hydrogen-bonded ribbons, a synthon commonly found in related compounds.