Halogenated C,N-diarylacetamides: molecular conformations and supramolecular assembly

The structures of four halogenated N,2-diaryl­acetamides are reported and compared with a range of analogues. N-(4-Chloro-3-methyl­phen­yl)-2-phenyl­acetamide, C₁₅H₁₄ClNO, (I), and N-(4-bromo-3-methyl­phen­yl)-2-phenyl­acetamide, C₁₅H₁₄BrNO, (II), are isostructural in the space group P. The mol­ecules of (I) and (II) are linked into chains of rings by a combination of N-H...O and C-H...π(arene) hydrogen bonds. The mol­ecules of N-(4-chloro-3-methyl­phen­yl)-2-(2,4-di­chloro­phen­yl)acetamide, C₁₅H₁₂Cl₃NO, (III), and N-(4-bromo-3-methyl­phen­yl)-2-(2-chloro­phen­yl)acetamide, C₁₅H₁₃BrClNO, (IV), are linked into simple C(4) chains by N-H...O hydrogen bonds, but significant C-H...π(arene) inter­actions are absent. The N-aryl groups in compounds (III) and (IV) adopt a different orientation, by ca 180°, from that of the corresponding groups in compounds (I) and (II), but otherwise the conformations of (I)-(IV) are very similar. Comparisons are drawn between compounds (I) and (IV) and a range of analogues of the type R¹CH₂CONHR², where R² represents a halogenated aryl ring and R¹ represents either another halogenated aryl ring or a naphthalen-1-yl unit.