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, C(15)H(14)ClNO, (I), and N-(4-bromo-3-methylphenyl)-2-phenylacetamide, C(15)H(14)BrNO, (II), are isostructural in the space group P-1. 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, C(15)H(12)Cl(3)NO, (III), and N-(4-bromo-3-methylphenyl)-2-(2-chlorophenyl)acetamide, C(15)H(13)BrClNO, (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 R(1)CH(2)CONHR(2), where R(2) represents a halogenated aryl ring and R(1) represents either another halogenated aryl ring or a naphthalen-1-yl unit.