Structural deviations of arenecarbothioamides from planarity

X-ray analyses of 2-methylisoquinoline-1(2<i>H</i>)-thione, <i>N</i>-methyl-<i>N</i>-phenyl-2-chlorobenzenecarbothioamide and <i>N</i>-methyl-<i>N</i>-phenylbenzenecarbothioamide have revealed that the CS-NR₂ moiety of these and similar thiobenzanilides are virtually planar and do not exhibit any significant bending of the NR₂ group. Steric hindrance is avoided instead by torsion around the <i>N</i>-aryl and <i>C</i>-aryl bonds which latter amounts to over 73° in the case of the <i>ortho</i>-chloro derivative. According to quantum chemical calculations, these torsions, moreover, favor noncovalent intra- and intermolecular bonding (van der Waals) interactions, thus inducing the <i>E</i>-configuration observed in the crystalline state.