Structure and hydrogen bonding of solid N-1-alkyl-N-2-(2-hydroxy, 4-or 5-methylphenyl)thioureas

Crystalline N-1-alkyl-N-2-arylthioureas with ortho hydroxyl and para or met a methyl substituents to the phenyl ring were studied by single crystal X-r ay diffraction, IR and solid state C-13 CP MAS NMR. Two different modes of association were found: i) intermolecular (NH)-H-1 ... S bonds and (NH)-H-2 not involved in hydrogen bonding in N-1-methyl-N-2- (2-hydroxy,5-methylphe nyl)thiourea 1, ii) cyclic dimers with two (NH)-H-2 ... S hydrogen bonds (S ... N-2 distance of 3.322 Angstrom) and (NH)-H-1 engaged in intermolecular (NH)-H-1 ... O bond in N-1-methyl-N-2-(2-hydroxy,4-methylphenyl)thiourea 2 . Changes of carbon chemical shifts between solution and solid state result mainly from the reorientation of the aromatic ring with respect to the thi ourea fragment.