2-Acetamido-4-p-tolyl-1,3-thiazole and 2-amino-4-p-tolyl-1,3-thiazolium chloride dihydrate.

The structures of 2-acetamido-4-tolyl-1,3-thiazole, C(12)H(12)N(2)OS, (I), and 2-amino-4-tolyl-1,3-thiazolium chloride dihydrate, C(10)H(11)N(2)S(+).Cl(-).2H(2)O, (II), reveal that both molecules are essentially planar, with the respective dihedral angles between the benzene and thiazole rings being 2.9 (1) and 10.39 (7) degrees . Compound (I) associates via a single N-H...O interaction to form a flat alternate-facing hydrogen-bonded chain [graph-set C(2)(2)(4)]. Compound (II) packs with the hydrogen-bonding associations of the Cl atoms and the water molecules creating a convoluted hydrogen-bonded ribbon made up of five-membered donor-acceptor rings, involving three water O atoms (with associated H atoms) and two Cl atoms. The thiazolium rings form stacked columns, aligned in the same direction as the hydrogen-bonded ribbons, of alternate-facing molecules that are also involved in the hydrogen-bonding network, linking to the Cl atoms and one of the water molecules. Subsequently, each Cl atom is the hydrogen-bond acceptor for five separate O/N-H associations.