The syntheses and crystal structures of four salts of amitriptynol (C20H25NO) with different carboxylic acids are described. The salts formed directly from solutions of amitriptyline (which first hydrolysed to amitriptynol) and the corresponding acid in acetonitrile to form amitriptynolium [systematic name: (3-{2-hydroxytricyclo[9.4.0.03,8]pentadeca-1(11),3,5,7,12,14-hexaen-2-yl}propyl)dimethylazanium] 4-methoxybenzoate monohydrate, C20H26NO+·C8H7O3 −·H2O, (I), amitriptynolium 3,4-dimethoxybenzoate trihydrate, C20H26NO+·C9H9O4 −·3H2O, (II), amitriptynolium 2-chlorobenzoate, C20H26NO+·C7H4ClO2 −, (III), and amitriptynolium thiophene-2-carboxylate monohydrate, C20H26NO+·C5H3O2S−·H2O, (IV). Compound (III) crystallizes with two cations, two anions and six water molecules in the asymmetric unit. The different conformations of the amitriptynolium cations are determined by the torsion angles in the dimethylamino-propyl chains and the –CH2–CH2- bridge between the benzene rings in the tricyclic ring system, and are complicated by disorder of the bridging unit in II and III. The packing in all four salts is dominated by N—H...O and O—H...O hydrogen bonds. Hirshfeld surface analyses show that the amitriptynolium cations make similar inter-species contacts, despite the distinctly different packing in each salt.

The synthesis and crystal structure of C3HF3N2OS, systematic name 5-(trifluoromethyl)-1,3,4-thiadiazol-2(3H)-one (5-TMD-2-one), a compound containing the pharmacologically important heterocycle 1,3,4-thiadiazole, is presented. The asymmetric unit comprises six independent molecules (Z′ = 6), all of which are planar. The r.m.s. deviations from each mean plane range from 0.0063 to 0.0381 Å, not including the CF3 fluorine atoms. Within the crystal, two of the molecules form hydrogen-bonded dimers that in turn combine with inversion-related copies to form tetrameric constructs. Similar tetramers, but lacking inversion symmetry, are formed by the remaining four molecules. The tetramers are linked into tape-like motifs by S...O and O...O close contacts. The environments of each symmetry-independent molecule were compared via a Hirshfeld surface analysis. The most abundant atom–atom contacts are between fluorine atoms, while the strongest result from N—H...O hydrogen bonds.

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The synthesis and crystal structure of the title compound, C12H16FNO3S, which is related to the herbicide flufenacet, are presented. The dihedral angle between the amide group and the fluorinated benzene ring is 87.30 (5)° and the N—C—C—S torsion angle defining the orientation of the methylsulfonyl substituent relative to the amide group is 106.91 (11)°. In the crystal, inversion-related molecules form dimers as a result of pairwise C—H...O hydrogen bonds, which appear to be reinforced by short O...π contacts [O...Cg = 3.0643 (11) Å]. A Hirshfeld surface analysis was used to quantify the various types of intermolecular contacts, which are dominated by H atoms.