The structure and properties of aromatic polyamides and polythioamides were investigated and compared with those of analogous polyesters, polythioesters, and polydithioesters.

Key indicators: single-crystal X-ray study; T = 223 K; mean (C-C) = 0.002 Å; R factor = 0.029; wR factor = 0.083; data-to-parameter ratio = 15.3.The title compound, C 16 H 16 N 2 S 2 , adopts a gauche) conformation in the NH-CH 2 -CH 2 -NH bond sequence. In the crystal, molecules are connected by pairs of N-HÁ Á ÁS C hydrogen bonds and C-HÁ Á Á interactions, forming a tape structure along the c-axis direction. Related literature

synopaisThe ring-opening copolymerization of propylene oxide with d-camphoric acid anhydride [ a ]~ -3.4' waa carried out with diethylzinc and triethylamine as catalysts. It wag found that the p-roducts were alternatin~co~plymen which were optically-active. The optical rotatory dispersion curves were found to fit a simple Drude equation having a A, value of 201 mp. The specific rotation increased with increasing intrinsic viscosity of the product. The propylene oxide recovered from the polymerization system wss optically active. Its specific rotation incressed with increasing polymerization time. It is thought that the asymmetric selective copolymerization of propylene oxide is caused by the influence of the optically active camphoryl group of the polymer end. 1207

The title compound, C17H18N2S2, exhibits a trans–trans–trans–gauche+ (tttg +) conformation with regard to the NH–CH2–CH2–CH2–NH bond sequence. In the crystal, mol­ecules are connected by N—H⋯S=C and C—H⋯S=C hydrogen bonds, forming a herringbone arrangement along the c-axis direction. The two thioamide groups make dihedral angles of 43.0 (2) and 33.1 (2)° with the adjacent phenyl rings.