RESUMO
Isocyanic acid, HNCO, the imide of carbon dioxide, was prepared by reaction of stearic acid and potassium cyanate (KOCN) at 60 °C in a sealed, thoroughly dried reactor. Interestingly, its crystal structure, solved by X-ray single crystal diffraction at 123(2) K, shows a group-subgroup relation for the NCO- anion to carbon dioxide: (for CO2, cP12, Pa3Ì , a = 5.624(2) Å, 150 K, C-O 1.151(2) Å; for HNCO, oP16, Pca21, a = 5.6176(9), b = 5.6236(8), c = 5.6231(7) Å, 123(2) K). Precise positions of H, N, C, and O were determined by DFT calculations with WIEN2k leading to interatomic distances C-O 1.17, C-N 1.22, N-H 1.03, and -N-H···N 2.14 Å, and the interatomic angle N-C-O 171°.
RESUMO
The synthesis, structure, and bonding of alkali salts of resonance stabilized amides, such as diformylamide (dfa), formylcyanoamide (fca), nitrocyanoamide (nca), and for comparision, the well-known dicyanoamide (dca), are discussed on the basis of experimental and theoretical data. The first structural reports of K(18-crown-6)+dfa-, K(18-crown-6)+fca-, Na+nca-, and Li(TMEDA)+dca- are presented. Examination of the X-ray data reveals almost planar anions with strong cation-anion interactions resulting in network-like structures in the solid state. For comparison, the X-ray structures of covalently bound phenyldicyanoamide and diformamide are also discussed. The thermal behavior of the alkali salts of these amides is studied by thermoanalytical experiments. Moreover, several novel ionic liquids based on resonance stabilized amides have been prepared and were fully characterized, namely the dfa, fca, and nca salts of EMIM (1-ethyl-3-methyl-imidazolium), BMIM (1-butyl-3-methyl-imidazolium), and HMIM (1-hexyl-3-methyl-imidazolium). Most of them are liquid at room temperature, except BMIM+fca- that melts at 32 degrees C. These ionic liquids are neither heat nor shock sensitive, are thermally stable up to over 200 degrees C, and can be prepared easily in large quantities.
