(Solid plus liquid) equilibria, i.r., and semi-empirical studies of carbazole with selected tertiary amides

(Carbazole+tert-amide) systems were investigated through measurement of (so lid + liquid) equilibria (s.l.e.) i.r. study, and semi-empirical calculatio ns. The s.l.e. studies included three systems, namely (carbazole + tetramet hylurea, or N, N-diphenylacetamide, or N-acetylcarbazole). In spite of the identical tertiary N-atom, and C=O group occurring in each studied amide as sumed to dominate molecular interactions, the liquidus curves have revealed the presence of a hydrogen-bond complex only in the first system. The rema ining two are simple eutectic systems, probably owing to sterical hindrance exhibited by large substituents. Each system, as well as (carbazole + N,N- dimethylformamide) were studied using i.r. spectroscopy in 1,1,2,2-tetrachl oroethene solutions. In contrast to s.l.e. data, hydrogen-bond formation ma nifested itself in each system studied by the i.r. method. The enthalpy of complex formation was determined from the spectroscopic data for each syste m except for (carbazole + N-acetylcarbazole). The i.r. studies were support ed by semi-empirical calculations performed for the optimized hydrogen-bond geometries. (C) 2001 Academic Press.