Replacement and systematic nomenclature (Hantzsch-Widman system) for monocyclic, fused and bridgedheterocycles.

General chemical behavior of aromatic heterocycles, classification (structural type), criteria of aromaticity (bond lengths, ring current and chemical shifts in 1H NMR-spectra, empirical resonance energy, delocalization energy and Dewar resonance energy, diamagnetic susceptibility exaltations), heteroaromatic reactivity and tautomerism in aromatic heterocycles.

Strain-bond angle, torsional strains and their consequences in small ring heterocycles. Conformation of six-membered heterocycles with reference to molecular geometry. Barrier to ring inversion, pyramidal inversion and 1,3-diaxial interaction, stereo-electronic effects- anomeric and related effects, attractive interactions, hydrogen bonding and intermolecular nucleophilic-electrophilic interactions.

Three-membered and four membered heterocycles-synthesis and reactions of aziridines, oxiranes, thiiranes, azetidines, oxetanes and thietanes, five membered heterocycles-synthesis and reactions of different isomers of diazoles (pyrazoles, imidazoles), oxazoles, thiazoles, 1,2,4- triazole, oxadiazole, thiadiazole, 1,2,3,4-tetrazole.

Porphyrins and applications.

Synthesis and reactions including medicinal applications of benzopyrroles, benzofurans and benzothiophenes.

Meso-ionic heterocycles-classification, chemistry of some important meso-ionic type-A and B heterocycles and their applications.

Sydnones.

With one heteroatom: Synthesis and reactions of pyrilium salts and pyrones and their comparison with pyridinium, thiopyrylium salts and pyridones, synthesis and reactions of quinolizinium and benzopyrylium salts, coumarins and chromones.

With two or more heteroatoms: Synthesis and reactions of diazines, triazines, tetrazines and thiazines. Some important macroheterocycles.