Heterocycles: small rings with only one heteroatom; pyrroles, thiophenes, and furans; indoles; pyridines; quinolines and isoquinolines; 1,2- and 1,3-azoles. Pyriliums, 2- and 4-pyrones. The diazines: pyridazine, pyrimidine, and pyrazine. Purines. Search for organic reactions pathways: chemical kinetics, kinetic and non-kinetic use of isotopes, study of reactions intermediates, steric and stereoelectronic effects, structure-reactivity correlations (Hammett, Taft). Pericyclic reactions: electrocyclic, cycloadditions, cheletropics and sigmatropic rearrangements. Retrosynthesis (disconnection approach to organic synthesis).