In this work is proposed a didactic alternative vision to teach pericyclic reactions. To this end, they were classified according to the connectivity of reactants systems, as connected atom reactions (CAR) and the other possibility, as not connected atom reactions (NOCAR). Electrocyclic reactions and sigmatropic rearrangements are examples of CAR categorization, and the cycloadditions being NOCAR. With these two categories, a pedagogical alternative description is proposed to the orbital topology in reactants to explain the pericyclic reactions. According to this classification, the HOMO's topology is adequate to all CAR, while the traditional HOMO-LUMO's topology is adequate to NOCAR. All issues typically deduced by the traditional treatment, such as allowed and forbidden reactions, and stereochemical aspects are also explained by the alternative approach.
Keywords:
orbital topology; sigmatropic reactions; organic chemistry teach
