Benzynes frontier orbitals

Fig. 2. Frontier Orbitals and Energies (eV). Calculated for 2-Butyne Models (4-31G)179) vs. C-C=C bond angles. The angles of 146° and 124° correspond to (31) and 1,2-benzyne, resp.

Let us now explore the reactivity of these compounds as dienes (furan, pyrrole, thiophene) with a dienophile (benzyne) in Diels-Alder reactions. One approach that, for a long time, has been widely employed by chemists, is the use of Frontier Molecular Orbital (FMO) [19] energy gap between two of the reactants. According to this theory, the most reactive reactant pair will be the one that has a lower FMO energy gap. The reaction is predicted to be HOMO diene-controlled. If... 

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