The Benzyne Mechanism to Aromatic Substitution
Structure of ortho-Benzyne


A benzyne is generated from a benzene by making two of the trivalent C-atoms di-valent. If these two divalent atoms are next to each other, then an ortho-benzyne is generated. If the two divalent atoms are in 1,3- or 1,4-positions, then a meta- or para-benzyne is generated. In aromatic substitution reactions, only the ortho-benzynes are important and the structure of the parent ortho-benzyne is shown.


Figure. The MP2(full)/6-31G* optimized structure of ortho-benzyne.