I recently came across this elaborate article on electrophilic aromatic subsitution.
In the third chapter "General mechanistic considerations in electrophilic aromatic substitution" the existence of a transition state in which the attacked double bond is nonplanar is mentioned.
To explain this phenomenon, the example of the 1,3-dienyl-2-cation is given.
However, I am struggling to unterstand this phenomenon in regards to the example given here. As one of the carbon atoms is sp-hybridized, the p-orbitals would already be perpendicular to each other. I could not find any other graphical explainations for this transition state, unfortunately. Specifically, I would like to understand in which way the protonation changes the orientation of the orbitals.
Literature:
Stamenković, N; Ulrih, N. P.; Cerkovnik, J. An analysis of electrophilic aromatic substitution: a “complex approach”. Phys. Chem. Chem. Phys. 2021, 23, 5051-5068. DOI: 10.1039/D0CP05245K
