Every introductory course or text on aromatic electrophilic substitution contains an explanation along the lines of the resonance diagram shown below. With an o / p directing group such as NH 2 , it is argued that negative charge accumulates in those positions as a result of the resonance structures shown.
We recently developed a new computational chemistry practical laboratory here at Imperial College. I gave a talk about it at the recent ACS meeting in Salt Lake City. If you want to see the details of the lab, do go here. The talk itself contains further links and examples.
The preceeding blog entries contain stories about chemical behaviour. If you have clicked on the diagrams, you may even have gotten a Jmol view of the relevant molecules popping up. But if you are truly curious, you may even have the urge to acquire the relevant 3D information about the molecule, and play with it yourself.
https://orcid.org/0000-0002-8635-8390
Click on diagram to see model. The reaction above is ostensibly a very simple pericyclic ring opening of a cyclopropyl carbocation to an allyl cation, preceeded by a preparatory step involving SN-1 solvolysis. As a 2-electron thermal process, the second step proceeds with disrotation of the terminii. Can this stereochemistry be illustrated with a computed model for the transition state for this process?
Mauksch and Tsogoeva have recently published an article illustrating how a thermal electrocyclic reaction can proceed with distoratory ring closure, whilst simultaneously also exhibiting 4n electron Möbius-aromatic character[cite]10.1002/anie.200806009[/cite]. Why is this remarkable?
https://orcid.org/0000-0002-8635-8390
