Mobius Aromaticity https://youtu.be/wt4mIJ0lCpw

1. Möbius Aromaticity: Aromatics do the twist
Orbital topology in cyclic systems can be classified as two
categories
Mobius
(twisted cylinder)
Huckel
(cylinder)
Heilbronner: Molecule could gain Möbius aromatic stabilization if the nuclear framework were twisted so the p-
orbitals composing the π-system would contain an odd number of nodes
Ideal Möbius aromatic
would exhibit neither bond
length localisation, nor any
localisation of the Möbius
twist present in the ring

2. The red ants marching along the surface of the twisted
loop show that the Möbius strip has a single continuous
surface
Single continuous surface

3. Möbius strip cyclic polyenes, one orients one side of the polygon horizontally at the bottom of the circle

4. Double Circle Mnemonics
Inscribe both a Cn+1 polygon (vertex down) and a Cn+1 polygon (side down) in the same circle
MO for the Hückel C2n+2 annulene

5. ❖ Möbius -twisted bands nevertheless have a smaller resonance energy per 𝜋-electron than 4n + 2 planar
aromatics, but for larger rings, this may be offset by less ring strain.
❖ A Mobius twist can be induced in an annulene by a certain number of trans double bonds at appropriate
positions
❖ Clear 𝜎−𝜋 separation possible for planar conjugated systems is blurred when such systems are twisted. Under
these circumstances, it becomes more difficult to separate the electronic influence of the 𝜎 framework from
the conjugated 𝜋 manifold.

6. Example

7. Application
Detailed application will be dealt in Pericyclic lecture