Consider what happens if we treat benzene with oxidizing or reducing agents

•	Treatment of benzene with strongly oxidising SbF5/SO2ClF has no effect. However, it is possible to oxidise substituted derivatives. Hexakis(dimethylamino)benzene (refcode GENFAG) can be oxidised with iodine to give the dication (refcode GENFEK).

•	Compare these two structures. This time you will notice that, unlike the neutral compound, the cation is nonplanar and all carbon-carbon bonds lengths are not the same.

•	Similar results are obtained when we reduce hexakis(trimethylsilyl)benzene (refcode KELVOM) to the dianion (refcode KINFUI). Again, compare these two structures, how do they differ?

•	Clearly the number of π electrons is important in determining whether or not cyclic alkenes adopt a planar geometry. Complete the table below with your findings:

 

Compound and CSD Refcode	Diagram	π Electrons	Geometry
benzene   BENZEN02		6	planar
hexakis(dimethy amino) benzene   GENFAG		6
hexakis(dimethy amino) benzene dica­tion   GENFEK
hexakis(trimethylsi­lyl) benzene   KELVOM			planar
hexakis(trimethylsi­lyl) benzene dianion,   KINFUI