Re: Why benzene doesn't conduct current even it has delocalized electrons?

When we are talking about conducting electricity, we are wanting to move electrons through a distance 
of at least millimetres.

Benzene has "delocalized electrons" when we look at benzene on a molecular scale. What that means is 
that benzene is unlike say, butane, where we write a bonding scheme that associates each of the 
electrons with an individual atom (for the core electrons) or bond (for the valence electrons). Some of 
the electrons in benzene we regard as smeared out over the whole molecule.

Now that is largely just a convenient model -- a caricature of what the electrons are really doing. 
(Actually all of the electrons in a molecule spread over the whole of the molecule, and we cannot tell 
which electron is which anyway). But it is true that benzene is much more polarizable than butane. That 
is, its electrons can move much more freely and readily from one end of the molecule to the other in 
response to an electric field.

The problem is that although very mobile within the molecule, the electrons in benzene are limited to 
moving within the single molecule they are in. They are not able easily to jump to the next molecule. 
That means that they can move very freely for a millionth of a millimetre, but they cannot conduct 
electricity over a distance of millimetres!

Graphite has a structure that is rather like benzene, but instead of a single hexagonal molecule, it has a 
continuous sheet in a hexagonal honeycomb pattern. The delocalized electrons in graphite are free to 
move through the whole sheet, which is large enough that they do effectively conduct electricity.