Question

If conjugated cyclic Polymers like polyacetylene conduct electricity why does benzene not conduct electricity?

Answer 1

Benzene does not conduct electricity because the delocalised electrons are in the molecule and stay there.
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