chemistry help desperately needed?

Question

what is the difference between benzene and 1,3,5 cyclohexatriene?
and why can we not unsaturate cyclopropane.

Answer 1

If you name the compound 1,3,5 cyclohexatriene, you give the impression that the double bonds remain in the same place. They can shift to give 2,4,6 cyclohexatriene, which is the same compound but looks as if it has been rotated 60 degrees. This kind of equivalent structures as a result of moving electrons is an extreme example of resonance called aromaticity. The double bonds are spread out over the entire molecule, so benzene does not react instantaneously with Br2/CCl4 the way something like pentene does. Cyclopropane has bond angles of 60 degrees, and if you tried to put a double bond between two of the carbons, that would force it to try and increase toward 120 degrees. There is just too much ring strain for it to exist.