Question

Provide an explanation as to why 3-Butadiene has resonance

Answer 1

Resonance structures is a result of flow of electrons through the p-orbital pathway.

In butadiene four p-orbitals are adjacent to one another, so it is possible to present the molecule in different structures, rather with two double bonds where carbons 1&2 and carbons 3&4 are involved in the formation of pi-bonds, or with one double bond at carbons 2&3.