Furan, C₄H₄O, is a substance derivable from oat hulls, corn cobs, and other cellulosic waste. It is a starting material for the synthesis of other chemicals used as pharmaceuticals and herbicides. The furan molecule is planar and the C and O atoms are bonded into a fivemembered pentagonal ring. The H atoms are attached to the C atoms. The chemical behavior of the molecule suggests that it is a resonance hybrid of several contributing structures. These structures show that the double bond character is associated with the entire ring in the form of a π electron cloud.

(a) Draw Lewis structures for the several contributing structures to the resonance hybrid mentioned above.

(b) Draw orbital diagrams to show the orbitals that are involved in the σ and π bonding in furan.

(c) How many π electrons are there in the furan molecule? Show that this number of π electrons is the same, regardless of the contributing structure you use for this assessment.