Chemistry Help plz

[virtueixi]

Please do not flame this thread. I have been trying to get the answer to this problem since this morning. I am soaking wet as I tried to get a TA to help me, but as it turned I knew more than her, so as I was leaving it started to pour. This is my last question on the set and it is due tonight. ANY help would be appreciated:

Pic from http://capa.chem.sunysb.edu/nan/butadiene.gif (of Butadiene )

Consider the delocalized pi orbitals of butadiene (above). Which of the following statements are true ?



a) Butadiene has 2 pi orbitals

b) Butadiene has 8 pi electrons

c) The highest energy pi orbital in butadiene has no nodes besides the plane of the molecule

d) Butadiene has two filled pi orbitals

e) The highest energy filled pi orbital in butadiene has one node, besides the plane of the molecule

f) The highest energy filled pi orbital in butadiene is antibonding between carbons 2 and 3


Could be several answers. Thank You

 

[Particle Man]

Physical Organic Chemisty? MO theory (molecular orbitals), HMO (Hückel molecular orbitals). The book on Frontier Orbitals (Fleming) can help out a lot with this problem. I perfer Frontier Orbitals more than the mathmatical computations (linear algebra) of HMO theory. Remember HOMOs and LUMOs with this problem. This problem can be explained fairly easily with frontier orbitals in mind.

Check out these websites:
http://www.ch.ic.ac.uk/local/organic/pericyclic/p1_theory.html
http://www.everyscience.com/Chemistry/Organic/Pericyclics/b.1086.php

They explain some details about this problem.

I really don't want to give away the answer directly, but if you still have problems with this let me know. Some of these concepts are not as intuitive as one would like.

 

[rjain]

Start by drawing the energy level diagram resulting from the mixing of 3 pi bonding orbitals. From there, fill in the electrons.

For c) you'll have to look at the geometry and how the mixing occurs.