highest bonding energy(sigma, pie)

[joonkimdds]

In ethene, which has the highest bond energy level?
sigma, sigma*, sigma * antibonding, pie, pie*, pie* antibonding are the choices.

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[D.D.S.]

Arent sigma the highest energy bonds since their location is like "inside" where as the pi bond electrons are "outside" and more available to break...??

 

[joonkimdds]

Well...according to
http://www.science.uwaterloo.ca/~cchieh/cact/fig/mo-hf.jpg
pie* has higher energy than sigma or pie.

but I don't know about antibonding.

 

[Flipper405]

Ok, it's pi... like the symbol that means 3.14 in mathematics? the Greek letter...
http://en.wikipedia.org/wiki/Pi_(letter)

or

http://en.wikipedia.org/wiki/Pi_bond


Anyway, I think it would be sigma since that would be the strongest bond.

 

[IcemanDDS]

pie* yummmmm.....




*key lime

 

[Sephisabin]

Can you state the question verbatim please? If you're asking which has the highest bonding energy, then the answer is the sigma since it is the strongest bond. The strongest bond requires the most energy to break.

HOWEVER, if you're asking which has the highest bond energy level (which is what I think the actual question is), then the answer is the pi* antibonding. This question has to do with the way the different bonding orbitals are actually oriented. In this case, the lower the bond energy level, the stronger (more stable) the bond. Hence, the sigma bonds would have the lowest bond energy level and pi would be higher. Further, since bonding orbitals are more stable than antibonding orbitals, the antibonding orbitals would be even higher in energy.

I took a full quarter course learning this stuff for my MS in chemistry. Sorry if it didn't make sense, I'm just trying to summarize the main points. PM me if you need further explanation.

 

[xdianaax]

Can you state the question verbatim please? If you're asking which has the highest bonding energy, then the answer is the sigma since it is the strongest bond. The strongest bond requires the most energy to break.

HOWEVER, if you're asking which has the highest bond energy level (which is what I think the actual question is), then the answer is the pi* antibonding. This question has to do with the way the different bonding orbitals are actually oriented. In this case, the lower the bond energy level, the stronger (more stable) the bond. Hence, the sigma bonds would have the lowest bond energy level and pi would be higher. Further, since bonding orbitals are more stable than antibonding orbitals, the antibonding orbitals would be even higher in energy.

I took a full quarter course learning this stuff for my MS in chemistry. Sorry if it didn't make sense, I'm just trying to summarize the main points. PM me if you need further explanation.

The OP did the right thing, he cannot post verbatim due to copyright laws.

 

[joonkimdds]

Can you state the question verbatim please?

In a carbon-carbon double bond, the carbon-carbon bonding electrons of highest energy reside in which molecular orbital?
a) the sigma bonding MO
b) the pie bonding MO
c) the pie* bonding MO
d) the sigma * antibonding MO
e) the sigma * bonding MO

should I tell u the answer or should I wait until someone comes up with right answer?

Hint : everyone who posted the answers are wrong 🙂 or maybe the way I change, reworded the problem caused confusion?

 

[Sephisabin]

Yeah, that changes it a slight bit... I thought you meant the highest existing orbital, not the highest occupied orbital. I believe that for ethene, the highest energy electrons reside in the pi ungerade MO, meaning that they should have some bonding character or, at worse, nonbonding character. Thus, I feel that B is the best answer.