|WikiProject Chemistry||(Rated C-class, Top-importance)|
This article desperately need expansion. Especially since it's such an important topic in MO theory.--Rejnal 06:10, 29 December 2006 (UTC)
- Agreed. The entire article, at this point, could be summed up as: Pi bonds are pi bonds. It is only informative if you were unaware of the existance of pi bonding to begin with. There is nothing here that would help someone understand why and how pi bonding occurs. --Matt D (talk) 09:37, 22 October 2008 (UTC)
Since when are double bonds weaker than single bonds?
pi bond is weaker, double bond is stronger: two different things
"Atoms with double bonds or triple bonds usually have one sigma bond and the rest are usually pi bonds"
Surely this is not the case; carbonyl carbon with three sigma and one pi, carbon of ethene with three sigma and one pi.....or is something else intended by the statement?
- I suspect it means that in a multiple-bond between two atoms, one of those bonds is σ and the rest are π, which is a generally reasonable explanation for most people for most compounds. DMacks 21:14, 16 November 2006 (UTC)
Perhaps a rephrasing is in order; along the lines of "a multiple bond between two atoms usually consists of one sigma bond together with one or more pi bonds" ?
It's referring to within that one double or triple bond. It could be misread quite easily though, perhaps the wording should be different.
- I reworded the sentence, no longer misleading V8rik 18:17, 23 February 2007 (UTC)
Contradiction concerning Dicarbon
Section Special Cases says...
In some cases of multiple bonds between two atoms, there is no sigma bond at all, only pi bonds. Examples include ... dicarbon (C2)
But the Dicarbon article says....
However, molecular orbital theory shows that there are two sets of paired electrons in the sigma system (one bonding, one antibonding), and two sets of paired electrons in a degenerate pi bonding set of orbitals.... This is surprising because the MO diagram of diatomic carbon would show that there are two pi bonds and no sigma bonds.
Is the section "Effect of bond rotation" necessary?
First of all, the section doesn't really fit. It is a series of pictures with long captions; furthermore, the third one only describes sigma bonds.
Second, it doesn't seem necessary. If I understand the intention of the section, it's to demonstrate that pi bonds cannot be rotated like sigma bonds can. This is already alluded to earlier in the article. Understandably, images would help understanding, but these images confuse me more than help me. What would work best are two 3D images side by sides of p orbitals parallel to each other and perpendicular.
- This section has already been trimmed down and the remaining images also do not get the point across. V8rik (talk) 21:22, 21 July 2010 (UTC)