Please explain difference between pi and sigma bonds to me. I've been reading chemistry all day long and my brain just can't absorb anything more from books so maybe someone can explain it simpler.
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Anonymous2007-11-05 15:06
All single bonds are sigma bonds. Sigma bonds can rotate. Therefore, single bonds can rotate. (there are other factors that restrict bond rotation, but for now we'll leave it at that)
A double bond is made of a sigma bond and a pi bond. The pi bond imparts an inability for that bond to rotate. This is why double bonds do not rotate.
Why is it that pi bonds impart an inability to rotate? Look in your book for a picture of two pi orbitals overlapping each other. It should be obvious why you cannot rotate this bond. To force the bond to rotate would mean breaking the pi bond. Since that isn't energetically favorable, double bonds - having one pi bond - are said to be unable to rotate.
Same goes for triple bonds. Triple bonds are made of one single bond and two pi bonds. The same logic follows.
just a bunch of silly math majors on this board, who will only end up teaching math (lol, good major guys)
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Anonymous2007-11-05 22:47
>>3
Whoops. My excuse is that gen chem was about 5 years ago for me :)
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Anonymous2007-11-06 8:35
>>2
sigma orbitals have no nodal plane.
pi orbitals have one.
That's it.
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Anonymous2007-11-06 18:33
the electron density of pi bonds 'looks' a lot like the greek letter pi... hence the name. two pis actually opposite each other with sigma electron density between. the sigma e- density is mostly centered between the two nuclei, allowing free rotation around the bond (the atoms can spin on the axis through the bond/nuclei). the pi bond, kinda like clamps on either side of the sigma e- prevent the atoms from rotating about the axis of the bond.
or something like that.
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Anonymous2007-11-07 3:43
>>7
Just die.
It doesn't look like a fucking pi, as a pi doesn't have a fucking nodal plane. It's called a pi orbital because that's the greek for p. Hence s -> sigma, d -> delta, as well.