Hey guys had a little request for a discussion of sigma and pi bonds almost certainly as they are with respect to carbon
So here's what I need you to know
sigma bonds
Between a carbon and anything else is the first bond the carbon makes with any other atom
First one is always sigma always
If the carbon makes multiple bonds with an atom like a carbon-carbon double bond or a Carbon-Carbon triple
Bond or something a carbon nitrogen triple. I don't care what it is any second or third, Bond
It makes with an atom those are going to be pi bonds check this out
here is a picture of a compound that I just invented I even know the name of it, but
The deal is that every first bond is a sigma Bond
so
Here's a bond between carbon and hydrogen the first one is a sigma Bond
This one is the first one. It's a sigma Bond
That one there the first one is a sigma bond, and that's a sigma bond. That's a sigma Bond
That's the first one. That's the first one
That's the first one one of these is a sigma bond because one of them is the first bond and that's a sigma Bond
Every single bond Carbon makes with something else is Gonna be a sigma Bond
but
Every second or third bond is a pi bond
See there is a bond there
One of those bonds is a pi bond the first one sigma the second one is Pi
Here there are two extra bonds. There's a second and third Bond
One of them is a pi bond and the other one is a pi bond
Every first one is sigma and every second or third is Pi
so it's easy for you to tell whether it's a sigma or pi bond, but what does that even mean is the real question
Well, here's the deal when it comes down to electron configurations
sigma bonds are always made from
hybridized
orbitals
Whereas
the Pi Bonds are made from
leftover P orbitals and
We decide what the hybridization of the carbon is based off of how many multiple bonds that it makes?
Check it out. Let's do the three examples the three examples. We're gonna Do are a
Carbon that has only single bonds a carbon that has a double bond and a carbon that has a triple bond
We're gonna do all three of those
Here are carbon atoms with only single bonds so sigma sigma sigma sigma
These are all sigma bonds
They are made from hybridized orbitals, so when we hybridize the normal carbon
atom we need to have four openings for
hybridized orbitals
when this carbon a carbon that has only single bonds
hybridizes the 1s gets left alone
But the 2s, and the peas have to combine in fact we need one two three four
sigma bonds one two three four that requires an s the 2s, and
three P's
So we end up with four Sp. Three?
Hybrid orbitals we take our electrons spread them out and boy isn't it just convenient that
We now have room for one two three four bonds to be made
This is the hybridized electron configuration for a carbon that has only single bonds
one two three four hybridized orbitals all
sigma bonds
When a carbon makes a double bond however it makes one two
three sigma Bonds and
One Pi bond the Pi bond is the second bond. This is just an example
Molecule it could be any molecule that has a double bond in it like the one. I showed you before
One two three hybridized orbitals are needed and one p orbital needs to be left over
Remember our rule Pi bonds are left over P orbitals
So when this hybridizes you end up with a 1s orbital?
one two three sigma bonds and
to hybridize into three
equivalent
orbitals we need 1 s and 2 P orbitals and
We need to leave one of the 2P orbitals alone
spread it your electrons 1 2 3 I'm not going to follow I
Have about principle or hund's rule or whatever that is but the point here is it can still make four bonds?
one two three sigma or single bonds and
one opening for a double bond to be made any
Carbon that has a single double bond
has this
Electron configuration for the hybridized Carbon
finally what happens when a carbon makes a triple bond or
really if it makes two double bonds
These are the same case in that this carbon has a sigma bond there and a sigma bond here
But it has two pi bonds
because the second and the third both Cowntess Pi
bonds
Here you have a sigma and a sigma
This second one counts as a pI and this second one counts as a pI so in both cases you have two pi bonds being
Made you should know by now
That means you have two p orbitals left over your 1s. Never gets touched
just like before and
That means you have two single bonds being made you need to hybridize the s with one of the peas
one two three four
Electrons you can make two single bonds and two double bonds
Look guys. We really just kept up with the sigma Pi
orbital
hybridisation rule stuff to explain why Carbon bonds the way that it does
Why it has the angles that it does and why to be honest? Why single bonds can rotate?
But double bonds can't I haven't explained the geometry but just trust me on that one
When a carbon has only single bonds, they're all sick of us, and you need four Sp
Three hybrid orbitals to do it
when you have a double bond you need three Sp2
hybrid orbitals for the three single bonds and one P orbital left over for the double Bond or
Pi Bond
Finally for the triple bond you need two single
Sp, two
single Bonds
Sp. Hybrid orbitals for the sigma bonds and you need two left over P orbitals
For the two pi bonds, it's all here ain't no fiction's best of luck