Newman Projections 2 Newman Projections 2
Newman Projections 2
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- In the last video, we visualized an ethane molecule
- with a Newman Projection.
- What I want to do in this video is show that you can
- really visualize longer chains, or even, we'll see in
- future videos, even cyclical, ring-based carbon molecules
- with Newman Projections as well.
- And I guess the next most complex molecule to study
- would be butane.
- We could do propane, but butane will be interesting.
- This was ethane right here, butane will have four carbons.
- And if I were to draw it in kind of a ball and stick
- model, it would look like something like this.
- So this would be one carbon right there.
- Then you would have another carbon right over there, and
- another carbon right over there.
- And then you'd have your fourth carbon.
- And then your hydrogens.
- You would have a hydrogen coming out like this, like
- that, and then up like that.
- This guy would have two hydrogens that would
- stick out like that.
- This guy would have two hydrogens that
- stick out like that.
- And then finally this guy will also have three hydrogens, the
- ch3, just like that.
- Now, if we try to draw a Newman Projection, here's
- like, well, what do you consider the front, or the
- back, carbon in all of that.
- And you actually can pick.
- And what's interesting in a butane molecule is, if you
- pick this guy, so this is a one, two, three, four carbon,
- if you pick the two carbon as our front, and our three
- carbon as our back, and then we viewed this carbon, the ch3
- as kind of one of the add-ons on to that carbon, you can
- then do a Newman Projection.
- So let's try to do this.
- So this'll be the front one.
- So we'll put this carbon in the front, and we'll put this
- carbon over here, we'll put this carbon
- over here in the back.
- And before I even draw the Newman Projection, let me
- redraw this.
- But I'm just going to draw this, instead of with the
- hydrogens, the bonds, explicitly defined, I'm just
- going to call this a ch3.
- So let me redraw this.
- So I'll do this in orange.
- So you have this carbon.
- I'll do this as kind of as a modified ball and stick.
- So that carbon, it has a hydrogen, it has that hydrogen
- and that hydrogen.
- And instead of drawing this out, I'm going to just draw
- this whole thing right here and I'll do it in, I'll do it
- in magenta.
- I'm going to draw this whole thing as just a ch3.
- So I'm going to draw this whole thing as just a ch3.
- So I'll draw it really big, because it's not just one
- atom, it's four atoms. So this is our ch3.
- And, well, to do ball and stick everything really should
- be a ball, so I'll draw a ball there, a ball there.
- So that's our carbon number two, and then it has this bond
- over here to this carbon number three.
- Which, when we do our Newman Projection,
- we'll put in the back.
- So our carbon number three is like that.
- And then the carbon number three, it has two hydrogens,
- and then it has this.
- You can kind of view it as this methyl group attached to
- it, if you want.
- It has this ch3 attached to it right there.
- So I'll do the ch3, I'll do it in this blue color.
- And so we could draw it like this.
- So the ch3 is coming off-- so I'll draw it really big
- because it's not just one atom.
- So it's a ch3.
- And then you have your two hydrogens and they're-- sorry,
- you have your two hydrogens down here.
- So let me be very clear here.
- This hydrogen and that hydrogen, that's that hydrogen
- and that hydrogen, this thing here is that thing there.
- That big ball right there is this whole ball.
- And then let me find a-- I'll do green.
- This hydrogen and this hydrogen is this hydrogen and
- this hydrogen.
- And when you look at it this way, now you say, oh, now I
- can see how I would draw a Newman Projection.
- I put this in the front, that in the back.
- I treat this whole part of the molecule as just a
- group, if you will.
- It is a group.
- So lets do the Newman Projection here.
- And we can think about where it's most stable.
- So the way I've drawn it right here-- I'll do this as the
- front, this carbon two is going to
- be the front molecule.
- So you have the ch3 group going down.
- And then you have these two hydrogens,
- hydrogen, and hydrogen.
- That's the front.
- And in the back you have this blue one.
- You can imagine in the front, if we want to, maybe I'll do a
- little small orange thing to show this
- is the orange carbon.
- And then the blue carbon is going to be in the back.
- The blue carbon is in the back, I'll draw it like this.
- So that's my blue carbon.
- The way we've done it here, we have a ch3 pointing straight
- up, and then we have our two hydrogens.
- Now, just like we talked about in the first video on Newman
- Projections, all of these groups have-- these hydrogens
- have electron clouds around them.
- This whole ch3 group has a larger electron
- cloud around it.
- It's a carbon atom plus hydrogens.
- They all want to get away from each other.
- The ch3 is even a bigger molecule.
- So to some degree, it's going to play a bigger role in
- whether something has a higher or lower potential energy or
- whether it's wound or not.
- So I guess the most obvious, or maybe it's not obvious, but
- the ch3 groups, since they have the biggest electron
- crowd, they're kind of crowding the molecule.
- This ch3 group and this ch3 group, they're going to want
- to get as far away from each other as possible.
- So the way we did this, it looks kind of like our
- staggered conformation, but when we're dealing with actual
- methyl groups that are separated as far as they can
- from each other, we call this the
- anti-conformation right here.
- And if we think about dihedral angles between the two methyl
- groups, the dihedral angle here is 180 degrees.
- 180 degrees dihedral angle.
- And this is the lowest potential
- energy or the most stable.
- And if that confuses you when I talk about lowest potential
- energy, just think about it.
- A rock on the ground has a lower potential energy than a
- rock that is 50 feet in the air.
- A rock on the ground is also more stable.
- It's less likely to do something.
- Something 50 feet in the air, maybe if you nudge it a little
- bit, it'll fall off the cliff or wherever it is.
- Or maybe it's already falling.
- Who knows?
- It's going to move when you have higher potential energy.
- Or it takes very little for it to release energy.
- But when you have lower potential
- energy, you're more stable.
- So this is the most stable conformation.
- Now what are the other situations you could do here?
- Well, you could keep rotating these-- let's say we rotated
- the back carbon around clockwise, what are the other
- conformations we could get?
- And so let me just draw the front portion right here.
- So you have your ch3, and then you have your two hydrogens,
- hydrogen, and hydrogen.
- And let me copy and paste this.
- So there's two other real-- I mean, there's everything in
- between, but these are the ones that are interesting.
- Control copy, and then let me copy it, copy, and then paste.
- So I'll actually draw three of these.
- So then you have that.
- Then let me paste it one more time, and then you have that.
- So obviously this would be the front
- carbon in every situation.
- If I want I could make it a little orange dot to show that
- that's the front carbon.
- And then let me draw the back carbon.
- I should've copied and pasted this as well.
- So you have your back carbon in every situation.
- Now, if we were to rotate this character by 60 degrees--
- actually if we were to rotate the back by 60 degrees, what
- would it look like?
- Well, then we would have-- this hydrogen would move up
- there-- so then you would have this hydrogen.
- Actually if we were to move it by 120 degrees, I should say.
- This would be 60, and then another 120 degrees.
- So this hydrogen would go up there.
- This methyl group would now be over here, and then this
- hydrogen would go over here.
- So we've just rotated to this whole thing by 120 degrees.
- Now, this conformation, this was called the
- It's the most stable because the carbon-- the methyl
- groups, are as far away from each other as possible.
- This right here is called the Gauche conformation.
- Let me do this in a different-- and you can view
- this as the second most stable.
- At least the methyls are staggered.
- They're not directly behind each other.
- So here the methyls are as far apart from
- each other as possible.
- If you look at the ball and stick model, I actually drew
- it in that conformation right here.
- They're as far apart from each other.
- If you were to flip this molecule, if you were to flip
- it, this methyl would get closer to this methyl, and
- their electron clouds would start to crowd each other.
- So in this situation this is anti, most stable.
- If you rotate a little bit they'll get a little bit
- closer but they'll still be staggered.
- You get the Gauche conformation.
- Now, if we rotate this, if we rotate the back guy now 60
- degrees clockwise, what's going to happen?
- Well, then you're going to have an eclipsed conformation,
- where the carbons are directly, but where the methyl
- groups are directly behind each other.
- And that's going to be your least stable situation.
- So you'd have this guy-- and I'll draw it slightly-- so
- you'd have this guy, ch3 there, and then you would have
- your hydrogens that are right behind each other.
- So a hydrogen and a hydrogen.
- So in this situation where eclipsed-- this is the least
- stable, and also the most potential energy.
- And then if we were to go another 60 degrees from this,
- then we'd go to another Gauche conformation.
- If you rotate this another 60 degrees, then you'd have a ch3
- here, and then you would have-- this hydrogen would be
- up here, and then this hydrogen here.
- So this is staggered.
- The methyl groups are, at least they're not directly
- behind each other, but they're not as far as they could be if
- we were to rotate another 120 degrees and get to the
- So this one right here is also a Gauche conformation.
- So hopefully you understand now that, you just have to
- pick two carbons and then you can, if there's, kind of, big
- things attached to each of those carbons, you can just
- represent them as groups.
- And when you do that-- you'd use a Newman Projection for
- any part of a molecule.
- And when you do that, you can start to think about how it
- can rotate and what parts, or what versions of it, will be more or less stable
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