Newman projections 2

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Kind: captions
Language: en

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In the last video, we visualized
an ethane molecule

00:00:03.850 --> 00:00:04.890
with a Newman Projection.

00:00:04.890 --> 00:00:06.820
What I want to do in this video
is show that you can

00:00:06.820 --> 00:00:11.120
really visualize longer chains,
or even, we'll see in

00:00:11.120 --> 00:00:15.500
future videos, even cyclical,
ring-based carbon molecules

00:00:15.500 --> 00:00:17.240
with Newman Projections
as well.

00:00:17.240 --> 00:00:20.860
And I guess the next most
complex molecule to study

00:00:20.860 --> 00:00:23.220
would be butane.

00:00:23.220 --> 00:00:26.520
We could do propane, but butane
will be interesting.

00:00:26.520 --> 00:00:29.650
This was ethane right here,
butane will have four carbons.

00:00:29.650 --> 00:00:33.070
And if I were to draw it in
kind of a ball and stick

00:00:33.070 --> 00:00:34.800
model, it would look like
something like this.

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So this would be one
carbon right there.

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Then you would have another
carbon right over there, and

00:00:40.470 --> 00:00:42.930
another carbon right
over there.

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And then you'd have your
fourth carbon.

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And then your hydrogens.

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You would have a hydrogen coming
out like this, like

00:00:50.210 --> 00:00:52.420
that, and then up like that.

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This guy would have two
hydrogens that would

00:00:55.450 --> 00:00:56.920
stick out like that.

00:00:56.920 --> 00:00:58.670
This guy would have
two hydrogens that

00:00:58.670 --> 00:01:00.330
stick out like that.

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And then finally this guy will
also have three hydrogens, the

00:01:03.370 --> 00:01:06.540
ch3, just like that.

00:01:06.540 --> 00:01:09.430
Now, if we try to draw a Newman
Projection, here's

00:01:09.430 --> 00:01:11.970
like, well, what do you consider
the front, or the

00:01:11.970 --> 00:01:13.690
back, carbon in all of that.

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And you actually can pick.

00:01:14.950 --> 00:01:17.540
And what's interesting in a
butane molecule is, if you

00:01:17.540 --> 00:01:23.830
pick this guy, so this is a one,
two, three, four carbon,

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if you pick the two carbon as
our front, and our three

00:01:26.970 --> 00:01:31.360
carbon as our back, and then we
viewed this carbon, the ch3

00:01:31.360 --> 00:01:34.610
as kind of one of the add-ons
on to that carbon, you can

00:01:34.610 --> 00:01:35.965
then do a Newman Projection.

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So let's try to do this.

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So this'll be the front one.

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So we'll put this carbon in the
front, and we'll put this

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carbon over here, we'll
put this carbon

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over here in the back.

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And before I even draw the
Newman Projection, let me

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redraw this.

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But I'm just going to draw
this, instead of with the

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hydrogens, the bonds, explicitly
defined, I'm just

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going to call this a ch3.

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So let me redraw this.

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So I'll do this in orange.

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So you have this carbon.

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I'll do this as kind of as a
modified ball and stick.

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So that carbon, it has a
hydrogen, it has that hydrogen

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and that hydrogen.

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And instead of drawing this out,
I'm going to just draw

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this whole thing right here and
I'll do it in, I'll do it

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in magenta.

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I'm going to draw this whole
thing as just a ch3.

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So I'm going to draw this whole
thing as just a ch3.

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So I'll draw it really big,
because it's not just one

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atom, it's four atoms.
So this is our ch3.

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And, well, to do ball and stick
everything really should

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be a ball, so I'll draw a ball
there, a ball there.

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So that's our carbon number two,
and then it has this bond

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over here to this carbon
number three.

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Which, when we do our
Newman Projection,

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we'll put in the back.

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So our carbon number
three is like that.

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And then the carbon number
three, it has two hydrogens,

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and then it has this.

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You can kind of view it as this
methyl group attached to

00:03:08.940 --> 00:03:09.570
it, if you want.

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It has this ch3 attached
to it right there.

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So I'll do the ch3, I'll do
it in this blue color.

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And so we could draw
it like this.

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So the ch3 is coming off-- so
I'll draw it really big

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because it's not
just one atom.

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So it's a ch3.

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And then you have your two
hydrogens and they're-- sorry,

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you have your two hydrogens
down here.

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So let me be very clear here.

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This hydrogen and that hydrogen,
that's that hydrogen

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and that hydrogen, this thing
here is that thing there.

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That big ball right there
is this whole ball.

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And then let me find
a-- I'll do green.

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This hydrogen and this hydrogen
is this hydrogen and

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this hydrogen.

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And when you look at it this
way, now you say, oh, now I

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can see how I would draw
a Newman Projection.

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I put this in the front,
that in the back.

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I treat this whole part of
the molecule as just a

00:04:07.810 --> 00:04:08.810
group, if you will.

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It is a group.

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So lets do the Newman
Projection here.

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And we can think about where
it's most stable.

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So the way I've drawn it right
here-- I'll do this as the

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front, this carbon
two is going to

00:04:19.940 --> 00:04:21.300
be the front molecule.

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So you have the ch3
group going down.

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And then you have these
two hydrogens,

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hydrogen, and hydrogen.

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That's the front.

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And in the back you have
this blue one.

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You can imagine in the front, if
we want to, maybe I'll do a

00:04:39.510 --> 00:04:41.350
little small orange
thing to show this

00:04:41.350 --> 00:04:42.700
is the orange carbon.

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And then the blue carbon is
going to be in the back.

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The blue carbon is in the back,
I'll draw it like this.

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So that's my blue carbon.

00:04:50.680 --> 00:04:56.230
The way we've done it here, we
have a ch3 pointing straight

00:04:56.230 --> 00:04:58.130
up, and then we have
our two hydrogens.

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Now, just like we talked about
in the first video on Newman

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Projections, all of these groups
have-- these hydrogens

00:05:08.220 --> 00:05:09.820
have electron clouds
around them.

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This whole ch3 group has
a larger electron

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cloud around it.

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It's a carbon atom
plus hydrogens.

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They all want to get away
from each other.

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The ch3 is even a
bigger molecule.

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So to some degree, it's going
to play a bigger role in

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whether something has a higher
or lower potential energy or

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whether it's wound or not.

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So I guess the most obvious, or
maybe it's not obvious, but

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the ch3 groups, since they
have the biggest electron

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crowd, they're kind of crowding
the molecule.

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This ch3 group and this ch3
group, they're going to want

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to get as far away from each
other as possible.

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So the way we did this, it
looks kind of like our

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staggered conformation, but when
we're dealing with actual

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methyl groups that are separated
as far as they can

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from each other, we
call this the

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anti-conformation right here.

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And if we think about dihedral
angles between the two methyl

00:06:04.870 --> 00:06:11.975
groups, the dihedral angle
here is 180 degrees.

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180 degrees dihedral angle.

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And this is the lowest
potential

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energy or the most stable.

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And if that confuses you when I
talk about lowest potential

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energy, just think about it.

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A rock on the ground has a lower
potential energy than a

00:06:30.380 --> 00:06:32.850
rock that is 50 feet
in the air.

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A rock on the ground is
also more stable.

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It's less likely to
do something.

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Something 50 feet in the air,
maybe if you nudge it a little

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bit, it'll fall off the cliff
or wherever it is.

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Or maybe it's already falling.

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Who knows?

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It's going to move when you have
higher potential energy.

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Or it takes very little for
it to release energy.

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But when you have
lower potential

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energy, you're more stable.

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So this is the most stable
conformation.

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Now what are the other
situations you could do here?

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Well, you could keep rotating
these-- let's say we rotated

00:07:00.050 --> 00:07:03.590
the back carbon around
clockwise, what are the other

00:07:03.590 --> 00:07:05.310
conformations we could get?

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And so let me just draw the
front portion right here.

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So you have your ch3, and then
you have your two hydrogens,

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hydrogen, and hydrogen.

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And let me copy and
paste this.

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So there's two other real-- I
mean, there's everything in

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between, but these are the ones
that are interesting.

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Control copy, and then let me
copy it, copy, and then paste.

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So I'll actually draw
three of these.

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So then you have that.

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Then let me paste it one more
time, and then you have that.

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So obviously this would
be the front

00:07:46.250 --> 00:07:48.330
carbon in every situation.

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If I want I could make it a
little orange dot to show that

00:07:51.755 --> 00:07:53.870
that's the front carbon.

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And then let me draw
the back carbon.

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I should've copied and
pasted this as well.

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So you have your back carbon
in every situation.

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Now, if we were to rotate this
character by 60 degrees--

00:08:07.150 --> 00:08:09.880
actually if we were to rotate
the back by 60 degrees, what

00:08:09.880 --> 00:08:11.100
would it look like?

00:08:11.100 --> 00:08:15.660
Well, then we would have-- this
hydrogen would move up

00:08:15.660 --> 00:08:19.300
there-- so then you would
have this hydrogen.

00:08:19.300 --> 00:08:22.220
Actually if we were to move it
by 120 degrees, I should say.

00:08:22.220 --> 00:08:25.650
This would be 60, and then
another 120 degrees.

00:08:25.650 --> 00:08:27.240
So this hydrogen would
go up there.

00:08:30.750 --> 00:08:37.299
This methyl group would now be
over here, and then this

00:08:37.299 --> 00:08:39.440
hydrogen would go over here.

00:08:39.440 --> 00:08:44.550
So we've just rotated to this
whole thing by 120 degrees.

00:08:44.550 --> 00:08:46.020
Now, this conformation,
this was called the

00:08:46.020 --> 00:08:47.060
anti-conformation.

00:08:47.060 --> 00:08:49.530
It's the most stable because
the carbon-- the methyl

00:08:49.530 --> 00:08:52.300
groups, are as far away from
each other as possible.

00:08:52.300 --> 00:08:54.110
This right here is called
the Gauche conformation.

00:08:57.010 --> 00:09:04.590
Let me do this in a different--
and you can view

00:09:04.590 --> 00:09:06.460
this as the second
most stable.

00:09:06.460 --> 00:09:08.720
At least the methyls
are staggered.

00:09:08.720 --> 00:09:10.470
They're not directly
behind each other.

00:09:10.470 --> 00:09:12.540
So here the methyls are
as far apart from

00:09:12.540 --> 00:09:13.450
each other as possible.

00:09:13.450 --> 00:09:16.560
If you look at the ball and
stick model, I actually drew

00:09:16.560 --> 00:09:18.140
it in that conformation
right here.

00:09:18.140 --> 00:09:19.650
They're as far apart
from each other.

00:09:19.650 --> 00:09:22.170
If you were to flip this
molecule, if you were to flip

00:09:22.170 --> 00:09:24.570
it, this methyl would get closer
to this methyl, and

00:09:24.570 --> 00:09:27.440
their electron clouds would
start to crowd each other.

00:09:27.440 --> 00:09:30.270
So in this situation this
is anti, most stable.

00:09:30.270 --> 00:09:31.960
If you rotate a little bit
they'll get a little bit

00:09:31.960 --> 00:09:34.360
closer but they'll still
be staggered.

00:09:34.360 --> 00:09:36.180
You get the Gauche
conformation.

00:09:36.180 --> 00:09:42.070
Now, if we rotate this, if we
rotate the back guy now 60

00:09:42.070 --> 00:09:48.350
degrees clockwise, what's
going to happen?

00:09:48.350 --> 00:09:50.410
Well, then you're going to have
an eclipsed conformation,

00:09:50.410 --> 00:09:53.320
where the carbons are directly,
but where the methyl

00:09:53.320 --> 00:09:56.240
groups are directly
behind each other.

00:09:56.240 --> 00:09:59.110
And that's going to be your
least stable situation.

00:09:59.110 --> 00:09:59.430
Right?

00:09:59.430 --> 00:10:03.380
So you'd have this guy-- and
I'll draw it slightly-- so

00:10:03.380 --> 00:10:06.950
you'd have this guy, ch3 there,
and then you would have

00:10:06.950 --> 00:10:09.720
your hydrogens that are right
behind each other.

00:10:09.720 --> 00:10:12.000
So a hydrogen and a hydrogen.

00:10:12.000 --> 00:10:14.600
So in this situation where
eclipsed-- this is the least

00:10:14.600 --> 00:10:19.080
stable, and also the most
potential energy.

00:10:19.080 --> 00:10:22.160
And then if we were to go
another 60 degrees from this,

00:10:22.160 --> 00:10:23.990
then we'd go to another
Gauche conformation.

00:10:23.990 --> 00:10:27.430
If you rotate this another 60
degrees, then you'd have a ch3

00:10:27.430 --> 00:10:30.750
here, and then you would have--
this hydrogen would be

00:10:30.750 --> 00:10:32.730
up here, and then this
hydrogen here.

00:10:32.730 --> 00:10:34.120
So this is staggered.

00:10:34.120 --> 00:10:37.670
The methyl groups are, at least
they're not directly

00:10:37.670 --> 00:10:39.990
behind each other, but they're
not as far as they could be if

00:10:39.990 --> 00:10:42.060
we were to rotate another 120
degrees and get to the

00:10:42.060 --> 00:10:43.460
anti-conformation.

00:10:43.460 --> 00:10:46.520
So this one right here is also
a Gauche conformation.

00:10:46.520 --> 00:10:49.020
So hopefully you understand
now that, you just have to

00:10:49.020 --> 00:10:52.030
pick two carbons and then you
can, if there's, kind of, big

00:10:52.030 --> 00:10:54.180
things attached to each of those
carbons, you can just

00:10:54.180 --> 00:10:55.850
represent them as groups.

00:10:55.850 --> 00:10:59.650
And when you do that-- you'd
use a Newman Projection for

00:10:59.650 --> 00:11:03.400
any part of a molecule.

00:11:03.400 --> 00:11:05.570
And when you do that, you can
start to think about how it

00:11:05.570 --> 00:11:10.490
can rotate and what parts, or
what versions of it, will be--


Newman projections

WEBVTT
Kind: captions
Language: en

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In the video on sp3 hybridized
orbitals, we went in pretty

00:00:04.500 --> 00:00:07.910
good detail about how a methane
molecule looks.

00:00:07.910 --> 00:00:10.590
But just as a bit of a review,
it's the tetrahedral shape.

00:00:10.590 --> 00:00:12.970
You have a carbon in the middle,
and then you would

00:00:12.970 --> 00:00:15.870
have a hydrogen-- you can
imagine I'm drawing it like

00:00:15.870 --> 00:00:18.580
this because this hydrogen is
poking out of the page.

00:00:18.580 --> 00:00:21.780
Then maybe you have another
hydrogen that's in the page.

00:00:21.780 --> 00:00:23.640
You have one above the carbon,
and you have one

00:00:23.640 --> 00:00:24.630
that's behind the page.

00:00:24.630 --> 00:00:30.760
You could imagine it's like a
tripod with a pole sticking

00:00:30.760 --> 00:00:32.409
out of the top of the tripod.

00:00:32.409 --> 00:00:34.690
Or if you were to imagine the
shape another way, if you were

00:00:34.690 --> 00:00:41.140
to connect the hydrogens, you
would have a four-sided

00:00:41.140 --> 00:00:44.530
pyramid with a triangle
as each of the sides.

00:00:44.530 --> 00:00:46.230
So it would to look something
like this.

00:00:50.096 --> 00:00:53.320
I'm trying my best to draw--
the pyramid would look

00:00:53.320 --> 00:00:55.060
something like this if you
could see through it.

00:00:55.060 --> 00:00:59.780
So this would be one side,
another side would be over

00:00:59.780 --> 00:01:04.685
here, and then the backside
would be over here, and then

00:01:04.685 --> 00:01:06.170
the fourth side is actually
the side that's

00:01:06.170 --> 00:01:07.430
transparent out front.

00:01:07.430 --> 00:01:11.970
So the fourth side would be the
actual kind of thing that

00:01:11.970 --> 00:01:13.790
we're looking through when
we look at this pyramid.

00:01:13.790 --> 00:01:16.610
It would be this front
side right over here.

00:01:16.610 --> 00:01:18.910
So you can imagine it different
ways, this was the

00:01:18.910 --> 00:01:20.160
case with methane.

00:01:22.700 --> 00:01:26.590
Now let's extend this into
a slightly more complex

00:01:26.590 --> 00:01:28.400
molecule, and that's ethane.

00:01:28.400 --> 00:01:30.710
So the way we've been drawing
it so far-- I guess the

00:01:30.710 --> 00:01:33.260
simplest way to draw ethane,
is just like that.

00:01:33.260 --> 00:01:36.580
By implication this is ethane.

00:01:36.580 --> 00:01:39.810
By implication you have a carbon
there, and a carbon

00:01:39.810 --> 00:01:43.010
there, and they'll each have
three hydrogens bonded to it.

00:01:43.010 --> 00:01:45.310
And we've drawn it something
like this.

00:01:45.310 --> 00:01:50.150
Three hydrogens bonded to
each of these guys.

00:01:50.150 --> 00:01:54.240
But now we know that carbon
has these sp3 hybridized

00:01:54.240 --> 00:01:56.970
orbitals, that it likes to form
more of a tetrahedral

00:01:56.970 --> 00:01:58.780
shape when it bonds.

00:01:58.780 --> 00:02:01.550
So an ethane molecule would
actually look more like this.

00:02:01.550 --> 00:02:03.270
Let me draw the carbons.

00:02:03.270 --> 00:02:04.810
So I'll do the carbons
in orange.

00:02:04.810 --> 00:02:07.030
So if that's the carbon
and that's the carbon.

00:02:07.030 --> 00:02:09.759
So you can imagine you have
a carbon molecule here.

00:02:09.759 --> 00:02:11.710
I'll draw it as this
little circle.

00:02:11.710 --> 00:02:13.370
And then if we have some
perspective, so the

00:02:13.370 --> 00:02:15.350
carbon-carbon bond is going
to look like that.

00:02:15.350 --> 00:02:16.520
And then you have
another carbon

00:02:16.520 --> 00:02:19.150
molecule right over there.

00:02:19.150 --> 00:02:21.160
So that's that bond over here.

00:02:21.160 --> 00:02:23.880
And we want both the carbons,
all of their bonds to be kind

00:02:23.880 --> 00:02:25.820
of in a tetrahedral shape.

00:02:25.820 --> 00:02:28.870
So then you could imagine
this bond over

00:02:28.870 --> 00:02:31.826
here going like this.

00:02:31.826 --> 00:02:33.630
This bond going like that.

00:02:33.630 --> 00:02:35.690
And you have your hydrogen
at the end.

00:02:35.690 --> 00:02:38.210
Let's make the green circles
the hydrogens.

00:02:38.210 --> 00:02:42.180
So you have that hydrogen, and
then-- or actually just the

00:02:42.180 --> 00:02:43.900
circles, we'll call them
hydrogen-- and then you can

00:02:43.900 --> 00:02:46.970
imagine this one, maybe it's
coming out of the page a

00:02:46.970 --> 00:02:47.510
little bit.

00:02:47.510 --> 00:02:48.760
That is that hydrogen.

00:02:51.420 --> 00:02:54.030
Let me label the hydrogens,
actually.

00:02:54.030 --> 00:02:56.470
I'm doing it in all different
colors so you can see what I'm

00:02:56.470 --> 00:02:56.900
talking about.

00:02:56.900 --> 00:02:59.920
And then this hydrogen is going
right below it, maybe

00:02:59.920 --> 00:03:01.200
pointed back a little bit.

00:03:01.200 --> 00:03:03.370
So that hydrogen is
right over there.

00:03:03.370 --> 00:03:06.380
So you can see this carbon,
its bonds have

00:03:06.380 --> 00:03:07.470
a tetrahedral shape.

00:03:07.470 --> 00:03:09.960
Or, if you just looked at this
part of it, these would be the

00:03:09.960 --> 00:03:11.630
base of the tripod and
this would be the

00:03:11.630 --> 00:03:12.580
thing sticking up.

00:03:12.580 --> 00:03:15.350
Now for this carbon it would
be very similar idea.

00:03:18.380 --> 00:03:21.990
This hydrogen right
here, might be

00:03:21.990 --> 00:03:23.240
sticking down like this.

00:03:25.730 --> 00:03:27.460
And I'll stop switching
colors soon enough.

00:03:27.460 --> 00:03:28.230
It takes a lot of time.

00:03:28.230 --> 00:03:31.100
That hydrogen over there, it's
pointing out in that

00:03:31.100 --> 00:03:33.870
direction like that.

00:03:33.870 --> 00:03:35.850
And then you would have,
let's see what

00:03:35.850 --> 00:03:36.820
colors do I have left?

00:03:36.820 --> 00:03:38.180
Well, I'll just do yellow.

00:03:38.180 --> 00:03:39.610
That hydrogen right
there, maybe it's

00:03:39.610 --> 00:03:41.110
pointing out like that.

00:03:41.110 --> 00:03:46.030
So this is a possible
configuration for ethane.

00:03:46.030 --> 00:03:48.220
And the way that I've drawn this
right now, and you can

00:03:48.220 --> 00:03:51.010
actually have a model that has
this, where you have little

00:03:51.010 --> 00:03:54.050
wooden sticks with balls and
this, the balls to represent

00:03:54.050 --> 00:03:58.100
the actual atoms, this is called
a ball and stick model.

00:04:04.550 --> 00:04:06.140
And this is a ball and stick
model for ethane.

00:04:06.140 --> 00:04:08.490
Now a simpler way we could
have drawn this, this is

00:04:08.490 --> 00:04:11.100
called a horse shoe projection--
or actually it's

00:04:11.100 --> 00:04:12.310
a sawhorse production.

00:04:12.310 --> 00:04:13.450
I always say horse shoe.

00:04:13.450 --> 00:04:15.290
A sawhorse projection.

00:04:15.290 --> 00:04:16.230
It would look like this.

00:04:16.230 --> 00:04:20.060
This exact same configuration
of ethane in a sawhorse

00:04:20.060 --> 00:04:21.110
projection.

00:04:21.110 --> 00:04:24.330
And you know what a sawhorse
looks like, well, it looks

00:04:24.330 --> 00:04:26.130
like what I'm about to draw.

00:04:26.130 --> 00:04:27.520
It looks like this.

00:04:27.520 --> 00:04:29.720
So you could, well I could
draw it exactly the

00:04:29.720 --> 00:04:30.760
way I drew it here.

00:04:30.760 --> 00:04:35.280
So you have the carbon, carbon,
and then you have the

00:04:35.280 --> 00:04:41.910
hydrogen, hydrogen, hydrogen,
and then you have a-- well,

00:04:41.910 --> 00:04:44.310
the way I've drawn it up
here is more like this.

00:04:44.310 --> 00:04:45.850
Just so we see the parallel
and then we can

00:04:45.850 --> 00:04:47.240
rotate things around.

00:04:47.240 --> 00:04:51.690
The way I drew it up here,
you have a hydrogen,

00:04:51.690 --> 00:04:53.810
hydrogen, and hydrogen.

00:04:53.810 --> 00:04:56.340
And then over here you
have a hydrogen,

00:04:56.340 --> 00:04:58.020
hydrogen, and hydrogen.

00:04:58.020 --> 00:05:04.830
This is a sawhorse projection.

00:05:04.830 --> 00:05:07.290
Now, either way you depict
it, I mean, these are

00:05:07.290 --> 00:05:08.030
really the same way.

00:05:08.030 --> 00:05:09.650
This is kind of just like
the lazier way of

00:05:09.650 --> 00:05:10.550
doing it on some level.

00:05:10.550 --> 00:05:12.620
You're not drawing all of these
circles and all of that,

00:05:12.620 --> 00:05:14.680
and you're putting a little
less care into actually

00:05:14.680 --> 00:05:17.130
showing the angle, how things
are angled away from the

00:05:17.130 --> 00:05:19.010
carbon and showing the
tetrahedral shape.

00:05:19.010 --> 00:05:21.885
But in either case, when you
start visualizing the molecule

00:05:21.885 --> 00:05:24.510
in this way, you start to
realize there's, well, there's

00:05:24.510 --> 00:05:26.430
actually infinite ways that
these things can be

00:05:26.430 --> 00:05:27.110
configured.

00:05:27.110 --> 00:05:31.370
And it all comes from the notion
that this is just a

00:05:31.370 --> 00:05:32.700
sigma bond right here.

00:05:32.700 --> 00:05:35.690
We learned that in the video on
sp3 hybridization and sigma

00:05:35.690 --> 00:05:36.890
and pi bonds.

00:05:36.890 --> 00:05:41.030
This is just a sigma bond.

00:05:41.030 --> 00:05:43.250
And so we can rotate
around the bonds.

00:05:43.250 --> 00:05:46.930
One of these carbons could
rotate around the axis of that

00:05:46.930 --> 00:05:49.150
bond without the other
carbon having to

00:05:49.150 --> 00:05:50.240
necessarily rotate with it.

00:05:50.240 --> 00:05:52.760
If this was a double bond, if
this was a pi bond, they would

00:05:52.760 --> 00:05:54.280
have to rotate together.

00:05:54.280 --> 00:05:57.230
So you could have a situation
like I've drawn here or you

00:05:57.230 --> 00:05:59.490
could have a situation where
they're kind of rotated the

00:05:59.490 --> 00:06:00.380
inverse of each other.

00:06:00.380 --> 00:06:01.570
And this is what I mean.

00:06:01.570 --> 00:06:03.210
So I'll do a ball and stick.

00:06:03.210 --> 00:06:06.760
So let's say this is our front
carbon, that is our back

00:06:06.760 --> 00:06:09.080
carbon, and we'll compare it
to this one over here.

00:06:09.080 --> 00:06:11.710
So let me draw this guy
the exact same way.

00:06:11.710 --> 00:06:18.900
So he's got a hydrogen down
here, he's got a hydrogen up

00:06:18.900 --> 00:06:23.890
there, and then he's got
a hydrogen up here.

00:06:23.890 --> 00:06:26.510
So that part of the ethane
looks identical.

00:06:26.510 --> 00:06:28.410
Now what I'm going to do is I'm
going to flip the other

00:06:28.410 --> 00:06:29.240
side of the ethane.

00:06:29.240 --> 00:06:31.850
I want you to pay close
attention, because hopefully

00:06:31.850 --> 00:06:34.310
you'll see the difference
between the two.

00:06:34.310 --> 00:06:37.440
So instead of doing this blue
ethane down here-- this blue

00:06:37.440 --> 00:06:39.610
hydrogen down here-- I'm
going to do it on top.

00:06:39.610 --> 00:06:44.310
So this blue one, I want to
do that in blue, this blue

00:06:44.310 --> 00:06:47.280
hydrogen, put it on top.

00:06:47.280 --> 00:06:48.720
So I'm just rotating
this around.

00:06:48.720 --> 00:06:50.850
So the blue hydrogen's on top.

00:06:50.850 --> 00:06:53.950
So I've rotated it so the
blue one's on top now.

00:06:53.950 --> 00:06:59.710
And now the green one is
going to go over here.

00:06:59.710 --> 00:07:04.060
So now the green hydrogen
is now over here.

00:07:04.060 --> 00:07:07.310
And then this purple, or this
magenta hydrogen, the way I've

00:07:07.310 --> 00:07:09.010
rotated it, is now going
to go over here.

00:07:11.780 --> 00:07:14.680
So what's the difference between
this configuration and

00:07:14.680 --> 00:07:15.830
this configuration right here?

00:07:15.830 --> 00:07:16.870
And we could have
had every other

00:07:16.870 --> 00:07:18.040
configuration in between.

00:07:18.040 --> 00:07:19.700
But what's the real
difference here?

00:07:19.700 --> 00:07:23.260
Well, here the hydrogen, you
could imagine that hydrogen is

00:07:23.260 --> 00:07:26.510
kind of, if you were looking
from that direction, that

00:07:26.510 --> 00:07:28.890
hydrogen is directly behind that
hydrogen, that hydrogen

00:07:28.890 --> 00:07:31.060
is directly behind that
hydrogen, that hydrogen is

00:07:31.060 --> 00:07:32.360
directly behind that.

00:07:32.360 --> 00:07:35.740
This is called an eclipsed
configuration, or eclipsed

00:07:35.740 --> 00:07:37.160
conformation.

00:07:37.160 --> 00:07:43.340
So eclipsed conformation.

00:07:47.050 --> 00:07:49.620
And this right here, nothing
is behind anything.

00:07:49.620 --> 00:07:51.380
If you went straight
back from this guy,

00:07:51.380 --> 00:07:52.140
you'd get to this point.

00:07:52.140 --> 00:07:53.010
And no one's behind it.

00:07:53.010 --> 00:07:54.470
And if you went straight forward
from this guy you'll

00:07:54.470 --> 00:07:58.850
get-- So in no way are any of
the guys in the back-- once

00:07:58.850 --> 00:08:00.750
again, if your viewing from
this direction-- are they

00:08:00.750 --> 00:08:02.400
blocked by any of
the people here.

00:08:02.400 --> 00:08:03.965
So we call this a staggered
conformation.

00:08:08.900 --> 00:08:10.670
Now, why do we even care?

00:08:10.670 --> 00:08:15.190
OK, I can twist around
this back molecule.

00:08:15.190 --> 00:08:19.890
What's that even going to do for
our actual-- why does it

00:08:19.890 --> 00:08:20.530
even matter?

00:08:20.530 --> 00:08:22.500
Well, one, it's just interesting
that you can

00:08:22.500 --> 00:08:25.720
actually change, that this thing
can twist around without

00:08:25.720 --> 00:08:29.870
changing the front-- without the
front molecule having to

00:08:29.870 --> 00:08:30.940
twist with it.

00:08:30.940 --> 00:08:33.600
But even more important, these
have different energy levels,

00:08:33.600 --> 00:08:36.590
so you can kind of think of
them as you're kind of

00:08:36.590 --> 00:08:39.630
twisting a spring and the spring
might want to go back

00:08:39.630 --> 00:08:41.610
to one conformation
or another.

00:08:41.610 --> 00:08:43.760
And to visualize it a little
better, I'll draw what's

00:08:43.760 --> 00:08:46.580
called a Newman Projection.

00:08:46.580 --> 00:08:49.150
So I'm going to draw this exact
thing, but with a Newman

00:08:49.150 --> 00:08:51.790
Projection, you draw the carbon
molecules directly in

00:08:51.790 --> 00:08:54.890
front or directly behind
each other.

00:08:54.890 --> 00:08:58.570
So in this situation, you would
draw the carbon molecule

00:08:58.570 --> 00:09:02.040
in front, would just be the
intersection of these bonds.

00:09:02.040 --> 00:09:06.640
So for a Newman Projection--
let me draw that out.

00:09:06.640 --> 00:09:14.320
So it's a Newman Projection and
I'll start with the Newman

00:09:14.320 --> 00:09:17.290
Projection for the staggered
conformation.

00:09:17.290 --> 00:09:20.460
So in the front-- we'll consider
this carbon the front

00:09:20.460 --> 00:09:23.340
carbon-- we have our
hydrogen pointing

00:09:23.340 --> 00:09:28.095
straight down like that.

00:09:28.095 --> 00:09:31.700
And we have a hydrogen
coming out to the

00:09:31.700 --> 00:09:33.420
top left, like that.

00:09:33.420 --> 00:09:36.020
And then we have this
hydrogen over here

00:09:36.020 --> 00:09:37.380
coming up to the right.

00:09:37.380 --> 00:09:39.400
I want to do that in
that same color.

00:09:42.020 --> 00:09:45.010
So the front carbon is
implicitly at the intersection

00:09:45.010 --> 00:09:47.060
of the bonds of these
three hydrogens.

00:09:47.060 --> 00:09:52.260
And then the back carbon-- I
said the front carbon is the

00:09:52.260 --> 00:09:54.490
intersection of the bonds of
these three hydrogens-- the

00:09:54.490 --> 00:09:57.480
back carbon you represented
as a circle.

00:09:57.480 --> 00:09:59.680
So the circle represents
the back of carbon.

00:09:59.680 --> 00:10:01.740
The front carbon is kind
of that point there.

00:10:01.740 --> 00:10:03.680
This is a way of
visualizing it.

00:10:03.680 --> 00:10:06.990
But if we were to draw it this
way, the back carbon now has

00:10:06.990 --> 00:10:09.520
that blue hydrogen popping
off of it.

00:10:09.520 --> 00:10:19.580
So it has that blue hydrogen,
this green hydrogen, and then

00:10:19.580 --> 00:10:20.830
this magenta hydrogen.

00:10:23.570 --> 00:10:26.300
And when you look at it like
this, it is more clear that

00:10:26.300 --> 00:10:26.830
it's staggered.

00:10:26.830 --> 00:10:29.820
We're just looking straight on
to this ethane molecule.

00:10:29.820 --> 00:10:31.520
When we look straight on, the
front carbon, they're

00:10:31.520 --> 00:10:32.880
obviously blocking each other.

00:10:32.880 --> 00:10:35.370
But this way you can see the
front carbon's hydrogens are

00:10:35.370 --> 00:10:37.020
staggered relative
to the back ones.

00:10:37.020 --> 00:10:40.230
So this is right here, once
again, this is staggered.

00:10:40.230 --> 00:10:43.600
Now let's draw the eclipsed
conformation as a Newman

00:10:43.600 --> 00:10:44.720
Projection.

00:10:44.720 --> 00:10:46.450
So as a Newman Projection
the front's

00:10:46.450 --> 00:10:47.390
going to look the same.

00:10:47.390 --> 00:10:53.860
You have a hydrogen there, you
have this hydrogen, you have

00:10:53.860 --> 00:10:56.800
that hydrogen, and then you
have that blue, or I guess

00:10:56.800 --> 00:10:58.820
that purple hydrogen,
down here.

00:10:58.820 --> 00:11:00.270
So that's the front of it.

00:11:00.270 --> 00:11:01.750
But the back, they're
right behind it's.

00:11:01.750 --> 00:11:03.260
So let me draw the
back carbon.

00:11:03.260 --> 00:11:06.590
The front carbon is kind of
represented by just that dot.

00:11:06.590 --> 00:11:11.020
The back carbon we'll
represent like that.

00:11:11.020 --> 00:11:13.770
And the staggered conformation,
if this guy's

00:11:13.770 --> 00:11:16.280
really behind that, you're going
to have to draw it like,

00:11:16.280 --> 00:11:18.070
right there, like
right behind it.

00:11:18.070 --> 00:11:21.100
But since that's a little bit
messy, normally when people

00:11:21.100 --> 00:11:27.780
draw a staggered projection-- an
eclipsed conformation, as a

00:11:27.780 --> 00:11:29.270
Newman Projection.

00:11:29.270 --> 00:11:32.910
Instead of directly eclipsing
that last, that back hydrogen,

00:11:32.910 --> 00:11:35.720
they'll put it to the right a
little, or they'll push it off

00:11:35.720 --> 00:11:36.500
a little bit.

00:11:36.500 --> 00:11:38.010
So that's that hydrogen.

00:11:38.010 --> 00:11:39.450
That magenta hydrogen
is right there.

00:11:39.450 --> 00:11:42.790
It's really right behind the
front one, but this is just so

00:11:42.790 --> 00:11:44.590
you can actually see
that it's there.

00:11:44.590 --> 00:11:47.210
And then finally you have this
blue one down there.

00:11:47.210 --> 00:11:51.590
So that blue one is going
to be right over here.

00:11:51.590 --> 00:11:57.690
So this is the eclipsed
conformation as a Newman

00:11:57.690 --> 00:11:58.940
Projection.

00:12:03.430 --> 00:12:05.290
And as you can see,
it's eclipsed.

00:12:05.290 --> 00:12:07.280
The back hydrogens are eclipsed
by the front ones.

00:12:07.280 --> 00:12:08.700
If I were to draw it perfectly,
they would be

00:12:08.700 --> 00:12:09.700
right behind it.

00:12:09.700 --> 00:12:13.510
Now there's one other piece of,
I guess one more idea, I

00:12:13.510 --> 00:12:16.250
want to introduce you to, and
that's the notion of the angle

00:12:16.250 --> 00:12:18.040
between the different
hydrogens.

00:12:18.040 --> 00:12:20.690
So if you wanted to say, well,
what is this angle?

00:12:20.690 --> 00:12:24.690
What is this angle between the
blue hydrogen and this pink

00:12:24.690 --> 00:12:25.770
hydrogen right here?

00:12:25.770 --> 00:12:27.720
Now, when you actually think
of it in three dimensions,

00:12:27.720 --> 00:12:30.340
it's like, wow, you can't really
say the angle over here

00:12:30.340 --> 00:12:31.350
between blue and the pink.

00:12:31.350 --> 00:12:33.840
But on a Newman Projection, when
you're just saying how

00:12:33.840 --> 00:12:36.560
much are they rotated away from
each other, this angle

00:12:36.560 --> 00:12:38.130
right here is called
a dihedral angle.

00:12:43.490 --> 00:12:46.200
Sometimes it's just said, you
know, this hydrogen relative

00:12:46.200 --> 00:12:50.160
to that hydrogen has a DA of,
in this case, 60 degrees.

00:12:50.160 --> 00:12:53.120
In this case, this hydrogen
relative to that hydrogen has

00:12:53.120 --> 00:12:54.970
a dihedral angle of
zero degrees.

00:12:54.970 --> 00:12:57.740
And it's a way of saying,
how staggered, or how

00:12:57.740 --> 00:12:58.920
eclipsed, you are.

00:12:58.920 --> 00:13:00.990
Now, one last thing I touched on
the idea, so again, why do

00:13:00.990 --> 00:13:02.250
we even care?

00:13:02.250 --> 00:13:05.230
Well, all of these hydrogens
have electron clouds around

00:13:05.230 --> 00:13:06.650
them, and all of these
bonds have electron

00:13:06.650 --> 00:13:07.270
clouds around them.

00:13:07.270 --> 00:13:09.960
And electron clouds, they're all
negative, so they want to

00:13:09.960 --> 00:13:12.140
get as far away from each
other as possible.

00:13:12.140 --> 00:13:14.580
And they're all stable now,
because they've bonded in ways

00:13:14.580 --> 00:13:17.090
that they have nice
stable structures.

00:13:17.090 --> 00:13:19.890
Everyone feels like they
have full valence

00:13:19.890 --> 00:13:21.820
shells, full orbitals.

00:13:21.820 --> 00:13:24.100
And so the electron
clouds want to get

00:13:24.100 --> 00:13:25.440
away from each other.

00:13:25.440 --> 00:13:31.560
Now in this situation, in the
eclipsed conformation, this

00:13:31.560 --> 00:13:35.190
hydrogen and this hydrogen--
let me do it in-- this

00:13:35.190 --> 00:13:40.050
hydrogen and this hydrogen are
closer to each other than when

00:13:40.050 --> 00:13:41.680
you go to the staggered
conformation.

00:13:41.680 --> 00:13:44.070
The staggered conformation, the
closest hydrogen to this

00:13:44.070 --> 00:13:47.960
guy is going to be either that
hydrogen or that hydrogen.

00:13:47.960 --> 00:13:51.300
But they're both further away
than this hydrogen was in the

00:13:51.300 --> 00:13:52.720
eclipsed conformation.

00:13:52.720 --> 00:13:56.060
So in general, the staggered
conformation is going to be

00:13:56.060 --> 00:13:57.020
more stable.

00:13:57.020 --> 00:13:58.920
It's going to have a lower
potential energy.

00:13:58.920 --> 00:14:00.990
You can imagine that if you
start with an eclipsed

00:14:00.990 --> 00:14:03.910
conformation, these guys are all
going to want to get away

00:14:03.910 --> 00:14:05.010
from each other.

00:14:05.010 --> 00:14:08.900
So it's kind of like this is
the wound conformation.

00:14:08.900 --> 00:14:10.300
It has higher potential
energy.

00:14:10.300 --> 00:14:13.300
So it'll want to unwind and
it'll want to unwind to a

00:14:13.300 --> 00:14:15.580
staggered conformation, because
in this conformation,

00:14:15.580 --> 00:14:17.640
all of the hydrogens
have gotten as far

00:14:17.640 --> 00:14:18.890
away from each other.


Pi bonds and sp2 hybridized orbitals

WEBVTT
Kind: captions
Language: en

00:00:00.460 --> 00:00:03.830
In the last video, I touched on
the idea of a sigma bond.

00:00:03.830 --> 00:00:06.830
And that was a bond-- well, let
me draw two nucleuses and

00:00:06.830 --> 00:00:08.630
let me just draw one
of the orbitals.

00:00:08.630 --> 00:00:12.330
Let's say this is an sp3
hybridized orbital, and that's

00:00:12.330 --> 00:00:16.219
on this atom and this is kind of
this big lobe right there.

00:00:16.219 --> 00:00:19.730
And then this guy has an sp3
hybridized orbital as well.

00:00:19.730 --> 00:00:21.740
That's the small lobe,
and then that's the

00:00:21.740 --> 00:00:24.330
big lobe like that.

00:00:24.330 --> 00:00:28.080
A sigma bond is one where
there's an overlap kind of in

00:00:28.080 --> 00:00:30.960
the direction in which the
lobes are pointed.

00:00:30.960 --> 00:00:33.520
And you might say, well, how can
there be any other type of

00:00:33.520 --> 00:00:34.830
bond than that?

00:00:34.830 --> 00:00:37.000
Well, the other type of bond,
so this right here-- let me

00:00:37.000 --> 00:00:37.760
make this clear.

00:00:37.760 --> 00:00:43.070
This right here is
a sigma bond.

00:00:43.070 --> 00:00:45.600
And you say, well, what other
kind of bond could there be

00:00:45.600 --> 00:00:50.650
where my two orbitals overlap
kind of in the direction that

00:00:50.650 --> 00:00:51.490
they're pointing?

00:00:51.490 --> 00:00:54.010
And the other type of bond you
could have, you can imagine if

00:00:54.010 --> 00:00:55.510
you have two p orbitals.

00:00:55.510 --> 00:00:59.300
So let me draw the nucleus of
two atoms, and I'll just draw

00:00:59.300 --> 00:01:01.390
one of each of their
p orbitals.

00:01:01.390 --> 00:01:04.410
So let's say that that's the
nucleus and I'll just draw

00:01:04.410 --> 00:01:05.170
their p orbitals.

00:01:05.170 --> 00:01:08.140
So a p orbital is just
that dumbbell shape.

00:01:08.140 --> 00:01:12.980
Let me draw them a little
bit closer together.

00:01:12.980 --> 00:01:15.452
So a p orbital is that
dumbbell shape.

00:01:15.452 --> 00:01:19.375
So let me draw this guy's--
one of his p orbitals.

00:01:19.375 --> 00:01:21.430
I want to draw it a little bit
bigger than that, and you'll

00:01:21.430 --> 00:01:23.320
see why a second.

00:01:23.320 --> 00:01:25.665
So one of his p orbitals
right there.

00:01:25.665 --> 00:01:28.210
It comes out like that.

00:01:28.210 --> 00:01:31.140
And then this guy over here also
has a p orbital that is

00:01:31.140 --> 00:01:35.050
parallel to this p orbital,
so it goes like that.

00:01:39.510 --> 00:01:42.740
Let me draw that other one
a little bit straighter.

00:01:42.740 --> 00:01:48.090
It goes-- I want it to overlap
more, so it goes like that.

00:01:48.090 --> 00:01:49.330
I think you get the idea.

00:01:49.330 --> 00:01:53.500
So here, our two p orbitals are
parallel to each other.

00:01:53.500 --> 00:01:56.400
This, you can imagine, these are
sp3 hybridized orbitals.

00:01:56.400 --> 00:01:57.430
They're pointing
at each other.

00:01:57.430 --> 00:01:58.590
Here, they're parallel.

00:01:58.590 --> 00:02:01.620
p orbitals are parallel to each
other, and you see that

00:02:01.620 --> 00:02:06.010
they overlap on this kind of
top lobe here and in this

00:02:06.010 --> 00:02:07.580
bottom lobe here.

00:02:07.580 --> 00:02:12.210
And this is a pi bond.

00:02:12.210 --> 00:02:15.100
Let me make this clear.

00:02:15.100 --> 00:02:17.880
And this is one pi bond.

00:02:17.880 --> 00:02:20.060
So you could call it a pi,
literally, with the Greek

00:02:20.060 --> 00:02:22.140
letter pi: pi bond.

00:02:22.140 --> 00:02:25.720
Sometimes you'll see this
just written as pi bond.

00:02:25.720 --> 00:02:28.540
And it's called a pi bond
because it's the Greek letter

00:02:28.540 --> 00:02:31.910
for essentially p, and we're
dealing with p orbitals

00:02:31.910 --> 00:02:32.600
overlapping.

00:02:32.600 --> 00:02:36.170
Now sigma bonds, which are
what form when you have a

00:02:36.170 --> 00:02:40.267
single bond, these are stronger
than pi bonds; pi

00:02:40.267 --> 00:02:43.530
bonds come into play once you
start forming double or triple

00:02:43.530 --> 00:02:45.440
bonds on top of a sigma bond.

00:02:45.440 --> 00:02:48.050
To kind of get a better
visualization of how that

00:02:48.050 --> 00:02:51.600
might work, let's think
about ethene.

00:02:51.600 --> 00:02:56.680
So it's molecular structure
looks like this.

00:02:56.680 --> 00:03:01.560
So you have C double-bonded to
C, and then each of those guys

00:03:01.560 --> 00:03:02.810
have two hydrogens.

00:03:05.990 --> 00:03:10.200
So let me draw what it would
look like, or our best visual,

00:03:10.200 --> 00:03:13.960
or our best ability to kind
of conceptualize what the

00:03:13.960 --> 00:03:16.395
orbitals around the carbon
might look like.

00:03:20.330 --> 00:03:25.340
So first I'll draw the sp2
hybridized orbitals.

00:03:25.340 --> 00:03:27.850
So let me just make it very
clear what's going on here.

00:03:27.850 --> 00:03:35.730
So when we were dealing with
methane, which is literally

00:03:35.730 --> 00:03:41.200
just a carbon bonded to four
hydrogens, and if I actually

00:03:41.200 --> 00:03:43.900
wanted to draw it in a way that
it kind of looks a little

00:03:43.900 --> 00:03:45.810
three-dimensional with a
tetrahedral structure, it

00:03:45.810 --> 00:03:46.640
might look like this.

00:03:46.640 --> 00:03:49.450
This hydrogen is pointing
out a little bit.

00:03:49.450 --> 00:03:52.360
This hydrogen is kind of in
the plane of the page, and

00:03:52.360 --> 00:03:55.100
then maybe that hydrogen is
behind it, and then you have

00:03:55.100 --> 00:03:56.880
one hydrogen popping up.

00:03:56.880 --> 00:03:57.440
That's methane.

00:03:57.440 --> 00:04:02.170
And we saw that these were all
sp3 hybridized orbitals around

00:04:02.170 --> 00:04:05.110
the carbon, and then they each
formed sigma bonds with each

00:04:05.110 --> 00:04:05.860
of the hydrogens.

00:04:05.860 --> 00:04:07.550
We saw that in the last video.

00:04:07.550 --> 00:04:10.470
And when we drew its electron
configuration, in order for

00:04:10.470 --> 00:04:13.780
this to happen, carbon's
electron configuration when

00:04:13.780 --> 00:04:16.899
bonding in methane needed
to look like this.

00:04:16.899 --> 00:04:20.540
It needed to look like 1s2.

00:04:20.540 --> 00:04:27.050
And then instead of having 2s2
and then 2p2, what you

00:04:27.050 --> 00:04:29.430
essentially have is-- let me
try it this way, actually,

00:04:29.430 --> 00:04:30.370
even better.

00:04:30.370 --> 00:04:31.180
Let me write this better.

00:04:31.180 --> 00:04:37.350
In 1s, you had two electrons,
and then instead of two s's,

00:04:37.350 --> 00:04:39.770
you had two electrons and on
each of the p's, you had one,

00:04:39.770 --> 00:04:48.010
the s's and the p's all got
mixed up and you had a 2sp3

00:04:48.010 --> 00:04:52.480
hybridized orbital, another
2sp3 hybridized orbital,

00:04:52.480 --> 00:04:55.650
another 2sp3 hybridized
orbital, and then

00:04:55.650 --> 00:04:57.970
another one, sp3.

00:04:57.970 --> 00:04:59.810
Normally, when carbon's sitting
by itself, you would

00:04:59.810 --> 00:05:03.600
expect a 2s here, and then
you'd have a 2p in the

00:05:03.600 --> 00:05:06.480
x-direction, a 2p in the
y-direction, and then a 2p in

00:05:06.480 --> 00:05:07.200
the z-direction.

00:05:07.200 --> 00:05:09.910
But we saw in the last video,
they all get mixed up and they

00:05:09.910 --> 00:05:14.610
all have a 25% s-character,
and a 75% p-character when

00:05:14.610 --> 00:05:18.080
carbon bonds in methane and the
electrons kind of separate

00:05:18.080 --> 00:05:20.700
out in that situation.

00:05:20.700 --> 00:05:26.050
When you're dealing with the
carbons in ethene, remember,

00:05:26.050 --> 00:05:28.560
eth- is for two carbons and
ene-, because we're dealing

00:05:28.560 --> 00:05:29.320
with an alkene.

00:05:29.320 --> 00:05:31.240
We have a double bond here.

00:05:31.240 --> 00:05:33.400
In this situation, the
carbon's electron

00:05:33.400 --> 00:05:35.050
configuration when they
bond in ethene

00:05:35.050 --> 00:05:36.580
looks more like this.

00:05:36.580 --> 00:05:43.530
So you have your 1s, and
the 1s orbital is

00:05:43.530 --> 00:05:44.870
still completely full.

00:05:44.870 --> 00:05:46.520
It has two electrons in it.

00:05:46.520 --> 00:05:53.250
But then in your 2 shell, I'll
just write-- let me do this in

00:05:53.250 --> 00:05:55.910
a different color.

00:05:55.910 --> 00:06:00.570
So in our 2 shell, I'll show you
what I mean in a second.

00:06:00.570 --> 00:06:02.990
I'm not writing the s or p's so
far on purpose, but we're

00:06:02.990 --> 00:06:06.350
going to have four electrons
just like we had before.

00:06:06.350 --> 00:06:07.600
We're still forming
four bonds.

00:06:07.600 --> 00:06:09.270
We're going to have these
four unpaired electrons.

00:06:09.270 --> 00:06:12.290
We're still forming one, two,
three, four bonds with each of

00:06:12.290 --> 00:06:14.470
the carbons, so they're going
to be separated out.

00:06:17.310 --> 00:06:20.130
But in this situation, instead
of all of them being a

00:06:20.130 --> 00:06:24.490
mixture, kind of one part s,
three parts p, the s mixes

00:06:24.490 --> 00:06:26.380
with two of the p orbitals.

00:06:26.380 --> 00:06:33.210
So what you have is
2sp2 orbital.

00:06:33.210 --> 00:06:36.660
So you can imagine that the s
orbital mixes with two of the

00:06:36.660 --> 00:06:37.200
p orbitals.

00:06:37.200 --> 00:06:40.260
So now it's one part
s, two parts p.

00:06:40.260 --> 00:06:43.540
And then one of the p orbitals
kind of stays by itself.

00:06:43.540 --> 00:06:46.860
And we need this p orbital to
stay by itself because it is

00:06:46.860 --> 00:06:50.800
going to be what's responsible
for the pi bond.

00:06:50.800 --> 00:06:52.210
And we're going to see that
the pi bond does something

00:06:52.210 --> 00:06:54.020
very interesting to
the molecule.

00:06:54.020 --> 00:06:56.910
It kind of makes it unrotatable

00:06:56.910 --> 00:06:58.640
around a bond axis.

00:06:58.640 --> 00:06:59.960
And you'll see what I
mean in a second.

00:06:59.960 --> 00:07:03.000
So let me see if I can, in three
dimensions, draw each of

00:07:03.000 --> 00:07:04.250
these carbons.

00:07:06.880 --> 00:07:10.270
So you have-- let me do
it a different color.

00:07:10.270 --> 00:07:12.530
You have this carbon
right there.

00:07:12.530 --> 00:07:13.880
So let's say that's
the nucleus.

00:07:13.880 --> 00:07:15.690
I'll put a C there so you
know which carbon

00:07:15.690 --> 00:07:16.680
we're dealing with.

00:07:16.680 --> 00:07:21.280
And then I'll draw-- you could
assume that the 1s orbital,

00:07:21.280 --> 00:07:23.210
it's really small right
around the carbon.

00:07:23.210 --> 00:07:26.930
And then you have these
hybridized orbitals, The 2sp2

00:07:26.930 --> 00:07:29.430
orbitals, and they're all going
to be planar, kind of

00:07:29.430 --> 00:07:33.990
forming a triangle, or I guess
maybe a peace sign on some

00:07:33.990 --> 00:07:37.160
level, but I'll try to draw it
in three dimensions here.

00:07:37.160 --> 00:07:40.480
So you have one, this is kind
of coming out a little bit.

00:07:40.480 --> 00:07:43.250
Then you have one that's
going in a little bit.

00:07:43.250 --> 00:07:46.140
And then you have-- and they
have another lobe a little bit

00:07:46.140 --> 00:07:47.580
on the other side, but I'm
not going to draw them.

00:07:47.580 --> 00:07:48.500
It'll complicate it.

00:07:48.500 --> 00:07:50.520
They still have characteristics
of p, so

00:07:50.520 --> 00:07:53.040
they'll have two lobes, but one
is bigger than the other.

00:07:53.040 --> 00:07:55.580
And then you have one that's
maybe going in this side.

00:07:55.580 --> 00:07:59.820
So you can imagine that this is
kind of a Mercedes sign if

00:07:59.820 --> 00:08:01.480
you drew a circle around
it, on its side.

00:08:01.480 --> 00:08:03.870
So that's this carbon
right here.

00:08:03.870 --> 00:08:06.090
And, of course, it has
its hydrogens.

00:08:06.090 --> 00:08:09.000
So you have this
hydrogen there.

00:08:09.000 --> 00:08:12.410
And so this hydrogen might
be sitting right here.

00:08:12.410 --> 00:08:16.830
It just has one electron
in its 1s orbital.

00:08:16.830 --> 00:08:19.270
You have this hydrogen
up here.

00:08:19.270 --> 00:08:22.260
It's sitting right over there.

00:08:22.260 --> 00:08:23.760
And now let's draw
this carbon.

00:08:27.270 --> 00:08:30.840
This carbon will be sitting--
I'm drawing it

00:08:30.840 --> 00:08:31.880
pretty close together.

00:08:31.880 --> 00:08:34.330
This carbon will be sitting
right there.

00:08:34.330 --> 00:08:37.679
He has his 1s orbital.

00:08:37.679 --> 00:08:39.610
They have the exact same
electron configuration.

00:08:39.610 --> 00:08:43.419
He has his 1s orbital right
around him, and then he has

00:08:43.419 --> 00:08:44.890
the exact same configuration.

00:08:44.890 --> 00:08:47.290
Either of these guys, we've so
far only-- or in this first

00:08:47.290 --> 00:08:48.860
guy, I've only drawn
these first three.

00:08:48.860 --> 00:08:53.140
I haven't drawn this
unhybridized p orbital yet.

00:08:53.140 --> 00:08:54.730
So I'll do that in a second.

00:08:54.730 --> 00:08:56.570
But let me draw his bonds.

00:08:56.570 --> 00:09:00.140
So first of all, he has this,
or you could imagine, that

00:09:00.140 --> 00:09:04.490
bond right there, which would
be an sp2 hybridized bond.

00:09:04.490 --> 00:09:07.410
Let me do that in
the same color.

00:09:07.410 --> 00:09:10.210
So he has this bond right here,
which would be an sp2

00:09:10.210 --> 00:09:14.310
hybridized bond,
just like that.

00:09:14.310 --> 00:09:16.250
And notice, this is
a sigma bond.

00:09:16.250 --> 00:09:18.480
They overlap in kind of the
direction that they're

00:09:18.480 --> 00:09:19.070
pointing in.

00:09:19.070 --> 00:09:20.520
That's the best I could
think about it.

00:09:20.520 --> 00:09:23.210
And then he's got these two
hydrogens, so one-- he's got

00:09:23.210 --> 00:09:31.200
this guy in the back, and then
there's one in the front.

00:09:31.200 --> 00:09:32.990
I'll draw it a little bigger so
it's kind of pointing out

00:09:32.990 --> 00:09:34.690
at us, right?

00:09:34.690 --> 00:09:39.470
And then we have this hydrogen
is sitting right over here.

00:09:39.470 --> 00:09:42.170
And these are also sigma bonds,
just to be very clear

00:09:42.170 --> 00:09:42.950
about things.

00:09:42.950 --> 00:09:46.330
This is an s orbital overlapping
with an sp2

00:09:46.330 --> 00:09:48.430
orbital, but they're kind of
overlapping in the direction

00:09:48.430 --> 00:09:51.270
that they're pointed, or kind of
along the direction of each

00:09:51.270 --> 00:09:55.830
other, of the two atoms. This
is a sigma bond, sigma bond,

00:09:55.830 --> 00:10:01.140
and then we have this hydrogen
in the back, which is also

00:10:01.140 --> 00:10:03.220
going to form a sigma bond.

00:10:03.220 --> 00:10:05.230
So everything I've drawn
so far is a sigma

00:10:05.230 --> 00:10:07.430
bond, so that, that.

00:10:07.430 --> 00:10:10.930
Maybe I don't want to make this
picture too-- so I can

00:10:10.930 --> 00:10:14.400
just put sigma bond there, sigma
bond there, sigma bond

00:10:14.400 --> 00:10:16.870
there, sigma, sigma.

00:10:16.870 --> 00:10:23.540
So far I've drawn this bond,
this bond, this bond, this

00:10:23.540 --> 00:10:26.600
bond, and this bond, all
of those sigma bonds.

00:10:26.600 --> 00:10:30.060
So, what happens to this
last p orbital for

00:10:30.060 --> 00:10:31.650
each of these guys?

00:10:31.650 --> 00:10:34.590
Well, that's going to be kind
of sticking out of the plane

00:10:34.590 --> 00:10:37.770
of the Mercedes sign, is the
best way I can describe it.

00:10:37.770 --> 00:10:40.330
And let me see if I can do
that in a color that I

00:10:40.330 --> 00:10:41.040
haven't done yet.

00:10:41.040 --> 00:10:43.070
Oh, maybe this purple color.

00:10:43.070 --> 00:10:45.480
So you can imagine
a pure p orbital.

00:10:45.480 --> 00:10:49.190
So a pure p orbital, I'm going
to need to draw it even bigger

00:10:49.190 --> 00:10:50.560
than that, actually.

00:10:50.560 --> 00:10:54.400
A pure p orbital, it normally
wouldn't be that big relative

00:10:54.400 --> 00:10:57.490
to things, but I have to
make them overlap.

00:10:57.490 --> 00:11:03.030
So it's a pure p orbital that's
kind of going in, maybe

00:11:03.030 --> 00:11:05.960
you can imagine, the z-axis,
that the other orbitals are

00:11:05.960 --> 00:11:08.230
kind of a Mercedes sign
in the x, y plane.

00:11:08.230 --> 00:11:10.610
And now you have the z-axis
going straight up and down,

00:11:10.610 --> 00:11:12.530
and those bottom two have
to overlap so let

00:11:12.530 --> 00:11:13.990
me draw them bigger.

00:11:16.680 --> 00:11:20.330
So it looks like that and
it looks like that.

00:11:20.330 --> 00:11:21.470
And they're going straight
up and down.

00:11:21.470 --> 00:11:24.510
And notice, they are
now overlapping.

00:11:24.510 --> 00:11:29.670
So this bond right here
is this bond.

00:11:29.670 --> 00:11:31.730
I could've drawn them in either
way, but it's that

00:11:31.730 --> 00:11:32.710
second bond.

00:11:32.710 --> 00:11:34.600
And so what's happening
now to the structure?

00:11:34.600 --> 00:11:36.310
So let me make it very clear.

00:11:36.310 --> 00:11:41.440
This right here, that is a pi
bond, and this right here is

00:11:41.440 --> 00:11:42.980
also-- it's the same pi bond.

00:11:42.980 --> 00:11:44.300
It's this guy right here.

00:11:44.300 --> 00:11:46.860
It's the second bond
in the double bond.

00:11:46.860 --> 00:11:47.680
But what's happening here?

00:11:47.680 --> 00:11:50.410
Well, first of all, by itself it
would be a weaker bond, but

00:11:50.410 --> 00:11:56.940
because we already have a sigma
bond that's making these

00:11:56.940 --> 00:11:59.100
molecules come closer together,
this pi bond will

00:11:59.100 --> 00:12:01.290
make them come even
closer together.

00:12:01.290 --> 00:12:04.010
So this distance right here is
closer than if we were to just

00:12:04.010 --> 00:12:06.270
have a single sigma
bond there.

00:12:06.270 --> 00:12:08.380
Now, on top of that, the really
interesting thing is,

00:12:08.380 --> 00:12:11.400
if we just had a sigma bond
here, both of these molecules

00:12:11.400 --> 00:12:14.300
could kind of rotate around
the bond axis.

00:12:14.300 --> 00:12:19.050
They would be able to rotate
around the bond axis if you

00:12:19.050 --> 00:12:20.910
just had one sigma bond there.

00:12:20.910 --> 00:12:24.120
But since we have these pi bonds
that are parallel to

00:12:24.120 --> 00:12:26.260
each other and they're kind of
overlapping and they're kind

00:12:26.260 --> 00:12:29.000
of locked in to that
configuration, you can no

00:12:29.000 --> 00:12:29.720
longer rotate.

00:12:29.720 --> 00:12:31.980
If one of these molecules
rotates, the other one's going

00:12:31.980 --> 00:12:33.610
to rotate with it because
these two

00:12:33.610 --> 00:12:35.020
guys are locked together.

00:12:35.020 --> 00:12:38.590
So what this pi bond does in the
situation is it makes this

00:12:38.590 --> 00:12:42.360
carbon-carbon double bond-- it
means that the double bonds

00:12:42.360 --> 00:12:47.060
are going to be rigid, that you
can't have one molecule

00:12:47.060 --> 00:12:49.500
kind of flipping, swapping these
two hydrogens, without

00:12:49.500 --> 00:12:51.340
the other one having
to flip with it.

00:12:51.340 --> 00:12:54.800
So you wouldn't be able to kind
of swap configurations of

00:12:54.800 --> 00:12:56.620
the hydrogens relative
to the other side.

00:12:56.620 --> 00:12:57.530
That's what it causes.

00:12:57.530 --> 00:12:59.380
So, hopefully, that gives you
a good understanding of the

00:12:59.380 --> 00:13:02.340
difference between sigma
and pi bond.

00:13:02.340 --> 00:13:06.990
And if you're curious, when
you're dealing with-- just to

00:13:06.990 --> 00:13:11.430
kind of make it clear, if we
were dealing with ethyne, this

00:13:11.430 --> 00:13:14.180
is an example of ethene, but
ethyne looks like this.

00:13:14.180 --> 00:13:15.670
You have a triple bond.

00:13:15.670 --> 00:13:19.340
And so you have each side
pointing to one hydrogen.

00:13:19.340 --> 00:13:24.140
In this case, one of these, so
the first bonds, you can

00:13:24.140 --> 00:13:27.420
imagine, so these bonds
are all sigma bonds.

00:13:27.420 --> 00:13:29.660
They're actually
sp hybridized.

00:13:29.660 --> 00:13:33.870
Your 2s orbital only mixes with
one of the p's, so these

00:13:33.870 --> 00:13:47.290
are sp hybrid orbitals forming
sigma bonds, so all of these

00:13:47.290 --> 00:13:48.170
right here.

00:13:48.170 --> 00:13:52.310
And then both of these-- let me
do this in different color.

00:13:52.310 --> 00:13:54.360
Both of these are pi bonds.

00:13:54.360 --> 00:13:58.150
And if you had to imagine it,
could imagine another pi bond

00:13:58.150 --> 00:14:00.820
kind of coming out of the page
and another one here coming

00:14:00.820 --> 00:14:03.540
out of the page and into the
page, out and into the page,

00:14:03.540 --> 00:14:05.270
and they, too, are overlapping,
and you just have

00:14:05.270 --> 00:14:07.660
one hydrogen pointing out
in each direction.

00:14:07.660 --> 00:14:09.320
Maybe I'll make another
video on that.

00:14:09.320 --> 00:14:10.960
So, hopefully, you--


sp3 hybridized orbitals and sigma bonds

WEBVTT
Kind: captions
Language: en

00:00:00.660 --> 00:00:03.160
Let's remind ourselves a little
bit of what we already

00:00:03.160 --> 00:00:06.200
know about orbitals and I've
gone over this early on in the

00:00:06.200 --> 00:00:09.710
regular chemistry playlist.
Let's say that this is the

00:00:09.710 --> 00:00:13.250
nucleus of our atom, super
small, and around that we have

00:00:13.250 --> 00:00:16.280
our first orbital,
the 1s orbital.

00:00:16.280 --> 00:00:21.290
The 1s orbital, you can kind
of just view it as a cloud

00:00:21.290 --> 00:00:22.940
around the nucleus.

00:00:22.940 --> 00:00:26.890
So you have your 1s orbital and
it can fit two electrons,

00:00:26.890 --> 00:00:29.820
so the first electron will go
into the 1s orbital and then

00:00:29.820 --> 00:00:33.140
the second electron will also
go into the 1s orbital.

00:00:33.140 --> 00:00:35.690
For example, hydrogen has
only one electron, so it

00:00:35.690 --> 00:00:37.020
would go into 1s.

00:00:37.020 --> 00:00:38.570
Helium has one more,
so that will also

00:00:38.570 --> 00:00:40.320
go into the 1s orbital.

00:00:40.320 --> 00:00:44.340
After that is filled, then you
move onto the 2s orbital.

00:00:50.390 --> 00:00:53.330
The 2s orbital, you can view
it as a shell around the 1s

00:00:53.330 --> 00:00:56.760
orbital, and all of these, you
can't really view it in our

00:00:56.760 --> 00:00:57.980
conventional way of thinking.

00:00:57.980 --> 00:01:00.340
You can kind of view it as a
probability cloud of where you

00:01:00.340 --> 00:01:01.820
might find the electrons.

00:01:01.820 --> 00:01:04.150
But for visualization purposes,
just imagine it's

00:01:04.150 --> 00:01:09.290
kind of a shell cloud around
the 1s orbital.

00:01:09.290 --> 00:01:13.850
So imagine that it's kind of
a fuzzy shell around the 1s

00:01:13.850 --> 00:01:17.390
orbital, so it's around the
1s orbital, and your next

00:01:17.390 --> 00:01:20.390
electron will go there.

00:01:20.390 --> 00:01:23.370
Then the fourth electron will
also go there, and I drew

00:01:23.370 --> 00:01:25.870
these arrows upward and downward
because the first

00:01:25.870 --> 00:01:29.750
electron that goes into the 1s
orbital has one spin and then

00:01:29.750 --> 00:01:33.190
the next electron to go into
1s orbital will have the

00:01:33.190 --> 00:01:35.950
opposite spin, and so they keep
pairing up in that way.

00:01:35.950 --> 00:01:38.070
They have opposite spins.

00:01:38.070 --> 00:01:41.125
Now, if we keep adding
electrons, now we move to the

00:01:41.125 --> 00:01:42.660
2p orbitals.

00:01:45.750 --> 00:01:49.960
Actually, you can view it as
there are three 2p orbitals

00:01:49.960 --> 00:01:53.760
and each of them can hold two
electrons, so it can hold a

00:01:53.760 --> 00:01:56.490
total of six electrons
in the 2p orbitals.

00:01:56.490 --> 00:01:58.960
Let me draw them for you just
so you can visualize it.

00:01:58.960 --> 00:02:01.710
So if we were to label our axis
here, so think in three

00:02:01.710 --> 00:02:02.490
dimensions.

00:02:02.490 --> 00:02:05.405
So imagine that that right
there is the x-axis.

00:02:09.509 --> 00:02:10.919
Let me do this in different
colors.

00:02:10.919 --> 00:02:17.550
Let's say that this right
here is our y-axis and

00:02:17.550 --> 00:02:19.700
then we have a z-axis.

00:02:19.700 --> 00:02:21.490
I'll do that in blue.

00:02:21.490 --> 00:02:25.340
Let's say we have a z-axis
just like that.

00:02:25.340 --> 00:02:28.080
You actually have a p orbital
that goes along

00:02:28.080 --> 00:02:30.190
each of those axes.

00:02:30.190 --> 00:02:35.810
So you could have your
two-- let me do

00:02:35.810 --> 00:02:37.020
it in the same color.

00:02:37.020 --> 00:02:43.560
So you have your 2p sub x
orbital, and so what that'll

00:02:43.560 --> 00:02:45.725
look like is a dumbbell shape
that's going in the

00:02:45.725 --> 00:02:46.500
x-direction.

00:02:46.500 --> 00:02:49.220
So let me try my best attempt
at drawing this.

00:02:49.220 --> 00:02:52.640
It's a dumbbell shape that goes
in the x-direction, in

00:02:52.640 --> 00:02:55.510
kind of both directions, and
it's actually symmetric.

00:02:55.510 --> 00:02:57.800
I'm drawing this end bigger than
that end so it looks like

00:02:57.800 --> 00:02:59.535
it's coming out at you a little
bit, but let me draw it

00:02:59.535 --> 00:03:00.950
a little bit better than that.

00:03:00.950 --> 00:03:03.230
I can do a better job.

00:03:03.230 --> 00:03:06.670
And maybe it comes
out like that.

00:03:06.670 --> 00:03:08.760
Remember, these are really just
probability clouds, but

00:03:08.760 --> 00:03:12.190
it's helpful to kind of
visualize them as maybe a

00:03:12.190 --> 00:03:14.690
little bit more things that we
would see in our world, but I

00:03:14.690 --> 00:03:16.640
think probability cloud is the
best way to think about it.

00:03:16.640 --> 00:03:20.350
So that is the 2px orbital,
and then I haven't talked

00:03:20.350 --> 00:03:22.340
about how they get filled yet,
but then you also have your

00:03:22.340 --> 00:03:26.220
2py orbital, which'll go in this
axis, but same idea, kind

00:03:26.220 --> 00:03:30.530
of a dumbbell shape in the
y-direction, going in both

00:03:30.530 --> 00:03:33.570
along the y-axis, going in that

00:03:33.570 --> 00:03:34.820
direction and in that direction.

00:03:34.820 --> 00:03:39.230
Then, of course, so let me do
this 2py, and then you also

00:03:39.230 --> 00:03:47.870
have your 2pz, and that goes
in the z-direction up like

00:03:47.870 --> 00:03:52.790
that and then downwards
like that.

00:03:52.790 --> 00:03:56.120
So when you keep adding
electrons, the first-- so far,

00:03:56.120 --> 00:03:57.480
we've added four electrons.

00:03:57.480 --> 00:04:04.700
If you add a fifth electron, you
would expect it to go into

00:04:04.700 --> 00:04:09.380
the 2px orbital right there.

00:04:09.380 --> 00:04:12.130
So even though this 2px orbital
can fit two electrons,

00:04:12.130 --> 00:04:13.220
the first one goes there.

00:04:13.220 --> 00:04:14.905
The very next one won't
go into that one.

00:04:14.905 --> 00:04:17.550
It actually wants to separate
itself within the p orbital,

00:04:17.550 --> 00:04:22.110
so the very next electron that
you add won't go into 2px,

00:04:22.110 --> 00:04:24.440
it'll go into 2py.

00:04:24.440 --> 00:04:27.170
And then the one after that
won't go into 2py or 2px,

00:04:27.170 --> 00:04:29.060
it'll go into 2pz.

00:04:29.060 --> 00:04:31.640
They try to separate
themselves.

00:04:31.640 --> 00:04:34.210
Then if you add another
electron, if you add-- let's

00:04:34.210 --> 00:04:36.880
see, we've added one, two,
three, four, five, six, seven.

00:04:36.880 --> 00:04:41.030
If you add an eighth electron,
that will then go into the 2px

00:04:41.030 --> 00:04:44.290
orbital, so the eighth electron
would go there, but

00:04:44.290 --> 00:04:46.290
it would have the
opposite spin.

00:04:46.290 --> 00:04:48.590
So this is just a little bit of
review with a little bit of

00:04:48.590 --> 00:04:49.790
visualization.

00:04:49.790 --> 00:04:52.010
Now, given what we just
reviewed, let's think about

00:04:52.010 --> 00:04:54.620
what's happening with carbon.

00:04:54.620 --> 00:04:58.795
Carbon has six electrons.

00:05:02.220 --> 00:05:07.300
Its electron configuration, it
is 1s2, two electrons in the

00:05:07.300 --> 00:05:09.090
1s orbital.

00:05:09.090 --> 00:05:14.700
Then 2s2, then 2p2, right?

00:05:14.700 --> 00:05:16.270
It only has two left,
because it has a

00:05:16.270 --> 00:05:17.310
total of six electrons.

00:05:17.310 --> 00:05:20.350
Two go here, then there,
then two are left

00:05:20.350 --> 00:05:22.260
to fill the p orbitals.

00:05:22.260 --> 00:05:24.780
If you go based on what we just
drew and what we just

00:05:24.780 --> 00:05:29.310
talked about here, what you
would expect for carbon-- let

00:05:29.310 --> 00:05:30.930
me just draw it out the
way I did this.

00:05:30.930 --> 00:05:35.930
So you have your 1s orbital,
your 2s orbital, and then you

00:05:35.930 --> 00:05:41.570
have your 2px orbital, your 2py
orbital, and then you have

00:05:41.570 --> 00:05:43.790
your 2pz orbital.

00:05:43.790 --> 00:05:46.460
If you just go straight from
the electron configuration,

00:05:46.460 --> 00:05:49.890
you would expect carbon, so the
1s orbital fills first, so

00:05:49.890 --> 00:05:51.520
that's our first electron,
our second

00:05:51.520 --> 00:05:53.900
electron, our third electron.

00:05:53.900 --> 00:05:56.580
Then we go to our 2s orbital,
That fills next, third

00:05:56.580 --> 00:05:59.000
electron, then fourth
electron.

00:05:59.000 --> 00:06:00.700
Then you would expect maybe
your fifth electron

00:06:00.700 --> 00:06:02.330
to go in the 2px.

00:06:02.330 --> 00:06:04.020
We could have said 2py or 2z.

00:06:04.020 --> 00:06:06.410
It just depends on how
you label the axis.

00:06:06.410 --> 00:06:10.150
But you would have your fifth
electron go into one of the p

00:06:10.150 --> 00:06:11.660
orbitals, and then you
would expect your

00:06:11.660 --> 00:06:13.780
sixth to go into another.

00:06:13.780 --> 00:06:15.720
So you would expect that
to be kind of the

00:06:15.720 --> 00:06:16.980
configuration for carbon.

00:06:16.980 --> 00:06:21.880
And if we were to draw it--
let me draw our axes.

00:06:21.880 --> 00:06:28.320
That is our y-axis and then
this is our x-axis.

00:06:28.320 --> 00:06:31.390
Let me draw it a little
bit better than that.

00:06:31.390 --> 00:06:35.190
So that is the x-axis and, of
course, you have your z-axis.

00:06:35.190 --> 00:06:37.130
You have to think in three
dimensions a little bit.

00:06:41.120 --> 00:06:45.230
Then you have your z-axis,
just like that.

00:06:45.230 --> 00:06:48.060
So first we fill the 1s orbital,
so if our nucleus is

00:06:48.060 --> 00:06:50.480
sitting here, our
1s orbital gets

00:06:50.480 --> 00:06:51.480
filled with two electrons.

00:06:51.480 --> 00:06:52.480
You can imagine that
as a little

00:06:52.480 --> 00:06:54.350
cloud around the nucleus.

00:06:54.350 --> 00:07:00.020
Then we fill the 2s orbital
and that would be a cloud

00:07:00.020 --> 00:07:02.630
around that, kind of a
shell around that.

00:07:02.630 --> 00:07:06.330
Then we would put one electron
in the 2px orbital, so one

00:07:06.330 --> 00:07:09.430
electron would start kind of
jumping around or moving

00:07:09.430 --> 00:07:11.920
around, depending how you want
to think about it, in that

00:07:11.920 --> 00:07:14.530
orbital over there, 2px.

00:07:14.530 --> 00:07:17.450
Then you'd have the next
electron jumping around or

00:07:17.450 --> 00:07:20.140
moving around in the 2py
orbital, so it would be moving

00:07:20.140 --> 00:07:23.580
around like this.

00:07:23.580 --> 00:07:25.950
If you went just off of this,
you would say, you know what?

00:07:25.950 --> 00:07:29.380
These guys, this guy over
here and that guy

00:07:29.380 --> 00:07:30.560
over there is lonely.

00:07:30.560 --> 00:07:33.780
He's looking for a opposite
spin partner.

00:07:33.780 --> 00:07:36.270
This would be the only places
that bonds would form.

00:07:36.270 --> 00:07:39.710
You would expect some type of
bonding to form with the

00:07:39.710 --> 00:07:42.190
x-orbitals or the y-orbitals.

00:07:42.190 --> 00:07:44.360
Now, that's what you would
expect if you just straight-up

00:07:44.360 --> 00:07:47.600
kind of stayed with this model
of how things fill and how

00:07:47.600 --> 00:07:49.040
orbitals look.

00:07:49.040 --> 00:07:52.210
The reality of carbon, and I
guess the simplest reality of

00:07:52.210 --> 00:07:57.040
carbon, is if you look at a
methane molecule, is very

00:07:57.040 --> 00:07:59.800
different than what you
would expect here.

00:07:59.800 --> 00:08:01.490
First of all, what you would
expect here is that carbon

00:08:01.490 --> 00:08:03.770
would probably-- maybe it
would form two bonds.

00:08:03.770 --> 00:08:07.840
But we know carbon forms four
bonds and it wants to pretend

00:08:07.840 --> 00:08:09.490
like it has eight electrons.

00:08:09.490 --> 00:08:12.390
Frankly, almost every atom wants
to pretend like it has

00:08:12.390 --> 00:08:13.550
eight electrons.

00:08:13.550 --> 00:08:15.800
So in order for that to happen,
you have to think

00:08:15.800 --> 00:08:16.840
about a different reality.

00:08:16.840 --> 00:08:20.450
This isn't really what's
happening when carbon bonds,

00:08:20.450 --> 00:08:31.400
so not what happens
when carbon bonds.

00:08:31.400 --> 00:08:34.890
What's really happening when
carbon bonds, and this will

00:08:34.890 --> 00:08:37.915
kind of go into the discussion
of sp3 hybridization, but what

00:08:37.915 --> 00:08:39.159
you're going to see
is it's not that

00:08:39.159 --> 00:08:40.120
complicated of a topic.

00:08:40.120 --> 00:08:41.830
It sounds very daunting, but
it's actually pretty

00:08:41.830 --> 00:08:42.919
straightforward.

00:08:42.919 --> 00:08:45.180
What really happens when carbon
bonds, because it wants

00:08:45.180 --> 00:08:48.740
to form four bonds with things,
is its configuration,

00:08:48.740 --> 00:08:50.510
you could imagine, looks
more like this.

00:08:53.290 --> 00:08:55.830
So you have 1s.

00:08:55.830 --> 00:08:57.050
We have two electrons there.

00:08:57.050 --> 00:09:04.760
Then you have your 2s,
2px, 2py and 2pz.

00:09:04.760 --> 00:09:07.480
Now what you can imagine is it
wants to form four bonds.

00:09:07.480 --> 00:09:09.740
It has four electrons that are
willing to pair up with

00:09:09.740 --> 00:09:11.680
electrons from other
molecules.

00:09:11.680 --> 00:09:15.100
In the case of methane, that
other molecule is a hydrogen.

00:09:15.100 --> 00:09:18.760
So what you could imagine is
that the electrons actually--

00:09:18.760 --> 00:09:23.900
maybe the hydrogen brings this
electron right here into a

00:09:23.900 --> 00:09:26.550
higher energy state and
puts it into 2z.

00:09:26.550 --> 00:09:28.200
That's one way to
visualize it.

00:09:28.200 --> 00:09:31.670
So this other guy here maybe
ends up over there, and then

00:09:31.670 --> 00:09:33.570
these two guys are over
there and over there.

00:09:33.570 --> 00:09:37.240
Now, all of a sudden, it looks
like you have four lonely guys

00:09:37.240 --> 00:09:39.520
and they are ready to bond,
and that's actually more

00:09:39.520 --> 00:09:42.060
accurate of how carbon bonds.

00:09:42.060 --> 00:09:44.670
It likes to bond with
four other people.

00:09:44.670 --> 00:09:47.440
Now, it's a little bit arbitrary
which electron ends

00:09:47.440 --> 00:09:50.350
up in each of these things, and
even if you had this type

00:09:50.350 --> 00:09:55.610
of bonding, you would expect
things to bond along the x, y,

00:09:55.610 --> 00:09:57.180
and z axis.

00:09:57.180 --> 00:10:01.850
The reality is, the reality of
carbon, is that these four

00:10:01.850 --> 00:10:05.870
electrons in its second shell
don't look like they're in

00:10:05.870 --> 00:10:07.895
just-- the first one doesn't
look like it's just in the s

00:10:07.895 --> 00:10:12.100
orbital and then the p and y
and z for the other three.

00:10:12.100 --> 00:10:14.340
They all look like they're a
little bit in the s and a

00:10:14.340 --> 00:10:17.010
little bit in the p orbitals.

00:10:17.010 --> 00:10:18.440
Let me make that clear.

00:10:18.440 --> 00:10:21.390
So instead of this being a 2s,
what it really looks like for

00:10:21.390 --> 00:10:26.570
carbon is that this looks
like a 2sp3 orbital.

00:10:26.570 --> 00:10:30.430
This looks like a 2sp3 orbital,
that looks like a

00:10:30.430 --> 00:10:34.310
2sp3 orbital, that looks
like a 2sp3 orbital.

00:10:34.310 --> 00:10:37.110
They all look like they're kind
of in the same orbital.

00:10:37.110 --> 00:10:39.520
This special type of--
it sounds very fancy.

00:10:39.520 --> 00:10:43.790
This sp3 hybridized orbital,
what it actually looks like is

00:10:43.790 --> 00:10:46.520
something that's in between
an s and a p orbital.

00:10:46.520 --> 00:10:51.050
It has a 25% s nature
and a 75% p nature.

00:10:51.050 --> 00:10:55.460
You can imagine it as being a
mixture of these four things.

00:10:55.460 --> 00:10:58.170
That's the behavior
that carbon has.

00:10:58.170 --> 00:11:02.750
So when you mix them all,
instead of having an s

00:11:02.750 --> 00:11:04.510
orbital, so if this is
a nucleus and we do a

00:11:04.510 --> 00:11:08.540
cross-section, an s orbital
looks like that and the p

00:11:08.540 --> 00:11:15.000
orbital looks something like
that in cross-section.

00:11:15.000 --> 00:11:19.080
So this is a an s
and that is a p.

00:11:19.080 --> 00:11:21.790
When they get mixed up, the
orbital looks like this.

00:11:21.790 --> 00:11:24.960
An sp3 orbital looks something
like this.

00:11:28.640 --> 00:11:33.170
This is a hybridized
sp3 orbital.

00:11:33.170 --> 00:11:36.500
Hybrid just means a combination
of two things.

00:11:36.500 --> 00:11:39.720
A hybrid car is a combination
of gas and electric.

00:11:39.720 --> 00:11:43.800
A hybridized orbital is a
combination of s and p.

00:11:43.800 --> 00:11:48.750
Hybridized sp3 orbitals are the
orbitals when carbon bonds

00:11:48.750 --> 00:11:50.300
with things like hydrogen
or really when

00:11:50.300 --> 00:11:52.320
it bonds with anything.

00:11:52.320 --> 00:11:55.480
So if you looked at a molecule
of methane, and people talk

00:11:55.480 --> 00:11:59.970
about sp3 hybridized orbitals,
all they're saying is that you

00:11:59.970 --> 00:12:03.400
have a carbon in the center.

00:12:03.400 --> 00:12:05.760
Let's say that's the carbon
nucleus right there.

00:12:05.760 --> 00:12:10.460
And instead of having one s and
three p orbitals, it has

00:12:10.460 --> 00:12:12.320
four sp3 orbitals.

00:12:16.030 --> 00:12:19.190
So let me try my best at drawing
the four sp3 orbitals.

00:12:19.190 --> 00:12:22.350
Let's say this is the big lobe
that is kind of pointing near

00:12:22.350 --> 00:12:25.320
us, and then it has a small
lobe in the back.

00:12:25.320 --> 00:12:30.180
Then you have another one that
has a big lobe like that and a

00:12:30.180 --> 00:12:32.110
small lobe in the back.

00:12:32.110 --> 00:12:35.852
Then you have one that's going
back behind the page, so let

00:12:35.852 --> 00:12:36.910
me draw that.

00:12:36.910 --> 00:12:39.940
You can kind of imagine a
three-legged stool, and then

00:12:39.940 --> 00:12:42.180
its small lobe will come
out like that.

00:12:42.180 --> 00:12:44.990
And then you have one where
the big lobe is pointing

00:12:44.990 --> 00:12:50.400
straight up, and it has a
small lobe going down.

00:12:50.400 --> 00:12:53.580
You can imagine it as kind
of a three-legged stool.

00:12:53.580 --> 00:12:55.410
One of them is behind like
that and it's pointing

00:12:55.410 --> 00:12:59.120
straight up, So a three-legged
stool with something-- it's

00:12:59.120 --> 00:13:00.960
kind of like a tripod, I
guess is the best way

00:13:00.960 --> 00:13:02.560
to think about it.

00:13:02.560 --> 00:13:05.690
So that's the carbon nucleus
in the center and then you

00:13:05.690 --> 00:13:08.720
have the hydrogens, so that's
our carbon right there.

00:13:08.720 --> 00:13:10.770
Then you have your hydrogens.

00:13:10.770 --> 00:13:11.935
You have a hydrogen here.

00:13:11.935 --> 00:13:16.530
A hydrogen just has one electron
in the 1s orbital, so

00:13:16.530 --> 00:13:19.520
the hydrogen has a 1s orbital.

00:13:19.520 --> 00:13:21.735
You have a hydrogen here that
just has a 1s orbital.

00:13:21.735 --> 00:13:24.400
It has a hydrogen here,
1s orbital,

00:13:24.400 --> 00:13:26.590
hydrogen here, 1s orbital.

00:13:26.590 --> 00:13:29.550
So this is how the hydrogen
orbital and the carbon

00:13:29.550 --> 00:13:30.710
orbitals get mixed.

00:13:30.710 --> 00:13:35.990
The hydrogens 1s orbital bonds
with-- well, each of the

00:13:35.990 --> 00:13:38.590
hydrogen's 1s orbital bonds
with each of the

00:13:38.590 --> 00:13:41.710
carbon's sp3 orbitals.

00:13:41.710 --> 00:13:43.540
Just so you get a little bit
more notation, so when people

00:13:43.540 --> 00:13:46.620
talk about hybridized sp3
orbitals, all they're saying

00:13:46.620 --> 00:13:50.580
is, look, carbon doesn't bond.

00:13:50.580 --> 00:13:52.900
Once carbon-- this
right here is a

00:13:52.900 --> 00:13:54.280
molecule of methane, right?

00:13:54.280 --> 00:14:01.500
This is CH4, or methane, and it
doesn't bond like you would

00:14:01.500 --> 00:14:03.240
expect if you just want
with straight

00:14:03.240 --> 00:14:05.060
vanilla s and p orbitals.

00:14:05.060 --> 00:14:06.910
If you just went with straight
vanilla s and p orbitals, the

00:14:06.910 --> 00:14:08.080
bonds would form.

00:14:08.080 --> 00:14:11.000
Maybe the hydrogen might be
there and there, and if it had

00:14:11.000 --> 00:14:14.450
four hydrogens, maybe there and
there, depending on how

00:14:14.450 --> 00:14:15.230
you want to think about it.

00:14:15.230 --> 00:14:17.180
But the reality is it doesn't
look like that.

00:14:17.180 --> 00:14:19.110
It looks more like a tripod.

00:14:19.110 --> 00:14:21.080
It has a tetrahedral shape.

00:14:26.360 --> 00:14:29.780
The best way that that can be
explained, I guess the shape

00:14:29.780 --> 00:14:33.950
of the structure, is if you have
four equally-- four of

00:14:33.950 --> 00:14:37.130
the same types of orbital
shapes, and those four types

00:14:37.130 --> 00:14:40.980
of orbital shapes are hybrids
between s's and p's.

00:14:40.980 --> 00:14:45.180
One other piece of notation to
know, sometimes people think

00:14:45.180 --> 00:14:49.550
it's a very fancy term, but when
you have a bond between

00:14:49.550 --> 00:14:52.390
two molecules, where the
orbitals are kind of pointing

00:14:52.390 --> 00:14:55.240
at each other, so you can
imagine right here, this

00:14:55.240 --> 00:14:57.330
hydrogen orbital is pointing
in that direction.

00:14:57.330 --> 00:15:00.130
This sp3 orbital is pointing
that direction, and they're

00:15:00.130 --> 00:15:04.170
overlapping right around here.

00:15:04.170 --> 00:15:13.730
This is called a sigma bond,
where the overlap is along the

00:15:13.730 --> 00:15:17.100
same axis as if you connected
the two molecules.

00:15:17.100 --> 00:15:20.420
Over here, you connect the two
molecules, the overlap is on

00:15:20.420 --> 00:15:21.510
that same axis.

00:15:21.510 --> 00:15:25.330
This is the strongest form of
covalent bonds, and this'll be

00:15:25.330 --> 00:15:27.480
a good basis for discussion
maybe in the next video when

00:15:27.480 --> 00:15:29.630
we talk a little bit
about pi bonds.

00:15:29.630 --> 00:15:32.110
The big takeaway of this video
is to just understand what

00:15:32.110 --> 00:15:32.910
does it mean?

00:15:32.910 --> 00:15:35.530
What is an sp3 hybridized
orbital?

00:15:35.530 --> 00:15:36.580
Nothing fancy, just a

00:15:36.580 --> 00:15:38.580
combination of s and p orbitals.

00:15:38.580 --> 00:15:44.670
It has 25% s character, 75% p
character, which makes sense.

00:15:44.670 --> 00:15:48.120
It's what exists when carbon
forms bonds, especially in the

00:15:48.120 --> 00:15:48.880
case of methane.

00:15:48.880 --> 00:15:52.920
That's what describes it's
tetrahedral structure.

00:15:52.920 --> 00:15:57.580
That's why we have an angle
between the various branches

00:15:57.580 --> 00:16:01.580
of a 109.5 degrees, which some
teachers might want you know,

00:16:01.580 --> 00:16:02.300
so it's useful to know.

00:16:02.300 --> 00:16:06.350
If you take this angle right
here, 109.5, that's the same

00:16:06.350 --> 00:16:08.910
thing as that angle, or if you
were to go behind it, that

00:16:08.910 --> 00:16:13.380
angle right there, 109.5
degrees, explained by sp3

00:16:13.380 --> 00:16:14.460
hybridization.

00:16:14.460 --> 00:16:16.500
The bonds themselves
are sigma bonds.

00:16:16.500 --> 00:16:20.420
The overlap is along the axis
connecting the hydrogen.


Naming alkyl halides

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:03.610
There are other things, other
than carbons, that might

00:00:03.610 --> 00:00:05.760
branch off of the main chain.

00:00:05.760 --> 00:00:07.560
And in this video, I want
to introduce you

00:00:07.560 --> 00:00:09.566
to the alkyl halides.

00:00:15.190 --> 00:00:17.650
And this is a situation where
one of the halogen elements,

00:00:17.650 --> 00:00:20.530
and the halogen elements are
the second to last, or the

00:00:20.530 --> 00:00:24.260
second to the right, or to the
right most column in the

00:00:24.260 --> 00:00:25.050
periodic table.

00:00:25.050 --> 00:00:28.920
Fluorine, chlorine,
bromine, iodine.

00:00:28.920 --> 00:00:32.400
It's when one of these replace
one of the hydrogens attached

00:00:32.400 --> 00:00:33.020
to a carbon.

00:00:33.020 --> 00:00:35.600
So I've drawn some alkyl
halides here.

00:00:35.600 --> 00:00:38.340
And let's think a little bit
of how to name them.

00:00:38.340 --> 00:00:42.670
So like we name all of our
organic molecules so far, you

00:00:42.670 --> 00:00:47.130
look for the longest chain
first. And the longest chain

00:00:47.130 --> 00:00:49.490
that contains a double
bond if there is one.

00:00:49.490 --> 00:00:51.840
In this case, there is no double
bond, so the longest

00:00:51.840 --> 00:00:53.280
chain looks like this.

00:00:53.280 --> 00:00:55.500
We start here and we
go over there.

00:00:55.500 --> 00:00:58.780
Or we could go either way, but
this is the longest chain.

00:00:58.780 --> 00:01:02.860
So it's one, two, three,
four, five, six,

00:01:02.860 --> 00:01:04.790
seven, eight carbons.

00:01:04.790 --> 00:01:05.430
Let me make sure of that.

00:01:05.430 --> 00:01:09.190
One, two, three, four, five,
six, seven, eight carbons.

00:01:09.190 --> 00:01:11.170
And we want to start at the end
where we're going to run

00:01:11.170 --> 00:01:17.770
into either some type of halide
first or some other

00:01:17.770 --> 00:01:18.920
type of branch off of it.

00:01:18.920 --> 00:01:21.070
Just something attached
to the carbon change

00:01:21.070 --> 00:01:22.000
other than a hydrogen.

00:01:22.000 --> 00:01:23.490
So we're going to start
at this end.

00:01:23.490 --> 00:01:35.500
So it's one, two, three, four,
five, six, seven, eight.

00:01:35.500 --> 00:01:37.800
So we're dealing
with an octane.

00:01:37.800 --> 00:01:39.870
Our main chain has eight
carbons, so we're

00:01:39.870 --> 00:01:41.880
dealing with an octane.

00:01:41.880 --> 00:01:45.300
And now we have to think about
these different halogens that

00:01:45.300 --> 00:01:45.970
we have here.

00:01:45.970 --> 00:01:52.660
So first we have a chlorine
at carbon number two.

00:01:52.660 --> 00:01:58.490
So that's going to be 2-chloro,
is what we're going

00:01:58.490 --> 00:01:59.000
to call that.

00:01:59.000 --> 00:02:00.810
And we're going to put them in
alphabetical order and then

00:02:00.810 --> 00:02:02.410
put them in front
of the octane.

00:02:02.410 --> 00:02:06.470
And then this right here is
a-- it's on the fourth

00:02:06.470 --> 00:02:07.834
carbon-- so it is a 4-bromo.

00:02:10.710 --> 00:02:14.340
The actual element is
called bromine.

00:02:14.340 --> 00:02:21.720
We change the ine to an
oro, so this is bromo.

00:02:21.720 --> 00:02:24.180
The ine to an o, I should say.

00:02:24.180 --> 00:02:26.590
So this is bromo.

00:02:26.590 --> 00:02:30.140
And B comes before C, but we're
not done yet, because we

00:02:30.140 --> 00:02:31.860
don't have just halides here.

00:02:31.860 --> 00:02:34.060
We don't just have these
halogens over here.

00:02:34.060 --> 00:02:36.320
We also have a methyl group.

00:02:36.320 --> 00:02:38.380
We have one carbon sitting
over here.

00:02:38.380 --> 00:02:40.080
So we don't want to
forget that guy.

00:02:40.080 --> 00:02:42.460
So that right there,
that is a 5-methyl.

00:02:46.390 --> 00:02:47.980
So when we write it all
out, we do it in

00:02:47.980 --> 00:02:49.280
alphabetical order.

00:02:49.280 --> 00:02:50.730
B takes precedence.

00:02:50.730 --> 00:02:56.215
So this will be 4-bromo-- I'll
do it over here-- 4-bromo.

00:02:59.050 --> 00:03:00.960
Then the next thing
we have is C.

00:03:00.960 --> 00:03:02.210
So 4-bromo-2-chloro
-5-methyloctane.

00:03:20.230 --> 00:03:23.790
Now if we take look at this
structure over here, our main

00:03:23.790 --> 00:03:29.710
carbon branch, we only have two
carbons in it right here.

00:03:29.710 --> 00:03:32.160
So we're dealing with
eth or ethane.

00:03:32.160 --> 00:03:33.440
It's a single bond.

00:03:33.440 --> 00:03:37.390
So this tells us that we're
dealing with an ethane.

00:03:37.390 --> 00:03:38.880
And let's see what we
have attached to it.

00:03:38.880 --> 00:03:40.740
We have a bunch of these
halogens attached to it.

00:03:40.740 --> 00:03:44.060
We replaced a bunch of our
hydrogens with halogens.

00:03:44.060 --> 00:03:48.160
So we have these
fluorines here.

00:03:48.160 --> 00:03:56.980
And so we can start at
the end that has more

00:03:56.980 --> 00:03:58.150
things attached to it.

00:03:58.150 --> 00:04:04.000
So in this case, we have one,
two, three fluorines attached.

00:04:04.000 --> 00:04:07.630
So this is going to start off
with-- and then fluorines,

00:04:07.630 --> 00:04:10.250
well I'll just leave it
like that for now.

00:04:10.250 --> 00:04:11.800
I was going to write it, but
then I have to remember,

00:04:11.800 --> 00:04:12.900
you're going to have
to alphabetize it.

00:04:12.900 --> 00:04:14.300
So let me just write out.

00:04:14.300 --> 00:04:18.560
So at some point in our name,
we're going to have attached--

00:04:18.560 --> 00:04:19.749
we're going to start
here-- that's going

00:04:19.749 --> 00:04:21.570
to be the one carbon.

00:04:21.570 --> 00:04:22.880
That is the one carbon.

00:04:22.880 --> 00:04:24.750
That is the two carbon.

00:04:24.750 --> 00:04:27.890
So at one point in our chain--
let me switch colors

00:04:27.890 --> 00:04:31.600
actually-- we're going to have
one, two, three flourines.

00:04:31.600 --> 00:04:35.420
So it's going to
be a trifluoro.

00:04:38.170 --> 00:04:39.730
And they're all at
the one carbon.

00:04:39.730 --> 00:04:40.980
So it's going to be
a 1,1,1-trifluoro.

00:04:43.450 --> 00:04:46.510
That'll take care of those
three fluorines there.

00:04:46.510 --> 00:04:49.600
And then we're going to have,
at some point in our name,

00:04:49.600 --> 00:04:54.730
this bromo is attached to the
two carbon, so 2-bromo.

00:04:54.730 --> 00:04:58.810
And then you also
have this chloro

00:04:58.810 --> 00:05:00.100
attached to the two carbon.

00:05:00.100 --> 00:05:01.350
So you're also going
to have 2,2-chloro.

00:05:03.810 --> 00:05:05.590
So then you go in alphabetical
order.

00:05:05.590 --> 00:05:06.910
B takes precedence.

00:05:06.910 --> 00:05:09.100
And then you're going to go to
C, and then the trifluoro.

00:05:09.100 --> 00:05:10.030
You ignore the tri.

00:05:10.030 --> 00:05:12.700
But F still comes
after B and C.

00:05:12.700 --> 00:05:24.258
So this is going to be 2-bromo
2-chloro-- I want to do that

00:05:24.258 --> 00:05:32.770
same shade of green--
2-chloro, same idea.

00:05:32.770 --> 00:05:35.310
And then we have
1,1,1-trifluoroethane.

00:05:51.830 --> 00:05:54.220
Now I want to make one thing
clear, when you do this.

00:05:54.220 --> 00:05:56.510
Double bonds, we saw on the
last video-- we learned a

00:05:56.510 --> 00:05:59.300
little bit about alkenes-- still
take precedence over

00:05:59.300 --> 00:05:59.880
everything.

00:05:59.880 --> 00:06:03.060
So if we go to this original
compound-- this original

00:06:03.060 --> 00:06:05.950
molecule up here-- if I were to
throw a double bond here.

00:06:05.950 --> 00:06:07.820
So let's say I threw
a double bond.

00:06:07.820 --> 00:06:10.230
Then all of a sudden that'll
change the naming mechanism.

00:06:10.230 --> 00:06:12.350
First of all, we're not doing
with an octane anymore.

00:06:12.350 --> 00:06:16.670
We're dealing with an octene.

00:06:16.670 --> 00:06:20.430
So in this situation, the
chain-- we'll start at the end

00:06:20.430 --> 00:06:26.980
closest to the double bond--
there's one, two, three, four,

00:06:26.980 --> 00:06:32.170
five, six, seven, eight.

00:06:32.170 --> 00:06:34.010
So now this becomes 7-chloro.

00:06:34.010 --> 00:06:35.930
This will be 5-bromo.

00:06:35.930 --> 00:06:37.940
This is 4-methyl.

00:06:37.940 --> 00:06:41.520
And this compound over here,
it will no longer be this

00:06:41.520 --> 00:06:44.250
thing over here, because I've
added this double bond.

00:06:44.250 --> 00:06:47.410
It will now be going in
alphabetical order.

00:06:47.410 --> 00:06:48.660
It would be 5-bromo.

00:06:51.170 --> 00:06:53.420
Let me have some space here.

00:06:53.420 --> 00:06:54.670
It will be
5-bromo-7-chloro-4-methyl.

00:07:16.820 --> 00:07:19.520
And then we have oct.

00:07:19.520 --> 00:07:22.470
But it's an alkene,
so it's oct.

00:07:22.470 --> 00:07:24.510
We have to specify where
we start our

00:07:24.510 --> 00:07:30.080
double bond, oct-2-ene.

00:07:30.080 --> 00:07:31.910
Now if we had two
double bonds.

00:07:31.910 --> 00:07:35.480
Let's say we had a situation
where it was, maybe we had,

00:07:35.480 --> 00:07:38.020
let's see we don't want to
put too many bonds here.

00:07:38.020 --> 00:07:39.350
Carbon will only have
four bonds.

00:07:39.350 --> 00:07:40.790
This carbon has three.

00:07:40.790 --> 00:07:42.840
This hydrogen, we could have
double bond over here.

00:07:42.840 --> 00:07:46.840
In that situation, we're going
to have-- and I actually

00:07:46.840 --> 00:07:49.060
didn't specify it correctly in
the last video, so this is a

00:07:49.060 --> 00:07:52.960
bit of a correction-- instead of
being 2-ene, this will now

00:07:52.960 --> 00:07:57.250
be-- well let me make it instead
of being 2-ene when I

00:07:57.250 --> 00:08:02.890
add that second carbon there, or
that second double bond, it

00:08:02.890 --> 00:08:06.890
will now be-- scroll over to
the right a little bit-- it

00:08:06.890 --> 00:08:11.540
will now be oct dash.

00:08:11.540 --> 00:08:13.210
We have a double bond
at the two.

00:08:13.210 --> 00:08:15.800
Starting at the two
and at the four.

00:08:15.800 --> 00:08:17.760
2 comma 4.

00:08:17.760 --> 00:08:19.280
And it's no longer
just an ene.

00:08:19.280 --> 00:08:20.570
That was a mistake I did
in the last video.

00:08:20.570 --> 00:08:22.870
I said hept, and I
just put an ene.

00:08:22.870 --> 00:08:24.780
Now that I have two double
bonds, it's a diene.

00:08:27.540 --> 00:08:29.240
So you don't want
to forget that.

00:08:29.240 --> 00:08:31.690
That tells us that we have
two double bonds here.

00:08:31.690 --> 00:08:32.860
Although it's kind of
obvious, because I'm

00:08:32.860 --> 00:08:34.130
listing a 2 and a 4.

00:08:34.130 --> 00:08:35.590
So it's a little
bit redundant.

00:08:35.590 --> 00:08:36.690
2 and 4 diene.

00:08:36.690 --> 00:08:38.289
So if you have it with these
two double bonds, we have

00:08:38.289 --> 00:08:39.539
5-bromo-7-chloro
-4-methyl-oct-2,4-diene.

00:08:45.190 --> 00:08:47.290
And the whole reason why I
introduced this is really to

00:08:47.290 --> 00:08:48.280
make a bit of a correction.

00:08:48.280 --> 00:08:50.430
Well to show you two things.

00:08:50.430 --> 00:08:53.250
One, that the double bond takes
precedence when you are

00:08:53.250 --> 00:08:55.170
deciding which direction
to number in.

00:08:55.170 --> 00:08:57.150
And then also to correct a
little bit of a mistake in the

00:08:57.150 --> 00:09:00.330
last video where I forgot to
put the di when I had two

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double bonds.