Chiral examples 2

WEBVTT
Kind: captions
Language: en

00:00:00.520 --> 00:00:04.050
Let's do a few more examples of
seeing if either an atom or

00:00:04.050 --> 00:00:06.990
an entire molecule is chiral.

00:00:06.990 --> 00:00:08.640
So here I have a molecule.

00:00:08.640 --> 00:00:11.810
Let's see if we can identify
any chiral centers, or any

00:00:11.810 --> 00:00:15.060
chiral atoms, or asymmetric
carbons, all words for the

00:00:15.060 --> 00:00:17.640
same thing, although I guess you
could have chiral centers

00:00:17.640 --> 00:00:19.960
that aren't necessarily carbon,
but it tends to be

00:00:19.960 --> 00:00:22.660
carbon most of the time,
especially in Organic

00:00:22.660 --> 00:00:24.010
Chemistry class.

00:00:24.010 --> 00:00:27.160
So if we look here, the one that
kind of jumps out, this

00:00:27.160 --> 00:00:29.460
carbon right here is
bonded to three

00:00:29.460 --> 00:00:31.400
hydrogens and another carbon.

00:00:31.400 --> 00:00:33.590
So this is obviously not going
to be a chiral center.

00:00:33.590 --> 00:00:35.710
It's bonded to three
of the same group.

00:00:35.710 --> 00:00:38.680
These three guys are all bonded
to two hydrogens each,

00:00:38.680 --> 00:00:40.830
so they're all bonded to two
of the same group, so they

00:00:40.830 --> 00:00:42.740
can't be chiral centers.

00:00:42.740 --> 00:00:45.620
This carbon right here is bonded
to three hydrogens,

00:00:45.620 --> 00:00:48.500
once again, three of the same
group, not going to be a

00:00:48.500 --> 00:00:49.500
chiral center.

00:00:49.500 --> 00:00:50.670
This one looks interesting.

00:00:50.670 --> 00:00:53.430
It looks like it could be a good
candidate it for a chiral

00:00:53.430 --> 00:00:57.330
center, or a chiral carbon,
or an asymmetric carbon.

00:00:57.330 --> 00:01:01.430
Over here on the left, it's
bonded to a methyl group, so

00:01:01.430 --> 00:01:06.200
this is a methyl group, and here
on the right, it's bonded

00:01:06.200 --> 00:01:07.590
to a butyl group.

00:01:16.390 --> 00:01:19.130
Over here, it's bonded to an OH,
and then over here, it's

00:01:19.130 --> 00:01:25.090
bonded to an H, so this is
definitely a chiral carbon.

00:01:25.090 --> 00:01:26.530
We could put a little
asterisk here.

00:01:26.530 --> 00:01:29.930
That's how they often denote
that this is a chiral carbon.

00:01:29.930 --> 00:01:31.510
And if this doesn't make sense
to you, because you might say,

00:01:31.510 --> 00:01:35.200
hey, Sal, look, this carbon is
bonded to two other carbons.

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Isn't that the same thing?

00:01:36.880 --> 00:01:38.780
But the point here is that
we're not looking at what

00:01:38.780 --> 00:01:40.690
atoms it's directly bonded to.

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We're looking at the groups
that it's bonded to.

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In this case, this hydrogen
is a group and an atom.

00:01:45.720 --> 00:01:47.220
Over here, it's an
entire group.

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It's an entire butyl group.

00:01:48.670 --> 00:01:50.160
We have four carbons here.

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We only have one over here.

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Another way to think about it,
we could have drawn this

00:01:56.680 --> 00:01:58.100
molecule like this.

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We could have had a carbon in
the center, and maybe this

00:02:02.590 --> 00:02:05.075
methyl group is popping
out like this.

00:02:08.970 --> 00:02:13.550
You have your CH3, and then you
would have this hydrogen

00:02:13.550 --> 00:02:16.740
coming out maybe in the plane,
and then behind it, you would

00:02:16.740 --> 00:02:18.930
have the butyl group.

00:02:18.930 --> 00:02:22.520
So kind of the back leg of the
tripod, you'd have a butyl,

00:02:22.520 --> 00:02:22.810
and what is that?

00:02:22.810 --> 00:02:26.670
That's C4H9, right?

00:02:26.670 --> 00:02:32.550
That's six plus-- C4H9, so it's
C4H9 in the back, and

00:02:32.550 --> 00:02:35.480
then above it, you
have your OH.

00:02:35.480 --> 00:02:40.480
Above it, in a different color,
you have your OH.

00:02:40.480 --> 00:02:42.500
And when you look at it like
this, it looks just like the

00:02:42.500 --> 00:02:47.100
other chiral carbons that we had
identified in actually the

00:02:47.100 --> 00:02:47.640
last video.

00:02:47.640 --> 00:02:50.720
It looks very similar to
something like this.

00:02:50.720 --> 00:02:52.500
And when you take its
mirror image,

00:02:52.500 --> 00:02:53.500
this is the same molecule.

00:02:53.500 --> 00:02:55.100
Here, I kind of made it a
little bit more three

00:02:55.100 --> 00:02:58.100
dimensional, but if you take
the mirror image of either

00:02:58.100 --> 00:03:01.160
one, you're going to find that
no matter how you try to

00:03:01.160 --> 00:03:03.375
rotate it or shift it, you won't
be able to superimpose

00:03:03.375 --> 00:03:06.600
it on its mirror image
for the same reasons

00:03:06.600 --> 00:03:07.060
as the other ones.

00:03:07.060 --> 00:03:10.710
And I challenge you
to, if you can.

00:03:10.710 --> 00:03:12.690
So this is a chiral carbon.

00:03:12.690 --> 00:03:22.300
This is a chiral center,
we could say.

00:03:22.300 --> 00:03:25.800
Or we could even call it
an asymmetric carbon.

00:03:25.800 --> 00:03:29.150
It could be considered
a stereocenter or

00:03:29.150 --> 00:03:31.360
a stereogenic center.

00:03:31.360 --> 00:03:34.070
All of those are valid
things to call this

00:03:34.070 --> 00:03:35.760
carbon right there.

00:03:35.760 --> 00:03:37.770
And this is also a
chiral molecule.

00:03:45.630 --> 00:03:49.030
Now let's look at this blue
example right here.

00:03:49.030 --> 00:03:52.280
And if we wanted to name it,
just so we get a little bit of

00:03:52.280 --> 00:03:55.860
review, we could start at this
fluorine right there: one,

00:03:55.860 --> 00:04:00.350
two, three, four, five.

00:04:00.350 --> 00:04:01.140
This is what?

00:04:01.140 --> 00:04:04.600
This is 1,
3-difluorocyclopentane.

00:04:12.440 --> 00:04:15.550
So that was a nice
review of naming.

00:04:15.550 --> 00:04:17.839
But let's think about whether
we have any chiral centers

00:04:17.839 --> 00:04:21.370
here and whether the molecule
as a whole is chiral.

00:04:21.370 --> 00:04:24.930
So the immediate ones that we
can kind of dismiss-- and

00:04:24.930 --> 00:04:27.940
actually let me get rid of this
numbering because I don't

00:04:27.940 --> 00:04:31.850
want you think that there are
somehow three hydrogens there.

00:04:31.850 --> 00:04:35.370
That was the number three
hydrogen, number three carbon,

00:04:35.370 --> 00:04:37.390
number two carbon, and so on so
forth, But let me get rid

00:04:37.390 --> 00:04:40.065
of them now that we've
named the molecule.

00:04:40.065 --> 00:04:42.800
I don't want to confuse how many
hydrogens we have at any

00:04:42.800 --> 00:04:44.520
of these points.

00:04:44.520 --> 00:04:45.930
So let's look at the carbons.

00:04:45.930 --> 00:04:48.720
Well, we could immediately
dismiss that carbon, that

00:04:48.720 --> 00:04:50.700
carbon, and that carbon, because
each of those are

00:04:50.700 --> 00:04:51.990
bonded to two hydrogens.

00:04:51.990 --> 00:04:56.100
If we wanted to break it out,
they would look like this.

00:04:56.100 --> 00:04:58.330
So they're bonded to carbons,
carbons, and then they're

00:04:58.330 --> 00:04:59.750
bonded to hydrogens.

00:04:59.750 --> 00:05:01.300
Now, these might be
different groups.

00:05:01.300 --> 00:05:04.310
These might be different types
of alkane groups that it's

00:05:04.310 --> 00:05:06.610
bonded to, so that doesn't
necessarily throw it out of

00:05:06.610 --> 00:05:07.210
the running.

00:05:07.210 --> 00:05:09.970
But these two, the two hydrogens
that it's bonded to,

00:05:09.970 --> 00:05:12.410
are definitely the same
atom, the same group.

00:05:12.410 --> 00:05:18.760
We have an axis of symmetry
through that atom, so it

00:05:18.760 --> 00:05:21.010
cannot be a stereogenic
center.

00:05:21.010 --> 00:05:23.220
It cannot be an asymmetric
carbon.

00:05:23.220 --> 00:05:27.730
It cannot be a chiral center
or a chiral atom, so we can

00:05:27.730 --> 00:05:30.180
knock those guys out
of the running.

00:05:30.180 --> 00:05:33.530
But this guy and that guy
seem pretty interesting.

00:05:33.530 --> 00:05:36.960
Because if we were to break it
out a little bit, you could

00:05:36.960 --> 00:05:40.400
break it out like that and break
it out like, so writing

00:05:40.400 --> 00:05:43.380
a CH and actually show the
bond to the hydrogen.

00:05:43.380 --> 00:05:46.860
And this guy is bonded to one
hydrogen, one fluorine.

00:05:46.860 --> 00:05:51.010
And then if we were to work our
way around the cycle, and

00:05:51.010 --> 00:05:55.580
these cyclic molecules are a
little bit-- it's sometimes a

00:05:55.580 --> 00:05:59.350
little tricky to identify
whether you're bonded to the

00:05:59.350 --> 00:06:01.360
same group or different
groups.

00:06:01.360 --> 00:06:03.310
But actually, let me not make
it too messy while we try to

00:06:03.310 --> 00:06:04.340
figure this out.

00:06:04.340 --> 00:06:05.820
To figure out whether it's
bonded to the same group,

00:06:05.820 --> 00:06:09.750
let's kind of take a walk around
the cycle, around the

00:06:09.750 --> 00:06:11.630
cyclopentane ring.

00:06:11.630 --> 00:06:14.960
If we go this way, if we go on
a counter-- we'll do it in

00:06:14.960 --> 00:06:16.170
different color.

00:06:16.170 --> 00:06:19.960
If we go in a counterclockwise
direction from the carbon in

00:06:19.960 --> 00:06:22.610
question, we're going
to hit a CH2.

00:06:22.610 --> 00:06:25.020
Then we're going to hit a CH.

00:06:25.020 --> 00:06:27.080
So we're going to hit a CH2,
then we're going to hit a CH.

00:06:27.080 --> 00:06:30.163
If we go this way, we're going
to hit a CH2 and then we're

00:06:30.163 --> 00:06:31.610
going to hit another CH2.

00:06:31.610 --> 00:06:34.980
So this guy is fundamentally--
this bond is bonded to a

00:06:34.980 --> 00:06:37.760
different group than that
bond up there is.

00:06:37.760 --> 00:06:39.230
It's also bonded to a hydrogen,

00:06:39.230 --> 00:06:41.160
also bonded to a fluorine.

00:06:41.160 --> 00:06:45.600
So this is bonded to four
different groups, so this is a

00:06:45.600 --> 00:06:48.980
chiral carbon, so that
is a chiral center.

00:06:52.520 --> 00:06:55.870
Now, the exact same argument
can be made for this carbon

00:06:55.870 --> 00:06:56.300
right here.

00:06:56.300 --> 00:06:58.610
You can make that exact same
argument, that, look, if you

00:06:58.610 --> 00:07:03.890
were to walk counterclockwise
from this, you'd hit a CH2,

00:07:03.890 --> 00:07:05.050
then a CH2.

00:07:05.050 --> 00:07:07.800
If you were to go clockwise,
you'd have CH2, then a CH,

00:07:07.800 --> 00:07:09.830
which happens to be connected
to a fluorine.

00:07:09.830 --> 00:07:12.730
So you're actually going to
see something different,

00:07:12.730 --> 00:07:16.190
depending whether you're going
down into that group or into

00:07:16.190 --> 00:07:16.970
that group.

00:07:16.970 --> 00:07:20.250
And then it's also bonded to a
hydrogen and a fluorine, four

00:07:20.250 --> 00:07:21.180
different groups.

00:07:21.180 --> 00:07:23.440
This is also a chiral center.

00:07:23.440 --> 00:07:25.510
Another way to think about it,
and it's actually interesting

00:07:25.510 --> 00:07:30.110
to compare it to this molecule
up here, which was not chiral

00:07:30.110 --> 00:07:32.350
and did not have a chiral
center, this molecule up

00:07:32.350 --> 00:07:34.830
here-- let me draw it a little
different to make it a little

00:07:34.830 --> 00:07:36.080
bit more clear.

00:07:40.940 --> 00:07:44.400
So this one, I could
draw it like this.

00:07:47.970 --> 00:07:50.930
If you have the chlorine like
that, over here, we thought

00:07:50.930 --> 00:07:53.290
about this as a potential chiral
center, and it's kind

00:07:53.290 --> 00:07:59.050
of playing the same role as in
that example down here, but

00:07:59.050 --> 00:08:02.110
you see over here, this is not
a chiral center because

00:08:02.110 --> 00:08:05.050
there's actually an axis of
symmetry for this molecule

00:08:05.050 --> 00:08:07.260
that goes through that carbon.

00:08:07.260 --> 00:08:10.980
So you can actually just draw an
axis of symmetry that goes

00:08:10.980 --> 00:08:14.910
exactly through that carbon.

00:08:14.910 --> 00:08:16.600
The way I drew it, it's not
completely neat, but you can

00:08:16.600 --> 00:08:18.920
see that that is the reflection
of that, if I were

00:08:18.920 --> 00:08:22.020
to draw the bonds actually a
little bit more symmetric.

00:08:22.020 --> 00:08:26.050
Over here, if we try to do the
exact same thing, if we try to

00:08:26.050 --> 00:08:29.170
draw an axis of symmetry over
here, if we try to draw an

00:08:29.170 --> 00:08:31.370
axis of symmetry, we can make
that bond to the fluorine go

00:08:31.370 --> 00:08:34.080
through our axis of symmetry,,
we'll see that that still is

00:08:34.080 --> 00:08:36.212
not the reflection of
this because we have

00:08:36.212 --> 00:08:37.330
a fluorine up here.

00:08:37.330 --> 00:08:39.320
We don't have a fluorine
over here.

00:08:39.320 --> 00:08:41.039
Now, we can do the same
thing with this end.

00:08:41.039 --> 00:08:44.230
If you try to do an axis of
symmetry, fluorine up there,

00:08:44.230 --> 00:08:45.980
no fluorine over here.

00:08:45.980 --> 00:08:48.790
So each of these are definitely
chiral centers,

00:08:48.790 --> 00:08:53.700
while this carbon up here
was not a chiral center.

00:08:53.700 --> 00:08:56.940
Now, the next question is, well,
this thing's got two

00:08:56.940 --> 00:08:58.880
chiral centers, two
chiral carbons.

00:08:58.880 --> 00:09:01.510
It's probably a chiral
molecule.

00:09:01.510 --> 00:09:03.440
Everything else we've seen so
far, if you had a chiral

00:09:03.440 --> 00:09:05.130
center, you had a
chiral molecule.

00:09:05.130 --> 00:09:07.920
But let's take its
mirror image.

00:09:07.920 --> 00:09:10.560
To take its mirror image, let me
clear out some real estate

00:09:10.560 --> 00:09:14.760
over here, So let me
clear out this.

00:09:14.760 --> 00:09:16.170
Let me clear it out.

00:09:16.170 --> 00:09:19.660
So what's the mirror image
going to look like?

00:09:19.660 --> 00:09:21.000
Let me draw first the mirror.

00:09:23.650 --> 00:09:24.800
So the mirror image, you're
going to have a

00:09:24.800 --> 00:09:26.620
fluorine over there.

00:09:26.620 --> 00:09:29.920
Then you're going to bond to a
carbon, which is also bonded

00:09:29.920 --> 00:09:31.030
to a hydrogen.

00:09:31.030 --> 00:09:33.520
That's going to bond to a CH2.

00:09:33.520 --> 00:09:35.670
That's going to bond to a CH.

00:09:35.670 --> 00:09:37.390
That's the mirror
image of that,

00:09:37.390 --> 00:09:38.800
which bonds to a fluorine.

00:09:38.800 --> 00:09:40.530
That's the mirror
image of that.

00:09:40.530 --> 00:09:41.910
And then you go down.

00:09:41.910 --> 00:09:45.050
This is the mirror image
of CH2 here.

00:09:45.050 --> 00:09:47.320
This is the mirror
image of this.

00:09:47.320 --> 00:09:48.640
You connect them.

00:09:48.640 --> 00:09:51.080
Now, these are mirror images
of each other.

00:09:51.080 --> 00:09:53.020
But they are also the
exact same molecule.

00:09:53.020 --> 00:09:56.720
I could just literally move this
guy over to the right,

00:09:56.720 --> 00:09:58.650
and it would be superimposed.

00:09:58.650 --> 00:10:00.600
They are exactly the same.

00:10:00.600 --> 00:10:04.190
So even though we have two
chiral atoms, two chiral

00:10:04.190 --> 00:10:07.770
carbons, the molecule as
a whole is not chiral.

00:10:12.120 --> 00:10:15.990
It is a non-chiral molecule.


Chiral examples 1

WEBVTT
Kind: captions
Language: en

00:00:00.510 --> 00:00:03.350
In the last video we learned a
little bit about what a chiral

00:00:03.350 --> 00:00:06.730
molecule or what a chiral carbon
or a chiral atom is.

00:00:06.730 --> 00:00:08.850
What I want to do in this video
is go through a bunch of

00:00:08.850 --> 00:00:11.920
examples and see if we can
identify if there are any

00:00:11.920 --> 00:00:14.770
chiral atoms and to also
see if we're dealing

00:00:14.770 --> 00:00:16.590
with a chiral molecule.

00:00:16.590 --> 00:00:18.840
So let's look at our
examples here.

00:00:18.840 --> 00:00:20.330
So here I have, what is this?

00:00:20.330 --> 00:00:21.580
This is chlorocyclopentane.

00:00:23.640 --> 00:00:28.680
So the first question is do
we have any chiral atoms?

00:00:28.680 --> 00:00:30.580
And when we look at our
definition that we thought of

00:00:30.580 --> 00:00:33.160
chiral atoms, it all comes from
this notion of handedness

00:00:33.160 --> 00:00:35.320
and not being able to be
superimposable on your mirror

00:00:35.320 --> 00:00:38.040
image, but we said that they're
usually carbons bonded

00:00:38.040 --> 00:00:39.770
to four different groups.

00:00:39.770 --> 00:00:42.160
Let's see, do we have any
carbons here bonded to four

00:00:42.160 --> 00:00:43.000
different groups?

00:00:43.000 --> 00:00:47.350
Well, all the CH2's, they're
bonded to another CH2

00:00:47.350 --> 00:00:48.320
and then two H'2.

00:00:48.320 --> 00:00:52.090
I could draw it like
this: H and H.

00:00:52.090 --> 00:00:54.500
So they're bonded to two of
the same group, so none of

00:00:54.500 --> 00:01:01.580
these CH2's are good candidates
for being a chiral

00:01:01.580 --> 00:01:03.500
center or chiral carbon.

00:01:03.500 --> 00:01:06.160
They're both bonded to-- or all
of them are bonded to two

00:01:06.160 --> 00:01:10.620
hydrogens and two other very
similar-looking CH2 groups,

00:01:10.620 --> 00:01:12.720
although you have to look
at the entire group

00:01:12.720 --> 00:01:13.480
that it's bonded to.

00:01:13.480 --> 00:01:15.970
But they're all definitely
bonded to two hydrogens, so

00:01:15.970 --> 00:01:17.660
it's not four different
groups.

00:01:17.660 --> 00:01:22.240
If we look at this CH
right here, we could

00:01:22.240 --> 00:01:24.510
separate it out like this.

00:01:24.510 --> 00:01:26.510
We could separate the H out like
this, and so since it's

00:01:26.510 --> 00:01:27.740
bonded to a hydrogen.

00:01:27.740 --> 00:01:31.540
This carbon is bonded to a
chlorine, and then it's bonded

00:01:31.540 --> 00:01:34.340
to-- well, it's not clear when
you look at it right from the

00:01:34.340 --> 00:01:37.960
get-go whether this group is
different than this group.

00:01:37.960 --> 00:01:45.840
But if you go around, if you
were to split it half-way like

00:01:45.840 --> 00:01:47.940
this, or maybe another better
way to think about is if you

00:01:47.940 --> 00:01:52.050
were to go around this molecule
in that direction,

00:01:52.050 --> 00:01:54.800
the counterclockwise direction,
you would encounter

00:01:54.800 --> 00:01:57.895
a CH2 group, and then you
encounter a CH2 group, and

00:01:57.895 --> 00:01:59.510
then you would encounter a
third, and then you would

00:01:59.510 --> 00:02:02.360
encounter a fourth CH2 group,
then you would come back to

00:02:02.360 --> 00:02:03.190
where you were before.

00:02:03.190 --> 00:02:06.180
So you would encounter four
CH2's and then you'd come back

00:02:06.180 --> 00:02:07.320
to where you were before.

00:02:07.320 --> 00:02:09.330
If you go in this direction,
what happens?

00:02:09.330 --> 00:02:13.200
You encounter one, two, three,
four CH2's and you come back

00:02:13.200 --> 00:02:14.780
to where you were before.

00:02:14.780 --> 00:02:18.950
So all of this, this bottom
group, depending on how far

00:02:18.950 --> 00:02:21.480
you want to extend it, and this
top group, are really the

00:02:21.480 --> 00:02:22.490
same group.

00:02:22.490 --> 00:02:36.650
So this is not a chiral center
or not a chiral carbon.

00:02:36.650 --> 00:02:39.690
It's not bonded to four
different groups.

00:02:39.690 --> 00:02:42.610
And this is also not a chiral
molecule, because it does not

00:02:42.610 --> 00:02:44.820
have a chiral center.

00:02:44.820 --> 00:02:46.970
And to see that it's not a
chiral molecule-- let me see

00:02:46.970 --> 00:02:49.610
if I can backtrack this
back to the way I

00:02:49.610 --> 00:02:51.060
wrote it right before.

00:02:51.060 --> 00:02:52.980
So you see that it's not
a chiral molecule.

00:02:52.980 --> 00:02:55.540
There's a couple of ways you
could think about it.

00:02:55.540 --> 00:02:58.170
The easiest way, or the way my
brain likes to think about it,

00:02:58.170 --> 00:03:00.180
is just to think about
its mirror image.

00:03:00.180 --> 00:03:02.720
Its mirror image will
look like this.

00:03:02.720 --> 00:03:06.340
So if that's the mirror, you
would have a chlorine.

00:03:06.340 --> 00:03:19.460
Then you have a CH, CH2, CH2,
and you have a CH2, CH2, and

00:03:19.460 --> 00:03:22.300
then you complete your
cyclopentane.

00:03:22.300 --> 00:03:25.470
Now, in this situation, is there
any way to rotate this

00:03:25.470 --> 00:03:26.630
to get this over there?

00:03:26.630 --> 00:03:29.400
Well, if you just took this
molecule right here and you

00:03:29.400 --> 00:03:37.000
just rotated it 180 degrees,
what would it look like?

00:03:37.000 --> 00:03:40.880
Well, maybe a little over--
yeah, well, not quite 180

00:03:40.880 --> 00:03:44.550
degrees, but if you were to
rotate it so that the chlorine

00:03:44.550 --> 00:03:48.430
goes about that far, you would
get this exact molecule.

00:03:48.430 --> 00:03:49.430
You would get something.

00:03:49.430 --> 00:03:50.750
It would look a little
bit different.

00:03:50.750 --> 00:03:52.040
It would look like this.

00:03:52.040 --> 00:03:55.040
Let me see if I can
do it justice.

00:03:55.040 --> 00:03:58.350
It would look like this.

00:03:58.350 --> 00:04:01.680
You would have a CH2.

00:04:01.680 --> 00:04:03.420
So let me let me do it up
here where I have a

00:04:03.420 --> 00:04:04.290
little bit more space.

00:04:04.290 --> 00:04:13.310
If I were to rotate this about
that far, I would get a CH.

00:04:13.310 --> 00:04:20.890
You get the chlorine and then
you have your CH2, and then

00:04:20.890 --> 00:04:28.380
you have another CH2, CH2,
and then you would

00:04:28.380 --> 00:04:30.760
have your CH2 up there.

00:04:30.760 --> 00:04:33.540
If you were to rotate this all
the way around, or actually

00:04:33.540 --> 00:04:36.200
this is almost exactly
180 degrees, it

00:04:36.200 --> 00:04:37.050
would look like this.

00:04:37.050 --> 00:04:38.570
And the only difference between
this and this is just

00:04:38.570 --> 00:04:39.870
how we drew this bond here.

00:04:39.870 --> 00:04:41.850
I could have easily, instead
of drawing that bond like

00:04:41.850 --> 00:04:45.010
that, I could draw it facing
up like that, and these are

00:04:45.010 --> 00:04:47.130
the exact same molecule.

00:04:47.130 --> 00:04:53.100
So this molecule is
also not chiral.

00:04:53.100 --> 00:04:56.600
So let's go to this
one over here.

00:04:56.600 --> 00:04:57.510
So what is this?

00:04:57.510 --> 00:05:02.915
This is a
bromochlorofluoromethane, just

00:05:02.915 --> 00:05:04.930
to practice our naming
a little bit.

00:05:04.930 --> 00:05:06.670
But it's very clear that
we are bonded to

00:05:06.670 --> 00:05:07.750
four different groups.

00:05:07.750 --> 00:05:10.500
All of the different groups, or
the atoms in this case that

00:05:10.500 --> 00:05:14.510
are bonded to this carbon, are
different, so this carbon is a

00:05:14.510 --> 00:05:15.760
chiral center.

00:05:18.140 --> 00:05:21.900
And it should also be pretty
clear that it is

00:05:21.900 --> 00:05:23.260
also a chiral molecule.

00:05:23.260 --> 00:05:25.010
If you were to take its mirror
image, and this is very

00:05:25.010 --> 00:05:27.900
similar to the example we did
in the first video on

00:05:27.900 --> 00:05:31.530
chirality, but its mirror image
will look like this.

00:05:31.530 --> 00:05:35.360
You have the bromine
on the right now.

00:05:35.360 --> 00:05:37.970
The hydrogen is still in
back, and you have the

00:05:37.970 --> 00:05:40.040
fluorine above it.

00:05:40.040 --> 00:05:42.220
No matter how you try to rotate
this thing, if you try

00:05:42.220 --> 00:05:44.690
to get the bromine all the way
over there, all the way to

00:05:44.690 --> 00:05:46.770
that position, then the hydrogen
would be in this

00:05:46.770 --> 00:05:48.790
position and the chlorine would
be in that position.

00:05:48.790 --> 00:05:51.580
And no matter how you try to
flip this around or rotate it

00:05:51.580 --> 00:05:55.040
or shift it, you will never be
able superimpose this molecule

00:05:55.040 --> 00:05:57.210
on that molecule right there.

00:05:57.210 --> 00:06:00.400
So that is a chiral center and
this is a chiral molecule.

00:06:04.400 --> 00:06:09.000
And there's a word for
these two versions.

00:06:09.000 --> 00:06:10.770
We're going to go into the
naming of them later on.

00:06:10.770 --> 00:06:11.850
It's a little bit
more involved.

00:06:11.850 --> 00:06:13.720
We'll have a whole separate
video on it.

00:06:13.720 --> 00:06:20.500
But these two versions of
bromochlorofluoromethane, they

00:06:20.500 --> 00:06:22.900
sometimes have different
chemical properties.

00:06:22.900 --> 00:06:24.150
And these are called
enantiomers.

00:06:27.650 --> 00:06:34.500
And enantiomers are just
the mirror images.

00:06:34.500 --> 00:06:37.500
Each enantiomer is a mirror
image of each other, but they

00:06:37.500 --> 00:06:38.750
are stereoisomers.

00:06:41.120 --> 00:06:42.600
This is all just terminology.

00:06:42.600 --> 00:06:44.450
Stereoisomers.

00:06:44.450 --> 00:06:47.570
You're familiar with the word
isomer, and isomer just means

00:06:47.570 --> 00:06:52.570
that you have the same atoms
in your molecule.

00:06:52.570 --> 00:06:54.800
But then you have different
types of isomers.

00:06:54.800 --> 00:06:57.360
You have constitutional
isomers that say, OK,

00:06:57.360 --> 00:06:59.410
different things are connected
to different things.

00:06:59.410 --> 00:07:02.510
Stereoisomers, the same
things are all

00:07:02.510 --> 00:07:03.520
connected to the same things.

00:07:03.520 --> 00:07:07.370
You have a carbon connected to
only a fluorine, a chlorine

00:07:07.370 --> 00:07:08.980
connected to the carbon, a
hydrogen connected to the

00:07:08.980 --> 00:07:10.840
carbon, a bromine connected
to the carbon.

00:07:10.840 --> 00:07:13.500
So all of the same things are
connected to the same things,

00:07:13.500 --> 00:07:14.930
but they're a three-dimensional

00:07:14.930 --> 00:07:15.860
configuration.

00:07:15.860 --> 00:07:17.620
That's where we're dealing
with the stereo part.

00:07:17.620 --> 00:07:22.300
Stereochemistry is the study
of three-dimensional

00:07:22.300 --> 00:07:24.450
chemistry, as essentially
understanding the actual

00:07:24.450 --> 00:07:26.390
three-dimensional structure
of things.

00:07:26.390 --> 00:07:31.140
So stereoisomers mean that we
have the same constituents,

00:07:31.140 --> 00:07:35.460
the same atoms. They
have the same

00:07:35.460 --> 00:07:38.530
connections to each other.

00:07:38.530 --> 00:07:41.140
Bromine is still connected
to carbon, which is still

00:07:41.140 --> 00:07:41.980
connected to hydrogen.

00:07:41.980 --> 00:07:43.160
That's all true over here.

00:07:43.160 --> 00:07:45.830
But their three-dimensional

00:07:45.830 --> 00:07:48.210
orientation is still different.

00:07:48.210 --> 00:07:50.900
And in this case where they
are mirror images of each

00:07:50.900 --> 00:07:53.880
other, we call them
enantiomers.

00:07:53.880 --> 00:07:55.640
And I should probably make
one clarification.

00:07:55.640 --> 00:07:58.160
In the last few videos, I've
been a little bit, you know,

00:07:58.160 --> 00:08:00.720
sometimes I'll say configuration
and sometimes I

00:08:00.720 --> 00:08:02.860
use the word conformation.

00:08:02.860 --> 00:08:07.200
So sometimes I'll use the word
configuration and sometimes I

00:08:07.200 --> 00:08:10.200
use the word conformation, and
I actually should be a little

00:08:10.200 --> 00:08:13.650
bit more, or I should have been
a little bit more exact

00:08:13.650 --> 00:08:14.380
about these.

00:08:14.380 --> 00:08:16.770
When you're talking about a
configuration, you're actually

00:08:16.770 --> 00:08:18.310
talking about a different
structure.

00:08:18.310 --> 00:08:21.205
To go from one configuration to
another configuration, you

00:08:21.205 --> 00:08:23.150
would actually have to
break bonds and kind

00:08:23.150 --> 00:08:23.940
of reassemble them.

00:08:23.940 --> 00:08:27.320
So these are different
configurations.

00:08:27.320 --> 00:08:30.000
Because in order for them to be
able to be the same thing,

00:08:30.000 --> 00:08:33.010
you would have to swap maybe the
bromine and the hydrogen

00:08:33.010 --> 00:08:35.679
in there where they are relative
to the carbon, so

00:08:35.679 --> 00:08:37.450
these are different
configurations.

00:08:37.450 --> 00:08:40.940
Confirmations are really just
different shapes or different

00:08:40.940 --> 00:08:42.880
orientations of the
same molecule.

00:08:42.880 --> 00:08:47.840
So when we talked about
cyclohexane being in a boat,

00:08:47.840 --> 00:08:51.590
so this is cyclohexane being
in a boat conformation, or

00:08:51.590 --> 00:08:55.910
this is cyclohexane being in a
chair conformation, it's the

00:08:55.910 --> 00:08:58.170
exact same molecule with the
exact same connections.

00:08:58.170 --> 00:09:01.340
We didn't detach any bonds
or reattach any bonds.

00:09:01.340 --> 00:09:03.100
They just flipped around
a little bit.

00:09:03.100 --> 00:09:05.720
So these are two different
conformations.

00:09:05.720 --> 00:09:07.820
These are two different
configurations.

00:09:07.820 --> 00:09:10.090
To go from one configuration
to another, you have to

00:09:10.090 --> 00:09:11.940
rearrange bonds.

00:09:11.940 --> 00:09:13.630
Now let's look at this
molecule over here.

00:09:13.630 --> 00:09:19.210
Can we identify any
stereocenters or chiral

00:09:19.210 --> 00:09:21.860
carbons or chiral atoms?

00:09:21.860 --> 00:09:23.520
And you have this carbon
right here.

00:09:23.520 --> 00:09:26.130
Let's see, this carbon right
here is bonded to a chlorine,

00:09:26.130 --> 00:09:28.700
a hydrogen, a bromine, and
then another carbon.

00:09:28.700 --> 00:09:32.880
So this is bonded to four
different things, so this is a

00:09:32.880 --> 00:09:33.940
chiral carbon.

00:09:33.940 --> 00:09:36.000
Sometimes they put a little
asterisk there.

00:09:36.000 --> 00:09:38.390
If we look at this carbon right
here you can-- well,

00:09:38.390 --> 00:09:40.340
it's bonded to a fluorine and
another carbon, but it's

00:09:40.340 --> 00:09:43.790
bonded to two hydrogens,
so it's not chiral.

00:09:43.790 --> 00:09:46.100
It has two of the same things
that it's bonded to.

00:09:46.100 --> 00:09:48.390
You can even see a little axis
of symmetry through it.

00:09:48.390 --> 00:09:50.840
If you look at that, you can
kind of flip it over, and it's

00:09:50.840 --> 00:09:51.860
going to be the same thing.

00:09:51.860 --> 00:09:55.820
But this one right here, that
is a chiral center.

00:09:55.820 --> 00:09:59.900
That is a chiral center, or
chiral carbon, or chiral atom,

00:09:59.900 --> 00:10:01.550
or a symmetric carbon.

00:10:01.550 --> 00:10:03.350
You'll see it used in
different ways.

00:10:03.350 --> 00:10:06.120
And because this molecule has
got that chiral center, you'll

00:10:06.120 --> 00:10:08.930
see that if you were to take its
mirror image, it would be

00:10:08.930 --> 00:10:10.000
an enantiomer.

00:10:10.000 --> 00:10:13.560
This is not superimposable
on its mirror image.

00:10:13.560 --> 00:10:14.690
We could even try to draw it.

00:10:14.690 --> 00:10:15.880
And just so you know, you don't
always have to do the

00:10:15.880 --> 00:10:17.660
mirror image on the
right side.

00:10:17.660 --> 00:10:20.210
We can draw the mirror image
on the left side.

00:10:20.210 --> 00:10:21.720
So if we want to draw
its mirror image, it

00:10:21.720 --> 00:10:22.490
would look like this.

00:10:22.490 --> 00:10:28.420
You would have a fluorine,
carbon, carbon, chlorine.

00:10:28.420 --> 00:10:32.180
You have your two hydrogens,
and then you would have a

00:10:32.180 --> 00:10:35.020
hydrogen here, and then you
would have your bromine here.

00:10:35.020 --> 00:10:37.890
No matter what you try to do, if
you try to flip this around

00:10:37.890 --> 00:10:40.670
or whatever, you will never be
able superimpose this on top

00:10:40.670 --> 00:10:42.670
of this, so these
are enantiomers.

00:10:42.670 --> 00:10:46.450
These are both stereoisomers
relative to each other.

00:10:46.450 --> 00:10:48.270
And either of these, regardless
of which one you

00:10:48.270 --> 00:10:49.520
pick, are chiral molecules.

00:10:55.220 --> 00:10:57.740
I'm over the time that I
normally want to go in the

00:10:57.740 --> 00:11:00.360
video, so in the next video
I'll do even more.


Introduction to chirality

WEBVTT
Kind: captions
Language: en

00:00:00.600 --> 00:00:04.030
If I were to draw a hand, and
let me just draw a hand really

00:00:04.030 --> 00:00:07.500
fast, so I'll draw
a left hand.

00:00:07.500 --> 00:00:10.620
It looks something like that.

00:00:10.620 --> 00:00:12.220
That is a left hand.

00:00:12.220 --> 00:00:14.970
Now, if I were to take its
mirror image, let's say that

00:00:14.970 --> 00:00:18.460
this is a mirror right there,
and I want to take its mirror

00:00:18.460 --> 00:00:20.970
image, and I'll draw the
mirror image in green.

00:00:20.970 --> 00:00:23.450
So its mirror image would look
something like this.

00:00:26.540 --> 00:00:28.910
Not exact, but you
get the idea.

00:00:28.910 --> 00:00:30.590
The mirror image of a left
hand looks a lot

00:00:30.590 --> 00:00:32.140
like a right hand.

00:00:32.140 --> 00:00:35.780
Now, no matter how I try to
shift or rotate this hand like

00:00:35.780 --> 00:00:39.750
this, I might try to maybe
rotate it 180 degrees, so that

00:00:39.750 --> 00:00:42.500
the thumb is on the other side
like this image right here.

00:00:42.500 --> 00:00:45.260
But no matter what I do, I will
never be able to make

00:00:45.260 --> 00:00:47.340
this thing look like
that thing.

00:00:47.340 --> 00:00:50.190
I can shift it and rotate it,
it'll just never happen.

00:00:50.190 --> 00:00:53.590
I will never be able to
superimpose the blue hand on

00:00:53.590 --> 00:00:54.870
top of this green hand.

00:00:54.870 --> 00:00:58.110
When I say superimpose,
literally put it exactly on

00:00:58.110 --> 00:01:00.490
top of the green hand.

00:01:00.490 --> 00:01:04.030
So whenever something is not
superimposable on its mirror

00:01:04.030 --> 00:01:25.040
image-- let me write this down--
we call it chiral.

00:01:25.040 --> 00:01:27.540
So this hand drawing
right here is an

00:01:27.540 --> 00:01:30.380
example of a chiral object.

00:01:30.380 --> 00:01:33.610
Or I guess the hand is an
example of a chiral object.

00:01:33.610 --> 00:01:36.750
This is not superimposable
on its mirror image.

00:01:36.750 --> 00:01:41.320
And it makes sense that it's
called chiral because the word

00:01:41.320 --> 00:01:43.950
chiral comes from the
Greek word for hand.

00:01:52.170 --> 00:01:54.990
And this definition of
not being able to be

00:01:54.990 --> 00:01:58.020
superimposable on its mirror
image, this applies whether

00:01:58.020 --> 00:02:01.560
you're dealing with chemistry,
or mathematics, or I guess,

00:02:01.560 --> 00:02:03.470
just hands in general.

00:02:03.470 --> 00:02:06.150
So if we extend this definition
to chemistry,

00:02:06.150 --> 00:02:08.110
because that's what we're
talking about, there's two

00:02:08.110 --> 00:02:09.259
concepts here.

00:02:09.259 --> 00:02:17.500
There are chiral molecules,
and then there are chiral

00:02:17.500 --> 00:02:21.310
centers or chiral-- well, I call
them chiral atoms. They

00:02:21.310 --> 00:02:23.430
tend to be carbon atoms, so
sometimes they call them

00:02:23.430 --> 00:02:24.650
chiral carbons.

00:02:24.650 --> 00:02:31.530
So you have these
chiral atoms.

00:02:31.530 --> 00:02:34.350
Now, chiral molecules are
literally molecules that are

00:02:34.350 --> 00:02:36.370
not superimposable on
their mirror image.

00:02:39.550 --> 00:02:40.720
I'm not going to write
the whole thing.

00:02:40.720 --> 00:02:43.120
You know, not superimposable--
I'll just

00:02:43.120 --> 00:02:44.480
write the whole thing.

00:02:44.480 --> 00:02:51.310
Not superimposable
on mirror image.

00:02:55.230 --> 00:02:59.300
Now, for chiral atoms, this is
essentially true, but when you

00:02:59.300 --> 00:03:04.790
look for chiral atoms within a
molecule, the best way to spot

00:03:04.790 --> 00:03:07.760
them is to recognize that these
generally, or maybe I

00:03:07.760 --> 00:03:13.620
should say usually, are carbons,
especially when we're

00:03:13.620 --> 00:03:16.550
dealing in organic chemistry,
but they could be phosphoruses

00:03:16.550 --> 00:03:24.590
or sulfurs, but usually are
carbons bonded to four

00:03:24.590 --> 00:03:25.840
different groups.

00:03:31.550 --> 00:03:34.720
And I want to emphasize
groups, not just four

00:03:34.720 --> 00:03:38.250
different atoms. And to kind of
highlight a molecule that

00:03:38.250 --> 00:03:41.470
contains a chiral atom or chiral
carbon, we can just

00:03:41.470 --> 00:03:42.390
think of one.

00:03:42.390 --> 00:03:45.230
So let's say that I have a
carbon right here, and I'm

00:03:45.230 --> 00:03:47.700
going to set this up so this
is actually a chiral atom,

00:03:47.700 --> 00:03:51.100
that the carbon specific is a
chiral atom, but it's partly a

00:03:51.100 --> 00:03:52.230
chiral molecule.

00:03:52.230 --> 00:03:54.410
And then we'll see examples
that one or both

00:03:54.410 --> 00:03:55.670
of these are true.

00:03:55.670 --> 00:04:02.780
Let's say it's bonded
to a methyl group.

00:04:02.780 --> 00:04:05.660
From that bond, it kind of
pops out of the page.

00:04:05.660 --> 00:04:07.990
Let's say there's a
bromine over here.

00:04:07.990 --> 00:04:12.390
Let's say behind it, there is a
hydrogen, and then above it,

00:04:12.390 --> 00:04:14.360
we have a fluorine.

00:04:14.360 --> 00:04:16.250
Now if I were to take the mirror
image of this thing

00:04:16.250 --> 00:04:20.892
right here, we have your carbon
in the center-- I want

00:04:20.892 --> 00:04:22.710
to do it in that same blue.

00:04:22.710 --> 00:04:26.210
You have the carbon in the
center and then you have the

00:04:26.210 --> 00:04:28.750
fluorine above the carbon.

00:04:28.750 --> 00:04:31.970
You have your bromine now
going in this direction.

00:04:31.970 --> 00:04:33.220
You have this methyl group.

00:04:33.220 --> 00:04:35.800
It's still popping out of the
page, but it's now going to

00:04:35.800 --> 00:04:39.800
the right instead of to
the left, So CH3.

00:04:39.800 --> 00:04:42.720
And then you have the hydrogen
still in the back.

00:04:42.720 --> 00:04:45.320
These are mirror images, if you
view this as kind of the

00:04:45.320 --> 00:04:47.970
mirror and you can see on both
sides of the mirror.

00:04:47.970 --> 00:04:50.240
Now, why is this chiral?

00:04:50.240 --> 00:04:53.090
Well, it's a little bit of a
visualization challenge, but

00:04:53.090 --> 00:04:56.870
no matter how you try to rotate
this thing right here,

00:04:56.870 --> 00:04:59.470
you will never make it exactly
like this thing.

00:04:59.470 --> 00:05:04.660
You might try to rotate it
around like that and try to

00:05:04.660 --> 00:05:08.690
get the methyl group over here,
to get it over there.

00:05:08.690 --> 00:05:10.160
So let's try to do that.

00:05:10.160 --> 00:05:13.260
If we try to get the methyl
group over there, what's going

00:05:13.260 --> 00:05:15.510
to happen to the other groups?

00:05:15.510 --> 00:05:18.070
Well, then the hydrogen group is
going-- or the hydrogen, I

00:05:18.070 --> 00:05:18.340
should say.

00:05:18.340 --> 00:05:20.930
The hydrogen atom is going to
move there and the bromine is

00:05:20.930 --> 00:05:23.410
going to move there.

00:05:23.410 --> 00:05:25.440
So this would be superimposable
if this was a

00:05:25.440 --> 00:05:28.130
hydrogen and this was a
bromine, but it's not.

00:05:28.130 --> 00:05:30.930
You can imagine, the hydrogen
and bromine are switched.

00:05:30.930 --> 00:05:33.110
And you could flip it and do
whatever else you want or try

00:05:33.110 --> 00:05:35.120
to rotate it in any direction,
but you're not going to be

00:05:35.120 --> 00:05:36.650
able to superimpose them.

00:05:36.650 --> 00:05:41.350
So this molecule right here is
a chiral molecule, and this

00:05:41.350 --> 00:05:50.710
carbon is a chiral center, so
this carbon is a chiral

00:05:50.710 --> 00:05:53.990
carbon, sometimes called
an asymmetric

00:05:53.990 --> 00:05:56.970
carbon or a chiral center.

00:05:56.970 --> 00:05:58.360
Sometimes you'll hear
something called a

00:05:58.360 --> 00:05:59.265
stereocenter.

00:05:59.265 --> 00:06:02.340
A stereocenter is a more general
term for any point in

00:06:02.340 --> 00:06:05.470
a molecule that is asymmetric
relative to the different

00:06:05.470 --> 00:06:07.000
groups that it is joined to.

00:06:07.000 --> 00:06:09.350
But all of these, especially
when you're in kind of in

00:06:09.350 --> 00:06:13.730
introductory organic chemistry
class, tends to be a carbon

00:06:13.730 --> 00:06:16.660
bonded to four different
groups.

00:06:16.660 --> 00:06:20.530
And I want to to stress that
it's not four different atoms.

00:06:20.530 --> 00:06:23.920
You could have had a methyl
group here and a propyl group

00:06:23.920 --> 00:06:27.010
here, and the carbon would still
be bonded directly to a

00:06:27.010 --> 00:06:30.740
carbon in either case, but that
would still be a chiral

00:06:30.740 --> 00:06:33.790
carbon, and this would still
actually be a chiral molecule.

00:06:33.790 --> 00:06:37.150
In the next video, we'll
do a bunch of examples.

00:06:37.150 --> 00:06:39.810
We'll look at molecules, try
to identify the chiral

00:06:39.810 --> 00:06:41.975
carbons, and then try to
figure out whether the

00:06:41.975 --> 00:06:44.180
molecule itself is--


Double Newman diagram for methylcyclohexane

WEBVTT
Kind: captions
Language: en

00:00:00.490 --> 00:00:03.640
In the last video we saw that
the two chair shapes, or the

00:00:03.640 --> 00:00:07.080
two chair configurations
of just plain vanilla

00:00:07.080 --> 00:00:09.370
cyclohexane, were
equally stable.

00:00:09.370 --> 00:00:12.560
There was nothing that would
imply that this is more stable

00:00:12.560 --> 00:00:14.190
than that or vice versa.

00:00:14.190 --> 00:00:17.610
What we want to do in this video
is address what happens

00:00:17.610 --> 00:00:21.090
if, instead of just a pure
cyclohexane, what if we added

00:00:21.090 --> 00:00:22.290
a methyl group to it?

00:00:22.290 --> 00:00:25.290
And so instead of just a
cyclohexane, let's think about

00:00:25.290 --> 00:00:29.740
a methylcyclohexane, so we know
what to do when we're

00:00:29.740 --> 00:00:30.520
naming things.

00:00:30.520 --> 00:00:35.720
So methylcyclohexane will
look like that.

00:00:35.720 --> 00:00:37.340
We'll have a hexagon here.

00:00:37.340 --> 00:00:39.990
This is the way we've been
drawing it historically.

00:00:39.990 --> 00:00:41.860
We've been drawing it
just like that.

00:00:41.860 --> 00:00:43.180
And then we'll have
a methyl group.

00:00:43.180 --> 00:00:46.040
And you could literally just
draw a methyl group like this

00:00:46.040 --> 00:00:48.120
or maybe like this.

00:00:48.120 --> 00:00:51.030
And by implication, you have a
carbon here, essentially a CH3

00:00:51.030 --> 00:00:52.950
group here, and, of course,
you have another hydrogen

00:00:52.950 --> 00:00:54.070
bonded here.

00:00:54.070 --> 00:00:57.360
Now, if you were to draw this
methyl group in three

00:00:57.360 --> 00:01:00.350
dimensions like this, it would
look just like our different

00:01:00.350 --> 00:01:03.980
chair positions before, but
instead of this H being just

00:01:03.980 --> 00:01:06.220
an H, we could make this entire
methyl group, so we

00:01:06.220 --> 00:01:11.200
could turn this CH3 right here,
so this-- let me draw it

00:01:11.200 --> 00:01:13.010
out in a different color.

00:01:13.010 --> 00:01:16.850
We could make this carbon that
implicitly has three hydrogens

00:01:16.850 --> 00:01:20.360
on it, so this is a CH3 group
that is a methyl group that's

00:01:20.360 --> 00:01:21.170
right there.

00:01:21.170 --> 00:01:24.670
We could substitute one of these
hydrogens with it, and

00:01:24.670 --> 00:01:27.250
then this would be one
of the shapes of this

00:01:27.250 --> 00:01:31.250
methylcyclohexane, CH3.

00:01:31.250 --> 00:01:33.410
Let me write it down, just
to practice our naming.

00:01:33.410 --> 00:01:34.660
So this is methylcyclohexane.

00:01:40.060 --> 00:01:42.660
Now, this is one of their chair
positions, and then if

00:01:42.660 --> 00:01:45.880
this were to flip down and the
other side were to flip up,

00:01:45.880 --> 00:01:49.120
the other chair position would
take this methyl group from

00:01:49.120 --> 00:01:51.690
being in an axial position,
and it would put it in an

00:01:51.690 --> 00:01:52.950
equatorial position.

00:01:52.950 --> 00:01:54.700
So this is the same
group right here.

00:01:54.700 --> 00:01:55.740
Let me put a circle around it.

00:01:55.740 --> 00:01:57.230
It's a whole group.

00:01:57.230 --> 00:01:58.840
That's the CH3.

00:01:58.840 --> 00:02:01.880
Now, the question we want to
answer in this video, is one

00:02:01.880 --> 00:02:05.610
of these two configurations
going to be more stable?

00:02:05.610 --> 00:02:07.960
Now, you might just be able to
eyeball it looking at this

00:02:07.960 --> 00:02:11.620
diagram, and say, hey, when
we're in the position where

00:02:11.620 --> 00:02:14.780
the methyl group is in the axial
position, it's going to

00:02:14.780 --> 00:02:17.300
be closer to all of these
other carbons over here,

00:02:17.300 --> 00:02:18.920
closer to their electron
clouds.

00:02:18.920 --> 00:02:20.710
Maybe it has higher
potential energy.

00:02:20.710 --> 00:02:22.080
Maybe it'll want
to spring away.

00:02:22.080 --> 00:02:24.470
And if that was what you're
guessing or what you're kind

00:02:24.470 --> 00:02:27.560
of eyeballing, you'd be right,
because in this position, this

00:02:27.560 --> 00:02:30.220
methyl is much further away
from all of the stuff out

00:02:30.220 --> 00:02:32.620
here, so there'll be less, I
guess you can consider it,

00:02:32.620 --> 00:02:37.680
electron cloud crowding,
if you will.

00:02:37.680 --> 00:02:42.420
Now, to see that a little bit
more clear, I want to do what

00:02:42.420 --> 00:02:44.590
we call a double
Newman diagram.

00:02:44.590 --> 00:02:46.420
And really, that's the whole
motivation of this video is to

00:02:46.420 --> 00:02:47.540
kind of expose you to that.

00:02:47.540 --> 00:02:51.260
A Newman diagram isn't just
useful for simple things like

00:02:51.260 --> 00:02:52.790
a butane or an ethane.

00:02:52.790 --> 00:02:54.810
You can actually do it
with cyclical rings.

00:02:54.810 --> 00:02:58.110
And to do the Newman diagram,
let me number these carbons.

00:02:58.110 --> 00:02:59.430
So we could number
them like this.

00:02:59.430 --> 00:03:05.020
So this is carbon one, two,
three, four, five, six.

00:03:05.020 --> 00:03:07.960
And you don't have to call this
one methylcyclohexane,

00:03:07.960 --> 00:03:12.370
because whenever you have only
one group attached to the

00:03:12.370 --> 00:03:15.760
ring, you implicitly start
numbering at the carbon that

00:03:15.760 --> 00:03:16.820
the group is attached.

00:03:16.820 --> 00:03:18.570
So that is the one
carbon over here.

00:03:18.570 --> 00:03:24.030
This is the one carbon, two,
three, four, five, six.

00:03:24.030 --> 00:03:27.740
And over here, once again, is
the one carbon, two, three,

00:03:27.740 --> 00:03:29.850
four, five, six.

00:03:29.850 --> 00:03:33.580
Now, what I want to do is draw
two Newman projections, and

00:03:33.580 --> 00:03:35.070
both of them will involve--
well, actually, I'll draw

00:03:35.070 --> 00:03:37.240
four, but you'll see what I'm
talking about in a second.

00:03:37.240 --> 00:03:39.030
So the first Newman projection,
I'm going to start

00:03:39.030 --> 00:03:43.610
at that carbon right
over there.

00:03:43.610 --> 00:03:45.220
So let's think about what
that would look like.

00:03:45.220 --> 00:03:47.230
So we're at the front.

00:03:47.230 --> 00:03:49.100
We're staring straight
on to that carbon.

00:03:49.100 --> 00:03:52.280
So this carbon's in the front,
this carbon over here.

00:03:52.280 --> 00:03:54.610
This carbon, carbon number
two, is in the back.

00:03:54.610 --> 00:03:55.470
So let me label this.

00:03:55.470 --> 00:03:58.550
This is carbon number one that
we're looking head on.

00:03:58.550 --> 00:04:00.150
Now, right in the axial
position you

00:04:00.150 --> 00:04:01.170
have that methyl group.

00:04:01.170 --> 00:04:02.800
So let me draw that.

00:04:02.800 --> 00:04:08.910
So in the axial position you
have that methyl group right

00:04:08.910 --> 00:04:09.810
over there.

00:04:09.810 --> 00:04:12.630
And then in the equatorial
position right here, you have

00:04:12.630 --> 00:04:13.626
this hydrogen.

00:04:13.626 --> 00:04:16.190
Let me draw that.

00:04:16.190 --> 00:04:18.700
So you have this hydrogen.

00:04:18.700 --> 00:04:21.709
And then over here, this bond
right over here, this gets us

00:04:21.709 --> 00:04:23.520
to another CH2 group.

00:04:23.520 --> 00:04:25.450
Let me draw that like this.

00:04:25.450 --> 00:04:29.240
So that gets us to
another CH2.

00:04:29.240 --> 00:04:30.800
That's a CH2 right
there, right?

00:04:30.800 --> 00:04:33.280
Or maybe I should circle
it like this.

00:04:33.280 --> 00:04:34.580
This whole thing is a CH2.

00:04:34.580 --> 00:04:36.660
So it's bonded to the carbon,
but the carbon has two

00:04:36.660 --> 00:04:37.700
hydrogens on it.

00:04:37.700 --> 00:04:41.540
And this is actually
carbon number six.

00:04:41.540 --> 00:04:42.460
So this is the front.

00:04:42.460 --> 00:04:45.260
Now, if we're staring straight
and carbon number two is right

00:04:45.260 --> 00:04:47.460
behind it-- let me draw
carbon number two.

00:04:47.460 --> 00:04:49.050
I'll do it in this blue color.

00:04:49.050 --> 00:04:53.040
So carbon number two,
that bigger circle.

00:04:53.040 --> 00:04:56.200
Now carbon number two, what's
going on over there?

00:04:56.200 --> 00:04:59.990
It has a hydrogen in the axial
position going straight down.

00:05:03.880 --> 00:05:05.660
This hydrogen right
over there.

00:05:05.660 --> 00:05:10.680
And it has another hydrogen
going equatorial.

00:05:10.680 --> 00:05:13.440
So this green hydrogen right
here is going equatorial.

00:05:13.440 --> 00:05:14.970
It looks like that.

00:05:14.970 --> 00:05:17.920
And then it connects to
carbon number three,

00:05:17.920 --> 00:05:19.060
which is another CH2.

00:05:19.060 --> 00:05:21.060
It has two hydrogens branching
off of it.

00:05:23.990 --> 00:05:25.340
In front, we have carbon
number one.

00:05:25.340 --> 00:05:27.692
In the back, we have
carbon number two.

00:05:27.692 --> 00:05:30.040
Let me color code it
a little better.

00:05:30.040 --> 00:05:31.670
Carbon number two.

00:05:31.670 --> 00:05:35.710
And then carbon number two
branches off to-- so if you

00:05:35.710 --> 00:05:40.850
think of this branch right here,
that's carbon number two

00:05:40.850 --> 00:05:44.440
branching off to carbon number
three, or CH3 right there.

00:05:44.440 --> 00:05:46.200
Let me do that in a new color.

00:05:46.200 --> 00:05:48.400
So this is actually
a CH2 group.

00:05:48.400 --> 00:05:49.130
That's a CH2.

00:05:49.130 --> 00:05:52.350
This is a carbon, and it has
two hydrogens, right?

00:05:52.350 --> 00:05:54.430
So this is a CH2.

00:05:54.430 --> 00:05:59.170
This is carbon number
three right there.

00:05:59.170 --> 00:06:03.920
And then that goes-- and
actually, I'll pause there.

00:06:03.920 --> 00:06:08.230
What I'll do now is I'll draw
another Newman projection, but

00:06:08.230 --> 00:06:14.190
for this Newman projection,
we'll be looking straight on

00:06:14.190 --> 00:06:17.830
our carbon number five.

00:06:17.830 --> 00:06:20.540
We're going to see we're going
to form a ring because the

00:06:20.540 --> 00:06:22.130
first Newman projection
we just did

00:06:22.130 --> 00:06:23.430
essentially covers this bond.

00:06:23.430 --> 00:06:26.010
This bond is sitting straight
into the screen the way I did

00:06:26.010 --> 00:06:26.410
it right now.

00:06:26.410 --> 00:06:29.870
Carbon number two is directly
behind carbon number one.

00:06:29.870 --> 00:06:33.670
So I guess the opposite side of
the ring is five to four.

00:06:33.670 --> 00:06:36.070
If you look at, here, one to two
is there, and then five to

00:06:36.070 --> 00:06:37.110
four is just like that.

00:06:37.110 --> 00:06:39.230
So you can imagine when we're
doing the Newman projections,

00:06:39.230 --> 00:06:41.920
we're looking straight on here
on the left Newman projection.

00:06:41.920 --> 00:06:44.370
We're going to look straight in
that direction on the right

00:06:44.370 --> 00:06:45.370
Newman projection.

00:06:45.370 --> 00:06:50.400
So if we have carbon number five
in front, what are its

00:06:50.400 --> 00:06:51.880
bonds going to look like?

00:06:51.880 --> 00:06:56.650
Well, it's going to bond to
carbon number six over here.

00:06:56.650 --> 00:07:00.070
So we can make this right--
let me do that

00:07:00.070 --> 00:07:01.450
in a different color.

00:07:01.450 --> 00:07:06.180
This right here, this bond right
here is this bond right

00:07:06.180 --> 00:07:09.190
here to that same CH2 that
our first Newman

00:07:09.190 --> 00:07:10.760
projection bonded to.

00:07:10.760 --> 00:07:14.070
And then he's going to
have two hydrogens.

00:07:14.070 --> 00:07:15.030
I haven't drawn them here.

00:07:15.030 --> 00:07:16.760
Let me draw them, just
so you can see them.

00:07:16.760 --> 00:07:19.420
It's going to have two
hydrogens, one in an axial

00:07:19.420 --> 00:07:23.310
position and one in an
equatorial position.

00:07:23.310 --> 00:07:25.425
It's hard to see now, but he's
going to have one hydrogen in

00:07:25.425 --> 00:07:28.260
an axial and one in an
equatorial position.

00:07:28.260 --> 00:07:29.740
And then in the back
we're going to draw

00:07:29.740 --> 00:07:30.710
carbon number four.

00:07:30.710 --> 00:07:33.570
And carbon number four, I will
do in this green color.

00:07:33.570 --> 00:07:36.140
So carbon number four--
actually, , well, yeah I'll do

00:07:36.140 --> 00:07:38.580
carbon number four in
that green color.

00:07:38.580 --> 00:07:40.720
This is really just an exercise
in visualization.

00:07:40.720 --> 00:07:41.990
That's why I wanted
to do it with you.

00:07:41.990 --> 00:07:45.480
So carbon number four has an
axial hydrogen, so it has a

00:07:45.480 --> 00:07:46.790
hydrogen pointing
straight down.

00:07:46.790 --> 00:07:48.470
That hydrogen is
that hydrogen.

00:07:48.470 --> 00:07:52.240
It has an equatorial hydrogen
going out like that.

00:07:52.240 --> 00:07:54.890
And then it bonds to carbon
number three.

00:07:54.890 --> 00:08:01.110
So this bond right here is
this bond just like that.

00:08:01.110 --> 00:08:04.580
So what do we see immediately
when we

00:08:04.580 --> 00:08:06.050
draw this chair position?

00:08:06.050 --> 00:08:09.070
When our methyl group
is in the axial

00:08:09.070 --> 00:08:10.140
position, what do we see?

00:08:10.140 --> 00:08:15.810
Methyl in axial position.

00:08:15.810 --> 00:08:17.930
We see that it's gauche,
or gowche.

00:08:17.930 --> 00:08:19.490
I don't know the best
way to pronounce it.

00:08:19.490 --> 00:08:23.810
It's only 60 degrees away from
carbon number three.

00:08:23.810 --> 00:08:27.010
This is only 60 degrees,
or a dihedral angle.

00:08:27.010 --> 00:08:30.130
When you use the Newman
projection, this is only a

00:08:30.130 --> 00:08:33.580
60-degree angle.

00:08:33.580 --> 00:08:38.309
It is gauche to carbon
number three.

00:08:38.309 --> 00:08:39.880
So maybe they're crowding
each other a little bit.

00:08:39.880 --> 00:08:43.070
Let's compare it to the
situation where our methyl

00:08:43.070 --> 00:08:48.010
group is equatorial, where the
carbon that it's attached to

00:08:48.010 --> 00:08:49.490
is on the down part
of the chair.

00:08:49.490 --> 00:08:51.920
Let's see what that Newman
projection looks like.

00:08:51.920 --> 00:08:54.300
So same thing.

00:08:54.300 --> 00:08:56.480
Let me scroll over to the
right a little bit.

00:08:56.480 --> 00:09:02.570
So this is this configuration
and it's in equilibrium with

00:09:02.570 --> 00:09:04.670
this configuration right here.

00:09:04.670 --> 00:09:06.200
We'll do the exact
same exercise.

00:09:06.200 --> 00:09:07.050
Carbon number one.

00:09:07.050 --> 00:09:11.080
But now carbon number one, in
carbon number one right here,

00:09:11.080 --> 00:09:15.250
the hydrogen is now axial and
it's pointing straight down.

00:09:15.250 --> 00:09:16.570
Let me draw that.

00:09:16.570 --> 00:09:20.830
So we have a hydrogen pointing
straight down now.

00:09:20.830 --> 00:09:27.490
Hydrogen's pointing down and
now the CH3 is in an

00:09:27.490 --> 00:09:30.910
equatorial position, which you
can see more clearly on this

00:09:30.910 --> 00:09:31.520
than over here.

00:09:31.520 --> 00:09:34.010
So you have a CH3.

00:09:34.010 --> 00:09:36.140
The methyl group
is right there.

00:09:36.140 --> 00:09:40.930
And now this bond to
carbon number six

00:09:40.930 --> 00:09:42.180
will look like this.

00:09:44.590 --> 00:09:45.890
So you have a CH2.

00:09:45.890 --> 00:09:49.260
This is number six
right over there.

00:09:49.260 --> 00:09:51.510
And now if we were to go to
the back, if we were go to

00:09:51.510 --> 00:09:54.490
carbon number two in the back,
which we had done in the blue

00:09:54.490 --> 00:09:57.130
color before, so I'll do it
in the blue color again.

00:09:57.130 --> 00:10:00.600
Carbon number two in black, it
has a hydrogen in the axial

00:10:00.600 --> 00:10:03.460
position going straight up.

00:10:03.460 --> 00:10:04.650
That's that hydrogen
right there.

00:10:04.650 --> 00:10:06.740
It has a hydrogen going
straight up.

00:10:06.740 --> 00:10:11.420
It has another hydrogen over
here, and then it bonds to

00:10:11.420 --> 00:10:17.390
carbon number three in the
back, so CH2 over here.

00:10:17.390 --> 00:10:19.340
So this guy's the same thing
as this guy, but now we've

00:10:19.340 --> 00:10:22.940
flipped configurations, so he
bonds to that guy in the back.

00:10:22.940 --> 00:10:26.840
And now we do the Newman diagram
looking straight on to

00:10:26.840 --> 00:10:30.870
carbon number five, or looking,
actually, straight on

00:10:30.870 --> 00:10:32.310
to-- right, carbon
number five.

00:10:32.310 --> 00:10:36.180
So we're looking straight in
this direction for this Newman

00:10:36.180 --> 00:10:36.650
projection.

00:10:36.650 --> 00:10:39.100
Now we're going to look straight
in this direction for

00:10:39.100 --> 00:10:40.670
our other Newman projection.

00:10:40.670 --> 00:10:46.200
So carbon number five, if we
draw it in the front-- I

00:10:46.200 --> 00:10:48.890
haven't drawn it here, but it
has a hydrogen at the axial

00:10:48.890 --> 00:10:50.785
position, and it has
a hydrogen in

00:10:50.785 --> 00:10:52.400
the equatorial position.

00:10:52.400 --> 00:10:58.430
So carbon number five, if we
look at this, and this is

00:10:58.430 --> 00:11:00.800
really-- if you're getting a
little stressed out about this

00:11:00.800 --> 00:11:02.490
because it's a little hard
to understand, you

00:11:02.490 --> 00:11:03.360
might want to rewatch.

00:11:03.360 --> 00:11:06.590
This is really just an example
of visualizations.

00:11:06.590 --> 00:11:08.480
I really hope this isn't
confusing you.

00:11:08.480 --> 00:11:10.950
If you find this really
daunting, this isn't going to

00:11:10.950 --> 00:11:14.130
really trip you up in the rest
of organic chemistry, but if

00:11:14.130 --> 00:11:15.200
you can get it, it's
even better.

00:11:15.200 --> 00:11:17.030
You'll be that much better
at visualizing

00:11:17.030 --> 00:11:18.720
some of these molecules.

00:11:18.720 --> 00:11:22.240
So if we look straight on at
carbon number five, we have a

00:11:22.240 --> 00:11:24.820
hydrogen in the axial position
coming straight down.

00:11:28.250 --> 00:11:31.000
It is bonded.

00:11:31.000 --> 00:11:37.180
Carbon number five is bonded to
carbon number six, which is

00:11:37.180 --> 00:11:41.150
right over there.

00:11:41.150 --> 00:11:42.450
So let me make it very clear.

00:11:42.450 --> 00:11:44.880
So this bond right here,
I want to do it

00:11:44.880 --> 00:11:47.070
in a different color.

00:11:47.070 --> 00:11:50.330
This bond it right here is the
same thing as this one.

00:11:50.330 --> 00:11:52.990
This is a really good way to--
if you can do this, then your

00:11:52.990 --> 00:11:55.490
brain is pretty good at
translating between Newman

00:11:55.490 --> 00:11:58.090
projections and these kind
of seat diagrams

00:11:58.090 --> 00:11:59.290
that we have up here.

00:11:59.290 --> 00:12:01.500
So this is this bond.

00:12:01.500 --> 00:12:06.750
This axial hydrogen is
this axial hydrogen.

00:12:06.750 --> 00:12:09.130
And then we have another
hydrogen.

00:12:09.130 --> 00:12:11.580
We have this hydrogen right
here, which would

00:12:11.580 --> 00:12:12.550
be that like that.

00:12:12.550 --> 00:12:15.030
And then behind it, you have
carbon number four.

00:12:15.030 --> 00:12:20.050
Carbon number four is like that,
so carbon number four,

00:12:20.050 --> 00:12:21.290
draw a circle.

00:12:21.290 --> 00:12:25.050
It has a hydrogen in its axial
position, another hydrogen

00:12:25.050 --> 00:12:27.900
like that, and then it bonds
to carbon number three.

00:12:27.900 --> 00:12:29.770
So this was number
three right here.

00:12:29.770 --> 00:12:31.120
So just like that.

00:12:31.120 --> 00:12:33.610
So what do we see about this
methyl group here?

00:12:33.610 --> 00:12:37.880
In this situation, this
methyl group is anti-.

00:12:37.880 --> 00:12:39.200
There's two ways to
think about it.

00:12:39.200 --> 00:12:43.270
It's dihedral angle versus
carbon number

00:12:43.270 --> 00:12:45.850
three is now 180 degrees.

00:12:45.850 --> 00:12:48.240
Over here it was gauche.

00:12:48.240 --> 00:12:51.080
Its dihedral angle to carbon
number three was 60 degrees.

00:12:51.080 --> 00:12:52.870
Now, it's 180 degrees.

00:12:52.870 --> 00:12:54.260
So it's much further.

00:12:54.260 --> 00:12:56.340
And now its dihedral angle
to carbon number

00:12:56.340 --> 00:13:00.000
six is also 120 degrees.

00:13:00.000 --> 00:13:03.550
So in this situation, where
our methyl group is

00:13:03.550 --> 00:13:05.820
equatorial, it's axial here.

00:13:05.820 --> 00:13:08.650
It's equatorial here when we
jumped back down because

00:13:08.650 --> 00:13:09.700
notice, it's parallel.

00:13:09.700 --> 00:13:12.060
The bond is parallel to
parts of the ring.

00:13:12.060 --> 00:13:14.730
In this situation, we are
farther away from the other

00:13:14.730 --> 00:13:15.570
methyl groups.

00:13:15.570 --> 00:13:17.490
There's less crowding,
and so this is

00:13:17.490 --> 00:13:19.230
a more stable situation.

00:13:19.230 --> 00:13:33.230
So you could say it is
anti-configuration relative to

00:13:33.230 --> 00:13:37.490
carbon number three, while over
here, it was gauche to

00:13:37.490 --> 00:13:38.650
carbon number three.

00:13:38.650 --> 00:13:39.390
I don't know if I'm saying it.

00:13:39.390 --> 00:13:40.270
Is it gowche, gauche?

00:13:40.270 --> 00:13:41.610
I don't know the best
way to pronounce it.

00:13:41.610 --> 00:13:43.330
So in this case, there's
less crowding.

00:13:43.330 --> 00:13:49.610
This is more stable, lower
potential energy.

00:13:49.610 --> 00:13:50.860
So hopefully you found
that interesting.

00:13:50.860 --> 00:13:54.670
This was really a way, just an
exercise in being able to go

00:13:54.670 --> 00:13:56.320
from this visualization
to kind of this

00:13:56.320 --> 00:13:58.040
double Newman diagram.

00:13:58.040 --> 00:14:00.550
And if it makes it any easier,
the way you could think about

00:14:00.550 --> 00:14:04.550
it is we're kind of viewing in
this Newman diagram right

00:14:04.550 --> 00:14:07.480
here, where this carbon number
six is this carbon number six.

00:14:07.480 --> 00:14:09.450
This CH2 is this
one back there.

00:14:09.450 --> 00:14:11.750
So when we're looking at it
from this, we're kind of

00:14:11.750 --> 00:14:15.940
looking at this hexane ring
from this direction.

00:14:15.940 --> 00:14:17.350
We see this in front.

00:14:17.350 --> 00:14:19.830
This is this, and we
see that in back.

00:14:19.830 --> 00:14:21.090
That is that.

00:14:21.090 --> 00:14:22.670
Over here, same thing.

00:14:22.670 --> 00:14:29.650
We're looking at it directly
from this direction.

00:14:29.650 --> 00:14:33.660
We see this guy on top is over
here, and this guy on the

00:14:33.660 --> 00:14:34.910
bottom is over here.


Chair and boat shapes for cyclohexane

WEBVTT
Kind: captions
Language: en

00:00:00.510 --> 00:00:03.550
For all the cyclic molecules
we've dealt with so far, we've

00:00:03.550 --> 00:00:05.000
just drawn them as rings.

00:00:05.000 --> 00:00:11.250
For example, for cyclohexane
we've literally just drawn it

00:00:11.250 --> 00:00:12.900
as a hexagon.

00:00:12.900 --> 00:00:17.420
So we've drawn cyclohexane
like that.

00:00:17.420 --> 00:00:20.570
Now, we know from the last
several videos that all the

00:00:20.570 --> 00:00:23.520
bonds for carbon don't sit
in the same plane.

00:00:23.520 --> 00:00:26.430
If we take the example
of methane, that's

00:00:26.430 --> 00:00:27.360
the simplest example.

00:00:27.360 --> 00:00:29.020
You have your carbon sitting
in the middle.

00:00:29.020 --> 00:00:32.180
You'll have kind of a hydrogen
popping out like that, another

00:00:32.180 --> 00:00:35.000
hydrogen that's in the plane
of the screen, another one

00:00:35.000 --> 00:00:37.240
that's behind the screen,
and another one

00:00:37.240 --> 00:00:38.210
that is straight up.

00:00:38.210 --> 00:00:41.570
So you kind of have this
tetrahedral structure, and in

00:00:41.570 --> 00:00:45.990
the case of methane you have
that 109.5 degree bond angles.

00:00:45.990 --> 00:00:48.410
Carbon likes to form bonds
of this shape.

00:00:48.410 --> 00:00:50.740
It won't always be
109.5 degrees.

00:00:50.740 --> 00:00:53.390
It'll be something close to
it, depending on what the

00:00:53.390 --> 00:00:57.010
different atoms or molecules
are that it is bonded to.

00:00:57.010 --> 00:01:01.150
So given that, what would a
cyclohexane molecule actually

00:01:01.150 --> 00:01:03.480
look like if we try to
visualize it in three

00:01:03.480 --> 00:01:04.420
dimensions?

00:01:04.420 --> 00:01:07.340
So to think about that, let's
think about these two bonds

00:01:07.340 --> 00:01:10.400
first. I'll try my best to
draw it in one of its

00:01:10.400 --> 00:01:12.780
three-dimensional shapes.

00:01:12.780 --> 00:01:17.890
So those bonds right there,
I will draw like that.

00:01:17.890 --> 00:01:23.260
And then this down here, in
orange, I will draw like this.

00:01:23.260 --> 00:01:25.230
And then this up here,
in magenta, I

00:01:25.230 --> 00:01:27.010
will draw like that.

00:01:27.010 --> 00:01:32.730
And then, let me see, in, in
purple, I'll do these two

00:01:32.730 --> 00:01:35.560
right over here, and I'll
draw them like this.

00:01:35.560 --> 00:01:38.010
So you have that
and like that.

00:01:38.010 --> 00:01:39.940
This hopefully makes clear that
over there is that end

00:01:39.940 --> 00:01:43.060
over there, this end over here
is this end over here, and

00:01:43.060 --> 00:01:48.170
this way that I've drawn the
cyclohexane is called a chair

00:01:48.170 --> 00:01:49.420
configuration.

00:01:51.530 --> 00:01:52.710
Chair shape.

00:01:52.710 --> 00:01:53.730
And it might be obvious.

00:01:53.730 --> 00:01:54.620
It looks like a chair.

00:01:54.620 --> 00:01:56.740
That's the back of the chair,
this is where you would sit

00:01:56.740 --> 00:01:59.050
down on the chair, and I guess
the back of your calves would

00:01:59.050 --> 00:01:59.570
go against here.

00:01:59.570 --> 00:02:01.560
Your knees would sit on it
someplace like that.

00:02:01.560 --> 00:02:03.310
That's called the chair
configuration.

00:02:03.310 --> 00:02:05.860
Now another configuration that
it could be in is called the

00:02:05.860 --> 00:02:08.949
boat configuration.

00:02:08.949 --> 00:02:11.150
And so if I were to put this
exact one in the boat

00:02:11.150 --> 00:02:13.630
configuration, if I take it
from a slightly different

00:02:13.630 --> 00:02:16.450
perspective, if I'm looking at
it, kind of, head on, it would

00:02:16.450 --> 00:02:24.700
look something like this in
the boat configuration.

00:02:24.700 --> 00:02:26.440
It would look like this.

00:02:29.800 --> 00:02:32.710
Now I want to use the purple.

00:02:32.710 --> 00:02:35.390
It would look like that.

00:02:35.390 --> 00:02:37.770
Now, the first thing you're
probably saying is, Sal, you

00:02:37.770 --> 00:02:39.690
said that the reason why it
looks like this is because

00:02:39.690 --> 00:02:44.000
carbon likes to form these kind
of tetrahedral, or this

00:02:44.000 --> 00:02:45.880
tripod shaped bonds.

00:02:45.880 --> 00:02:49.120
I don't see the tripod shaped
bonds either here or here.

00:02:49.120 --> 00:02:51.480
Let me draw that boat a little
bit, at least this end of the

00:02:51.480 --> 00:02:52.880
boat a little bit better.

00:02:52.880 --> 00:02:54.720
There you go.

00:02:54.720 --> 00:02:57.610
And you say, well I don't see
that tripod shape over there.

00:02:57.610 --> 00:02:59.270
And to see the tripod
shape, you just

00:02:59.270 --> 00:03:01.330
have to draw the hydrogens.

00:03:01.330 --> 00:03:03.900
So let me draw some
hydrogens here.

00:03:03.900 --> 00:03:08.520
So let me draw a hydrogen
here that will go

00:03:08.520 --> 00:03:12.525
straight down like this.

00:03:12.525 --> 00:03:16.840
A hydrogen that goes straight
down over here, a hydrogen

00:03:16.840 --> 00:03:21.030
that goes straight up over here,
straight up over here,

00:03:21.030 --> 00:03:24.430
straight down over here,
straight up over there.

00:03:24.430 --> 00:03:27.420
I've now drawn one hydrogen
on every carbon.

00:03:27.420 --> 00:03:30.290
And now let me draw
some hydrogens.

00:03:30.290 --> 00:03:40.540
Let me draw a hydrogen here that
goes straight up, not up

00:03:40.540 --> 00:03:43.510
really-- to the side
over here.

00:03:43.510 --> 00:03:47.900
So a hydrogen there, let me draw
a hydrogen over here that

00:03:47.900 --> 00:03:48.960
does the same thing.

00:03:48.960 --> 00:03:50.415
So those guys have
their hydrogens.

00:03:50.415 --> 00:03:53.520
A hydrogen right over here.

00:03:53.520 --> 00:03:56.840
And then, let's see, this guy
needs his hydrogens still, so

00:03:56.840 --> 00:03:59.810
he'll have a hydrogen that goes
down like that, and a

00:03:59.810 --> 00:04:01.280
hydrogen and it goes
like that.

00:04:01.280 --> 00:04:04.650
And this guy will have a
hydrogen that goes like that.

00:04:04.650 --> 00:04:09.230
And when you see it like this,
if you look at any one carbon

00:04:09.230 --> 00:04:12.180
on this molecule, if you look at
any one carbon, you can see

00:04:12.180 --> 00:04:15.430
that's forming the same
tetrahedral shape that has a

00:04:15.430 --> 00:04:17.320
tripod at every one.

00:04:17.320 --> 00:04:21.410
Over here, you have that close
to, roughly 109 degree, 110

00:04:21.410 --> 00:04:24.290
degree angle between each of
the constituents that are

00:04:24.290 --> 00:04:27.090
bonding to the carbon.

00:04:27.090 --> 00:04:30.210
Now, I've drawn the different
hydrogens that are coming off

00:04:30.210 --> 00:04:31.770
of these carbons in different
colors, and I've

00:04:31.770 --> 00:04:32.940
done it for a purpose.

00:04:32.940 --> 00:04:35.650
The ones that are going straight
up or straight down,

00:04:35.650 --> 00:04:37.160
we call those axial hydrogens.

00:04:41.980 --> 00:04:44.460
And the ones I drew in orange
that are kind of going to the

00:04:44.460 --> 00:04:46.880
side in some level, we call
these equatorial.

00:04:53.420 --> 00:04:56.410
These are equatorial
hydrogens.

00:04:56.410 --> 00:04:58.940
And the reason why it's useful
to know that name is when we

00:04:58.940 --> 00:05:01.100
talk about the different
configurations, the different

00:05:01.100 --> 00:05:03.800
chair and boats, whether
something is equatorial or

00:05:03.800 --> 00:05:06.920
axial can change if this were to
flip up, or vice versa, and

00:05:06.920 --> 00:05:07.360
things like that.

00:05:07.360 --> 00:05:09.360
And we'll talk more about
that in the next video.

00:05:09.360 --> 00:05:11.510
And the reason why they're
called equatorial is if you

00:05:11.510 --> 00:05:14.060
think about it, and it's
sometimes hard to visualize,

00:05:14.060 --> 00:05:18.880
this bond right here is parallel
to this bond right

00:05:18.880 --> 00:05:19.640
over there.

00:05:19.640 --> 00:05:22.810
And this bond right over here
is parallel to that.

00:05:22.810 --> 00:05:27.080
It's parallel, the equatorial
bonds are parallel, to some

00:05:27.080 --> 00:05:28.020
part of the ring.

00:05:28.020 --> 00:05:30.390
So that one is parallel to
that right over there.

00:05:30.390 --> 00:05:33.020
Actually I should even, I could
even color-code that.

00:05:33.020 --> 00:05:35.700
This, well, I don't want
to use that same color.

00:05:35.700 --> 00:05:44.300
This is parallel to this and
this is parallel to that.

00:05:44.300 --> 00:05:47.090
And we could do it for all
the equatorial bonds.

00:05:47.090 --> 00:05:49.440
So for example, I don't
want to-- I'm running

00:05:49.440 --> 00:05:50.650
out of colors here.

00:05:50.650 --> 00:05:57.840
So this right here is parallel
to this, and this, and that

00:05:57.840 --> 00:05:58.440
over there.

00:05:58.440 --> 00:06:00.370
So we could keep doing
it for all of them.

00:06:00.370 --> 00:06:02.710
I could do it for the other
set right here.

00:06:02.710 --> 00:06:05.060
This guy right here
is parallel to

00:06:05.060 --> 00:06:06.600
that guy over there.

00:06:06.600 --> 00:06:09.230
I didn't quite draw it like
that, but hopefully it makes

00:06:09.230 --> 00:06:09.880
the idea clear.

00:06:09.880 --> 00:06:11.580
And I'll do one more of
these just to show

00:06:11.580 --> 00:06:12.760
what's parallel to what.

00:06:12.760 --> 00:06:14.710
This bond is parallel to that.

00:06:14.710 --> 00:06:17.310
So the ones that are parallel to
some part of the ring we're

00:06:17.310 --> 00:06:18.910
calling equatorial.

00:06:18.910 --> 00:06:21.990
And the ones that kind of jump
out of the ring, that aren't

00:06:21.990 --> 00:06:23.960
parallel to any other part
of the ring, we're

00:06:23.960 --> 00:06:24.960
calling those axial.

00:06:24.960 --> 00:06:27.940
And the way I've drawn it here,
the axials are the ones

00:06:27.940 --> 00:06:29.880
that point up and point
straight up and

00:06:29.880 --> 00:06:31.050
point straight down.

00:06:31.050 --> 00:06:33.620
We can do the same thing on
a boat configuration.

00:06:33.620 --> 00:06:36.200
Now, one question you might ask
is, well, there's these

00:06:36.200 --> 00:06:37.090
two configurations.

00:06:37.090 --> 00:06:40.740
Both of these would result in
tetrahedral type shapes at

00:06:40.740 --> 00:06:41.500
each of the carbons.

00:06:41.500 --> 00:06:44.530
In fact, let me draw
it for you.

00:06:44.530 --> 00:06:47.540
So this axial hydrogen is
pointing straight down, this

00:06:47.540 --> 00:06:49.370
one is pointing straight down.

00:06:49.370 --> 00:06:52.930
Here, this hydrogen is actually
going to point

00:06:52.930 --> 00:06:55.480
straight down because
we flipped it up.

00:06:55.480 --> 00:06:59.820
And then over here you would
have a hydrogen point straight

00:06:59.820 --> 00:07:02.180
up, and then one that's
kind of pointing down.

00:07:02.180 --> 00:07:03.920
This gives a tripod there.

00:07:03.920 --> 00:07:06.520
To have the tripod over here,
you'll have to have a hydrogen

00:07:06.520 --> 00:07:10.540
that points a little bit like
that, one that's pointing a

00:07:10.540 --> 00:07:13.790
little bit like that, along,
well, you can kind of view it

00:07:13.790 --> 00:07:17.870
along the same plane as this
guy would be parallel.

00:07:17.870 --> 00:07:19.180
It's hard to see it in
this, but he would

00:07:19.180 --> 00:07:20.760
actually parallel to that.

00:07:20.760 --> 00:07:23.060
This guy would be out like this,
and then this guy would

00:07:23.060 --> 00:07:26.240
have an axial hydrogen, and
then he would have one

00:07:26.240 --> 00:07:28.520
equatorial one just like that.

00:07:28.520 --> 00:07:30.910
So you could draw the tripod
shapes in either the chair or

00:07:30.910 --> 00:07:32.320
boat configuration.

00:07:32.320 --> 00:07:34.820
But one question is, well,
what's more stable?

00:07:34.820 --> 00:07:36.820
That's actually one of the main
points of being able to

00:07:36.820 --> 00:07:40.650
visually think about the three
dimensional structure of any

00:07:40.650 --> 00:07:47.020
of these hydrocarbons, or in
this case cyclohexane.

00:07:47.020 --> 00:07:50.890
So in this situation, we know
from past videos, that all of

00:07:50.890 --> 00:07:53.320
these carbons with their
hydrogens around them, these

00:07:53.320 --> 00:07:56.240
bonds, these have electron
clouds around them.

00:07:56.240 --> 00:07:59.130
The electron clouds are
negative, and so they want to

00:07:59.130 --> 00:08:03.780
get as far away from each
other as possible.

00:08:03.780 --> 00:08:09.020
In this chair configuration, you
have this carbon up here,

00:08:09.020 --> 00:08:11.750
the ch2 we could consider it,
has two hydrogens and is

00:08:11.750 --> 00:08:13.240
connected to the rest
of the ring.

00:08:13.240 --> 00:08:16.410
It's as far as possible from
this ch2 as possible.

00:08:16.410 --> 00:08:20.280
So in that situation, we have
a lower potential energy, or

00:08:20.280 --> 00:08:24.780
it is a more stable shape.

00:08:24.780 --> 00:08:26.270
Or more stable configuration.

00:08:26.270 --> 00:08:30.120
In the boat configuration,
this ch2 up here is much

00:08:30.120 --> 00:08:32.799
closer to this ch2, I mean,
that's really the main

00:08:32.799 --> 00:08:34.210
difference between the two.

00:08:34.210 --> 00:08:35.919
And they want to get away
from each other.

00:08:35.919 --> 00:08:37.059
They want to repel ech other.

00:08:37.059 --> 00:08:40.080
So this one will have higher
potential energy, or it will

00:08:40.080 --> 00:08:41.330
be less stable.

00:08:46.280 --> 00:08:50.740
So this is just a starting
point of how to visualize

00:08:50.740 --> 00:08:54.900
cyclic hydrocarbons and we'll
use this information in the

00:08:54.900 --> 00:08:58.050
next video to think a little
bit more about, maybe, the

00:08:58.050 --> 00:09:00.420
different chair configurations
that a molecule could have,

00:09:00.420 --> 00:09:01.990
and what could be more stable.

00:09:01.990 --> 00:09:05.530
In this situation, in the case
of just cyclohexane, the two

00:09:05.530 --> 00:09:07.430
chair configurations
are equally stable.

00:09:07.430 --> 00:09:09.320
And let me just touch
on that a second.

00:09:09.320 --> 00:09:11.290
So you have, well,
I don't have to--

00:09:11.290 --> 00:09:12.220
actually, let me see.

00:09:12.220 --> 00:09:13.250
I won't copy and paste.

00:09:13.250 --> 00:09:14.770
I'll just redraw
the other chair

00:09:14.770 --> 00:09:16.420
configuration for this guy.

00:09:16.420 --> 00:09:18.520
Actually let me just do it
separately over here because

00:09:18.520 --> 00:09:20.860
I've made the colors
here so confusing.

00:09:20.860 --> 00:09:26.230
Let me draw two, the same
cyclohexane, but in two

00:09:26.230 --> 00:09:27.790
different chair configurations
that it could

00:09:27.790 --> 00:09:28.790
be equilibrium in.

00:09:28.790 --> 00:09:34.570
So you could have this one, you
could have this one, so

00:09:34.570 --> 00:09:38.920
this could be one chair
configuration, and I'll draw

00:09:38.920 --> 00:09:41.450
it like this.

00:09:41.450 --> 00:09:44.090
And then the same hydrocarbon
could be in-- or the same

00:09:44.090 --> 00:09:46.450
cyclohexane could be in
equilibrium with the this

00:09:46.450 --> 00:09:48.850
other chair configuration
that looks like this.

00:09:52.520 --> 00:09:54.800
Let me have a little
more space here.

00:09:54.800 --> 00:09:56.655
So it looks like this.

00:09:56.655 --> 00:09:58.050
Let me do the pink.

00:09:58.050 --> 00:10:02.640
It goes up like that,
like that.

00:10:02.640 --> 00:10:08.544
Let me make sure I'm-- no,
I want to do it actually.

00:10:08.544 --> 00:10:14.940
This pink guy goes like this.

00:10:14.940 --> 00:10:19.320
And then the blue guy is going
to be just like this.

00:10:19.320 --> 00:10:23.370
So notice, in this situation
this carbon appears kind of at

00:10:23.370 --> 00:10:26.250
the top of the chair, and this
carbon is at the bottom, and

00:10:26.250 --> 00:10:27.210
then they've flipped.

00:10:27.210 --> 00:10:29.440
But these are equally stable
configurations.

00:10:29.440 --> 00:10:33.500
But one way to think about is
all of the axial guys on this

00:10:33.500 --> 00:10:37.070
carbon here turned into
equatorial on this carbon and

00:10:37.070 --> 00:10:37.900
vice versa on the two.

00:10:37.900 --> 00:10:38.640
Let me show it to you.

00:10:38.640 --> 00:10:42.270
Let me just draw the hydrogens
on this carbon.

00:10:42.270 --> 00:10:47.560
This carbon's hydrogens has an
axial hydrogen, and has an

00:10:47.560 --> 00:10:51.040
equatorial hydrogen, whose bond
would be parallel to that

00:10:51.040 --> 00:10:52.320
just like that.

00:10:52.320 --> 00:10:55.080
And this guy would have an
equatorial hydrogen whose bond

00:10:55.080 --> 00:10:57.440
is parallel to actually
both of these guys.

00:10:57.440 --> 00:10:58.690
And an axial hydrogen.

00:11:01.190 --> 00:11:03.690
But when it flips, and I'm
just drawing those guys'

00:11:03.690 --> 00:11:07.190
hydrogens, but when this
structure flips like that,

00:11:07.190 --> 00:11:08.390
what happens?

00:11:08.390 --> 00:11:14.330
Well, this hydrogen over here
goes into this position, and

00:11:14.330 --> 00:11:17.720
this yellow hydrogen over here
goes into this position.

00:11:17.720 --> 00:11:19.850
So over here, it was
equatorial, and

00:11:19.850 --> 00:11:23.500
now it becomes axial.

00:11:23.500 --> 00:11:25.900
The same argument can
be made over here.

00:11:25.900 --> 00:11:28.990
This equatorial hydrogen, when
it flips-- when this whole

00:11:28.990 --> 00:11:32.030
blue part flips down--
now becomes axial.

00:11:34.740 --> 00:11:38.230
And this axial hydrogen, when
you flip it down, becomes

00:11:38.230 --> 00:11:39.480
equatorial.

00:11:41.860 --> 00:11:44.040
And you can actually do that
for all of the hydrogens.

00:11:44.040 --> 00:11:47.970
Over here you have an
axial hydrogen.

00:11:47.970 --> 00:11:53.180
Once you flip it, you have an
axial hydrogen, and then you

00:11:53.180 --> 00:11:57.140
have an equatorial hydrogen.

00:11:57.140 --> 00:11:59.050
When you flip it, these
two equatorial

00:11:59.050 --> 00:12:01.970
hydrogens become axial.

00:12:01.970 --> 00:12:05.190
So they become axial and then
both of these guys become

00:12:05.190 --> 00:12:07.050
equatorial.

00:12:07.050 --> 00:12:08.790
So let me do that in yellow.

00:12:08.790 --> 00:12:13.480
Both this guy and this guy
become equatorial So this and

00:12:13.480 --> 00:12:14.830
that become equatorial.

00:12:14.830 --> 00:12:16.880
They become parallel
to the other end.

00:12:16.880 --> 00:12:19.440
And you could do it for these
two hydrogens, as well.

00:12:19.440 --> 00:12:20.990
So that's another interesting
to think about.

00:12:20.990 --> 00:12:23.630
And this is really just practice
on visualizing what's

00:12:23.630 --> 00:12:26.610
going on when we when
we visualize--