Drawing enantiomers

- [Instructor] We've already
seen in an earlier video,

that enantiomers are
stereoisomers that are

nonsuperimposable mirror
images of each other.

Let's say we want to draw the
enantiomer of this compound

on the left.

One way to do it would
be reflect this compound

in the mirror and if you
look at this carbon skeleton,

here we have our carbon
skeleton with our OH group

coming out at us in space.

That's this model on the left.

There's our carbon skeleton with our OH

coming out at us in space.

If we reflect this compound in the mirror,

we'll see the enantiomer in the mirror.

Our mirror image on the right is

nonsuperimposable upon
our model on the left.

Let's just draw what we see,

we see our carbon skeleton, like this,

so let's draw that.

So there is our carbon skeleton,

and our OH group is
coming out at us in space.

So we could represent that with a wedge,

let's fill in our wedge here.

Now let's draw our OH,

and so this drawing on the right,

is the enantiomer to
the drawing on the left.

There's another way to
represent the enantiomer

on the right and to do that,
let's check out the video.

So, in the video I imagine an
axis going through this carbon

and then I rotate about
this axis to give us

another viewpoint of our other enantiomer.

So here's a model of our enantiomer,

and you can see our carbon skeleton

with our OH coming out at us,

attached to this carbon
and then a hydrogen

going away from us in space.

If we imagine rotating about an axis,

through this carbon.

Let's go ahead and do that.

We'll see another way to
look at the enantiomer.

So now we have, for our carbon skeleton,

you can see our carbon
skeleton looks like this now,

and then as this carbon has the OH going

away from us in space,

and the hydrogen coming out at us.

So here we have some
pictures from the video

to help us with our drawings.

We can see that this
picture is this compound,

if you look at that carbon skeleton

and you can see the OH
coming out at us in space.

So in the video, we took this
compound and we rotated it

to give us this image on the right.

So these are just two
images of the same compound.

And this gives us another
way to draw our enantiomer.

This time our carbon
skeleton's going like that.

Let me go ahead and draw
in our carbon skeleton,

and our OH group is going
away from us in space.

So we have to put in the OH
group with a dash, like that.

So these two drawings,
represent the same compound,

the enantiomer that we
were trying to draw.

There are two main ways
to draw an enantiomer,

at least two ways that I like to use.

The first way is to reflect
the compound in a mirror>

That's what we did first,
we took this compound

and we reflected it in the
mirror and we drew what we saw

and that gave us this
drawing of the enantiomer.

We've seen that this drawing on the right,

is the same thing as this
drawing on the left here

and notice the difference
between this drawing

and our original compound.

The carbon skeletons are the
same if you look at these two,

the only difference is that we
changed the wedge to a dash.

So that's another very convenient
way to draw an enantiomer.

If your starting with a
wedge, change it to a dash.

If your starting with a
dash, change it to a wedge.

Now let's draw the
enantiomer of this compound.

The first method that we'll
use is the mirror method.

So here's a simplified
representation of our compounds

so ignoring things like
confirmations of our ring.

On this carbon, our Bromine
is going down in space

so that's this carbon,

so you can see that Bromine's going down.

And on this carbon
Bromine's going up in space,

that's this carbon with
our Bromine going up.

In the mirror we can see the mirror image

or the enantiomer.

So let's go ahead and
draw our enantiomer here.

So we draw our cyclohexane
ring, and at this carbon,

we have our Bromine going down in space,

so let's go ahead and put
our Bromine going down.

Then at this carbon, we have
our Bromine going up in space,

so that's a wedge.

We draw in our Bromine here,
let me fill in this wedge,

and let's put in the Bromine.

So this on the right, is the enantiomer.

Sometimes you don't have
model sets or a mirror,

but you can draw the mirror image

by just using this drawing on the left.

Imagine a mirror right here,
and just as you see up here,

this Bromine is reflected in the mirror,

this Bromine is reflected
in the mirror, right.

So these two, these Bromine's
are reflecting each other.

This carbon is opposite of this carbon,

so that's this carbon and this one,

and this carbon is opposite of this one,

so this carbon is opposite of that one.

Just a few tricks to help
you draw the mirror image.

There's another way to
represent our enantiomer

on the right, and let's go to the video

to see the other way.

So here we have our two enantiomer's,

you can see they're mirror
images of each other.

If I rotate the enantiomer on the right,

you can see it from a
different view point.

Notice that both chiral
center's have been inverted

and just to prove that these
are enantiomer's of each other,

let's try to superimpose
one on top of the other.

Notice how you can't do it.

These are nonsuperimposable
mirror images of each other.

This picture on the right in the video,

shows you the relationship
between our two enantiomer's.

So thinking about reflecting
the molecule on the left

in a mirror, we can see the
enantiomer on the right.

But we took this molecule on
the right, this enantiomer

and rotated it into this position.

So now let's draw the enantiomer
from this perspective.

We start out with our cyclohexane ring

and you can see at this carbon our Bromine

is going down in space
so that must be a dash,

so there's my Bromine.

And then at this carbon,
our Bromine is coming up

in space, coming out at
us, so that's a wedge.

Let me go ahead and draw in our wedge,

and we'll put in our Bromine.

So this is just another way to represent

our enantiomer's on the right.

So this drawing and this
drawing are two different ways

to represent the same molecule.

So this is the enantiomer
to the compound on the left.

Let's look at our original
compound and compare

this drawing on the right.

Notice that this carbon
your Bromine is coming

out at you in space.

Where as with this carbon
your Bromine is going

away from you in space.

At this carbon your Bromine is
going away from you in space,

at this carbon your Bromine
is coming out at you in space.

So to draw our enantiomer,

we just invert all chirality center's.

So if you have a wedge,
change it to a dash.

If you have a dash, change it to a wedge.

So this way is often easier,

so just make sure to invert
all your chiral center's

to draw the enantiomer.

For bicyclic compounds it's easiest to use

the mirror method.

So if our goal is to draw the
enantiomer of this compound,

we can imagine a mirror right here.

And we can use this
picture above as a guide.

You can see that the Hydrogen
is reflected in the mirror,

and the Chlorine is
reflected in the mirror,

let's go ahead and draw those in.

So we draw our Hydrogen here
and then our bond going down

to this carbon and then the Chlorine going

straight down from here.

Notice how this Hydrogen is reflected

and this Chlorine is reflected.

Next let's think about
reflecting this carbon,

so we need to draw a line
in this way right here.

So now this carbon is
reflected with that one.

Let me highlight those carbons right here.

I'm going to extend this
line out a little bit

so we can see where the
horizontal is approximately,

like that.

So that's this carbon and this carbon,

so that's carbon's
reflected in our mirror.

Next, let's draw a line
up in space relative

to that line like that so
that takes us to this carbon

which is reflecting
this one in our mirror.

Now let's worry about this
one, so this should go up

in space, let me draw a
horizontal line down here

just to help us with our drawing.

So approximately horizontal at this point.

We know we want to go up
in space from this point,

so let's do that, so that's this line.

This carbon is reflecting this carbon.

Next, let's go ahead and
reflect our top carbon here.

Let's draw this line over
to here, so you can think

about this top carbon reflecting that one.

Let's draw our lines
over here, so from here

and then back down to here.

It's more of a drawing exercise
really, we're going to go

down a little bit, we'll leave
that line broken so we can

see that one's going behind.

And then we'll draw this
to the carbon in the back

and then we know what
draw down from this line

to the carbon in the back

and then we can connect those line.

Finally, we've drawn our enantiomer.

So on the right is the
enantiomer to the compound

on the left.

And just to prove that this on the right

is the enantiomer, let's look at a video

where I tried to
superimpose the mirror image

on original compound.

Here we have our two enantiomer's,

so mirror images of each other that are

nonsuperimposable, just to prove they're

nonsuperimposable, I'll rotate
the enantiomer on the right

and try to superimpose it
onto the one on the left.

You can see that they don't match up.

So these are enantiomer's