Dehydration synthesis or a condensation reaction

WEBVTT
Kind: captions
Language: en

00:00:00.010 --> 00:00:01.450
- [Voiceover] In the previous video, we talked about

00:00:01.450 --> 00:00:04.990
the importance of glucose as a simple sugar.

00:00:04.990 --> 00:00:06.950
We talked about its molecular structure.

00:00:06.950 --> 00:00:09.890
What I wanna do in this video is study how glucose

00:00:09.890 --> 00:00:12.930
can be, how we can use it as a building block

00:00:12.930 --> 00:00:17.420
for more complex sugars and more complex carbohydrates.

00:00:17.420 --> 00:00:19.330
So this right over here, I've copy and pasted

00:00:19.330 --> 00:00:23.090
two glucose molecules, we can number their carbons.

00:00:23.090 --> 00:00:27.700
This is one, two, three, four, five, six.

00:00:27.700 --> 00:00:32.020
One, two, three, four, five, six.

00:00:32.020 --> 00:00:34.710
We have them in their cyclic form.

00:00:34.710 --> 00:00:36.390
And what we're going to do is explore

00:00:36.390 --> 00:00:40.120
what would happen if this oxygen right over here,

00:00:40.120 --> 00:00:42.250
I'll highlight it in this magenta color,

00:00:42.250 --> 00:00:44.650
were to use one of its lone pairs,

00:00:44.650 --> 00:00:47.020
one of its lone pairs, to do,

00:00:47.020 --> 00:00:49.200
what's in organic chemistry, referred to

00:00:49.200 --> 00:00:52.530
as a nucleophilic attack on the number one carbon

00:00:52.530 --> 00:00:55.120
on the left-hand glucose molecule.

00:00:55.120 --> 00:00:57.050
And the reason why that could happen

00:00:57.050 --> 00:01:00.090
is this number one carbon right over here,

00:01:00.090 --> 00:01:02.120
it's attached to two oxygens.

00:01:02.120 --> 00:01:04.490
Oxygens are very electronegative, they like to

00:01:04.490 --> 00:01:07.220
hog electrons when they're in a covalent bond.

00:01:07.220 --> 00:01:08.620
So that's gonna give this carbon

00:01:08.620 --> 00:01:10.450
a partially positive charge.

00:01:10.450 --> 00:01:12.450
And this oxygen is very electronegative.

00:01:12.450 --> 00:01:14.520
It's gonna hog the electrons from this hydrogen

00:01:14.520 --> 00:01:16.290
and the number four carbon

00:01:16.290 --> 00:01:17.890
on the right-hand glucose molecule,

00:01:17.890 --> 00:01:19.850
so it's gonna have a partially negative charge.

00:01:19.850 --> 00:01:21.920
And so it is going to be nucleophilic.

00:01:21.920 --> 00:01:24.420
It's going to be attracted to, I guess you could say,

00:01:24.420 --> 00:01:29.590
the carbon nucleus, to the partially positive charge

00:01:29.590 --> 00:01:31.990
right over here, and so as it does,

00:01:31.990 --> 00:01:34.920
it's gonna use a lone pair to form a bond.

00:01:34.920 --> 00:01:36.550
It's gonna share it with the carbon,

00:01:36.550 --> 00:01:39.190
and then the carbon can let go of another bond.

00:01:39.190 --> 00:01:42.290
So it could let go of, it could let go of

00:01:42.290 --> 00:01:44.990
both of these electrons in that bond.

00:01:44.990 --> 00:01:46.720
Now you could say maybe that just goes

00:01:46.720 --> 00:01:51.150
back to the oxygen and it forms a hydroxide anion.

00:01:51.150 --> 00:01:54.650
Or we could imagine, well, maybe it'll be used,

00:01:54.650 --> 00:01:57.990
maybe it forms a hydroxide anion first,

00:01:57.990 --> 00:01:59.620
or maybe that bond immediately goes

00:01:59.620 --> 00:02:04.220
and picks up a hydrogen ion out of the solution

00:02:04.220 --> 00:02:08.890
from another, from a hydronium ion sitting someplace.

00:02:08.890 --> 00:02:11.690
So this could be used to form

00:02:11.690 --> 00:02:14.520
a bond with this hydrogen ion, which is really,

00:02:14.520 --> 00:02:15.950
this is just a proton here.

00:02:15.950 --> 00:02:17.420
You take an electron away from hydrogen,

00:02:17.420 --> 00:02:19.790
it's just going to be a proton.

00:02:19.790 --> 00:02:21.250
Well, what's that going to do?

00:02:21.250 --> 00:02:25.250
Well, that's going to link these two glucose molecules.

00:02:25.250 --> 00:02:28.720
And it's gonna link it just like this,

00:02:28.720 --> 00:02:31.720
and it's important to keep track of our molecules here.

00:02:31.720 --> 00:02:35.820
So this oxygen is now going to be this oxygen.

00:02:35.820 --> 00:02:37.920
It's now going to be that oxygen.

00:02:37.920 --> 00:02:41.220
This bond between the number four carbon

00:02:41.220 --> 00:02:42.920
on the right-hand side of that oxygen

00:02:42.920 --> 00:02:45.820
is this bond right over here.

00:02:45.820 --> 00:02:48.650
This, where we took this electron pair

00:02:48.650 --> 00:02:51.320
to form this bond with the number one carbon,

00:02:51.320 --> 00:02:54.790
that is, let me do it in that magenta color.

00:02:54.790 --> 00:02:59.620
That is this bond, this bond right over here.

00:02:59.620 --> 00:03:05.820
The oxygen, this oxygen, is now this oxygen right over here.

00:03:05.820 --> 00:03:09.750
And this electron pair is now formed a bond

00:03:09.750 --> 00:03:11.350
with this hydrogen, so we could say,

00:03:11.350 --> 00:03:15.020
oh, that could be, let me do that blue,

00:03:15.020 --> 00:03:20.890
that could be, that could be this bond right over here.

00:03:20.890 --> 00:03:23.990
Now the one difference is, based on how I've drawn it,

00:03:23.990 --> 00:03:28.120
this oxygen, or sorry, this oxygen, the way I've drawn it,

00:03:28.120 --> 00:03:30.230
it's attached to the number one carbon here,

00:03:30.230 --> 00:03:31.480
the number four carbon here.

00:03:31.480 --> 00:03:33.490
We have that over, we've already done that over here.

00:03:33.490 --> 00:03:34.990
Number one carbon on the left molecule,

00:03:34.990 --> 00:03:37.050
number four carbon on the right molecule.

00:03:37.050 --> 00:03:38.890
But we also have it bonded,

00:03:38.890 --> 00:03:41.690
we also have it bonded to a hydrogen.

00:03:41.690 --> 00:03:43.520
So just the way I've done it right now,

00:03:43.520 --> 00:03:45.690
it's still bonded to a hydrogen.

00:03:45.690 --> 00:03:50.430
It's going to have a net positive charge.

00:03:50.430 --> 00:03:52.153
Over here, it was neutral.

00:03:52.153 --> 00:03:53.520
It was neutral right over here, but then

00:03:53.520 --> 00:03:56.490
it's now sharing its electrons.

00:03:56.490 --> 00:03:58.120
It's now sharing both of those electrons

00:03:58.120 --> 00:04:00.850
in a covalent bond, and so you can think of it as

00:04:00.850 --> 00:04:05.090
it's giving away an electron to this carbon,

00:04:05.090 --> 00:04:07.350
so it's going to have a net positive charge.

00:04:07.350 --> 00:04:10.620
But then to get back to neutral, you could imagine,

00:04:10.620 --> 00:04:15.250
well, maybe some type of a water molecule

00:04:15.250 --> 00:04:20.720
could grab that ion, so maybe this one right over here.

00:04:20.720 --> 00:04:25.750
This one right over here could grab that hydrogen,

00:04:25.750 --> 00:04:27.720
and then these electrons, both of them,

00:04:27.720 --> 00:04:30.450
and it would just grab the hydrogen nucleus of the proton,

00:04:30.450 --> 00:04:32.320
and so these two electrons could go back

00:04:32.320 --> 00:04:36.520
to this oxygen and then this oxygen would become neutral.

00:04:36.520 --> 00:04:38.350
And so what we would be left with,

00:04:38.350 --> 00:04:43.690
actually, let me just erase this,

00:04:43.690 --> 00:04:48.810
is that this hydrogen would now be attached

00:04:51.440 --> 00:04:56.290
to this oxygen, and we would have a hydronium ion.

00:04:56.290 --> 00:04:57.320
And this is reasonable.

00:04:57.320 --> 00:04:59.320
We essentially had some hydronium.

00:04:59.320 --> 00:05:02.127
We had a hydrogen proton out here before and we still do.

00:05:02.127 --> 00:05:03.720
Now it's attached to a water,

00:05:03.720 --> 00:05:08.620
so we've take a proton and we've given back a proton,

00:05:08.620 --> 00:05:12.990
so we have a net-net kind of added charge

00:05:12.990 --> 00:05:16.890
or taken charge away from the system.

00:05:16.890 --> 00:05:18.590
But the important thing that we just saw is

00:05:18.590 --> 00:05:22.890
as these two things essentially attached,

00:05:22.890 --> 00:05:27.690
we lost a water molecule, or I guess net-net,

00:05:27.690 --> 00:05:30.820
this system lost a water molecule.

00:05:30.820 --> 00:05:35.990
It took up a charge to do it, to build that water molecule,

00:05:35.990 --> 00:05:38.190
but the thing that really kind of escaped

00:05:38.190 --> 00:05:42.590
from both of these two molecules is this,

00:05:42.590 --> 00:05:46.720
is this right over here.

00:05:46.720 --> 00:05:51.990
This H is this H, this oxygen is this oxygen.

00:05:51.990 --> 00:05:56.920
And this hydrogen is this hydrogen right over here.

00:05:56.920 --> 00:05:59.190
And so this type of a reaction in which

00:05:59.190 --> 00:06:02.250
we're synthesizing a more complex molecule,

00:06:02.250 --> 00:06:08.190
a longer chain of glucose molecules,

00:06:08.190 --> 00:06:12.130
this is called a dehydration synthesis.

00:06:12.130 --> 00:06:14.550
So what we just did, this right over here

00:06:14.550 --> 00:06:20.360
is called a dehydration synthesis.

00:06:20.360 --> 00:06:23.320
Why are we calling it a dehydration synthesis?

00:06:23.320 --> 00:06:24.890
Well, we've just taken a water out.

00:06:24.890 --> 00:06:26.460
If you imagine losing water, we talk about

00:06:26.460 --> 00:06:28.790
you're getting dehydrated.

00:06:28.790 --> 00:06:30.220
And why synthesis?

00:06:30.220 --> 00:06:31.720
Well, we put two things together.

00:06:31.720 --> 00:06:34.050
We synthesized a larger molecule.

00:06:34.050 --> 00:06:38.120
Sometimes this would be called a condensation reaction.

00:06:38.120 --> 00:06:43.590
Condensation reaction.

00:06:43.590 --> 00:06:47.350
And by doing this, these two glucose molecules

00:06:47.350 --> 00:06:50.950
are able to form a disaccharide now.

00:06:50.950 --> 00:06:55.720
So each individually, they were monosaccharides,

00:06:55.720 --> 00:07:00.150
so this one on the right, that's a monosaccharide.

00:07:00.150 --> 00:07:01.920
What does monosaccharide mean?

00:07:01.920 --> 00:07:05.750
Well, it means, mono means single or one

00:07:05.750 --> 00:07:09.050
and saccharide comes from the Greek word for sugar.

00:07:09.050 --> 00:07:10.650
The Greek word for sugar is,

00:07:10.650 --> 00:07:13.420
I'm gonna mispronounce it, is sakcharon.

00:07:13.420 --> 00:07:14.950
When people talk about something being saccharine,

00:07:14.950 --> 00:07:16.788
they're saying something is very, very sweet.

00:07:16.788 --> 00:07:19.250
The Greek word for sugar is sakcharon.

00:07:19.250 --> 00:07:22.690
So saccharide means it's a sugar, it's a single sugar.

00:07:22.690 --> 00:07:27.150
So that meaning there, sugar.

00:07:27.150 --> 00:07:29.120
And the general term saccharide refers to

00:07:29.120 --> 00:07:32.150
not just the simple sugars, monosaccharides,

00:07:32.150 --> 00:07:34.960
but it could mean two of these things put together.

00:07:34.960 --> 00:07:37.920
And there's other simple sugars, fructose and others.

00:07:37.920 --> 00:07:40.710
Or it could mean a huge number of these put together.

00:07:40.710 --> 00:07:42.190
You could have polysaccharides.

00:07:42.190 --> 00:07:43.550
And that whole class, saccharides,

00:07:43.550 --> 00:07:46.720
we also associate with carbohydrates.

00:07:46.720 --> 00:07:51.720
Now we went from two monosaccharides to right over here.

00:07:51.720 --> 00:07:53.620
This is a disaccharide.

00:07:53.620 --> 00:07:56.220
This is a disaccharide, we have two.

00:07:56.220 --> 00:07:59.390
Two monosaccharides were involved.

00:07:59.390 --> 00:08:02.990
This is a disaccharide, and this particular disaccharide

00:08:02.990 --> 00:08:07.070
is maltose, or malt sugar. Maltose.

00:08:09.080 --> 00:08:10.750
So the whole point of this video is to see

00:08:10.750 --> 00:08:12.720
how you can start with these simple sugars,

00:08:12.720 --> 00:08:15.690
these monosaccharides, and form disaccharides.

00:08:15.690 --> 00:08:17.110
In fact, you could keep going.

00:08:17.110 --> 00:08:19.590
You could keep having dehydration synthesis,

00:08:19.590 --> 00:08:21.850
condensation reactions to keep adding

00:08:21.850 --> 00:08:23.690
more and more monosaccharides to build

00:08:23.690 --> 00:08:25.720
longer and longer chains.

00:08:25.720 --> 00:08:27.050
So if you were to keep doing that,

00:08:27.050 --> 00:08:29.790
it you were to keep building chains of these things,

00:08:29.790 --> 00:08:34.550
now you're getting into the world of polysaccharides.

00:08:34.550 --> 00:08:39.450
Polysaccharides, or many simple sugars,

00:08:39.450 --> 00:08:43.853
many monosaccharides, many monosaccharides put together.

00:08:43.853 --> 00:08:46.020
And this is the case for sugar, but this is something

00:08:46.020 --> 00:08:48.150
that you'll see often in chemistry,

00:08:48.150 --> 00:08:51.450
where you have a single unit, here's a single sugar,

00:08:51.450 --> 00:08:54.220
but if we talk in more general terms,

00:08:54.220 --> 00:08:56.320
we would call it a monomer.

00:08:58.140 --> 00:09:01.020
And then if we have a bunch of these monomers put together,

00:09:01.020 --> 00:09:05.020
we would call it a polymer.

00:09:05.020 --> 00:09:07.520
Now polysaccharides are super important,

00:09:07.520 --> 00:09:10.790
and you have probably eaten some polysaccharides today,

00:09:10.790 --> 00:09:12.490
and you probably have some, in fact,

00:09:12.490 --> 00:09:14.150
I'm sure you have some polysaccharides

00:09:14.150 --> 00:09:16.850
stored in your cells right now.

00:09:16.850 --> 00:09:18.990
If you put a bunch of glucose molecules,

00:09:18.990 --> 00:09:20.890
if we were to keep this process going

00:09:20.890 --> 00:09:24.730
and we were to have a bunch of glucose molecules together,

00:09:24.730 --> 00:09:27.786
when you find it in plants, it'll often be

00:09:27.786 --> 00:09:30.020
in the form of a starch.

00:09:30.020 --> 00:09:32.350
So a polysaccharide that you'll find in a plant

00:09:32.350 --> 00:09:37.630
is a starch, a bunch of glucoses put together

00:09:37.630 --> 00:09:40.790
in your own cells to have a immediate energy store,

00:09:40.790 --> 00:09:45.720
a bunch of glucoses put together is glycogen.

00:09:48.490 --> 00:09:51.810
So these macromolecules, these polysaccharides

00:09:51.810 --> 00:09:54.560
that are made up of a bunch of simple sugars,

00:09:54.560 --> 00:09:56.250
a bunch of monosaccharides put together,

00:09:56.250 --> 00:09:58.260
these are very common in biology.

00:09:58.260 --> 00:10:00.050
You have eaten them and you are storing them

00:10:00.050 --> 00:10:01.720
in your body right now.


Molecular structure of glucose

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:06.600
What I wanted to do in this video is familiarize ourselves with one of the most important molecules in biology

00:00:06.700 --> 00:00:08.000
And that is Glucose

00:00:08.000 --> 00:00:11.320
sometimes referred to as Dextrose

00:00:11.480 --> 00:00:13.720
and the term Dextrose comes from the fact

00:00:13.720 --> 00:00:15.720
that the form of Glucose typically

00:00:16.700 --> 00:00:23.160
Typically found in nature if you form a solution of it, it's going to polarize light to the right and Dextre means

00:00:23.289 --> 00:00:23.980
Right

00:00:23.980 --> 00:00:30.299
But the more typical term glucose this literally means sweet in greek if you ask a greek friend to say sweet

00:00:30.300 --> 00:00:35.160
it sounds like Lucas or I'm not saying it perfectly, but it sounds a lot like a glucose

00:00:35.160 --> 00:00:40.799
And that's because that's where the word comes from and it is super important because it is it is it is how

00:00:40.870 --> 00:00:48.360
energy [is] stored and transferred in biological systems in fact right [now] when if someone were to talk about your blood your blood sugar

00:00:48.370 --> 00:00:52.620
they're talking about the glucose content, so when people talk about blood

00:00:53.379 --> 00:01:00.269
blood sugar they're talking about your they're talking about your glucose content the whole process of photosynthesis

00:01:00.270 --> 00:01:02.909
this is all about plants using harnessing the [sun's] energy and

00:01:03.160 --> 00:01:07.860
storing that energy in the form of glucose when we talk about when we talk about things like

00:01:08.409 --> 00:01:10.739
respiration in our in our cells cellular respiration

00:01:10.740 --> 00:01:17.759
that's all about taking glucose and using it to full and to create atp's which are the molecular currency of energy

00:01:18.009 --> 00:01:22.199
Inside of our body, so these are in credit is an incredibly important molecule

00:01:22.600 --> 00:01:26.549
We can start wreaking chains of glucose to form Glycogen to form

00:01:26.950 --> 00:01:33.269
Starches this along with another similar another simple sugar fructose you can use to form our table sugar

00:01:33.270 --> 00:01:37.979
But even glucose by itself is sweet so let's get familiar with it as a molecule

00:01:38.560 --> 00:01:39.729
so immediately

00:01:39.729 --> 00:01:45.929
When you look at this is it kind of drawn as a as an open chain we see that we have one two three

00:01:46.060 --> 00:01:48.629
Actually, let me number these we have one two

00:01:49.240 --> 00:01:53.729
three four five six carbons, so

00:01:54.369 --> 00:01:55.799
chemical formula would be C

00:01:55.799 --> 00:01:59.819
sub six a subscript of six we have how many hydrogen's

00:02:00.070 --> 00:02:06.839
How many hydrogen's we have we have 1 2 3 4 5 6 7 8 9 10 11 12 hydrogen's?

00:02:07.420 --> 00:02:12.149
C6H12 and then we have how many oxygens do we have?

00:02:12.760 --> 00:02:17.200
Have one two three four five six oxygens

00:02:17.780 --> 00:02:24.519
Six oxygens, so you might notice we have six carbons and then the ratio for every one oxygen

00:02:24.519 --> 00:02:28.449
We have two hydrogen's which is really the ratio of Hydrogen's to oxygens in

00:02:28.519 --> 00:02:33.369
Water and if we want to really if we really want to if we add obviously here

00:02:33.370 --> 00:02:34.930
We don't have just two hydrogen's and one oxygen

00:02:34.930 --> 00:02:40.959
We have 12 hydrogen's and six oxygens, but it's really good to even just familiarize yourselves with what are the different parts here

00:02:40.959 --> 00:02:44.438
So we see on the number one carbon it is part of a carbonyl group

00:02:45.140 --> 00:02:47.140
when a carbon is bonded to

00:02:47.659 --> 00:02:50.439
double bonded to an oxygen like that. That's a carbonyl

00:02:51.620 --> 00:02:53.180
Carbonyl

00:02:53.180 --> 00:02:55.780
carbonyL group and in fact because this carbon

00:02:55.780 --> 00:03:00.489
it's double bonded to an oxygen, but then it's other bonds are I guess you could say a

00:03:01.700 --> 00:03:06.489
Carbon chain right over here and then but this other bond right here is a hydrogen

00:03:06.590 --> 00:03:10.509
we would call this an aldehyde we would call this an

00:03:11.359 --> 00:03:13.839
aldehyde group and it makes Al

00:03:14.989 --> 00:03:19.418
Aldehyde and it would officially make the entire molecule an aldehyde if you contain an aldehyde group

00:03:19.419 --> 00:03:22.209
You are an aldehyde, so glucose

00:03:22.209 --> 00:03:28.029
and when it's written when it's drawn as a straight chain or it's a straight chain form it would be considered an aldehyde and then

00:03:28.030 --> 00:03:32.769
Of course it has all these hydroxyl groups on them, and these hydroxyl groups these O-H groups over here

00:03:32.810 --> 00:03:39.819
That would officially make glucose also it would officially make it an alcohol, and it's neat to keep in mind

00:03:39.819 --> 00:03:41.819
How the structure is so you have six carbons?

00:03:42.079 --> 00:03:44.559
One of them is part of this aldehyde group

00:03:44.560 --> 00:03:47.199
It's part of this carbonyl right over here

00:03:47.199 --> 00:03:52.749
And then the other five are each bonded to a hydroxyl and what I've oriented it this way

00:03:53.720 --> 00:03:59.559
four of the hydroxyls are on the right-hand side and the one on the three carbon is on the left-hand side and

00:03:59.690 --> 00:04:02.109
all of the other carbon bonds are with

00:04:02.269 --> 00:04:08.649
hydrogen carbon likes to form four covalent bonds every one of these six carbons has formed four covalent bonds

00:04:08.650 --> 00:04:12.459
And so you would fill up all the rest once you've accounted for this carbonyl here

00:04:12.459 --> 00:04:16.029
And you've accounted for all of these hydroxyls everything else is going to be hydrogen

00:04:16.579 --> 00:04:21.038
Now this is when you've drawn when you've drawn glucose just as a straight chain

00:04:21.039 --> 00:04:24.158
but many times you will see it in its cyclical form

00:04:24.590 --> 00:04:29.680
It's neat to kind of think of how do you go from this form to this form over here?

00:04:29.680 --> 00:04:34.389
And so what I've drawn here is this exact same this exact open chain

00:04:34.390 --> 00:04:39.520
But I've started to I've started to bend it a little bit and just to be able to keep track of things let's renumber

00:04:39.700 --> 00:04:43.029
The carbons, so this is the carbon. That's part of the carbonyl group

00:04:43.240 --> 00:04:46.840
So it's carbon one and then we number up from there two three

00:04:47.690 --> 00:04:48.970
four five

00:04:48.970 --> 00:04:55.390
And then that is the number six carbon the reason why I've made these this bond over here nice and fat is

00:04:55.490 --> 00:04:57.789
To show that it's it's kind of closer to us

00:04:57.790 --> 00:05:02.200
It's popping out of the page and as we go from the the second carbon of the first carbon

00:05:02.200 --> 00:05:06.129
We're going back into the page when we go from the third carbon to the fourth Carbon

00:05:06.130 --> 00:05:12.070
We are going we are going back into the page right over here, so this big fat bond. This is

00:05:12.710 --> 00:05:15.549
between Carbon three and Carbon two, that's this

00:05:16.190 --> 00:05:19.930
That's this right over here and this going from two to one

00:05:20.090 --> 00:05:21.250
That's this bond

00:05:21.250 --> 00:05:24.640
And I'll draw it a little bit kind of going in and then this bond is

00:05:24.890 --> 00:05:31.659
This bond right over here and so it take a second pause the video if you need but try to orient yourself to orient yourself

00:05:31.940 --> 00:05:36.100
Imagine we're going to take this to the right like this to bring it over here

00:05:36.100 --> 00:05:40.840
And then we're going to rotate we're going to rotate this end and bend it up backwards like that

00:05:41.120 --> 00:05:46.840
To get to this form C six is now bent all the way up is now rotated all the way up there

00:05:46.840 --> 00:05:52.929
We've bent we've bent this chain and the whole reason is is because this will typically react the hydroxyl group

00:05:52.930 --> 00:05:53.470
This is it

00:05:53.470 --> 00:05:58.300
This is the the most typical form of glucose you will see when you see in a sick little form there's actually other forms that

00:05:58.300 --> 00:06:02.740
You can have but the oxygen that forms a hydroxyl group on the fifth carbon

00:06:02.930 --> 00:06:07.120
it can it can attack it can attack the the

00:06:07.430 --> 00:06:10.570
The number one carbon that forms this carbonyl group

00:06:10.570 --> 00:06:14.890
And that's because oxygen we've talked a lot about it is very electronegative likes to hog electrons

00:06:14.930 --> 00:06:19.720
So this carbon is partially positive and so you could take one of the lone pairs

00:06:20.570 --> 00:06:24.099
You could take one of this oxygen right over here. It's going to have two lone pairs

00:06:24.100 --> 00:06:29.950
Let me just draw them as neatly as I can that's one lone pair, and then this is another lone pair right over here

00:06:30.080 --> 00:06:31.730
so this oxygen

00:06:31.730 --> 00:06:32.990
can

00:06:32.990 --> 00:06:38.470
Form a bond with this carbon when we learn organic chemistry and more depth, we'd call that a nucleophilic attack

00:06:38.470 --> 00:06:40.760
it sounds very fancy. Just the fact that these are drawn to each other this has a partially positive charge this guy has a

00:06:40.760 --> 00:06:46.780
lone pairs of electrons that can be used to form bonds with things and so when that when those electrons form this bond or

00:06:53.180 --> 00:06:55.300
Bond to this carbon that's going to be this bond

00:06:55.880 --> 00:06:57.680
this Bond right

00:06:57.680 --> 00:06:58.450
over here

00:06:58.450 --> 00:07:03.939
And then this carbon can let go this carbon can let go of the electrons in

00:07:04.310 --> 00:07:07.239
One of these let me do this in a more obvious color

00:07:07.820 --> 00:07:12.669
and in the double bond right [over] here it could let go of one of the bonds the electrons in one of the bonds and

00:07:12.669 --> 00:07:20.199
then that can be taken back by the oxygen or even better that can be used by that oxygen to capture a

00:07:20.419 --> 00:07:23.589
Hydrogen proton in the solution and actually probably part of a

00:07:24.200 --> 00:07:25.460
Hydronium Molecule

00:07:25.460 --> 00:07:27.460
But let me just draw it this way

00:07:27.470 --> 00:07:30.489
this would just be used to capture a

00:07:31.100 --> 00:07:37.269
Hydrogen proton that would just be a hydrogen a hydrogen atom without its electron. It's just a hydrogen ion

00:07:37.490 --> 00:07:41.049
It would just be a hydrogen proton and that would form this bond

00:07:41.479 --> 00:07:48.129
That would form this bond right over here and let me let me just be very clear this carbon this carbon right over here is

00:07:48.770 --> 00:07:53.919
This carbon right over there this oxygen this oxygen is

00:07:54.500 --> 00:08:01.239
This oxygen is that oxygen right over there, and so hopefully you see how it forms a cyclone. You're probably saying Oh, wait wait

00:08:01.240 --> 00:08:03.240
don't we have a little hydrogen attached here

00:08:03.350 --> 00:08:07.929
isn't the way I've drawn it looks like there's an extra hydrogen over here, and then that would leave this guy with a

00:08:08.630 --> 00:08:14.529
Positive charge we leave with a positive charge, but you can imagine we're in a solution of water then hey

00:08:14.530 --> 00:08:17.919
I have some I have another water molecule right over here

00:08:17.919 --> 00:08:21.489
And you know these things are all bouncing around and interacting in different ways

00:08:21.680 --> 00:08:25.660
But it could use let me do that in the right color it could use

00:08:26.360 --> 00:08:32.500
So that's oxygen it could use one of its lone pairs instead of this you know this will become positive temporarily

00:08:32.500 --> 00:08:39.250
But then it can use it can do it can use one of its lone pairs to grab just the hydrogen proton which would allow

00:08:39.529 --> 00:08:42.969
Which will allow this character to take its to take its

00:08:43.250 --> 00:08:48.880
Electrons to take these electrons back and turn into this character and just be neutral and then this this guy

00:08:49.010 --> 00:08:53.349
Would have gained so we have a proton going into the solution you have hi

00:08:53.920 --> 00:08:55.510
But we took a proton from [the] solution

00:08:55.510 --> 00:08:58.569
We took a proton we gave a proton to the solution

00:08:58.570 --> 00:09:01.570
And so you could end up with this so the whole reason I did

00:09:01.570 --> 00:09:05.770
This is [just] so when you see it in biology class or chemistry class you're not intimidated by it in fact

00:09:05.770 --> 00:09:09.939
This is something that's really valuable to get very very familiar [with] because you're going to see

00:09:10.430 --> 00:09:14.109
Glucose and other sugars in many many many different molecules

00:09:14.720 --> 00:09:16.720
throughout your academic career


Functional groups

WEBVTT
Kind: captions
Language: en

00:00:00.120 --> 00:00:02.662
- [Voiceover] We spent some time talking about hydrocarbons

00:00:02.662 --> 00:00:03.985
and hydrocarbons are interesting

00:00:03.985 --> 00:00:06.087
especially if you want to combust things,

00:00:06.087 --> 00:00:08.408
if you want some fuel, but now we're going to

00:00:08.408 --> 00:00:09.883
make things a little bit more interesting

00:00:09.883 --> 00:00:12.432
by adding things to the hydrocarbons

00:00:12.432 --> 00:00:15.479
and the things we're gonna add we call functional groups.

00:00:15.479 --> 00:00:17.928
Functional groups.

00:00:17.928 --> 00:00:19.368
And my goal in my video is to give you

00:00:19.368 --> 00:00:21.225
an overview of the major functional groups

00:00:21.225 --> 00:00:23.628
that you might see attached to carbon backbones

00:00:23.628 --> 00:00:26.717
that make the molecules interesting biologically.

00:00:26.717 --> 00:00:28.517
Now, the first one I will focus on

00:00:28.517 --> 00:00:30.397
is an OH group.

00:00:30.397 --> 00:00:33.538
So, we have an OH attached to a carbon backbone over here.

00:00:33.538 --> 00:00:35.140
It doesn't have to be attached to a carbon backbone

00:00:35.140 --> 00:00:38.657
but the OH right over here, this is called a hydroxyl group.

00:00:38.657 --> 00:00:42.031
Hy, hydroxyl group,

00:00:42.031 --> 00:00:43.935
and when it is attached to a

00:00:43.935 --> 00:00:45.815
carbon backbone like this one is

00:00:45.815 --> 00:00:49.333
then it turns the entire molecule into an alcohol.

00:00:49.333 --> 00:00:52.351
Alcohol. This an alcohol.

00:00:52.351 --> 00:00:54.034
And this one in particular if you want the name

00:00:54.034 --> 00:00:56.751
we have two carbons on the longest, longest chain

00:00:56.751 --> 00:00:58.388
and it is an alcohol so we use the

00:00:58.388 --> 00:01:00.456
prefix Eth for the two carbons.

00:01:00.456 --> 00:01:02.005
So, let me write that down.

00:01:02.005 --> 00:01:03.921
We're going to use the prefix Eth

00:01:03.921 --> 00:01:05.499
because we have two carbons here.

00:01:05.499 --> 00:01:07.485
And we're gonna say Ethanol.

00:01:07.485 --> 00:01:09.400
Now, what are the properties here?

00:01:09.400 --> 00:01:12.059
Well, you have oxygen which is very electronegative

00:01:12.059 --> 00:01:14.845
bonded to a hydrogen and to a carbon

00:01:14.845 --> 00:01:16.319
but the oxygen is a lot more

00:01:16.319 --> 00:01:17.979
electronegative than the hydrogen

00:01:17.979 --> 00:01:20.220
so you're going to have a partially negative charge

00:01:20.220 --> 00:01:22.147
at this end away from the hydrogen.

00:01:22.147 --> 00:01:24.457
A partial positive charge at the hydrogen

00:01:24.457 --> 00:01:26.605
and to a lesser degree the carbon end too

00:01:26.605 --> 00:01:27.766
but hydrogen is even less,

00:01:27.766 --> 00:01:31.513
is a less electronegative than even carbon.

00:01:31.513 --> 00:01:34.369
And this one, so, a hydroxyl group

00:01:34.369 --> 00:01:36.737
they are polar, they are polar,

00:01:36.737 --> 00:01:40.394
and because they are polar you can dissolve them into water.

00:01:40.394 --> 00:01:41.973
They are hydrophilic.

00:01:41.973 --> 00:01:46.152
They can form hydrogen bonds so that you can dissolve this.

00:01:46.152 --> 00:01:49.751
Now, similar, a similar functional group

00:01:49.751 --> 00:01:52.477
or one that has somewhat similar properties

00:01:52.477 --> 00:01:54.425
is right over here.

00:01:54.425 --> 00:01:56.565
And you might say, "Wait, why is this one similar?

00:01:56.565 --> 00:01:58.806
"I have sulfur here instead of oxygen."

00:01:58.806 --> 00:02:00.106
But if you look at the periodic table

00:02:00.106 --> 00:02:01.731
you will see that sulfur and oxygen

00:02:01.731 --> 00:02:03.728
both have six valence electrons.

00:02:03.728 --> 00:02:06.270
They both would love nothing more than to grab

00:02:06.270 --> 00:02:08.441
or pretend to grab two other electrons

00:02:08.441 --> 00:02:09.625
and this is why they form,

00:02:09.625 --> 00:02:11.448
they tend to form two covalent bonds.

00:02:11.448 --> 00:02:13.004
And so, this group right over here,

00:02:13.004 --> 00:02:14.861
which is called a sulfhydryl group.

00:02:14.861 --> 00:02:19.148
This is a sulf....

00:02:19.148 --> 00:02:21.284
Sulfhydryl.

00:02:21.284 --> 00:02:23.385
Sulfhydryl group.

00:02:23.385 --> 00:02:25.893
It's kind of similar to a hydroxyl group

00:02:25.893 --> 00:02:27.588
with the one difference,

00:02:27.588 --> 00:02:29.713
with the one difference that sulfur is electronegative

00:02:29.713 --> 00:02:32.127
but it is less electronegative than oxygen.

00:02:32.127 --> 00:02:33.950
So, you're still gonna have a partially negative charge

00:02:33.950 --> 00:02:35.993
and a partially positive charge,

00:02:35.993 --> 00:02:37.711
but it's going to be less polar.

00:02:37.711 --> 00:02:41.229
So, it's not quite as polar as if you had a hydroxyl group.

00:02:41.229 --> 00:02:43.551
Now, when you have this sulfhydryl group

00:02:43.551 --> 00:02:45.791
it's attached to, say, a carbon chain

00:02:45.791 --> 00:02:49.448
and when I use this R right over here, when I have this R.

00:02:49.448 --> 00:02:51.503
This is just shorthand for carbon

00:02:51.503 --> 00:02:52.583
and a bunch of other stuff.

00:02:52.583 --> 00:02:54.405
I could've, if I wanted to generalize

00:02:54.405 --> 00:02:55.647
an alcohol right over here

00:02:55.647 --> 00:02:57.342
I could've written R and then

00:02:57.342 --> 00:02:59.908
I could've written the hydroxyl group.

00:02:59.908 --> 00:03:04.308
O and then bond that, bond that to an H.

00:03:04.308 --> 00:03:07.742
So, over here the shorthand R would have been the shorthand

00:03:07.742 --> 00:03:09.101
for all of...

00:03:09.101 --> 00:03:10.401
The R would've been the shorthand

00:03:10.401 --> 00:03:12.214
for all of this business.

00:03:12.214 --> 00:03:14.927
All of this business right over here.

00:03:14.838 --> 00:03:16.011
And so that's what we're doing over there.

00:03:16.011 --> 00:03:17.450
I'm not saying that this R is exactly this.

00:03:17.450 --> 00:03:20.074
It means that some carbon backbone

00:03:20.074 --> 00:03:23.278
and some carbons, hydrogens, and maybe other stuff,

00:03:23.278 --> 00:03:24.949
maybe even some other functional groups,

00:03:24.949 --> 00:03:28.177
but we're just focused on the sulfhydryl right over here.

00:03:28.177 --> 00:03:29.570
And so if you see something like this, you'd say

00:03:29.570 --> 00:03:30.917
"Okay, yeah, this is still going to be polar,

00:03:30.917 --> 00:03:33.087
"but not quite as polar as if I were dealing

00:03:33.087 --> 00:03:35.432
"with a hydroxyl group."

00:03:35.432 --> 00:03:38.288
Now over here we have a more complex molecule,

00:03:38.288 --> 00:03:39.855
but this is a molecule that you run into

00:03:39.855 --> 00:03:41.945
probably on a daily basis.

00:03:41.945 --> 00:03:45.612
This is the sugar fructose.

00:03:45.672 --> 00:03:47.889
This is the sugar fructose.

00:03:47.889 --> 00:03:50.571
And this is when it is not in a ring.

00:03:50.571 --> 00:03:51.944
If you were to throw this into--

00:03:51.944 --> 00:03:53.244
If you were to throw this into water,

00:03:53.244 --> 00:03:56.065
it'll readily form a ring, but when it is not in a ring form

00:03:56.065 --> 00:03:58.689
you can recognize already the hydroxyl groups.

00:03:58.689 --> 00:04:00.569
You have a hydroxyl group on this carbon.

00:04:00.639 --> 00:04:02.427
You have a hydroxyl group on this carbon.

00:04:02.427 --> 00:04:04.435
Hydroxyl group on this carbon.

00:04:04.435 --> 00:04:06.606
You have a hydroxyl group on that carbon.

00:04:06.606 --> 00:04:09.148
You have a hydroxyl group on this carbon.

00:04:09.148 --> 00:04:14.037
And then, on this carbon, it's double bonded to an oxygen.

00:04:14.037 --> 00:04:16.818
We call this a carbonyl group.

00:04:16.818 --> 00:04:20.660
So this is a carbonyl.

00:04:20.660 --> 00:04:22.483
Carbonyl.

00:04:22.483 --> 00:04:24.236
Carbonyl group.

00:04:24.236 --> 00:04:25.663
Now this is actually how you would tell a sugar,

00:04:25.663 --> 00:04:27.462
it's like, look, especially when it's in a straight chain,

00:04:27.462 --> 00:04:30.923
all my carbons have one hydroxyl on them

00:04:30.923 --> 00:04:34.161
except for this one, it has a carbonyl group.

00:04:34.161 --> 00:04:36.483
And one of the take aways for a carbonyl group,

00:04:36.483 --> 00:04:37.435
we've already talked about

00:04:37.435 --> 00:04:39.223
oxygen being very electronegative,

00:04:39.223 --> 00:04:41.800
even more electronegative than carbon, it's double bonds,

00:04:41.800 --> 00:04:44.629
it's going to hog the electrons on the oxygen end,

00:04:44.629 --> 00:04:48.657
so you're going to have a partially negative charge.

00:04:48.657 --> 00:04:50.955
Partially negative charge over here,

00:04:50.955 --> 00:04:53.313
partially positive charge over here,

00:04:53.313 --> 00:04:56.586
and so this, this one is also going to be polar.

00:04:56.586 --> 00:04:58.734
And then, in fact, the entire molecule is very polar

00:04:58.734 --> 00:05:00.928
because it has all these hydroxyl groups on it as well,

00:05:00.928 --> 00:05:03.575
but this is also going to give it polarity here

00:05:03.575 --> 00:05:07.093
and, because this carbon has a slightly positive charge,

00:05:07.093 --> 00:05:09.752
it is susceptible to nucleophilic attack,

00:05:09.752 --> 00:05:10.921
and when you take organic chemistry,

00:05:10.921 --> 00:05:14.274
you'll see that things that want to share--

00:05:14.274 --> 00:05:17.514
That have a predisposition to share their electrons

00:05:17.514 --> 00:05:19.999
in a bond might want to come and form a bond

00:05:19.999 --> 00:05:23.040
with this carbon and maybe one of these electron pairs

00:05:23.040 --> 00:05:26.476
go back to this oxygen and maybe bond with something else,

00:05:26.476 --> 00:05:27.719
but we'll talk about it in the future

00:05:27.719 --> 00:05:30.331
when we study some organic chemistry mechanisms.

00:05:30.331 --> 00:05:31.701
The important thing here is just recognize,

00:05:31.701 --> 00:05:33.175
"Okay, I've got some hydroxyl groups?

00:05:33.175 --> 00:05:37.691
"Okay, I've got a carbonyl group right over here as well."

00:05:37.691 --> 00:05:41.245
Now this molecule, this is an amino acid,

00:05:41.245 --> 00:05:44.959
and you will see amino acids a lot when you study biology.

00:05:44.959 --> 00:05:48.756
And this has actually a couple of interesting groups on it.

00:05:48.756 --> 00:05:53.734
The first group of note is this stuff

00:05:53.734 --> 00:05:57.412
that I am circling in orange because you have a carbon that,

00:05:57.412 --> 00:05:59.792
you could say it's part of a carbonyl group,

00:05:59.792 --> 00:06:04.087
but it is also bound to a hydroxyl group.

00:06:04.087 --> 00:06:07.430
It is also bound to a hydroxyl group right over there.

00:06:07.430 --> 00:06:09.381
And when you have this configuration where you have

00:06:09.381 --> 00:06:11.865
a carbon bond double-bonded to an oxygen

00:06:11.865 --> 00:06:13.850
and then single-bonded to a hydroxyl group,

00:06:13.850 --> 00:06:17.170
we call this a carboxyl group.

00:06:17.170 --> 00:06:20.655
This is a carboxyl.

00:06:20.655 --> 00:06:25.051
Carboxyl, carboxyl group.

00:06:25.051 --> 00:06:28.843
And one of the take aways from this is that it is acidic

00:06:28.843 --> 00:06:31.862
because this can readily give up the hydrogen proton.

00:06:31.862 --> 00:06:34.543
This oxygen, we already know oxygen likes to hog electrons,

00:06:34.543 --> 00:06:37.759
it can take up both of these electrons and become negative,

00:06:37.759 --> 00:06:39.442
and actually, there's actually resonance here

00:06:39.442 --> 00:06:42.043
because those electrons get shared throughout the group

00:06:42.043 --> 00:06:43.924
and actually even potentially even beyond the group

00:06:43.924 --> 00:06:46.002
but especially inside of the group,

00:06:46.002 --> 00:06:47.940
then leaving the hydrogen proton.

00:06:47.940 --> 00:06:51.202
So this can readily donate a hydrogen proton...

00:06:51.202 --> 00:06:54.142
This can readily donate a hydrogen proton,

00:06:54.142 --> 00:06:57.982
so this is generally viewed as acidic.

00:06:57.982 --> 00:06:59.489
Acidic.

00:06:59.489 --> 00:07:03.204
Now, this amino acid over here,

00:07:03.204 --> 00:07:05.468
it also, and this is where this name comes from,

00:07:05.468 --> 00:07:07.933
actually the acid comes from this carboxyl group,

00:07:07.933 --> 00:07:12.219
this is the acidic part, and then you have an animo group.

00:07:12.219 --> 00:07:15.477
You have an amino group right,

00:07:15.477 --> 00:07:18.252
right over here.

00:07:18.252 --> 00:07:20.748
And because it's involving a nitrogen,

00:07:20.748 --> 00:07:22.036
this is the amino group.

00:07:22.036 --> 00:07:25.368
This is what gives the amino part of the name amino acid.

00:07:25.368 --> 00:07:26.912
Amino acid.

00:07:26.912 --> 00:07:28.839
And this actually is generally basic.

00:07:28.839 --> 00:07:30.511
Because nitogen could--

00:07:30.511 --> 00:07:31.997
It has a lone pair.

00:07:31.997 --> 00:07:35.398
It has a lone pair of electrons right over here.

00:07:35.398 --> 00:07:38.138
And so it could use that lone pair to pick up,

00:07:38.138 --> 00:07:41.156
to form a bond with a hydrogen ion,

00:07:41.156 --> 00:07:42.596
to pick up a hydrogen ion.

00:07:42.596 --> 00:07:45.939
So, under the right circumstances, it can form a bond

00:07:45.939 --> 00:07:49.201
with a hydrogen ion, which, we know, a positive ion,

00:07:49.201 --> 00:07:50.478
which would just be a proton,

00:07:50.478 --> 00:07:52.243
and so it would have a positive charge.

00:07:52.243 --> 00:07:55.180
And so since it can sop up hydrogen ions,

00:07:55.180 --> 00:07:59.139
we can view this, the amino group, as being basic.

00:07:59.139 --> 00:08:01.054
But this right over here is leucine,

00:08:01.054 --> 00:08:03.759
it's an amino acid super important for muscle growth,

00:08:03.759 --> 00:08:05.315
but there you can appreciate.

00:08:05.315 --> 00:08:08.182
You have essentially a hydrocarbon chain,

00:08:08.182 --> 00:08:09.856
but it has a carboxyl group at this end

00:08:09.856 --> 00:08:11.783
and an animo group right over here.

00:08:11.783 --> 00:08:13.583
And another thing that you'll sometimes people talk about

00:08:13.583 --> 00:08:15.220
is even hydrocarbon groups.

00:08:15.220 --> 00:08:17.866
For example, if you consider the main chain of this,

00:08:17.866 --> 00:08:18.958
and we could consider to

00:08:18.958 --> 00:08:20.606
either using this carbon or this carbon,

00:08:20.606 --> 00:08:24.795
but if we consider this to be the main chain of carbons,

00:08:24.795 --> 00:08:27.384
if we consider that to be the main chain of carbons,

00:08:27.384 --> 00:08:30.344
then we would consider this right over here

00:08:30.344 --> 00:08:31.784
to be a methyl group.

00:08:31.784 --> 00:08:34.628
Remember, the prefix "meth" refers to one carbon,

00:08:34.628 --> 00:08:37.159
so it's one carbon bonded to a bunch of hydrogens,

00:08:37.159 --> 00:08:38.343
to three hydrogens here,

00:08:38.343 --> 00:08:40.339
and so we would call this a methyl group.

00:08:40.339 --> 00:08:42.824
And in general, if you have a hydrocarbon

00:08:42.824 --> 00:08:45.041
bonded to other hydrocarbon groups,

00:08:45.041 --> 00:08:47.084
these things are hydrophobic.

00:08:47.084 --> 00:08:49.139
So these things, there's nothing polar about them,

00:08:49.139 --> 00:08:50.776
and so they're not going to want to,

00:08:50.776 --> 00:08:53.028
at least these parts of the molecule

00:08:53.028 --> 00:08:56.755
are not going to naturally dissolve inside of water.

00:08:56.755 --> 00:08:58.449
Now the last group we're going to focus on,

00:08:58.449 --> 00:09:00.539
and you're going to see a lot of these, and especially

00:09:00.539 --> 00:09:02.803
in biology, you're going to see this as a part of ATP,

00:09:02.803 --> 00:09:05.426
you're going to see it's the backbone of DNA,

00:09:05.426 --> 00:09:07.469
and that's phosphate groups.

00:09:07.469 --> 00:09:09.953
And this right over here,

00:09:09.953 --> 00:09:13.332
this right over here is the phosphate group.

00:09:13.332 --> 00:09:16.234
I've drawn it bonded to a bunch of,

00:09:16.234 --> 00:09:18.974
kind of a group over here, who knows what it is,

00:09:18.974 --> 00:09:20.634
bunch of carbons, a bunch of other things,

00:09:20.634 --> 00:09:22.433
and then I've bonded it to two hydrogens,

00:09:22.433 --> 00:09:24.488
but it doesn't always have to be bound to hydrogens.

00:09:24.488 --> 00:09:26.310
But when it is bound to hydrogens like this,

00:09:26.310 --> 00:09:28.806
it's considered to be protonated,

00:09:28.806 --> 00:09:31.012
and so it can actually take up, it can actually

00:09:31.012 --> 00:09:33.566
hog these electrons and dump these hydrogens,

00:09:33.566 --> 00:09:35.911
and dump these hydrogens into a solution.

00:09:35.911 --> 00:09:39.696
So a phosphate group is considered to be acidic.

00:09:39.696 --> 00:09:42.807
It is considered as well, especially when it is protonated

00:09:42.807 --> 00:09:44.769
like this, it is considered to be acidic

00:09:44.769 --> 00:09:46.533
because it can donate protons.

00:09:46.533 --> 00:09:47.509
So this is just an overview

00:09:47.509 --> 00:09:49.519
of a lot of the functional groups you will see throughout

00:09:49.519 --> 00:09:52.346
biology and a lot of big, hairy complex molecules,

00:09:52.346 --> 00:09:53.658
when you actually break it down, you say,

00:09:53.658 --> 00:09:55.120
"Okay, there's a hydrocarbon chain there.

00:09:55.120 --> 00:09:56.200
"Oh, I see a sugar there!

00:09:56.200 --> 00:09:58.917
"I see a bunch of hydroxyls, and I have a carbonyl group.

00:09:58.917 --> 00:10:00.797
"Oh, I see an amine group, I see--

00:10:00.797 --> 00:10:01.621
"Or, amino group.

00:10:01.621 --> 00:10:03.583
"I see a carboxyl group."

00:10:03.583 --> 00:10:04.837
You can think about this going to be acidic?

00:10:04.837 --> 00:10:05.917
Is it going to be polar?

00:10:05.917 --> 00:10:07.298
Or do different parts of the molecule

00:10:07.298 --> 00:10:09.266
have different functions?


Functional groups

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:03.880
We've spent some time talking about hydrocarbons and hydrocarbons are interesting

00:00:03.880 --> 00:00:07.840
--especially  if you want to combust things,
if you want some fuel.

00:00:07.840 --> 00:00:10.980
But now we're going to make things a little more interesting by adding things

00:00:10.980 --> 00:00:15.650
to the hydrocarbons and the things we're
gonna add we call functional groups...

00:00:15.650 --> 00:00:20.130
functional groups. And my goal in this
video is to give you an overview of the

00:00:20.130 --> 00:00:24.060
major functional groups that you might
see attached to carbon backbones that

00:00:24.060 --> 00:00:26.560
make the molecules interesting biologically.

00:00:26.560 --> 00:00:30.200
Now the first one I will focus on is an -OH group

00:00:30.200 --> 00:00:33.360
So you have an -OH attached to
a carbon backbone over here.

00:00:33.480 --> 00:00:36.510
It doesn't have to be attached to a
carbon backbone but the -OH right over

00:00:36.510 --> 00:00:42.719
here this is called a hydroxyl group
...hydroxyl... group and when it is

00:00:42.719 --> 00:00:47.280
attached to a carbon backbone like this
one is then it turns the entire molecule

00:00:47.280 --> 00:00:53.550
into an alcohol...alcohol.  This is an
alcohol and this one in particular, if

00:00:53.550 --> 00:00:57.270
you want the name, we have two carbons
all along its longest chain and it is an

00:00:57.270 --> 00:01:02.190
alcohol so we use a prefix eth- for the two
carbons, so let me write that down. We're

00:01:02.190 --> 00:01:06.080
gonna use the prefix eth- because we have
two carbons here and we're gonna say

00:01:06.080 --> 00:01:13.320
"eth"-anol, ethanol, which you might more
commonly know as rubbing, as rubbing

00:01:13.320 --> 00:01:17.909
alcohol. Now what are the properties here?
Well you have an oxygen which is very

00:01:17.909 --> 00:01:23.040
electronegative bonded to a hydrogen and
to a carbon but the oxygen is a lot more

00:01:23.040 --> 00:01:26.369
electronegative than the hydrogen, so
you're going to have a partially

00:01:26.369 --> 00:01:30.140
negative charge at this end away from
the hydrogen, a partial positive charge

00:01:30.200 --> 00:01:33.680
at the hydrogen end and, to a lesser
degree, at the carbon end too, but hydrogen

00:01:33.689 --> 00:01:38.670
is even less electronegative
than even carbon.  And so

00:01:38.670 --> 00:01:44.220
this one, so a hydroxyl group, they are
polar, they are polar, and because they're

00:01:44.260 --> 00:01:49.460
polar you can dissolve them into
water.  They are hydrophilic they can form

00:01:49.460 --> 00:01:56.360
hydrogen bonds so you can dissolve this.
Now a similar a similar functional group

00:01:56.369 --> 00:02:01.170
or one that has somewhat similar
properties is right over here and you

00:02:01.170 --> 00:02:04.649
might say wait why is this one similar, I
have sulfur here instead of

00:02:04.649 --> 00:02:08.009
oxygen.  But if you look at the periodic
table you will see that sulfur and

00:02:08.009 --> 00:02:12.540
oxygen both have six valence electrons,
they both would love nothing more than

00:02:12.540 --> 00:02:15.660
to grab or pretend to grab
two other electrons and this is why they

00:02:15.660 --> 00:02:19.680
tend to form two covalent
bonds.  And so this group right over here,

00:02:19.680 --> 00:02:29.670
which is called a sulfhydryl group.  This
is a sulfhydryl group.

00:02:29.670 --> 00:02:34.530
It's kind of similar to a hydroxyl
group with the one difference, with the

00:02:34.530 --> 00:02:37.050
one difference, that sulfur is
electronegative but it is less

00:02:37.050 --> 00:02:40.050
electronegative than oxygen so you're
still gonna have a partially negative

00:02:40.050 --> 00:02:44.640
charge and a partially positive charge
but it's going to be less polar so it's

00:02:44.640 --> 00:02:49.200
not quite as polar as if you had a
hydroxyl group.  Now when you have this

00:02:49.200 --> 00:02:53.519
sulfhydryl group it's attached to say a
carbon chain, and when I use this

00:02:53.519 --> 00:02:58.380
R right over here, when I have this R,
this is just shorthand for carbon and a

00:02:58.380 --> 00:03:01.890
bunch of other stuff.  I could have, if I
wanted to generalize an alcohol right

00:03:01.890 --> 00:03:06.090
over here I could have written R and
then I could have written the hydroxyl

00:03:06.090 --> 00:03:13.140
group O and then bond that to
an H so over here this shorthand R would

00:03:13.140 --> 00:03:17.640
have been the shorthand for all of, the R
would have been the shorthand for all of

00:03:17.640 --> 00:03:22.290
this business, all of this business, right
over here.  And so that's what we're doing

00:03:22.290 --> 00:03:25.740
over there.  I'm not saying that this R is
exactly this.  It means it's some, you know,

00:03:25.740 --> 00:03:29.850
carbon backbone and carbons,
hydrogens, and maybe other stuff,

00:03:29.850 --> 00:03:33.450
maybe even some other functional groups,
but we're just focused on the

00:03:33.450 --> 00:03:36.690
sulfhydryl right over here.  And so if you see
something like this you'd say, okay yeah

00:03:36.690 --> 00:03:40.109
this is still gonna be polar but not
quite as polar as if I were dealing with

00:03:40.109 --> 00:03:45.420
a hydroxyl group.  Now over here we have a
more complex molecule but this is a

00:03:45.420 --> 00:03:51.410
molecule that you run into probably on a
daily basis.  This is the sugar fructose.

00:03:51.410 --> 00:03:57.299
This is the sugar fructose and
this is when it is not in a ring.  If you

00:03:57.299 --> 00:04:00.750
were to throw this into, if you were
throw this into water it'll readily form

00:04:00.750 --> 00:04:04.769
a ring but when it's not in a ring form you
can recognize already the hydroxyl

00:04:04.769 --> 00:04:08.700
groups.  You have a hydroxyl group on this
carbon.  You have a hydroxyl group on this

00:04:08.700 --> 00:04:13.500
carbon.  Hydroxyl group on this carbon.  You
have a hydroxyl group on that carbon, you

00:04:13.500 --> 00:04:19.350
have a hydroxyl group on this carbon and
then, on this carbon, it's double

00:04:19.350 --> 00:04:25.550
bonded to an oxygen.  We call this a
carbonyl group.  So this is a, this is a

00:04:25.550 --> 00:04:31.170
carbonyl...carbonyl group and this is

00:04:31.170 --> 00:04:33.330
actually how you would tell a sugar is
like it look especially when it's in a

00:04:33.330 --> 00:04:37.950
straight chain, all my carbons
have one hydroxyl on them except

00:04:37.950 --> 00:04:42.900
for this one, it has a carbonyl group.  And
one of the takeaways for a carbonyl

00:04:42.900 --> 00:04:46.260
group, we've already talked about oxygen
being very electronegative, even more

00:04:46.260 --> 00:04:50.250
electronegative than carbon, it's double
bonds, it's going to hog the electrons on

00:04:50.250 --> 00:04:53.940
the oxygen end so you're gonna have a
partial, you're gonna have a partially

00:04:53.940 --> 00:04:58.860
negative charge, partially negative
charge over here, partially positive

00:04:58.860 --> 00:05:04.080
charge over here, and so this one is
also going to be polar, and in fact the

00:05:04.080 --> 00:05:07.230
entire molecule is very polar because it
has all these hydroxyl groups on it as

00:05:07.230 --> 00:05:11.850
well, but this is also going to give it
polarity here and, because this carbon

00:05:11.850 --> 00:05:16.650
has a slightly positive charge, it is
susceptible to nucleophilic attack.  And

00:05:16.650 --> 00:05:19.740
when you take organic chemistry you'll
see that things that want to,

00:05:19.740 --> 00:05:23.670
want to share, that have a
predisposition to share their

00:05:23.670 --> 00:05:27.540
electrons in a bond, might want to come
and form a bond with this carbon.  And

00:05:27.540 --> 00:05:31.960
maybe one of these electron pairs
go back to this, go back to this oxygen

00:05:31.960 --> 00:05:34.560
and maybe bond with something else.  But
we'll talk about that in the future when

00:05:34.560 --> 00:05:37.830
we study some organic chemistry
mechanisms.  The important thing here is

00:05:37.830 --> 00:05:42.240
just recognize, okay I got some hydroxyl
groups, hey I got a carbonyl group right

00:05:42.240 --> 00:05:48.720
over here as well.  Now this molecule, this
is an amino acid.  And you will see amino

00:05:48.720 --> 00:05:53.760
acids a lot when you study biology and
this has actually a couple of

00:05:53.760 --> 00:06:00.990
interesting groups on it.  The first group
of note is this stuff that I am

00:06:00.990 --> 00:06:05.280
circling in orange because you have a
carbon that is, you could say it's part

00:06:05.280 --> 00:06:11.160
of a carbonyl group, but it is also, it is
also bound to a hydroxyl group.  It is

00:06:11.160 --> 00:06:14.940
also bound to a hydroxyl group right
over there.  And when you have this

00:06:14.940 --> 00:06:18.660
configuration where you have a carbon
bond double bonded to an oxygen and then

00:06:18.660 --> 00:06:26.690
single bonded to a hydroxyl group we
call this a carboxyl group.  This is a

00:06:26.690 --> 00:06:34.860
carboxyl group and one
of the takeaways from this is that it is

00:06:34.860 --> 00:06:39.360
acidic because this can readily give up
the hydrogen proton.  This oxygen, we

00:06:39.360 --> 00:06:41.400
already know oxygen likes to hog electrons,

00:06:41.400 --> 00:06:45.120
it can take up both of these electrons
and become negative.  And actually there's

00:06:45.120 --> 00:06:48.479
actually resonance here because those
electrons get shared throughout the

00:06:48.479 --> 00:06:52.110
group and actually even potentially even
beyond the group but especially inside

00:06:52.110 --> 00:06:55.720
of the group then leaving the
hydrogen proton.  So this can readily

00:06:55.720 --> 00:07:01.680
donate a hydrogen, this can readily
donate a hydrogen proton so this is

00:07:01.680 --> 00:07:09.980
generally viewed as acidic.  Now
this amino acid over here,

00:07:10.050 --> 00:07:13.360
it also, and this is where this name comes
from.  Actually the acid comes from this

00:07:13.360 --> 00:07:18.940
carboxyl group, that's the acidic part,
and then you have an amino group,

00:07:18.940 --> 00:07:27.120
you have an amino group right over
here because it's involving nitrogen.

00:07:27.120 --> 00:07:31.530
This is the amino group.  This is what
gives the amino part of the name "amino acid",

00:07:31.760 --> 00:07:37.140
Amino acid.  And this is actually
generally basic because nitrogen could,

00:07:37.140 --> 00:07:41.580
it has a lone pair, it has a, it has a
lone pair of electrons right over here

00:07:41.580 --> 00:07:46.860
and so it could use that lone pair to
pick up, to form a bond with

00:07:46.860 --> 00:07:51.449
a hydrogen ion, to pick up a hydrogen ion.
So under the right circumstances it can

00:07:51.449 --> 00:07:56.280
form a bond with a hydrogen ion, which we
know a positive ion which would just be

00:07:56.280 --> 00:08:00.680
a proton, and so it would have a positive
charge.  And so since it can sop up

00:08:00.680 --> 00:08:06.210
hydrogen ions we can view this as,
the amino group, as being basic.  But this

00:08:06.210 --> 00:08:10.240
right over here is leucine.  It's an amino
acid.  Super important for muscle growth.

00:08:10.240 --> 00:08:15.030
But there you can appreciate, you have
essentially a hydrocarbon chain but it

00:08:15.030 --> 00:08:18.870
has a carboxyl group at this end and an
amino group right over here.  And another

00:08:18.870 --> 00:08:22.199
thing that you'll sometimes people talk
about is even hydrocarbon groups.  For

00:08:22.199 --> 00:08:25.620
example if you consider the main chain
of this, and we could consider it either

00:08:25.620 --> 00:08:29.630
using this carbon or this carbon, but if
we consider this to be the main chain of

00:08:29.630 --> 00:08:34.589
carbons, if we consider that to be the
main chain of carbons, then we would

00:08:34.589 --> 00:08:39.539
consider this right over here to be a
methyl group. Rremember the prefix "meth"

00:08:39.539 --> 00:08:44.610
refers to one carbon.  So it's one carbon
bonded to a bunch of hydrogens, to three hydrogens

00:08:44.610 --> 00:08:48.720
here, and so we would call this a methyl
group.  And in general if you have a

00:08:48.720 --> 00:08:53.459
hydrocarbon bonded to other hydrocarbon
groups these things are are hydrophobic

00:08:53.459 --> 00:08:56.630
so these things, there's nothing
polar about them and so they're not

00:08:56.630 --> 00:08:59.899
going to want to, at least
these parts of the molecules, are

00:08:59.900 --> 00:09:04.550
not going to naturally dissolve inside of
water.  Now the last group we're going to

00:09:04.550 --> 00:09:07.560
focus on and you're going to see a lot
of these.  And especially in biology

00:09:07.560 --> 00:09:10.760
you're going to see it as part of ATP.
You're going to see it as the backbone of

00:09:10.760 --> 00:09:17.870
DNA and that's phosphate groups.  And this
right over here, this right over here, is

00:09:17.870 --> 00:09:24.889
the phosphate group.  I've drawn it bonded
to a bunch of kind of a group over here

00:09:24.889 --> 00:09:27.680
who knows what it is, a bunch of carbons,
a bunch of other things.  And then

00:09:27.680 --> 00:09:30.460
I've bonded it to two hydrogens but it
doesn't always have to be bound to

00:09:30.460 --> 00:09:33.620
hydrogens.  But when it is bound to
hydrogens like this it's considered to be

00:09:33.620 --> 00:09:37.970
pro-, it's protonated, and so it can
actually take up, it can actually hog

00:09:37.970 --> 00:09:41.510
these electrons and dump these
hydrogens, and dump these hydrogens

00:09:41.510 --> 00:09:47.480
into a solution.  So a phosphate group is
considered to be acidic, it is considered

00:09:47.480 --> 00:09:51.260
as, well especially when it is protonated
like this, it is considered to be acidic

00:09:51.260 --> 00:09:54.740
because it can donate protons.  So this is
just an overview of a lot of the

00:09:54.740 --> 00:09:57.649
functional groups you will see
throughout biology and a lot of big

00:09:57.649 --> 00:10:00.589
hairy complex molecules.  When you
actually break it down you say, okay

00:10:00.589 --> 00:10:03.320
there's a hydrocarbon chain there.  Oh I
see a sugar there.  I see a bunch of

00:10:03.320 --> 00:10:07.910
hydroxyls and I have a carbonyl group.  Oh
I see an amine group, I see... or amino

00:10:07.910 --> 00:10:11.240
group.  I see a carboxyl group
you can think about is this going to be

00:10:11.240 --> 00:10:14.180
acidic, is it going to be polar, or do
different parts of the molecules have

00:10:14.180 --> 00:10:17.320
different functions


Silicon-based life

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:01.620
We've already spent a lot of time

00:00:01.620 --> 00:00:02.800
thinking about how awesome

00:00:02.800 --> 00:00:07.800
carbon is for life, that really life as we know is carbon based.

00:00:07.800 --> 00:00:10.300
And this all comes out of carbon's ability

00:00:10.600 --> 00:00:16.000
to bond with other carbons and form all sorts of neat structures, bonds with oxygen, hydrogens,

00:00:16.000 --> 00:00:19.490
and other things. In fact, we have a whole
class of molecules

00:00:19.490 --> 00:00:23.580
called organic molecules that just are
molecules that involve carbon

00:00:23.580 --> 00:00:27.939
and carbons bonding capabilities really
come out of its electron structure.

00:00:27.939 --> 00:00:30.099
We talked about this in the previous video

00:00:30.099 --> 00:00:34.500
but if we think about carbon, it has six
protons and a neutral carbon will have

00:00:34.500 --> 00:00:35.660
six electrons.

00:00:35.660 --> 00:00:39.649
Two of them are sitting at its innermost
shell and then the other four are on its

00:00:39.649 --> 00:00:43.500
outermost shell, and those  four are the ones
that tend to react and we call them

00:00:43.500 --> 00:00:47.789
the valence electrons. And so these
valence electrons tend to form four

00:00:47.789 --> 00:00:49.780
covalent bonds, for example if

00:00:49.780 --> 00:00:54.300
you wanted a bond with four hydrogens,
well each hydrogen would contribute

00:00:54.300 --> 00:00:58.530
each hydrogen would contribute an
electron to one of these pairs, which are essentially

00:00:58.530 --> 00:01:00.180
going to be a covalent bond

00:01:00.180 --> 00:01:03.399
and then the hydrogens,

00:01:03.399 --> 00:01:06.930
can feel that their outer shell is
complete because hydrogen is just trying to get to

00:01:07.450 --> 00:01:11.100
two to fill its outer shell to try to be a
little bit more like helium

00:01:11.100 --> 00:01:16.000
and carbon is trying to get to eight in its
outer shell to be a little bit more like

00:01:16.000 --> 00:01:18.460
neon. Neon has two in its inner shell and

00:01:18.460 --> 00:01:22.400
eight in its outer shell. You might remember
the octet rule that,

00:01:22.400 --> 00:01:26.610
that atoms try to get to eight or pretend like they have

00:01:26.610 --> 00:01:29.760
eight electrons in the outer shell to
feel stable.

00:01:29.770 --> 00:01:33.500
And here carbon is sharing eight
electrons. It contributed four and the

00:01:33.500 --> 00:01:35.150
four hydgrogens contributed four

00:01:35.150 --> 00:01:40.579
and it forms, it forms methane. Now those of you who are quite astute

00:01:40.579 --> 00:01:44.100
might have said: okay you know what, I know of
other elements that

00:01:44.100 --> 00:01:48.049
tend to form four covalent bonds, that
have four valence electrons.

00:01:48.049 --> 00:01:51.119
And in particular there's one that's
awfully close to carbon

00:01:51.119 --> 00:01:54.619
on the periodic table and that's right
over here. This is,

00:01:54.619 --> 00:02:00.090
this is silicon. Silicon has 14
protons and a neutral

00:02:00.090 --> 00:02:04.649
silicon would have 14 electrons. So
let me draw that. So, if we have silicon

00:02:04.649 --> 00:02:06.800
right over here. I'm just gonna focus on the electrons.

00:02:06.960 --> 00:02:10.020
You would have two
electron sitting in its innermost,

00:02:10.030 --> 00:02:13.380
in its innermost shell, so they are
jumping here

00:02:13.380 --> 00:02:16.100
They're not these neat, well-defined orbits.

00:02:16.120 --> 00:02:17.600
They are just jumping around

00:02:17.610 --> 00:02:20.960
in that, in that lowest energy in that, in
that,

00:02:20.960 --> 00:02:24.260
in the innermost shell. Then you have
another eight

00:02:24.260 --> 00:02:28.170
in its second shell. So, one... I'll just draw them

00:02:28.170 --> 00:02:32.810
three, four, five, six, seven, eight, all jumping around

00:02:32.810 --> 00:02:36.880
all jumping around in the second shell. And it has a total of fourteen, so we already used up

00:02:36.880 --> 00:02:39.350
ten so it is going to have four in its
outermost shell.

00:02:39.350 --> 00:02:42.540
So, one, two, three, four

00:02:42.540 --> 00:02:46.040
and these four in its outermost
shell, these are the ones that tend to do

00:02:46.040 --> 00:02:48.960
the reacting. We call them valence
electrons.

00:02:48.960 --> 00:02:52.550
So if we want to just draw the valence
electrons, we could do silicon

00:02:52.550 --> 00:02:56.380
has four valence electrons, four

00:02:56.380 --> 00:02:59.930
has four. One, two, three, four

00:02:59.930 --> 00:03:03.500
valence electrons, just like carbon. It has a
different number of electrons.

00:03:03.500 --> 00:03:04.800
These four valence electrons

00:03:04.800 --> 00:03:07.810
are actually one shell further
out but it has four that tend to react.

00:03:07.810 --> 00:03:10.120
And it does tend to form four covalent bonds.

00:03:10.120 --> 00:03:13.630
So, you might be saying, well, can't we have
life that is dependent,

00:03:13.630 --> 00:03:16.970
that a silicon-based as opposed to
carbon-based

00:03:16.970 --> 00:03:20.090
and if you thought that, you would not be
the first person to think about that.

00:03:20.100 --> 00:03:21.210
Science fiction or

00:03:21.210 --> 00:03:24.750
authors have have have theorized that,
and this right actually

00:03:24.750 --> 00:03:27.940
This is a, this is a screenshot from

00:03:27.960 --> 00:03:32.940
"The Devil In The Dark " episode 1967, from
the original Star Trek, where they said

00:03:32.940 --> 00:03:36.370
maybe they encounter, Kirk encounters
that, the enterprise encounters

00:03:36.370 --> 00:03:41.060
these creatures that are silicon-based. They are called Hortas and they have all

00:03:41.060 --> 00:03:41.710
sorts of

00:03:41.710 --> 00:03:45.590
interesting properties. So, there's
you know, there's some folks who like to

00:03:45.590 --> 00:03:46.560
think maybe

00:03:46.560 --> 00:03:49.760
maybe silicon. But when you actually look at
the chemistry,

00:03:49.760 --> 00:03:53.660
things start to break down a little bit.
For example, one of the neat things about

00:03:53.660 --> 00:03:57.520
carbon is it readily forms bonds with
other carbons and that these bonds can

00:03:57.520 --> 00:04:01.050
actually be quite long. You can form all
sorts of these hydrocarbons and all sorts

00:04:01.050 --> 00:04:01.650
of other

00:04:01.650 --> 00:04:05.940
carbon-carbon structures, long chains
of carbon. So you can do that with carbon

00:04:05.940 --> 00:04:09.900
but it turns out that silicon-silicon
bonds are not that strong and silicon is

00:04:09.900 --> 00:04:11.070
not going to form,

00:04:11.070 --> 00:04:15.580
is not going to form really long chains.
So silicon is not going to do that.

00:04:15.580 --> 00:04:19.200
Even if you look at a simple, a
simple molecule

00:04:19.200 --> 00:04:22.740
like methane there is, there is a
molecule called

00:04:22.740 --> 00:04:23.660
silane but this does

00:04:23.660 --> 00:04:26.710
not readily form, it doesn't have the
same characteristics.

00:04:26.710 --> 00:04:30.150
So this is also not going to be as good
as methane

00:04:30.150 --> 00:04:33.940
and even if you think about something
like carbon dioxide which is carbon

00:04:33.940 --> 00:04:38.560
which is carbon bonded, having two double
bonds

00:04:38.560 --> 00:04:42.830
so this is carbon having two double
bonds to oxygens

00:04:42.830 --> 00:04:47.350
so two, so one double bond to one oxygen, another
double bond to another oxygen

00:04:47.350 --> 00:04:52.440
And we're used to thinking about carbon
dioxide in our everyday life as a gas.

00:04:52.440 --> 00:04:55.920
Plants are using these to

00:04:55.920 --> 00:05:00.170
fix into their structure, to
actually grow, they are taking the carbon

00:05:00.170 --> 00:05:02.040
out of it in their carbon fixation.

00:05:02.040 --> 00:05:05.850
We are, we exhale this carbon dioxide, it's
essential to life

00:05:05.850 --> 00:05:09.200
and you might think well what about, what
about silicon oxide.

00:05:09.200 --> 00:05:13.030
And silicon dioxide, is actually a fairly
common

00:05:13.030 --> 00:05:17.960
molecule, fairly common compound but it
does not exist at a gaseous state

00:05:17.960 --> 00:05:21.280
at the temperatures that we are normally, that
we normally associate

00:05:21.280 --> 00:05:25.690
with life. Most of silicon oxide is
in the form of quartz

00:05:25.690 --> 00:05:29.070
in the ground. So that is quartz over there.

00:05:29.070 --> 00:05:32.770
So when you look at the
actual ways that

00:05:32.770 --> 00:05:35.870
silicon forms bonds

00:05:35.870 --> 00:05:40.330
it actually does not seem actually close
to as good as carbon.

00:05:40.330 --> 00:05:40.960
Something like silicon

00:05:40.960 --> 00:05:45.419
when silicon bonds with oxygen it's a much --
not only is it in the solid form at

00:05:45.419 --> 00:05:46.419
normal temperatures

00:05:46.420 --> 00:05:50.800
where we normally associate life but
these are very, very, very strong bonds,

00:05:50.800 --> 00:05:53.730
much stronger than the bonds that carbon
is forming with oxygen.

00:05:53.730 --> 00:05:57.750
They're so strong,  they make it hard for
them to be manipulated with the types of

00:05:57.760 --> 00:05:58.890
chemical reactions

00:05:58.890 --> 00:06:02.880
that we're used to seeing inside of
organisms.

00:06:02.880 --> 00:06:06.090
So, you know, it's fun to theorize
about this and I'd be the last person

00:06:06.090 --> 00:06:09.110
to rule anything out. I think the
universe will continue

00:06:09.110 --> 00:06:13.600
to surprise us with things that
right now we cannot even imagine.

00:06:13.600 --> 00:06:17.040
But based on the chemistry we know and
based on life as we know it

00:06:17.040 --> 00:06:20.660
even though silicon can form these four
covalent bonds and does have four

00:06:20.660 --> 00:06:21.850
valence electrons,

00:06:21.850 --> 00:06:23.360
it's still

00:06:23.360 --> 00:06:26.430
nowhere near as good as carbon

00:06:26.430 --> 00:06:30.050
in doing the types of processes
that we think are necessary for life.


Hydrocarbon overview

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:01.410
We've already spent a lot of time

00:00:01.410 --> 00:00:04.440
talking about how neat carbon is for

00:00:04.440 --> 00:00:07.259
life and for biology and for chemical

00:00:07.259 --> 00:00:08.610
reactions so much so that there's a

00:00:08.610 --> 00:00:11.730
whole field of organic chemistry devoted

00:00:11.730 --> 00:00:13.830
to studying the chemistry of molecules

00:00:13.830 --> 00:00:16.320
that involve carbon and one of the

00:00:16.320 --> 00:00:17.970
things that carbon - or two of the things

00:00:17.970 --> 00:00:19.619
that carbon will often bond with are

00:00:19.619 --> 00:00:23.070
itself and with hydrogens so much so

00:00:23.070 --> 00:00:24.390
that there's an entire class of

00:00:24.390 --> 00:00:26.910
molecules that are only made up of

00:00:26.910 --> 00:00:29.039
carbons and hydrogens and we call these

00:00:29.039 --> 00:00:31.289
it's a very creative name we call them

00:00:31.289 --> 00:00:34.920
hydrocarbons - hydrocarbons and you will

00:00:34.920 --> 00:00:37.230
see many many types of pure hydrocarbons

00:00:37.230 --> 00:00:38.850
and you'll see many other types of

00:00:38.850 --> 00:00:40.739
molecules that at least are partially

00:00:40.739 --> 00:00:42.899
hydrocarbons or are based on

00:00:42.899 --> 00:00:44.219
hydrocarbons so it's a really

00:00:44.219 --> 00:00:47.280
interesting thing to study here's three

00:00:47.280 --> 00:00:49.530
examples of hydrocarbons these all have

00:00:49.530 --> 00:00:52.079
the prefix eth- in the beginning of them

00:00:52.079 --> 00:00:54.539
because they have a chain their longest

00:00:54.539 --> 00:00:56.940
chain has two carbons and if you want to

00:00:56.940 --> 00:01:00.059
study how to name hydrocarbons or

00:01:00.059 --> 00:01:01.980
actually organic compounds in general I

00:01:01.980 --> 00:01:03.809
encourage you to look at the organic

00:01:03.809 --> 00:01:06.270
chemistry section of Khan Academy where

00:01:06.270 --> 00:01:07.770
we go into depth on it but this is just

00:01:07.770 --> 00:01:09.630
going to get you just kind of dip our

00:01:09.630 --> 00:01:11.070
toe in the water just so we get a little

00:01:11.070 --> 00:01:12.720
bit familiar so these all have the

00:01:12.720 --> 00:01:14.549
prefix eth- which says our longest

00:01:14.549 --> 00:01:15.689
chain of carbon we're gonna have two

00:01:15.689 --> 00:01:17.939
carbons over here but then we see that

00:01:17.939 --> 00:01:20.759
the ending is different over here we

00:01:20.759 --> 00:01:24.150
have ethane and it's it's an ane because

00:01:24.150 --> 00:01:27.330
we have a single bond over here this

00:01:27.330 --> 00:01:30.150
over here we have an ene and that's

00:01:30.150 --> 00:01:32.220
because we have a double bond we have at

00:01:32.220 --> 00:01:34.170
least one double bond in that chain that

00:01:34.170 --> 00:01:36.150
and the carbon chain is only two carbons

00:01:36.150 --> 00:01:40.229
over here and it's ethyne here because we

00:01:40.229 --> 00:01:43.020
have a triple bond the general term for

00:01:43.020 --> 00:01:45.750
a carbon chain that has no double or

00:01:45.750 --> 00:01:48.060
triple bonds is an alkane this is a

00:01:48.060 --> 00:01:50.460
specific form of an alkane ethane that

00:01:50.460 --> 00:01:53.700
has two carbons if the general form for

00:01:53.700 --> 00:01:55.619
carbons that have a double bond that's

00:01:55.619 --> 00:01:57.810
an alkene actually let me write these

00:01:57.810 --> 00:02:01.219
general terms down so I could write al

00:02:01.219 --> 00:02:04.920
alkane alkane is the general term for a

00:02:04.920 --> 00:02:08.220
chain of carbons that has no double or

00:02:08.220 --> 00:02:10.289
triple bonds and specifically this is

00:02:10.289 --> 00:02:12.750
ethane if I were generally here and say

00:02:12.750 --> 00:02:13.890
alkene now it's

00:02:13.890 --> 00:02:17.010
alkine right over here let's think a

00:02:17.010 --> 00:02:18.870
little bit about how this bond effects

00:02:18.870 --> 00:02:21.870
effects its shape well here I have a

00:02:21.870 --> 00:02:24.060
single bond so it essentially forms two

00:02:24.060 --> 00:02:26.430
tetrahedrons with one of the carbons at

00:02:26.430 --> 00:02:27.569
each of the centers of those

00:02:27.569 --> 00:02:29.910
tetrahedrons for example on the left

00:02:29.910 --> 00:02:32.250
hand side here when I when I draw this

00:02:32.250 --> 00:02:34.320
bond popping when I draw it like this it

00:02:34.320 --> 00:02:35.880
means that it's popping out and when I

00:02:35.880 --> 00:02:37.290
draw it like this with these lies that

00:02:37.290 --> 00:02:40.410
means it's going into into the screen so

00:02:40.410 --> 00:02:41.910
I could draw a tetrahedron that looks

00:02:41.910 --> 00:02:44.580
that looks like this that's the base of

00:02:44.580 --> 00:02:46.620
it and then the top of it is that this

00:02:46.620 --> 00:02:49.530
other carbon and it has it has this

00:02:49.530 --> 00:02:51.690
carbon at the center and I could also

00:02:51.690 --> 00:02:53.730
draw another tetrahedron that has this

00:02:53.730 --> 00:02:56.130
carbon at the center this carbon at its top

00:02:56.130 --> 00:02:58.500
and it would look it would look

00:02:58.500 --> 00:03:01.310
something it would look something like

00:03:01.310 --> 00:03:04.440
it would look something like this so for

00:03:04.440 --> 00:03:05.880
at least for this molecule you have the

00:03:05.880 --> 00:03:08.120
shape is kind of it looks like these two

00:03:08.120 --> 00:03:09.660
tetrahedrons that are kind of

00:03:09.660 --> 00:03:11.730
overlapping with each other and because

00:03:11.730 --> 00:03:13.980
these carbons are they have a single

00:03:13.980 --> 00:03:16.140
bond in between them they these two

00:03:16.140 --> 00:03:19.079
tetrahedrons can rotate so they could

00:03:19.079 --> 00:03:22.620
rotate they could rotate around they

00:03:22.620 --> 00:03:26.310
could rotate around that single bond now

00:03:26.310 --> 00:03:27.450
things are a little bit different when

00:03:27.450 --> 00:03:29.130
you have a double bond when you have a

00:03:29.130 --> 00:03:30.900
double bond like this it actually forces

00:03:30.900 --> 00:03:33.209
all of these all of these atoms in this

00:03:33.209 --> 00:03:36.329
molecule to be in the same plane so this

00:03:36.329 --> 00:03:38.400
right over here this ethane this is

00:03:38.400 --> 00:03:40.860
planar this is planar right over here

00:03:40.860 --> 00:03:43.620
and these this double bond locks it into

00:03:43.620 --> 00:03:45.329
place there's not going to be any

00:03:45.329 --> 00:03:48.329
rotation when you have a triple bond not

00:03:48.329 --> 00:03:49.350
only are you not going to have any

00:03:49.350 --> 00:03:50.880
rotation but it's gonna make the whole

00:03:50.880 --> 00:03:52.530
thing it's going to make the whole thing

00:03:52.530 --> 00:03:54.750
a linear molecule so when we're talking

00:03:54.750 --> 00:03:55.860
about its shape we're talking about

00:03:55.860 --> 00:03:58.200
these molecules their conformation how

00:03:58.200 --> 00:04:00.900
do they arrange themselves in three

00:04:00.900 --> 00:04:02.250
dimensions and if you're curious what

00:04:02.250 --> 00:04:04.650
these are ethane is a component of

00:04:04.650 --> 00:04:06.570
natural gas most of natural gas is

00:04:06.570 --> 00:04:10.530
methane methane is just so if I were to

00:04:10.530 --> 00:04:13.769
write methane most of natural gas is

00:04:13.769 --> 00:04:16.829
methane which is just one which is just

00:04:16.829 --> 00:04:20.190
one carbon bonded to four hydrogens

00:04:20.190 --> 00:04:22.229
that's methane right over here this is

00:04:22.229 --> 00:04:25.979
most of this is the biggest constituent

00:04:25.979 --> 00:04:26.650
of natural

00:04:26.650 --> 00:04:28.000
gas but you're going to find a little

00:04:28.000 --> 00:04:30.820
bit of ethane in there ethene which is

00:04:30.820 --> 00:04:33.040
often known as ethylene this has many

00:04:33.040 --> 00:04:35.169
industrial uses but maybe most

00:04:35.169 --> 00:04:37.449
interestingly it can be used as a plant

00:04:37.449 --> 00:04:40.380
hormone that can be used to ripen fruit

00:04:40.380 --> 00:04:43.740
ethyne a lot most commonly known as

00:04:43.740 --> 00:04:46.449
acetylene this can be used because it

00:04:46.449 --> 00:04:48.789
burns very very hot it can be used to

00:04:48.789 --> 00:04:50.860
fuel blowtorches so once again you know

00:04:50.860 --> 00:04:52.750
these are they seem similar but there

00:04:52.750 --> 00:04:54.400
can be used for very very different

00:04:54.400 --> 00:04:56.740
things and I could go all day showing

00:04:56.740 --> 00:04:58.600
more and more different types of

00:04:58.600 --> 00:05:00.160
hydrocarbons but here's just a little

00:05:00.160 --> 00:05:01.870
bit more variety just so we can think

00:05:01.870 --> 00:05:03.100
about how they're named and the

00:05:03.100 --> 00:05:05.139
different forms they take and these are

00:05:05.139 --> 00:05:06.880
just three of the different types of

00:05:06.880 --> 00:05:08.620
molecules you might find in the gasoline

00:05:08.620 --> 00:05:09.669
that you have in your car and there's

00:05:09.669 --> 00:05:12.070
many many more than just these and

00:05:12.070 --> 00:05:13.870
that's because you mix them with oxygen

00:05:13.870 --> 00:05:15.940
put them in an engine and and and spite

00:05:15.940 --> 00:05:17.979
and spark them right that they burn well

00:05:17.979 --> 00:05:20.139
there they're good fuels to to power

00:05:20.139 --> 00:05:22.180
cars but just so get familiar with the

00:05:22.180 --> 00:05:24.070
naming mechanism a little bit more this

00:05:24.070 --> 00:05:26.410
is pentane it's an alkane with five

00:05:26.410 --> 00:05:31.300
carbons one two three four five carbons

00:05:31.300 --> 00:05:33.190
in its longer longest chain that's why

00:05:33.190 --> 00:05:36.010
it's called pentane because hydrogens

00:05:36.010 --> 00:05:37.150
are all of the other bonds that a

00:05:37.150 --> 00:05:39.070
carbons are forming sometimes you'll see

00:05:39.070 --> 00:05:40.510
a shorthand where something like a

00:05:40.510 --> 00:05:41.949
pentane instead of drawing all the Cs

00:05:41.949 --> 00:05:44.530
and Hs it would be drawn like this it

00:05:44.530 --> 00:05:46.449
could be drawn like this where you

00:05:46.449 --> 00:05:47.919
assume that there's just a carbon at

00:05:47.919 --> 00:05:50.199
each of these points over there so you

00:05:50.199 --> 00:05:51.610
actually don't have to draw the carbon

00:05:51.610 --> 00:05:53.590
and then if you don't see if you don't

00:05:53.590 --> 00:05:55.180
if something's not bonded to a carbon it

00:05:55.180 --> 00:05:57.580
there's no other atom that is drawn in

00:05:57.580 --> 00:05:59.620
that the carbon is bonded to you assume

00:05:59.620 --> 00:06:01.720
it's just a bunch of hydrogen so this is

00:06:01.720 --> 00:06:04.030
a shorthand for pentane which is exactly

00:06:04.030 --> 00:06:05.650
this molecule here and you see it has

00:06:05.650 --> 00:06:07.599
this kind of it has this bend shape

00:06:07.599 --> 00:06:09.729
because carbon is each of the carbons

00:06:09.729 --> 00:06:11.560
are trying to get to that tetrahedral

00:06:11.560 --> 00:06:14.940
type of shape now this this is

00:06:14.940 --> 00:06:18.370
cyclohexane once again it's an alkane we

00:06:18.370 --> 00:06:21.159
have no double bonds here hex- is the

00:06:21.159 --> 00:06:23.620
prefix because you have six carbons in

00:06:23.620 --> 00:06:26.139
your longest chain one two three or you

00:06:26.139 --> 00:06:28.750
could say your cycle in this case 5 6

00:06:28.750 --> 00:06:31.210
and the cyclo is because instead of it

00:06:31.210 --> 00:06:33.159
just being a instead of it being an open

00:06:33.159 --> 00:06:34.779
instead of it just being an open chain

00:06:34.779 --> 00:06:36.669
it's connected at the end it forms it

00:06:36.669 --> 00:06:40.300
forms actual cycle this over here looks

00:06:40.300 --> 00:06:40.540
a little

00:06:40.540 --> 00:06:43.660
more complex you see the -ene at the end

00:06:43.660 --> 00:06:45.970
and that's because the longest chain has

00:06:45.970 --> 00:06:48.940
a double bond right over here and the

00:06:48.940 --> 00:06:52.210
but- this is the prefix for four this

00:06:52.210 --> 00:06:54.160
means that our longest chain has four

00:06:54.160 --> 00:06:57.250
carbons and you see that one two three

00:06:57.250 --> 00:07:00.100
four carbons but then on this number two

00:07:00.100 --> 00:07:02.530
carbon not only did you have your double

00:07:02.530 --> 00:07:05.410
bond there but you also have a methyl

00:07:05.410 --> 00:07:08.170
group a methyl group 1 carbon meth- is

00:07:08.170 --> 00:07:11.020
the meth is the prefix meth- is the

00:07:11.020 --> 00:07:13.540
prefix for one so anyway the goal of

00:07:13.540 --> 00:07:14.680
this video is really just to give you a

00:07:14.680 --> 00:07:17.020
little bit familiar with with

00:07:17.020 --> 00:07:19.120
hydrocarbons and and to think about how

00:07:19.120 --> 00:07:21.940
they'll be useful in chemistry and parts

00:07:21.940 --> 00:07:23.950
of and and and you'll see many molecules

00:07:23.950 --> 00:07:26.260
in biology that have hydrocarbon parts

00:07:26.260 --> 00:07:27.790
that have chains of hydrocarbons

00:07:27.790 --> 00:07:29.320
attached to them so we can think about

00:07:29.320 --> 00:07:32.940
the properties associated with them.


Isomers

WEBVTT
Kind: captions
Language: en

00:00:00.809 --> 00:00:03.612
- Many times in chemistry
we'll see different molecules

00:00:03.612 --> 00:00:06.779
that have the same constituent atoms.

00:00:06.779 --> 00:00:08.906
For example, these two molecules here,

00:00:08.906 --> 00:00:10.445
they both have four carbons.

00:00:10.445 --> 00:00:11.721
One, two, three, four.

00:00:11.721 --> 00:00:13.715
One, two, three, four.

00:00:13.715 --> 00:00:15.663
So if I were to write
their chemical formula,

00:00:15.663 --> 00:00:18.806
it would be C4 and then they both have,

00:00:18.806 --> 00:00:22.548
one, two, three, four, five,
six, seven, eight, nine, ten.

00:00:22.548 --> 00:00:25.859
One, two, three, four, five,
six, seven, eight, nine, ten

00:00:25.859 --> 00:00:26.775
hydrogens.

00:00:26.775 --> 00:00:30.635
So both of them, both of them
have the chemical formula

00:00:30.635 --> 00:00:31.468
C4H10.

00:00:33.259 --> 00:00:36.905
C4H10, but they're still
fundamentally different molecules

00:00:36.905 --> 00:00:39.887
and you can see that because
they have different bonding.

00:00:39.887 --> 00:00:42.701
For example, over here we
have a carbon that is bonded

00:00:42.701 --> 00:00:45.391
to three other carbons and a hydrogen.

00:00:45.391 --> 00:00:47.452
Over here I can't find
any carbon that's bonded

00:00:47.452 --> 00:00:48.959
to three other carbons.

00:00:48.959 --> 00:00:50.733
I can find ones that are
bonded to two other carbons,

00:00:50.733 --> 00:00:53.019
but not one that's bonded
to three other carbons.

00:00:53.019 --> 00:00:56.560
So, how we've put the atoms
together, is actually different.

00:00:56.560 --> 00:00:58.639
They're bonded to different things.

00:00:58.639 --> 00:01:01.141
And so when we have the
situation where you have

00:01:01.141 --> 00:01:03.156
the same constituent atoms,
where you have the same

00:01:03.156 --> 00:01:05.293
chemical formula, but
you're still dealing with

00:01:05.293 --> 00:01:09.539
different molecules
because either how their

00:01:09.539 --> 00:01:13.465
bonds are made or what their shape is,

00:01:13.465 --> 00:01:15.799
we call those isomers.

00:01:15.799 --> 00:01:17.549
So an isomer, isomer,

00:01:19.530 --> 00:01:21.909
you have the same chemical formula,

00:01:21.909 --> 00:01:23.742
same chemical formula.

00:01:26.627 --> 00:01:30.794
But you could have different
bonding but different,

00:01:33.102 --> 00:01:34.602
different bonding,

00:01:37.352 --> 00:01:38.769
bonding or shape,

00:01:39.888 --> 00:01:42.388
bonding, shape or orientation.

00:01:44.326 --> 00:01:45.892
Orientation.

00:01:45.892 --> 00:01:48.273
So over here you have
just different bonding

00:01:48.273 --> 00:01:51.237
and this type of isomer is
called a structural isomer.

00:01:51.237 --> 00:01:54.655
So these characters
are structural isomers,

00:01:54.655 --> 00:01:57.950
same constituent atoms,
but different bonding.

00:01:57.950 --> 00:01:59.533
Structural isomers.

00:02:01.101 --> 00:02:04.907
So that's structural
isomers right over there.

00:02:04.907 --> 00:02:06.324
Now when you look at this pair

00:02:06.324 --> 00:02:07.443
or this pair,

00:02:07.443 --> 00:02:08.672
you'll say those don't look
like structural isomers.

00:02:08.672 --> 00:02:10.465
Not only do they have
the same constituents,

00:02:10.465 --> 00:02:12.571
both of these for example
have four carbons,

00:02:12.571 --> 00:02:14.515
four carbons and they both have

00:02:14.515 --> 00:02:16.316
one, two, three, four, five, six,

00:02:16.316 --> 00:02:20.067
one, two, three, four,
five, six, seven, eight,

00:02:20.067 --> 00:02:22.283
and they both have eight hydrogens.

00:02:22.283 --> 00:02:24.200
So these are both C4H8,

00:02:28.012 --> 00:02:30.727
it's looks like they're bonded similarly.

00:02:30.727 --> 00:02:33.162
For example, I mean the
left hand side here,

00:02:33.162 --> 00:02:34.265
these look identical

00:02:34.265 --> 00:02:35.719
and one the right hand side,

00:02:35.719 --> 00:02:37.880
you have a carbon bonded to another carbon

00:02:37.880 --> 00:02:39.478
that's bonded to three hydrogens,

00:02:39.478 --> 00:02:40.813
carbon bonded to another carbon

00:02:40.813 --> 00:02:42.185
that's bonded to three hydrogens.

00:02:42.185 --> 00:02:43.599
Carbon bonded to a hydrogen,

00:02:43.599 --> 00:02:45.427
carbon bonded to a hydrogen,

00:02:45.427 --> 00:02:47.584
so it looks like the
structure of the bonding,

00:02:47.584 --> 00:02:49.666
everything's bonded to the same things,

00:02:49.666 --> 00:02:51.230
but you might notice a difference.

00:02:51.230 --> 00:02:54.490
Over here, on the right hand side,

00:02:54.490 --> 00:02:57.703
this CH3 is on the bottom right,

00:02:57.703 --> 00:03:00.786
while over here it's on the top right

00:03:01.716 --> 00:03:03.138
and you might say okay well we know,

00:03:03.138 --> 00:03:04.204
what's the big deal there,

00:03:04.204 --> 00:03:06.040
these, you know, all these molecules,

00:03:06.040 --> 00:03:07.330
they're all moving around,

00:03:07.330 --> 00:03:09.173
maybe they're rotating
with respect to each other

00:03:09.173 --> 00:03:10.620
and these things could,

00:03:10.620 --> 00:03:12.471
this thing could have rotated down

00:03:12.471 --> 00:03:14.316
to become what we have up here.

00:03:14.316 --> 00:03:15.932
If this was a single bond.

00:03:15.932 --> 00:03:18.692
A single bond would allow
for that type of rotation,

00:03:18.692 --> 00:03:22.461
it would allow for these things
to rotate around each other.

00:03:22.461 --> 00:03:24.902
For the molecule to
rotate around that bond,

00:03:24.902 --> 00:03:28.164
but a double bond does
not allow that rotation.

00:03:28.164 --> 00:03:30.004
So this fixes these two things,

00:03:30.004 --> 00:03:33.391
this fixes these two things in place.

00:03:33.391 --> 00:03:35.350
And because of that, these are actually

00:03:35.350 --> 00:03:37.221
two different molecules.

00:03:37.221 --> 00:03:40.529
Over here on the top,
you have the CH3 groups,

00:03:40.529 --> 00:03:43.655
they're both, they're both,
I guess you could say,

00:03:43.655 --> 00:03:46.316
facing down or their both on the same side

00:03:46.316 --> 00:03:48.163
of the double bond,

00:03:48.163 --> 00:03:51.899
while over here they're on different sides

00:03:51.899 --> 00:03:53.755
of the double bond

00:03:53.755 --> 00:03:55.603
and so this type of isomerism,

00:03:55.603 --> 00:03:58.220
where you have the same constituents

00:03:58.220 --> 00:03:59.868
and you even have the same bonding,

00:03:59.868 --> 00:04:02.286
this is called stereoisomerism.

00:04:02.286 --> 00:04:05.730
So over here we're caring
much more about how things sit

00:04:05.730 --> 00:04:07.407
in three dimensions.

00:04:07.407 --> 00:04:09.026
We don't just care about
what's bonded to what

00:04:09.026 --> 00:04:10.949
or the constituents

00:04:10.949 --> 00:04:12.472
and actually this one is, as we'll see,

00:04:12.472 --> 00:04:14.378
is also a stereoisomer because this carbon

00:04:14.378 --> 00:04:16.986
is bonded to the same
things in either case.

00:04:16.986 --> 00:04:19.456
So these are both, these
are both situations,

00:04:19.456 --> 00:04:22.108
there are both stereoisomers,

00:04:22.108 --> 00:04:23.275
stereoisomers,

00:04:25.625 --> 00:04:28.231
and this particular
variation of stereoisomer

00:04:28.231 --> 00:04:30.236
is called a cis trans isomer.

00:04:30.236 --> 00:04:32.973
Cis is when you have the
two groups on the same side,

00:04:32.973 --> 00:04:34.444
cis,

00:04:34.444 --> 00:04:36.061
and trans is when you have the two groups

00:04:36.061 --> 00:04:38.506
on the opposite sides of the double bond.

00:04:38.506 --> 00:04:40.006
Cis trans isomers.

00:04:41.026 --> 00:04:42.526
Cis trans isomers.

00:04:46.260 --> 00:04:47.174
Isomers,

00:04:47.174 --> 00:04:49.951
and these are often
called geometric isomers.

00:04:49.951 --> 00:04:50.784
Geometric,

00:04:51.871 --> 00:04:54.193
geometric isomers.

00:04:54.193 --> 00:04:56.733
So that's a subset, so when
I'm talking about cis trans

00:04:56.733 --> 00:04:58.386
or geometric, I'm talking about

00:04:58.386 --> 00:04:59.697
these two characters over here.

00:04:59.697 --> 00:05:03.280
They are a subset of the stereoisomers.

00:05:03.280 --> 00:05:04.456
Now what's going on over here?

00:05:04.456 --> 00:05:07.212
I have no double bond, I'm not
talking about cis and trans.

00:05:07.212 --> 00:05:09.064
The carbon, as I've just said,

00:05:09.064 --> 00:05:11.557
is bonded to fluorine, chlorine,
bromine, and a hydrogen,

00:05:11.557 --> 00:05:13.584
fluorine, chlorine,
bromine, and a hydrogen.

00:05:13.584 --> 00:05:14.927
How are these two things different?

00:05:14.927 --> 00:05:17.188
And the way that they're different

00:05:17.188 --> 00:05:19.415
is if you were to actually
try to superimpose them

00:05:19.415 --> 00:05:20.672
on each other.

00:05:20.672 --> 00:05:22.125
You will see that it is impossible.

00:05:22.125 --> 00:05:23.792
There are mirror images of each other

00:05:23.792 --> 00:05:25.754
and because there's four
different constituents here,

00:05:25.754 --> 00:05:28.986
you can actually not
superimpose this molecule

00:05:28.986 --> 00:05:31.285
onto this molecule over here

00:05:31.285 --> 00:05:32.415
and actually because of that,

00:05:32.415 --> 00:05:35.497
they actually have different
chemical properties,

00:05:35.497 --> 00:05:38.504
and so this over here,
these two characters,

00:05:38.504 --> 00:05:40.673
which is a subset of stereoisomers.

00:05:40.673 --> 00:05:42.994
Stereoisomers are
concerned with how things

00:05:42.994 --> 00:05:45.172
are positioned in three dimensions,

00:05:45.172 --> 00:05:47.661
not just how their bonding is different,

00:05:47.661 --> 00:05:50.266
but this subset where you
have these mirror images

00:05:50.266 --> 00:05:51.637
that cannot be superimposed,

00:05:51.637 --> 00:05:54.081
we call these enantiomers.

00:05:54.081 --> 00:05:56.024
So these two characters,

00:05:56.024 --> 00:05:57.857
these are enantiomers.

00:05:58.843 --> 00:06:00.177
Enantiomers,

00:06:00.177 --> 00:06:02.200
and enantio comes from Greek,

00:06:02.200 --> 00:06:04.560
the Greek word or the Greek root opposite.

00:06:04.560 --> 00:06:06.713
So these are opposites of each other,

00:06:06.713 --> 00:06:08.077
they cannot be superimposed,

00:06:08.077 --> 00:06:10.042
they're mirror, they're mirror images.

00:06:10.042 --> 00:06:13.519
So all of these are different
variations of isomers

00:06:13.519 --> 00:06:15.116
and once again, you might say,

00:06:15.116 --> 00:06:16.956
okay theses are clearly
two different molecules

00:06:16.956 --> 00:06:18.246
that have different bonding,

00:06:18.246 --> 00:06:20.333
but even cis trans isomer will have

00:06:20.333 --> 00:06:22.833
different chemical properties.

00:06:23.866 --> 00:06:26.072
These two in particular,
they aren't that different

00:06:26.072 --> 00:06:28.088
but they do have different
chemical properties,

00:06:28.088 --> 00:06:29.654
but sometimes they're so different

00:06:29.654 --> 00:06:32.182
that one might be able to
exist in a biological system

00:06:32.182 --> 00:06:33.497
while the other is not.

00:06:33.497 --> 00:06:34.969
One might be okay for your health,

00:06:34.969 --> 00:06:36.984
and the other might not
be okay for your health.

00:06:36.984 --> 00:06:39.357
Same thing for enantiomers.

00:06:39.357 --> 00:06:41.612
One might be biologically
active in a certain way

00:06:41.612 --> 00:06:45.332
and the other one might
not be biologically active

00:06:45.332 --> 00:06:46.749
in that same way.