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PROFESSOR: OK.

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00:00:21,450 --> 00:00:24,040
Couple of announcements.

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First of all, the Wolf Lecture
is tomorrow, right here in

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10-250 at 4:00.

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00:00:30,930 --> 00:00:34,790
As also, there will be the
weekly quiz, the mini

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00:00:34,790 --> 00:00:36,060
celebration.

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00:00:36,060 --> 00:00:42,200
But there's going to be, a week
from today, celebration

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00:00:42,200 --> 00:00:44,330
part trois.

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00:00:44,330 --> 00:00:48,510
Yes, third celebration
of learning.

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00:00:48,510 --> 00:00:50,410
And remember, what we're
shooting for

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is the smiley face.

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00:00:53,830 --> 00:00:54,320
None of this.

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00:00:54,320 --> 00:00:57,000
And those of you who are over
here on the grade point

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distribution curve, we want
to move you to the right.

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So I'll say a little bit more
later in the week about what

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00:01:03,300 --> 00:01:06,800
the coverage will be.

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00:01:06,800 --> 00:01:10,550
I'll be available for office
hours later, and

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00:01:10,550 --> 00:01:14,790
I thought to try to cheer you
up, and remind you that

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studying is not something
you do only the

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00:01:16,920 --> 00:01:18,960
night before the exam.

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00:01:18,960 --> 00:01:21,140
You have to be studying
on a regular basis.

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00:01:21,140 --> 00:01:21,910
All right?

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00:01:21,910 --> 00:01:25,860
So from the iconic film
Ghostbusters,

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there's this one scene.

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00:01:29,736 --> 00:01:31,090
[FILM PLAYBACK]

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00:01:31,090 --> 00:01:35,160
For a moment, pretend that I
don't know anything about

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00:01:35,160 --> 00:01:39,280
metallurgy, engineering, or
physics, and just tell me what

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00:01:39,280 --> 00:01:41,710
the hell is going on.

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00:01:41,710 --> 00:01:42,960
You never studied.

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00:01:45,483 --> 00:01:46,960
[END FILM PLAYBACK]

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00:01:46,960 --> 00:01:51,230
You don't want to be a character
in that scene.

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00:01:51,230 --> 00:01:53,090
So what are you going
to do about it?

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00:01:53,090 --> 00:01:55,040
You're going to study.

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00:01:55,040 --> 00:01:56,120
All right.

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00:01:56,120 --> 00:01:57,130
Let's get down to work.

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00:01:57,130 --> 00:02:01,050
Today I'm going to take one
day and I'm going to talk

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00:02:01,050 --> 00:02:02,250
about organic chemistry.

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00:02:02,250 --> 00:02:05,090
Now, I'm not going to pretend
that after one lecture, you're

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00:02:05,090 --> 00:02:08,200
going to walk out of here and
know much organic chemistry.

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00:02:08,200 --> 00:02:09,820
I'm going to give you, if
you want to know organic

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00:02:09,820 --> 00:02:11,440
chemistry, you're going
to have to take 512,

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00:02:11,440 --> 00:02:12,750
and many if you will.

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00:02:12,750 --> 00:02:15,150
But I'm going to give you enough
that it will set up for

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00:02:15,150 --> 00:02:19,480
the subsequent units on polymers
and on biochemistry.

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00:02:19,480 --> 00:02:22,300
So we'll know enough that
we can move forward.

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00:02:22,300 --> 00:02:24,720
So let's get into the

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definition of organic chemistry.

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00:02:26,480 --> 00:02:29,310
It's the chemistry of compounds,
containing both

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00:02:29,310 --> 00:02:31,450
carbon and hydrogen.

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00:02:31,450 --> 00:02:33,980
There can be, of course, other
elements present, but you've

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00:02:33,980 --> 00:02:35,580
got to have carbon and
hydrogen to get

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00:02:35,580 --> 00:02:38,180
yourself into Orgo.

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00:02:38,180 --> 00:02:40,460
And what makes carbon and
hydrogen so special?

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We've been studying these
elements through the semester.

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But just to be reminded.

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00:02:45,250 --> 00:02:48,260
First of all, hydrogen is
peculiar because it's got the

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00:02:48,260 --> 00:02:50,210
lowest atomic number.

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00:02:50,210 --> 00:02:54,850
It's got the lone proton,
and a single electron.

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00:02:54,850 --> 00:02:58,170
And when hydrogen ionizes,
it forms the

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00:02:58,170 --> 00:02:59,930
hydrogen ion, or the proton.

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00:02:59,930 --> 00:03:00,840
That's all that's left.

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And this thing's very
tiny, and it can

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form covalent bonds.

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00:03:06,400 --> 00:03:13,680
It forms covalent bonds as
primary bonds, and it can form

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00:03:13,680 --> 00:03:16,890
hydrogen bonds as
secondary bonds.

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00:03:16,890 --> 00:03:20,020
So it's peculiar for
that reason.

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00:03:20,020 --> 00:03:21,840
It does not form ions.

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00:03:21,840 --> 00:03:25,640
You cannot imagine something is
tiny as a proton occupying

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00:03:25,640 --> 00:03:28,310
a lattice site in an
ionic crystal.

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00:03:28,310 --> 00:03:28,630
OK.

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00:03:28,630 --> 00:03:31,950
Now when it comes to carbon,
carbon is also peculiar.

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It's smack dab in the middle of
the periodic table, in the

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00:03:35,470 --> 00:03:36,220
second row.

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Four valence electrons, which
means that it's very

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difficult to ionize.

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If it wants to achieve octet
stability, it's going to have

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to form covalent compounds.

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00:03:44,770 --> 00:03:47,700
It's not going to acquire four
electrons or lose four

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00:03:47,700 --> 00:03:48,310
electronics.

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00:03:48,310 --> 00:03:51,620
In rare exceptional
circumstances it, might, but

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00:03:51,620 --> 00:03:53,340
commonly, it does not.

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00:03:53,340 --> 00:03:56,330
And with that intermediate
average valence electron

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00:03:56,330 --> 00:04:00,040
energy, it's going
to be capable of

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00:04:00,040 --> 00:04:02,050
all sorts of bonding.

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00:04:02,050 --> 00:04:08,620
And in particular, because of
its small size, it's capable,

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00:04:08,620 --> 00:04:12,110
with its small size and the
intermediate value of average

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00:04:12,110 --> 00:04:13,770
valence electron energy--

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00:04:13,770 --> 00:04:15,490
and this is critical--

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00:04:15,490 --> 00:04:18,115
is that it's capable of forming
multiple bonds.

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00:04:26,540 --> 00:04:29,630
And this is key, as we'll see
later when things try to

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00:04:29,630 --> 00:04:32,770
polymerize and form
multiple bonds.

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00:04:32,770 --> 00:04:38,690
And this is not common, for
example, not the case if you

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00:04:38,690 --> 00:04:40,920
look underneath carbon.

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00:04:40,920 --> 00:04:43,410
Silicon, germanium,
for example.

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00:04:43,410 --> 00:04:44,720
Same thing.

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00:04:44,720 --> 00:04:48,160
Group 4, same kind of mid-stream
average valence

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00:04:48,160 --> 00:04:49,010
electron energy.

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00:04:49,010 --> 00:04:50,570
But they're too big.

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00:04:50,570 --> 00:04:54,900
Silicon and Germanium do not
form double and triple bonds.

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00:04:54,900 --> 00:04:57,880
So the other thing is that it's
capable of self-linking.

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00:05:01,210 --> 00:05:06,990
It can link to itself, form
carbon chains, and also with

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00:05:06,990 --> 00:05:09,380
nitrogen, oxygen, sulfur.

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00:05:09,380 --> 00:05:11,040
So this gives it--

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00:05:11,040 --> 00:05:13,490
and let's put up phosphorus
as well.

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00:05:13,490 --> 00:05:14,860
Phosphorus and sulfur.

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00:05:14,860 --> 00:05:16,740
So with these kinds
of links-- we've

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00:05:16,740 --> 00:05:18,740
already seen oxygen links.

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00:05:18,740 --> 00:05:21,850
We'll see, pretty soon, nitrogen
links and so on.

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00:05:21,850 --> 00:05:24,960
There's millions of organic
compounds, and today I'm just

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00:05:24,960 --> 00:05:25,690
going to look at a few.

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00:05:25,690 --> 00:05:27,790
I'm just going to give
you some taxonomy and

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00:05:27,790 --> 00:05:31,510
nomenclature, and we're going
to walk through this.

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00:05:31,510 --> 00:05:33,170
And here's the way to
keep it straight.

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You know all this stuff.

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00:05:34,440 --> 00:05:36,720
I'm just going to organize
it in your minds for you.

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00:05:36,720 --> 00:05:39,100
We've already studied the
three different types of

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hybridization.

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00:05:39,970 --> 00:05:42,480
sp, sp2, and sp3.

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00:05:42,480 --> 00:05:44,690
And we've already seen that if
you're going to have a double

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00:05:44,690 --> 00:05:49,100
bond, you need sp2 hybridization
to reserve 1p

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00:05:49,100 --> 00:05:52,330
orbital, to make that
pi second bond.

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00:05:52,330 --> 00:05:55,770
And if you want to make triple
bonds, you make sp

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00:05:55,770 --> 00:05:59,932
hybridization, thereby reserving
two p orbitals to

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00:05:59,932 --> 00:06:01,740
make two pi bonds.

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00:06:01,740 --> 00:06:06,280
So this is sigma, sigma plus
pi, sigma plus pi plus pi.

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00:06:06,280 --> 00:06:06,920
That's it.

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00:06:06,920 --> 00:06:10,570
Now what we're going to do is to
is go back and look at this

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00:06:10,570 --> 00:06:13,830
in the context of
hydrocarbons.

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00:06:13,830 --> 00:06:18,520
So hydrocarbons is going to be
now the focus here, and the

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00:06:18,520 --> 00:06:22,860
hydrocarbons are the simplest
of the organic compounds.

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00:06:22,860 --> 00:06:26,640
So let's look at hydrocarbons.

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00:06:26,640 --> 00:06:29,470
I'm going to look at their
nomenclature and their

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00:06:29,470 --> 00:06:30,150
properties.

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00:06:30,150 --> 00:06:36,580
But the structure behind
everything, the treatment, is

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00:06:36,580 --> 00:06:38,990
the type of hybridization.

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00:06:38,990 --> 00:06:42,520
So these consist only of
hydrogen and carbon.

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00:06:42,520 --> 00:06:49,420
Compounds containing only
hydrogen and carbon.

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00:06:49,420 --> 00:06:53,790
So I'm just going to
go down that chart.

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00:06:53,790 --> 00:06:54,620
And we'll go through.

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00:06:54,620 --> 00:06:59,520
So the first one on the left is
the alkanes We'll look at

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00:06:59,520 --> 00:07:01,290
the alkanes.

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00:07:01,290 --> 00:07:04,030
And the alkanes are
characterized by sp3

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00:07:04,030 --> 00:07:05,410
hybridization.

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00:07:05,410 --> 00:07:09,123
And so this gives the maximum
number of carbon linkages.

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00:07:13,390 --> 00:07:13,730
Why?

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00:07:13,730 --> 00:07:15,570
Because you can only
form single bonds.

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00:07:15,570 --> 00:07:18,960
So if I can only form single
bonds, every bond goes to a

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00:07:18,960 --> 00:07:19,890
different atom.

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00:07:19,890 --> 00:07:22,260
Whereas if I form double bonds,
then I'm burning up

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00:07:22,260 --> 00:07:23,370
some of the capability.

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00:07:23,370 --> 00:07:26,030
Because if I used two bonds
to get to one neighboring

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00:07:26,030 --> 00:07:29,740
element, instead of two single
bonds each to two different

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00:07:29,740 --> 00:07:32,440
neighboring elements, I don't
have as many linkages.

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00:07:32,440 --> 00:07:35,630
So the maximum number of carbon
linkages-- and because

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00:07:35,630 --> 00:07:37,980
they have the maximum number,
we're going to borrow

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00:07:37,980 --> 00:07:41,430
terminology from the last
unit on solutions.

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00:07:41,430 --> 00:07:45,310
What's the maximum amount of
solute you can get into a

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00:07:45,310 --> 00:07:46,380
solution called?

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00:07:46,380 --> 00:07:48,400
It's called the saturation
value.

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00:07:48,400 --> 00:07:49,880
And they use that term here.

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00:07:49,880 --> 00:07:56,760
These are called saturated
hydrocarbons, because they've

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00:07:56,760 --> 00:08:00,620
got the maximum number
of linkages, bonds.

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00:08:00,620 --> 00:08:04,360
And they're all sigma bonds.

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00:08:04,360 --> 00:08:07,170
All of this is a consequence
of the choice of sp3.

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00:08:07,170 --> 00:08:10,200
I could have led you through all
of this, but we're putting

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00:08:10,200 --> 00:08:11,750
it up quickly here.

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00:08:11,750 --> 00:08:12,070
All right.

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00:08:12,070 --> 00:08:13,940
And so they have a
common formula.

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00:08:13,940 --> 00:08:18,590
CNH2N plus 2.

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00:08:21,790 --> 00:08:23,350
I think I've got some--

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00:08:23,350 --> 00:08:25,970
yeah, this is taking from
one of the other books.

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00:08:25,970 --> 00:08:27,810
I know you've got a list like
this in your own book.

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00:08:27,810 --> 00:08:28,880
So here they are.

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00:08:28,880 --> 00:08:34,710
So this is just CNH2N plus 2,
and you go down, and there's

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00:08:34,710 --> 00:08:37,560
the nomenclature.

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00:08:37,560 --> 00:08:41,910
The meth, for historical reasons
represents n equals 1.

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00:08:41,910 --> 00:08:46,110
So here's what the hidden
message is.

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00:08:46,110 --> 00:08:55,470
You name them by the carbon
number plus the suffix A N E.

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00:08:55,470 --> 00:08:59,710
So the -anes, the alk-anes,
are all these sp3.

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00:08:59,710 --> 00:09:05,810
So 1 is meth, 2 is eth, 3
is pro, and 4 is but.

188
00:09:05,810 --> 00:09:09,560
And they all have historical
derivations.

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00:09:09,560 --> 00:09:16,040
But- comes from butyric acid,
which is the acid that's

190
00:09:16,040 --> 00:09:18,110
formed when butter turns
rancid, and so on.

191
00:09:18,110 --> 00:09:20,640
After you get up to N equals
4, it's just your Latin.

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00:09:20,640 --> 00:09:23,520
So you just take your high
school Latin, pentane, hexane,

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00:09:23,520 --> 00:09:25,630
heptane, and so on.

194
00:09:25,630 --> 00:09:27,400
And if you didn't take high
school Latin, this is a great

195
00:09:27,400 --> 00:09:30,310
chance to learn the
ordinals in Latin.

196
00:09:30,310 --> 00:09:31,290
So there they are.

197
00:09:31,290 --> 00:09:33,030
Now, I'm not going to
expect you to--

198
00:09:33,030 --> 00:09:36,880
if I say decane, you're supposed
to slam down C10H22.

199
00:09:36,880 --> 00:09:40,480
But I would expect that I could
say decane, and I'd give

200
00:09:40,480 --> 00:09:44,100
you that formula and you'd
be comfortable with it.

201
00:09:44,100 --> 00:09:47,250
What's the other thing to note
here, while we've got this up

202
00:09:47,250 --> 00:09:48,960
on the chart.

203
00:09:48,960 --> 00:09:53,790
You can see that all of these
are symmetric molecules, and

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00:09:53,790 --> 00:09:55,300
they're non-polar.

205
00:09:55,300 --> 00:09:57,550
They're perfectly symmetric
non-polar.

206
00:09:57,550 --> 00:10:01,840
And what happens as the
molecular mass increases, the

207
00:10:01,840 --> 00:10:05,190
melting point increases, the
boiling point increases, and

208
00:10:05,190 --> 00:10:09,050
the state of matter transitions
from gas at room

209
00:10:09,050 --> 00:10:11,850
temperature to liquid at room
temperature to solid at room

210
00:10:11,850 --> 00:10:12,340
temperature.

211
00:10:12,340 --> 00:10:16,810
So here's an excellent example
of polarizability in action.

212
00:10:16,810 --> 00:10:19,590
Because the only way one methane
can bond to another

213
00:10:19,590 --> 00:10:24,390
methane is by induced
dipole-induced dipole

214
00:10:24,390 --> 00:10:25,520
interaction.

215
00:10:25,520 --> 00:10:29,200
So the only difference between
methane and icosane is that

216
00:10:29,200 --> 00:10:33,550
icosane is a honking big
molecule, non-polar, but very

217
00:10:33,550 --> 00:10:35,290
polarizable.

218
00:10:35,290 --> 00:10:39,160
And so as the polarizability
increases, you can see the

219
00:10:39,160 --> 00:10:40,370
effect here.

220
00:10:40,370 --> 00:10:42,790
OK, so that's good.

221
00:10:42,790 --> 00:10:45,450
So you get to learn your
Latin ordinals.

222
00:10:45,450 --> 00:10:50,380
Now these are also termed
straight chains.

223
00:10:50,380 --> 00:10:52,980
They can be termed straight
chains, but I want you to look

224
00:10:52,980 --> 00:10:56,350
carefully at what's
going on here.

225
00:10:56,350 --> 00:10:59,270
So here's a diagram used, the
first one on the left, you've

226
00:10:59,270 --> 00:11:01,060
seen methane many times.

227
00:11:01,060 --> 00:11:03,860
There's ethane and
then propane.

228
00:11:03,860 --> 00:11:05,120
And what do you notice here?

229
00:11:05,120 --> 00:11:08,050
Because of the sp3
hybridization, all of these

230
00:11:08,050 --> 00:11:10,170
angles are 109 degrees,
including the

231
00:11:10,170 --> 00:11:12,100
carbon-carbon angles.

232
00:11:12,100 --> 00:11:15,310
And when the thing is really
short, you get

233
00:11:15,310 --> 00:11:16,880
this zig-zaggy nature.

234
00:11:16,880 --> 00:11:21,600
So because of the sp3
hybridization, you see the

235
00:11:21,600 --> 00:11:23,960
carbon doing this.

236
00:11:23,960 --> 00:11:26,490
This is carbon-carbon, and
then the rest, forget it.

237
00:11:26,490 --> 00:11:28,110
I mean, this is the backbone.

238
00:11:28,110 --> 00:11:31,300
But if I get up to icosane and
I have about 20 of these

239
00:11:31,300 --> 00:11:33,750
things, forget the zig-zag.

240
00:11:33,750 --> 00:11:36,050
From here, yeah, I know there's
a little bit of fine

241
00:11:36,050 --> 00:11:39,990
structure, but for all intents
and purposes, this as a chain.

242
00:11:39,990 --> 00:11:41,390
Straight chain.

243
00:11:41,390 --> 00:11:43,090
And that's where you get
the terminology from.

244
00:11:43,090 --> 00:11:46,490
But keep in mind that there is
this zig-zagging back and

245
00:11:46,490 --> 00:11:49,750
forth, due to the sp3
hybridization.

246
00:11:49,750 --> 00:11:50,690
OK?

247
00:11:50,690 --> 00:11:52,550
So that's the first point.

248
00:11:52,550 --> 00:11:57,930
The second point is that the
bonds between the carbons are

249
00:11:57,930 --> 00:11:59,300
not fully specified.

250
00:11:59,300 --> 00:12:02,560
So for example, take the carbon
here on the left.

251
00:12:02,560 --> 00:12:06,070
The sticks to go to the 3
hydrogens here depicted in

252
00:12:06,070 --> 00:12:09,400
white, and then the fourth
stick goes to the carbon.

253
00:12:09,400 --> 00:12:12,370
And then off of that carbon
comes 3 more sticks, and all

254
00:12:12,370 --> 00:12:14,520
of these are 109
degree angles.

255
00:12:14,520 --> 00:12:17,340
All of that specified,
and nothing more.

256
00:12:17,340 --> 00:12:20,750
There's nothing saying that
these 2 hydrogens in the back

257
00:12:20,750 --> 00:12:21,740
have to line up.

258
00:12:21,740 --> 00:12:24,890
These two hydrogens out front
have to the line up.

259
00:12:24,890 --> 00:12:27,270
That's all free to rotate.

260
00:12:27,270 --> 00:12:30,310
And so we have that degree
of freedom there.

261
00:12:30,310 --> 00:12:33,800
The result is that you can have
something that zig-zags

262
00:12:33,800 --> 00:12:34,570
back and forth.

263
00:12:34,570 --> 00:12:37,860
So for example, this is called
eclipse, because if I were to

264
00:12:37,860 --> 00:12:40,340
stand here, these two hydrogens

265
00:12:40,340 --> 00:12:41,790
are on a direct line.

266
00:12:41,790 --> 00:12:44,910
So the front hydrogen covers
the back hydrogen.

267
00:12:44,910 --> 00:12:46,080
It eclipses.

268
00:12:46,080 --> 00:12:54,210
This hydrogen out front to your
and my right is on the

269
00:12:54,210 --> 00:12:57,420
same line is this hydrogen
to your and my left.

270
00:12:57,420 --> 00:13:00,110
And so if I were to look here
from the end, this hydrogen

271
00:13:00,110 --> 00:13:01,930
eclipses, and so on.

272
00:13:01,930 --> 00:13:04,820
So if I get something eclipsed,
I'm going to have a

273
00:13:04,820 --> 00:13:06,290
perfect straight line.

274
00:13:06,290 --> 00:13:09,530
If I have something that's
staggered, it's free to

275
00:13:09,530 --> 00:13:12,560
zig-zag, but it's free to
zig-zag and meander, and this

276
00:13:12,560 --> 00:13:13,270
is what happens.

277
00:13:13,270 --> 00:13:20,650
So here's 2 C17H36 molecules,
and the top confirmation is

278
00:13:20,650 --> 00:13:22,310
more or less straight.

279
00:13:22,310 --> 00:13:27,170
These are more or less eclipsed
configurations.

280
00:13:27,170 --> 00:13:29,560
Whereas the lower one, you can
see, there's a fair bit of

281
00:13:29,560 --> 00:13:33,640
stagger, and as a result, the
backbone can actually loop

282
00:13:33,640 --> 00:13:34,860
back on itself.

283
00:13:34,860 --> 00:13:38,670
But in both cases, we still call
these straight chains.

284
00:13:38,670 --> 00:13:39,840
They're still straight chain.

285
00:13:39,840 --> 00:13:43,340
Because as you start at one
end and go from carbon to

286
00:13:43,340 --> 00:13:46,580
carbon, you linearly go
to the other end.

287
00:13:46,580 --> 00:13:49,450
It doesn't mean it's straight
like straight as an arrow.

288
00:13:49,450 --> 00:13:52,550
It just means there's
no branches.

289
00:13:52,550 --> 00:13:54,430
So now I'm going to distinguish
this from the

290
00:13:54,430 --> 00:13:56,940
other one by branching.

291
00:13:56,940 --> 00:13:58,910
So let's just get
this up here.

292
00:13:58,910 --> 00:14:03,300
So we have straight chains,
is one case.

293
00:14:03,300 --> 00:14:04,330
Straight chains.

294
00:14:04,330 --> 00:14:06,580
And the straight chains
can either be

295
00:14:06,580 --> 00:14:10,945
staggered or eclipsed.

296
00:14:13,510 --> 00:14:16,470
And the closer you get
to eclipsed, the

297
00:14:16,470 --> 00:14:17,720
closer you get to--

298
00:14:21,410 --> 00:14:23,400
the more eclipsed,
the straighter.

299
00:14:23,400 --> 00:14:25,600
I think you'll understand
what this means.

300
00:14:25,600 --> 00:14:29,930
Staggered allows it to
make large loops--

301
00:14:29,930 --> 00:14:34,670
I'll just put here, straight
but looped.

302
00:14:34,670 --> 00:14:37,420
You can use that to describe
some of your friends, too.

303
00:14:37,420 --> 00:14:37,820
All right.

304
00:14:37,820 --> 00:14:38,850
Now--

305
00:14:38,850 --> 00:14:40,780
it's a Monday, it's a joke!

306
00:14:40,780 --> 00:14:42,120
Wake up!

307
00:14:42,120 --> 00:14:43,660
Wake up!

308
00:14:43,660 --> 00:14:44,070
All right.

309
00:14:44,070 --> 00:14:45,500
Now we can look at
another one.

310
00:14:45,500 --> 00:14:46,750
Branched chains.

311
00:14:49,590 --> 00:14:53,840
And now, this will be a major
departure, whether the chain

312
00:14:53,840 --> 00:14:58,490
is super-straight or does a lot
of looping back and forth,

313
00:14:58,490 --> 00:15:00,900
the branched chain is in marked
contrast. Now let me

314
00:15:00,900 --> 00:15:03,720
give you an example of
the branch chain.

315
00:15:03,720 --> 00:15:05,130
Best to just do it.

316
00:15:05,130 --> 00:15:07,210
So here's the branch chain.

317
00:15:07,210 --> 00:15:10,640
I'm going to use a butane.

318
00:15:10,640 --> 00:15:14,340
So you know B U T is 4.

319
00:15:14,340 --> 00:15:19,220
So that means 4 carbons, and
A means 4 carbons, sp3

320
00:15:19,220 --> 00:15:20,170
hybridized.

321
00:15:20,170 --> 00:15:21,040
So that's it.

322
00:15:21,040 --> 00:15:22,120
So now I'm going
to write this.

323
00:15:22,120 --> 00:15:22,920
Here's butane.

324
00:15:22,920 --> 00:15:25,840
C, C, C, C.

325
00:15:25,840 --> 00:15:29,770
And I'm going to write this as
just a straight chain, instead

326
00:15:29,770 --> 00:15:31,250
of doing this.

327
00:15:31,250 --> 00:15:35,040
I'm going to contrast. I'm
going to do 1, 2, 3, 4.

328
00:15:35,040 --> 00:15:37,850
1, 2, 3, 4.

329
00:15:37,850 --> 00:15:39,780
1, 2, 3, 4.

330
00:15:39,780 --> 00:15:42,830
1, 2, 3, 4.

331
00:15:42,830 --> 00:15:43,760
OK?

332
00:15:43,760 --> 00:15:44,400
So there we are.

333
00:15:44,400 --> 00:15:47,000
So this is, instead of writing
all this stuff, this is

334
00:15:47,000 --> 00:15:49,270
butane, and this is butane.

335
00:15:49,270 --> 00:15:50,340
But now here's the thing.

336
00:15:50,340 --> 00:15:51,590
Four stick rule.

337
00:15:55,370 --> 00:15:57,910
Whenever you're doing Orgo,
four stick rule.

338
00:15:57,910 --> 00:16:00,580
That means, four sticks
out of every carbon.

339
00:16:00,580 --> 00:16:02,820
So here's the carbon-carbon
bond, so I

340
00:16:02,820 --> 00:16:04,040
need three more sticks.

341
00:16:04,040 --> 00:16:05,040
1, 2, 3.

342
00:16:05,040 --> 00:16:08,140
And I know these are sp3
hybridized, but just, in

343
00:16:08,140 --> 00:16:10,240
compressed notation,
you can do this.

344
00:16:10,240 --> 00:16:13,490
And I'm not even going to
write all the hydrogens.

345
00:16:13,490 --> 00:16:17,180
Here I'm going to write the
hydrogens because it's our

346
00:16:17,180 --> 00:16:19,580
first time through, and it's
Monday, and everybody needs a

347
00:16:19,580 --> 00:16:22,420
little bit of TLC.

348
00:16:22,420 --> 00:16:24,390
But now the TLC is gone.

349
00:16:24,390 --> 00:16:25,470
This is it, all right?

350
00:16:25,470 --> 00:16:27,270
I'm not even going to put
the H's on the end.

351
00:16:27,270 --> 00:16:30,380
The stick coming off of carbon
means there's a hydrogen here.

352
00:16:30,380 --> 00:16:30,860
All right?

353
00:16:30,860 --> 00:16:31,680
So how about this one?

354
00:16:31,680 --> 00:16:36,670
1, 2, 3, 4, 1, 2, 3,
4, 1, 2, 3, 4.

355
00:16:36,670 --> 00:16:38,090
And now let's count
the hydrogens.

356
00:16:38,090 --> 00:16:41,910
1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

357
00:16:41,910 --> 00:16:44,120
C4H10.

358
00:16:44,120 --> 00:16:45,580
Butane.

359
00:16:45,580 --> 00:16:46,090
All right.

360
00:16:46,090 --> 00:16:50,040
Now there's another
way to write this.

361
00:16:50,040 --> 00:16:51,700
I could go like so.

362
00:16:51,700 --> 00:16:54,230
1, 2, 3.

363
00:16:54,230 --> 00:16:57,990
And I could put a
carbon up here.

364
00:16:57,990 --> 00:16:59,100
This is a branch, you see?

365
00:16:59,100 --> 00:17:00,530
It's not in a straight line.

366
00:17:00,530 --> 00:17:03,930
And I'm not talking
about eclipsed.

367
00:17:03,930 --> 00:17:06,590
Because if I start at 1n and go
down the backbone, I get to

368
00:17:06,590 --> 00:17:07,860
the other end, I
only hit three.

369
00:17:07,860 --> 00:17:09,950
I never got to this one.

370
00:17:09,950 --> 00:17:10,640
But let's see.

371
00:17:10,640 --> 00:17:11,900
You know, maybe this
is different.

372
00:17:11,900 --> 00:17:13,520
So four stick rule.

373
00:17:13,520 --> 00:17:15,500
1, 2, 3, 4.

374
00:17:15,500 --> 00:17:17,620
1, 2, 3, 4.

375
00:17:17,620 --> 00:17:19,990
1, 2, 3, 4.

376
00:17:19,990 --> 00:17:21,700
1, 2, 3, 4.

377
00:17:21,700 --> 00:17:23,050
Now let's count the hydrogens.

378
00:17:23,050 --> 00:17:27,360
1, 2, 3, 4, 4, 6, 7, 8, 9, 10.

379
00:17:27,360 --> 00:17:30,730
This is C4H10.

380
00:17:30,730 --> 00:17:33,790
It's a different molecule,
you can see.

381
00:17:33,790 --> 00:17:36,450
With what you've already learned
in 3091, this has a

382
00:17:36,450 --> 00:17:38,980
different dipole moment,
doesn't it?

383
00:17:38,980 --> 00:17:40,190
It's got a different
dipole moment.

384
00:17:40,190 --> 00:17:42,660
It's going to have a different
polarizability.

385
00:17:42,660 --> 00:17:45,450
But it's a butane,
it's a C4H10.

386
00:17:45,450 --> 00:17:48,780
So this is called
butane, right?

387
00:17:48,780 --> 00:17:49,740
And this one, over here,

388
00:17:49,740 --> 00:17:51,580
historically, was called isobutane.

389
00:17:55,610 --> 00:17:59,500
Because it's an isomer.

390
00:17:59,500 --> 00:18:06,830
It's got the same chemical
composition, but it's got a

391
00:18:06,830 --> 00:18:08,840
different makeup.

392
00:18:08,840 --> 00:18:10,950
It's got a different
structural makeup.

393
00:18:10,950 --> 00:18:13,820
It's got a different--

394
00:18:13,820 --> 00:18:17,500
I'm going to use the material
science-y word.

395
00:18:17,500 --> 00:18:19,320
Different structure.

396
00:18:19,320 --> 00:18:21,180
It's got a different molecular
structure.

397
00:18:24,500 --> 00:18:27,780
But the chemists going back 50
years ago didn't use these

398
00:18:27,780 --> 00:18:30,920
terms. They called it different
constituents.

399
00:18:30,920 --> 00:18:32,390
So I'm going to use
that as well.

400
00:18:32,390 --> 00:18:35,786
Different molecular structure
or different constituents.

401
00:18:38,970 --> 00:18:41,740
And what do we mean
by constituents?

402
00:18:41,740 --> 00:18:43,160
Now comes the color chalk.

403
00:18:43,160 --> 00:18:45,500
So we're going to do,
is I want to circle

404
00:18:45,500 --> 00:18:46,400
the makeup of this.

405
00:18:46,400 --> 00:18:49,100
So at this end, I've got--

406
00:18:49,100 --> 00:18:52,150
this is a CH3 here, correct?

407
00:18:52,150 --> 00:18:56,040
There's a CH3 over here.

408
00:18:56,040 --> 00:19:02,420
And then in between, I've
got CH2 and a CH2.

409
00:19:02,420 --> 00:19:05,520
Now let's go over here
and diagram this one.

410
00:19:05,520 --> 00:19:11,380
The isobutane, I've got a CH3
at the end, and a CH3 at the

411
00:19:11,380 --> 00:19:12,100
opposite end.

412
00:19:12,100 --> 00:19:14,290
So far, same as the butane.

413
00:19:14,290 --> 00:19:15,290
But now look.

414
00:19:15,290 --> 00:19:20,320
There's a third CH3 here,
and then there's this

415
00:19:20,320 --> 00:19:22,960
thing, which is a CH.

416
00:19:22,960 --> 00:19:24,750
You could argue it's
a CH2 that got

417
00:19:24,750 --> 00:19:26,140
methylated, but, you know.

418
00:19:26,140 --> 00:19:31,780
So I'm going to put a CH2 here
that's been methylated.

419
00:19:31,780 --> 00:19:33,970
And I'll tell you
what that means.

420
00:19:33,970 --> 00:19:34,370
OK?

421
00:19:34,370 --> 00:19:37,910
So it's really a CH2 group
that got methylated.

422
00:19:37,910 --> 00:19:42,900
So it's called isobutane, but
you can see, it's got

423
00:19:42,900 --> 00:19:43,320
different--

424
00:19:43,320 --> 00:19:46,420
all I'm doing here is making
the justification for the

425
00:19:46,420 --> 00:19:48,500
different constitution,
different dielectric

426
00:19:48,500 --> 00:19:52,460
constants, and so
on and so forth.

427
00:19:52,460 --> 00:19:54,460
So this is where the chemists
must come in.

428
00:19:54,460 --> 00:19:56,870
They would say, different
constituents.

429
00:19:56,870 --> 00:19:59,490
And so these are isomers that
have the same chemical

430
00:19:59,490 --> 00:20:02,070
composition, and are different
on the basis of their

431
00:20:02,070 --> 00:20:03,620
constitution.

432
00:20:03,620 --> 00:20:05,820
So they call these
constitutional isomers.

433
00:20:09,880 --> 00:20:11,310
This is a constitutional
isomer.

434
00:20:11,310 --> 00:20:13,570
Isobutane is a constitutional
isomer.

435
00:20:13,570 --> 00:20:16,240
Now the last piece
is nomenclature.

436
00:20:16,240 --> 00:20:18,700
They don't use this today.

437
00:20:18,700 --> 00:20:21,080
Because isobutane was
a term that came

438
00:20:21,080 --> 00:20:22,510
out of chemical industry.

439
00:20:22,510 --> 00:20:24,440
Because it looks like butane,
has got the same molecular

440
00:20:24,440 --> 00:20:26,040
weight, but it's
very different.

441
00:20:26,040 --> 00:20:28,010
Today we use the
IUPAC notation.

442
00:20:28,010 --> 00:20:28,480
Remember this?

443
00:20:28,480 --> 00:20:31,260
International Union of Pure
and Applied Chemistry.

444
00:20:31,260 --> 00:20:33,850
They're the ones, when one of
you discovers and stabilizes

445
00:20:33,850 --> 00:20:37,530
element 113, And you want to
name it after dadadadada, you

446
00:20:37,530 --> 00:20:40,000
have to get past the
IUPAC committee.

447
00:20:40,000 --> 00:20:40,360
OK?

448
00:20:40,360 --> 00:20:44,570
So their nomenclature committee
would say, this is

449
00:20:44,570 --> 00:20:48,460
an alkane, but it's only three
carbon units long.

450
00:20:48,460 --> 00:20:50,000
So it is not a butane.

451
00:20:50,000 --> 00:20:51,920
It is a propane.

452
00:20:51,920 --> 00:20:53,230
It is a type of propane.

453
00:20:53,230 --> 00:20:55,720
But it's not simple propane,
because there's a methyl

454
00:20:55,720 --> 00:20:57,130
hanging off the side.

455
00:20:57,130 --> 00:21:03,750
So in point of fact, this, in
IUPAC nomenclature, is a

456
00:21:03,750 --> 00:21:05,830
methyl propane.

457
00:21:05,830 --> 00:21:09,010
And furthermore, if you want
to get really pedantic, and

458
00:21:09,010 --> 00:21:12,100
IUPAC loves to get pedantic, is
what they'll do, is they'll

459
00:21:12,100 --> 00:21:14,050
number these, starting
from left to right.

460
00:21:14,050 --> 00:21:17,150
So this is the number 1 carbon,
this is the number 2

461
00:21:17,150 --> 00:21:19,540
carbon, and this is
number 3 carbon.

462
00:21:19,540 --> 00:21:22,450
And the methyl group
is pendent on

463
00:21:22,450 --> 00:21:23,840
the number 2 carbon.

464
00:21:23,840 --> 00:21:26,950
So if we want to get really,
really, really pedantic, and

465
00:21:26,950 --> 00:21:31,090
who wouldn't, on a Monday
morning, what we would do, is

466
00:21:31,090 --> 00:21:32,475
we would call this
2-methylpropane.

467
00:21:36,580 --> 00:21:39,390
So it's a propane, 3 carbon
units, there's a methyl group

468
00:21:39,390 --> 00:21:40,550
hanging off of number 2.

469
00:21:40,550 --> 00:21:43,510
Now, I don't expect you to be
able to do these on sight, but

470
00:21:43,510 --> 00:21:46,510
I would like you to be
appreciative of what this is.

471
00:21:46,510 --> 00:21:50,130
So I'll give it to
you on an exam.

472
00:21:50,130 --> 00:21:50,390
All right.

473
00:21:50,390 --> 00:21:52,550
So we've got the isomers.

474
00:21:52,550 --> 00:21:54,290
And I think I've got some--

475
00:21:54,290 --> 00:21:54,990
I think I've got this.

476
00:21:54,990 --> 00:21:55,690
No.

477
00:21:55,690 --> 00:21:58,500
OK, this is good.

478
00:21:58,500 --> 00:21:58,640
Oh.

479
00:21:58,640 --> 00:22:01,030
There's one other thing I want
to talk about with alkanes.

480
00:22:01,030 --> 00:22:04,350
There's another thing that we
need to know, and that's about

481
00:22:04,350 --> 00:22:05,290
the radicals.

482
00:22:05,290 --> 00:22:06,750
The radicals that form.

483
00:22:06,750 --> 00:22:08,610
The radical is a species
with one or

484
00:22:08,610 --> 00:22:11,860
more unpaired electrons.

485
00:22:11,860 --> 00:22:13,110
Right?

486
00:22:22,290 --> 00:22:24,130
This is broken bond.

487
00:22:24,130 --> 00:22:25,220
One pair electrons.

488
00:22:25,220 --> 00:22:30,310
That's equivalent
to broken bond.

489
00:22:30,310 --> 00:22:30,910
OK.

490
00:22:30,910 --> 00:22:32,260
So this is highly reactive.

491
00:22:32,260 --> 00:22:34,170
Because this unpaired
electron is going to

492
00:22:34,170 --> 00:22:36,800
go look for a mate.

493
00:22:36,800 --> 00:22:38,540
So if you take a look at CH4--

494
00:22:42,270 --> 00:22:44,170
now I'm going to put
the hydrogens in.

495
00:22:44,170 --> 00:22:48,010
So this is methane, CH4.

496
00:22:48,010 --> 00:22:52,000
I'm going to break this bond in
the lower right corner, and

497
00:22:52,000 --> 00:22:55,150
just have an unpaired
electron.

498
00:22:55,150 --> 00:22:57,290
And this is called the
methyl radical.

499
00:23:00,860 --> 00:23:01,730
Very reactive.

500
00:23:01,730 --> 00:23:04,800
So you can see that this methyl
radical could go up and

501
00:23:04,800 --> 00:23:08,570
stick on to the fourth strut of
that number 2 carbon, and

502
00:23:08,570 --> 00:23:10,350
thereby form the carbon-carbon
bond.

503
00:23:10,350 --> 00:23:12,600
So that's why they call
this methylpropane.

504
00:23:12,600 --> 00:23:13,950
So the methyl radical.

505
00:23:13,950 --> 00:23:19,160
And you can write it this way,
H3C with dot indicating

506
00:23:19,160 --> 00:23:20,450
unpaired electrons.

507
00:23:20,450 --> 00:23:23,750
But I want you to be literate
with the way chemists will

508
00:23:23,750 --> 00:23:27,230
write this in various
compact notations.

509
00:23:27,230 --> 00:23:32,120
So you might even see
it written this way.

510
00:23:32,120 --> 00:23:33,850
Now, that doesn't mean
that the unpaired

511
00:23:33,850 --> 00:23:35,380
electron is on a hydrogen.

512
00:23:35,380 --> 00:23:39,990
This is just a way of saying,
you know, CH4 is methane, CH3

513
00:23:39,990 --> 00:23:42,760
is methyl, and who cares.

514
00:23:42,760 --> 00:23:44,630
There's only one possible
meaning to

515
00:23:44,630 --> 00:23:46,515
this, so it's all good.

516
00:23:46,515 --> 00:23:47,470
All right?

517
00:23:47,470 --> 00:23:49,600
Let's do two unpaired
electrons.

518
00:23:49,600 --> 00:23:51,600
So I'm going to take two
unpaired electrons.

519
00:23:51,600 --> 00:23:55,180
Again, this is out of the
alkane, so I'll put a hydrogen

520
00:23:55,180 --> 00:23:56,200
above and below.

521
00:23:56,200 --> 00:23:58,390
So that would be like
this one here.

522
00:23:58,390 --> 00:24:00,080
You see the CH2?

523
00:24:00,080 --> 00:24:03,423
So it's got carbon-carbon bonds
on either side, but in

524
00:24:03,423 --> 00:24:05,490
point of fact, this is
part of a zig-zag.

525
00:24:05,490 --> 00:24:10,395
So I'm going to break
bonds here and here.

526
00:24:10,395 --> 00:24:11,180
All right?

527
00:24:11,180 --> 00:24:13,370
So now I've got the possibility
of putting a bond

528
00:24:13,370 --> 00:24:14,610
on either side.

529
00:24:14,610 --> 00:24:18,410
And this one here is
called methylene.

530
00:24:18,410 --> 00:24:20,350
This is methylene.

531
00:24:20,350 --> 00:24:22,300
This is the methylene radical,
and it's got

532
00:24:22,300 --> 00:24:23,430
two unpaired electrons.

533
00:24:23,430 --> 00:24:30,620
So we could write that as H2C
with 2 unpaired electrons.

534
00:24:30,620 --> 00:24:32,500
And, you know, these
are electrons.

535
00:24:32,500 --> 00:24:34,090
They're not just anywhere.

536
00:24:34,090 --> 00:24:37,560
They're sitting in an orbital,
and that orbital is as at 109

537
00:24:37,560 --> 00:24:40,020
degrees from the other bond.

538
00:24:40,020 --> 00:24:43,250
So it has to be sitting there
in reserve, in waiting.

539
00:24:43,250 --> 00:24:46,370
So if I bring another carbon
here, I get the carbon-carbon

540
00:24:46,370 --> 00:24:48,860
bond, and I start forming
the zig-zag.

541
00:24:48,860 --> 00:24:53,220
And there's one more, a common
one that we'll need to know.

542
00:24:53,220 --> 00:24:59,770
And that's from ethane,
which is C2H6, right?

543
00:24:59,770 --> 00:25:04,480
Let's start with ethane, C2H6,
and I'm going to make a

544
00:25:04,480 --> 00:25:05,283
radical out of that.

545
00:25:05,283 --> 00:25:08,240
It will be C2H5, like this.

546
00:25:08,240 --> 00:25:11,780
To which I can add a hydroxyl,
and now I'll make ethyl

547
00:25:11,780 --> 00:25:14,050
alcohol, and then
it's party time.

548
00:25:14,050 --> 00:25:15,400
But so this is how you start.

549
00:25:15,400 --> 00:25:16,510
All right?

550
00:25:16,510 --> 00:25:19,130
This is the ethyl radical.

551
00:25:22,520 --> 00:25:24,070
Starting from methane.

552
00:25:24,070 --> 00:25:25,100
And that's pretty much it.

553
00:25:25,100 --> 00:25:27,520
That's about all I want
you to really take

554
00:25:27,520 --> 00:25:29,460
away with the alkanes.

555
00:25:32,230 --> 00:25:34,190
C4H10.

556
00:25:34,190 --> 00:25:34,770
Yeah, there you go.

557
00:25:34,770 --> 00:25:37,960
So there you can see, to the
left, the zig-zagging of the

558
00:25:37,960 --> 00:25:41,430
linear and the butane, and
then the methyl propane.

559
00:25:41,430 --> 00:25:42,050
That's good.

560
00:25:42,050 --> 00:25:42,330
OK.

561
00:25:42,330 --> 00:25:44,190
Now let's go to sp2.

562
00:25:44,190 --> 00:25:46,420
Now we're going to look
at the alkenes.

563
00:25:46,420 --> 00:25:49,340
So alkenes represent--

564
00:25:49,340 --> 00:25:50,830
the alkenes--

565
00:25:50,830 --> 00:25:54,140
this is sp2 hybridization.

566
00:25:54,140 --> 00:25:56,430
And they contain--

567
00:25:56,430 --> 00:25:59,010
this means there's the
possibility of a carbon-carbon

568
00:25:59,010 --> 00:26:00,690
double bond.

569
00:26:00,690 --> 00:26:05,160
And they're also known
as unsaturated.

570
00:26:05,160 --> 00:26:07,390
Because they don't optimize.

571
00:26:07,390 --> 00:26:11,560
The fact that you spent two of
your bonds going between two

572
00:26:11,560 --> 00:26:14,490
atoms instead of taking one bond
to one carbon and another

573
00:26:14,490 --> 00:26:17,950
bond somewhere else, means that
you're undermaximized.

574
00:26:17,950 --> 00:26:22,160
So unsaturated hydrocarbons.

575
00:26:22,160 --> 00:26:22,520
OK?

576
00:26:22,520 --> 00:26:29,030
And the formula for these is
CNH2N, where obviously N is

577
00:26:29,030 --> 00:26:29,930
greater than 1.

578
00:26:29,930 --> 00:26:31,970
We can't form a carbon-carton
double bond

579
00:26:31,970 --> 00:26:33,050
with only one carbon.

580
00:26:33,050 --> 00:26:36,020
So you know, the prototypical
one we looked at was this one

581
00:26:36,020 --> 00:26:38,720
here, just to C2.

582
00:26:38,720 --> 00:26:39,560
That's the first one.

583
00:26:39,560 --> 00:26:41,420
So it's going to be C2H4.

584
00:26:41,420 --> 00:26:42,980
So carbon-carbon double bond.

585
00:26:42,980 --> 00:26:46,180
There's a sigma bond here,
and a pi bond.

586
00:26:46,180 --> 00:26:48,230
And they lie in a plane.

587
00:26:48,230 --> 00:26:49,700
The molecule is planar.

588
00:26:49,700 --> 00:26:51,850
120 degrees here.

589
00:26:51,850 --> 00:26:53,530
So we'll put the hydrogens
on it--

590
00:26:53,530 --> 00:26:55,760
you know already, I don't have
to put the hydrogens there.

591
00:26:55,760 --> 00:26:56,910
That's good enough.

592
00:26:56,910 --> 00:26:57,240
All right.

593
00:26:57,240 --> 00:26:59,300
So what's this one called?

594
00:26:59,300 --> 00:27:02,240
This is called ethylene,
historically.

595
00:27:02,240 --> 00:27:04,100
Ethylene.

596
00:27:04,100 --> 00:27:07,410
But the IUPAC notation is
similar to this one.

597
00:27:07,410 --> 00:27:11,070
It's carbon number
plus -ene, E N E.

598
00:27:11,070 --> 00:27:14,070
So strictly speaking, this
is what everybody knows.

599
00:27:14,070 --> 00:27:16,640
But IUPAC insists--

600
00:27:16,640 --> 00:27:17,660
and I don't know.

601
00:27:17,660 --> 00:27:21,370
As you publish, some editors
are really fastidious, and

602
00:27:21,370 --> 00:27:23,720
they'll force you to change
if you use this kind of

603
00:27:23,720 --> 00:27:24,660
terminology.

604
00:27:24,660 --> 00:27:27,350
So you're going to have
to call it ethene.

605
00:27:27,350 --> 00:27:30,310
Or in the UK they
call it ethene.

606
00:27:30,310 --> 00:27:32,170
But everybody knows
it is ethylene.

607
00:27:32,170 --> 00:27:32,460
OK.

608
00:27:32,460 --> 00:27:34,370
So there it is.

609
00:27:34,370 --> 00:27:37,755
And you only need 1
carbon-carbon bond.

610
00:27:37,755 --> 00:27:41,580
So you can have long
chains where the

611
00:27:41,580 --> 00:27:43,090
position isn't fixed.

612
00:27:43,090 --> 00:27:46,440
So let's look at a couple
of examples.

613
00:27:46,440 --> 00:27:48,500
So let's look at butene.

614
00:27:48,500 --> 00:27:50,260
OK, let me just write
that down.

615
00:27:50,260 --> 00:27:50,960
That's good.

616
00:27:50,960 --> 00:28:00,410
The position of carbon-carbon
is not fixed.

617
00:28:00,410 --> 00:28:04,220
It just has to be somewhere in
the molecule, which consists

618
00:28:04,220 --> 00:28:05,560
only of hydrogen and carbon

619
00:28:05,560 --> 00:28:07,500
So here's a couple
of examples.

620
00:28:07,500 --> 00:28:08,390
I'll start with this one.

621
00:28:08,390 --> 00:28:09,640
This is going to be--

622
00:28:11,630 --> 00:28:16,670
so this is 1, 2, 3, 4, so
that's a but- something.

623
00:28:16,670 --> 00:28:19,610
And it's got a double bond,
so that's a butene.

624
00:28:19,610 --> 00:28:20,810
It's all hydrocarbon.

625
00:28:20,810 --> 00:28:22,670
So that's butene here.

626
00:28:22,670 --> 00:28:24,930
But I could also-- well,
let's finish this.

627
00:28:24,930 --> 00:28:25,300
How many?

628
00:28:25,300 --> 00:28:28,500
This is 1, 2, 3, 4.

629
00:28:28,500 --> 00:28:32,680
See, I even tried to indicate
the 120 degrees here.

630
00:28:32,680 --> 00:28:36,190
This is going to
be 1, 2, 3, 4.

631
00:28:36,190 --> 00:28:39,260
1, 2, 3, 4, 1, 2, 3, 4.

632
00:28:39,260 --> 00:28:39,990
All right.

633
00:28:39,990 --> 00:28:41,350
So there's the butene.

634
00:28:41,350 --> 00:28:44,570
But there's another place I
could put the carbon-carbon

635
00:28:44,570 --> 00:28:45,140
double bond.

636
00:28:45,140 --> 00:28:46,500
I could do it this way.

637
00:28:46,500 --> 00:28:48,910
Make a carbon-carbon single
bond, move the carbon-carbon

638
00:28:48,910 --> 00:28:51,820
double bond over to the
number 2 position.

639
00:28:51,820 --> 00:28:55,390
this is 1, 2, 3, 4.

640
00:28:55,390 --> 00:28:58,180
So this is going to be 1-butene,
and this one here is

641
00:28:58,180 --> 00:29:00,420
going to be 1, 2.

642
00:29:00,420 --> 00:29:02,010
So we'll make this 2-butene.

643
00:29:05,260 --> 00:29:06,370
And let's keep counting here.

644
00:29:06,370 --> 00:29:13,640
1, 2, 3, 4, 1, 2, 3, 4, 1,
2, 3, 4, 1, 2, 3, 4.

645
00:29:13,640 --> 00:29:15,460
And I've proven to you,
I hope, by now that I

646
00:29:15,460 --> 00:29:16,650
can count to four.

647
00:29:16,650 --> 00:29:19,620
So this is 2-butene, right?

648
00:29:19,620 --> 00:29:20,540
2-butene.

649
00:29:20,540 --> 00:29:23,500
And if you go through this
using the same kind of

650
00:29:23,500 --> 00:29:26,800
diagrammatic analysis as over
here, you're going to come to

651
00:29:26,800 --> 00:29:29,770
the conclusion that even though
these both have the

652
00:29:29,770 --> 00:29:35,880
same composition, which is going
to be C4H8, they're both

653
00:29:35,880 --> 00:29:41,620
C4H8, but as you diagram them,
you'll find that they have

654
00:29:41,620 --> 00:29:42,750
different constituents.

655
00:29:42,750 --> 00:29:45,730
So these, in fact, are
constitutional

656
00:29:45,730 --> 00:29:47,700
isomers of one another.

657
00:29:47,700 --> 00:29:51,200
Constitutional isomers.

658
00:29:54,840 --> 00:29:57,320
Yeah, that's pretty good.

659
00:29:57,320 --> 00:29:58,730
There's even more.

660
00:29:58,730 --> 00:30:00,150
It gets even better.

661
00:30:00,150 --> 00:30:05,070
I want to focus on the bottom
one, the 2-butene, and I want

662
00:30:05,070 --> 00:30:08,170
to write it out with a little
bit more detail.

663
00:30:08,170 --> 00:30:13,450
So let's start with that
carbon-carbon double bond.

664
00:30:13,450 --> 00:30:17,410
And we know the carbon-carbon
double bond requires planar

665
00:30:17,410 --> 00:30:20,580
structures at 120 degrees
from one another.

666
00:30:20,580 --> 00:30:22,080
So let's look at that one.

667
00:30:22,080 --> 00:30:25,220
And what we've got here, is on
the carbon, I've got on the

668
00:30:25,220 --> 00:30:27,880
one side, I've got a hydrogen
strut, right?

669
00:30:27,880 --> 00:30:30,150
And on the other side,
I've got a methyl.

670
00:30:30,150 --> 00:30:34,520
I've put a methyl
here, like that.

671
00:30:34,520 --> 00:30:35,420
OK?

672
00:30:35,420 --> 00:30:36,240
Or actually, let's get--

673
00:30:36,240 --> 00:30:37,080
OK, I'll do that.

674
00:30:37,080 --> 00:30:39,220
I was-- what I wanted to
do, to get really--

675
00:30:39,220 --> 00:30:40,000
OK, watch this.

676
00:30:40,000 --> 00:30:40,210
All right.

677
00:30:40,210 --> 00:30:42,360
So what I'm going to
do on this side,

678
00:30:42,360 --> 00:30:43,250
this side, same thing.

679
00:30:43,250 --> 00:30:47,110
The carbon has a hydrogen strut
down here, and on the

680
00:30:47,110 --> 00:30:50,130
other side, you've
got the methyl.

681
00:30:50,130 --> 00:30:51,070
OK?

682
00:30:51,070 --> 00:30:52,410
So that looks good.

683
00:30:52,410 --> 00:30:56,140
But there's another way to do
this, and still keep the

684
00:30:56,140 --> 00:30:58,000
carbon-carbon bond
in the center.

685
00:30:58,000 --> 00:30:59,860
So I'm going to do
that over here.

686
00:30:59,860 --> 00:31:02,090
So 1, 2, 1, 2.

687
00:31:02,090 --> 00:31:05,100
And in this instance, I'll put
the same thing I have on the

688
00:31:05,100 --> 00:31:08,050
left side, H3C.

689
00:31:08,050 --> 00:31:09,310
So so far, so good.

690
00:31:09,310 --> 00:31:10,850
I've got the same molecule.

691
00:31:10,850 --> 00:31:13,330
But now what I'm going to do,
just for grins and chuckles,

692
00:31:13,330 --> 00:31:17,300
I'm going to put the hydrogen in
the upper position, and the

693
00:31:17,300 --> 00:31:20,480
methyl in the lower position.

694
00:31:20,480 --> 00:31:24,770
Now, these are not
constitutional isomers.

695
00:31:24,770 --> 00:31:27,140
They have the same constitution,
right?

696
00:31:27,140 --> 00:31:30,660
Carbon-carbon double bond, two
methyl groups, two hydrogens.

697
00:31:30,660 --> 00:31:34,250
Carbon-carbon double bond, two
methyl groups, two hydrogens.

698
00:31:34,250 --> 00:31:37,510
So they're constitutionally
identical, yet these have very

699
00:31:37,510 --> 00:31:38,820
different properties.

700
00:31:38,820 --> 00:31:40,890
Can you see?

701
00:31:40,890 --> 00:31:42,790
I mean, the dipole moment is
going to be different.

702
00:31:42,790 --> 00:31:43,010
Look.

703
00:31:43,010 --> 00:31:46,510
Here's the charge, all up on one
side, and here the charge

704
00:31:46,510 --> 00:31:50,580
is more symmetrically
straddled.

705
00:31:50,580 --> 00:31:53,300
Which means, they're going to
have different melting points.

706
00:31:53,300 --> 00:31:55,020
They're going to have different
boiling points.

707
00:31:55,020 --> 00:31:57,130
And they have the same chemical
formula, and they

708
00:31:57,130 --> 00:32:00,390
have the same chemical
constitution.

709
00:32:00,390 --> 00:32:01,520
So they're different kinds.

710
00:32:01,520 --> 00:32:03,040
There's some kind of isomers--

711
00:32:03,040 --> 00:32:04,190
what's the difference here?

712
00:32:04,190 --> 00:32:07,210
It's not the constitution,
it's the way things are

713
00:32:07,210 --> 00:32:08,510
arranged in space!

714
00:32:08,510 --> 00:32:10,250
This is great material
science.

715
00:32:10,250 --> 00:32:12,590
Spatial orientation
is everything.

716
00:32:12,590 --> 00:32:14,950
And what do you call it when
you're listening to some

717
00:32:14,950 --> 00:32:18,840
loudspeakers and a really good
audio system, and you can

718
00:32:18,840 --> 00:32:22,740
close your eyes, and the violins
are over here, and the

719
00:32:22,740 --> 00:32:27,170
cello is here, and
you can hear the

720
00:32:27,170 --> 00:32:28,370
percussion way in the back.

721
00:32:28,370 --> 00:32:30,230
What is that called?

722
00:32:30,230 --> 00:32:31,910
Stereophonic sound.

723
00:32:31,910 --> 00:32:36,940
Stereo phonic, meaning you can
render spacial resolution.

724
00:32:36,940 --> 00:32:38,365
So these are called
stereoisomers.

725
00:32:43,950 --> 00:32:46,090
One's a stereoisomer
of the other.

726
00:32:46,090 --> 00:32:48,580
So they're spacially
distinguishable.

727
00:32:48,580 --> 00:32:49,560
So they have--

728
00:32:49,560 --> 00:32:52,710
for example, I went and
looked this up.

729
00:32:52,710 --> 00:32:52,980
Oh.

730
00:32:52,980 --> 00:32:54,860
Let's give some names to this.

731
00:32:54,860 --> 00:32:59,080
In this case, all the methyls
are on the same side, and the

732
00:32:59,080 --> 00:33:00,390
hydrogens are on
the same side.

733
00:33:00,390 --> 00:33:04,450
So I can a dividing plane
here, if you like,

734
00:33:04,450 --> 00:33:05,990
parallel to the floor.

735
00:33:05,990 --> 00:33:07,540
And I'll just cut right through
the center of the

736
00:33:07,540 --> 00:33:09,980
carbons, parallel
to the floor.

737
00:33:09,980 --> 00:33:13,420
And so in one instance, all the
methyls are on the same

738
00:33:13,420 --> 00:33:15,940
side, and here the methyls are
on opposite sides of the

739
00:33:15,940 --> 00:33:17,000
double bond.

740
00:33:17,000 --> 00:33:19,510
So when they're on the same
side, this is called

741
00:33:19,510 --> 00:33:21,730
cis-butene.

742
00:33:21,730 --> 00:33:23,650
And let's be super pedantic.

743
00:33:23,650 --> 00:33:26,710
It was a 2-butene, so now
it's a cis-2-butene.

744
00:33:29,290 --> 00:33:31,720
This is terrific.

745
00:33:31,720 --> 00:33:34,800
And this is a 2-butene, but
it's on opposite side.

746
00:33:34,800 --> 00:33:36,253
So this is called a
trans-2-butene.

747
00:33:38,820 --> 00:33:41,870
Cis-2-butene and
trans-2-butene.

748
00:33:41,870 --> 00:33:46,940
And I looked up-- so let's see,
which one do you think

749
00:33:46,940 --> 00:33:50,450
has tighter, which one's going
to be more tightly packed?

750
00:33:50,450 --> 00:33:55,110
Which one's going to have
the greater density?

751
00:33:55,110 --> 00:33:57,740
Which one's going
to pack better?

752
00:33:57,740 --> 00:33:58,990
Cis or trans?

753
00:34:04,250 --> 00:34:16,740
The density here is 0.627, and
the density here is 0.61.

754
00:34:16,740 --> 00:34:17,440
OK?

755
00:34:17,440 --> 00:34:22,370
Now, which one's going to have
the higher boiling point?

756
00:34:22,370 --> 00:34:25,200
Which one's going to have the
higher boiling point?

757
00:34:25,200 --> 00:34:26,530
Gee, that should be
a no-brainer.

758
00:34:26,530 --> 00:34:28,250
Once you know which one's
got the higher density.

759
00:34:28,250 --> 00:34:30,520
Why does it have the
higher density?

760
00:34:30,520 --> 00:34:32,040
Because it's more nearest
neighbors is

761
00:34:32,040 --> 00:34:33,050
more tightly packed.

762
00:34:33,050 --> 00:34:35,620
So I would bet on the one
with the higher density.

763
00:34:35,620 --> 00:34:42,040
And this one boils at, boiling
point is 3.7 degrees Celsius,

764
00:34:42,040 --> 00:34:45,040
and this one, the boiling
point is--

765
00:34:45,040 --> 00:34:48,270
hang on, I've got
this backwards.

766
00:34:48,270 --> 00:34:49,370
This is 3.7.

767
00:34:49,370 --> 00:34:51,860
Boiling point is 1
degree Celsius.

768
00:34:51,860 --> 00:34:54,450
So those are the data
as they come up.

769
00:34:54,450 --> 00:34:58,890
So stereoisomer, spacially
distinguishable.

770
00:34:58,890 --> 00:35:01,210
By the way, we can form
multiple bonds.

771
00:35:01,210 --> 00:35:03,320
We can form multiple
double bonds.

772
00:35:03,320 --> 00:35:04,720
So they're -enes as well.

773
00:35:04,720 --> 00:35:10,990
So if we have two double bonds
in the molecule, so we'll call

774
00:35:10,990 --> 00:35:12,600
that a diene.

775
00:35:15,240 --> 00:35:17,070
And we can have--

776
00:35:17,070 --> 00:35:19,520
you can keep going with the
Latin, but common ones you

777
00:35:19,520 --> 00:35:21,350
might find is the triene.

778
00:35:21,350 --> 00:35:23,920
And this will come back later
when we look at polymers.

779
00:35:23,920 --> 00:35:27,040
So if we have two bonds,
we will have--

780
00:35:27,040 --> 00:35:33,680
You know, some of that hard
luggage that you're seeing

781
00:35:33,680 --> 00:35:37,680
that's coming back, they got the
roller boards, but instead

782
00:35:37,680 --> 00:35:39,940
of the fabric, now they're
coming back with the really

783
00:35:39,940 --> 00:35:41,040
hard polymer?

784
00:35:41,040 --> 00:35:46,650
That's ABS, and the
b is butadiene.

785
00:35:46,650 --> 00:35:49,080
So let's look at a-- here's
a pentadiene.

786
00:35:49,080 --> 00:35:50,190
I'll give you a pentadiene.

787
00:35:50,190 --> 00:35:54,390
So that's going to
be 1, 2, 3, 4, 5.

788
00:35:54,390 --> 00:35:56,510
It's five carbons,
for starters.

789
00:35:56,510 --> 00:35:58,510
And I'm going to put
the double bonds on

790
00:35:58,510 --> 00:36:00,240
the 1 and the 3 carbon.

791
00:36:00,240 --> 00:36:03,600
It'll be a penta-, it's
five carbons.

792
00:36:03,600 --> 00:36:06,070
And it's an -ene, because
there's going to be some

793
00:36:06,070 --> 00:36:07,450
double bonds here.

794
00:36:07,450 --> 00:36:10,040
And it's a di-, because I'm
going to put double bonds at

795
00:36:10,040 --> 00:36:10,870
the 1 and the 3.

796
00:36:10,870 --> 00:36:14,510
So 1 gets a double bond, and
3 gets a double bond.

797
00:36:14,510 --> 00:36:18,100
So this is a pentadiene.

798
00:36:18,100 --> 00:36:19,040
OK?

799
00:36:19,040 --> 00:36:21,830
And then the last thing is--

800
00:36:21,830 --> 00:36:22,370
pardon me.

801
00:36:22,370 --> 00:36:25,330
Last thing is radicals.

802
00:36:25,330 --> 00:36:27,310
So here's the common radical.

803
00:36:27,310 --> 00:36:34,770
We'll start with ethylene, and
I'm going to make an ethylene

804
00:36:34,770 --> 00:36:35,395
radical here.

805
00:36:35,395 --> 00:36:39,440
I'll break off the hydrogen at
this point, and I can write

806
00:36:39,440 --> 00:36:40,690
that as CH2CH.

807
00:36:45,580 --> 00:36:49,110
And we can't call this ethyl
radical, because ethyl was

808
00:36:49,110 --> 00:36:52,130
already used for C2H5.

809
00:36:52,130 --> 00:36:55,070
So we need to indicate that
there's a double bond, and so

810
00:36:55,070 --> 00:36:58,360
this radical is known
as vinyl.

811
00:36:58,360 --> 00:37:01,010
This is the vinyl radical.

812
00:37:01,010 --> 00:37:04,020
And so you could react this with
chlorine, for example, in

813
00:37:04,020 --> 00:37:07,260
which case you'd make vinyl
chloride, and then you'd

814
00:37:07,260 --> 00:37:08,790
polymerize that, and
you make PVC.

815
00:37:08,790 --> 00:37:13,070
And we're going to see that
in the next coming days.

816
00:37:13,070 --> 00:37:16,040
Or you could you can put
alcohol on there.

817
00:37:16,040 --> 00:37:17,690
I've already told you that.

818
00:37:17,690 --> 00:37:20,230
I don't need to remind you
twice about that, I bet.

819
00:37:20,230 --> 00:37:20,570
OK.

820
00:37:20,570 --> 00:37:22,130
So now--

821
00:37:22,130 --> 00:37:23,360
oh, there's one other one.

822
00:37:23,360 --> 00:37:25,570
There's one other one that will
come up if you take a lot

823
00:37:25,570 --> 00:37:28,390
of biochemistry, and
that's the one that

824
00:37:28,390 --> 00:37:29,650
comes off of propene.

825
00:37:29,650 --> 00:37:31,545
So if you start with propene,
propene's going

826
00:37:31,545 --> 00:37:32,820
to look like this.

827
00:37:32,820 --> 00:37:36,000
1, 2, 3.

828
00:37:36,000 --> 00:37:37,120
So there's propene.

829
00:37:37,120 --> 00:37:37,990
3.

830
00:37:37,990 --> 00:37:42,770
There's a saying double bond
here, and I'm going to put 1,

831
00:37:42,770 --> 00:37:44,550
2, 3 in here.

832
00:37:44,550 --> 00:37:48,470
1, 2, 3, 1, 2, 3.

833
00:37:48,470 --> 00:37:49,580
1, 2, 3, 4.

834
00:37:49,580 --> 00:37:50,260
OK.

835
00:37:50,260 --> 00:37:54,510
So this is the radical that
comes from propene.

836
00:37:54,510 --> 00:38:01,790
So this one is derived from
ethylene, and this one here is

837
00:38:01,790 --> 00:38:06,520
derived from propylene.

838
00:38:06,520 --> 00:38:09,990
So again, as in this case, we
couldn't call this ethyl.

839
00:38:09,990 --> 00:38:12,280
We can't call this propyl,
because that's the one that

840
00:38:12,280 --> 00:38:15,140
you get from the alkane.

841
00:38:15,140 --> 00:38:18,000
So instead, this one
is called allyl.

842
00:38:18,000 --> 00:38:19,770
A L L Y L.

843
00:38:19,770 --> 00:38:24,950
And if you take 7012 at some
point, Professor Weinberg will

844
00:38:24,950 --> 00:38:27,090
refer to these pendant groups.

845
00:38:27,090 --> 00:38:29,370
He likes to pronounce
this all-YL.

846
00:38:29,370 --> 00:38:31,630
You'll hear him talk about,
and the all-YLS are

847
00:38:31,630 --> 00:38:32,400
over here and here.

848
00:38:32,400 --> 00:38:35,330
That's what we're
talking about.

849
00:38:35,330 --> 00:38:35,960
OK, good.

850
00:38:35,960 --> 00:38:41,560
So this is C3H7 dot.

851
00:38:41,560 --> 00:38:42,900
Good.

852
00:38:42,900 --> 00:38:43,300
All right.

853
00:38:43,300 --> 00:38:44,660
Moving right along.

854
00:38:44,660 --> 00:38:47,220
Now I want to turn
to the alkynes.

855
00:38:50,230 --> 00:38:56,140
That's the sp hybridization.

856
00:38:56,140 --> 00:38:57,740
sp.

857
00:38:57,740 --> 00:39:01,590
And that means there's going
to be at least one

858
00:39:01,590 --> 00:39:05,120
carbon-carbon triple bond.

859
00:39:05,120 --> 00:39:06,880
One carbon-carbon triple bond.

860
00:39:06,880 --> 00:39:14,010
So the formula there is CNH2N
minus 2, and obviously N has

861
00:39:14,010 --> 00:39:16,590
to be greater than
1, otherwise you

862
00:39:16,590 --> 00:39:18,010
can't form a bond.

863
00:39:18,010 --> 00:39:20,300
And there's very little
that you need to

864
00:39:20,300 --> 00:39:21,570
remember about this one.

865
00:39:21,570 --> 00:39:26,740
The dominant one that you'll
come upon is C2H2.

866
00:39:30,250 --> 00:39:34,770
So according IUPAC nomenclature,
the two carbons

867
00:39:34,770 --> 00:39:40,270
means it has to be F, and these
are all alkynes, so this

868
00:39:40,270 --> 00:39:41,830
should be ethyne.

869
00:39:41,830 --> 00:39:44,080
And if you ask for ethyne,
nobody knows what you're

870
00:39:44,080 --> 00:39:46,300
talking about, although
it's very correct.

871
00:39:46,300 --> 00:39:51,830
This is known as acetylene,
which is a fuel gas for

872
00:39:51,830 --> 00:39:54,720
welding, cutting, torches
and so on.

873
00:39:54,720 --> 00:39:56,990
You've got two lines, you've got
a big tank of acetylene,

874
00:39:56,990 --> 00:39:58,710
you've got a big
tank of oxygen.

875
00:39:58,710 --> 00:40:02,340
And this is used because there
is enormous energy stored in

876
00:40:02,340 --> 00:40:03,830
this carbon-carbon
double bond.

877
00:40:03,830 --> 00:40:07,500
And so when you combust this
with the stoichiometric amount

878
00:40:07,500 --> 00:40:14,400
of oxygen, you can cut through
steel, you can use this to

879
00:40:14,400 --> 00:40:19,380
make very elaborate glassware
with pure silica, making fused

880
00:40:19,380 --> 00:40:20,770
quartz glassware.

881
00:40:20,770 --> 00:40:23,830
Very, very high energy
contained in here.

882
00:40:23,830 --> 00:40:28,900
And just to give one more
example, let's look at

883
00:40:28,900 --> 00:40:32,370
something that's got
four carbons in it.

884
00:40:32,370 --> 00:40:34,960
So it's going to have four
carbons and a triple bond.

885
00:40:34,960 --> 00:40:38,490
So if it's 4, it's going to have
the B U T but-, and it's

886
00:40:38,490 --> 00:40:39,430
going to need an -yne.

887
00:40:39,430 --> 00:40:41,090
So this will be a butyne.

888
00:40:41,090 --> 00:40:44,150
And depending on where we want
to put the triple bond, I

889
00:40:44,150 --> 00:40:45,830
don't know, if you want to
put a triple bond here,

890
00:40:45,830 --> 00:40:47,550
there's 1, 2, 3, 4.

891
00:40:47,550 --> 00:40:53,580
So this we could call 2-butyne,
and it's C4H6, If

892
00:40:53,580 --> 00:40:58,510
you go through the
stoichiometry.

893
00:40:58,510 --> 00:41:00,220
Let's try it, just
for practice.

894
00:41:00,220 --> 00:41:03,720
So this carbon on the
end is 1, 2, 3, 4.

895
00:41:03,720 --> 00:41:05,360
Look at the second carbon.

896
00:41:05,360 --> 00:41:09,130
It's got one strut bonding to
the neighboring carbon, and

897
00:41:09,130 --> 00:41:11,170
three struts bonding
to the neighboring

898
00:41:11,170 --> 00:41:12,610
carbon on the right.

899
00:41:12,610 --> 00:41:14,020
It's saturated now.

900
00:41:14,020 --> 00:41:15,740
Nothing comes of
without carbon.

901
00:41:15,740 --> 00:41:16,380
Look at this one.

902
00:41:16,380 --> 00:41:18,090
1, 2, 3, 4.

903
00:41:18,090 --> 00:41:19,370
Nothing comes off of this one.

904
00:41:19,370 --> 00:41:21,130
And then finally 1, 2, 3.

905
00:41:21,130 --> 00:41:23,360
So there's three hydrogens here,
there's three hydrogens

906
00:41:23,360 --> 00:41:25,070
here, there's your
sixth hydrogen.

907
00:41:25,070 --> 00:41:26,740
C4H6.

908
00:41:26,740 --> 00:41:27,970
OK.

909
00:41:27,970 --> 00:41:30,280
That's good.

910
00:41:30,280 --> 00:41:30,630
All right.

911
00:41:30,630 --> 00:41:33,300
There's one other set that I
want to look at, and these are

912
00:41:33,300 --> 00:41:35,790
called the arynes.

913
00:41:35,790 --> 00:41:37,342
These are aromatic
hydrocarbons.

914
00:41:46,320 --> 00:41:49,860
Some people refer to
them as arynes.

915
00:41:49,860 --> 00:41:55,770
And the most notable one is
C6H6, which is benzine.

916
00:41:59,200 --> 00:42:05,670
And benzine's molecular weight
was determined long ago, in

917
00:42:05,670 --> 00:42:07,400
the early 1800s.

918
00:42:07,400 --> 00:42:17,990
And it was Kekule who, in 1865,
dared to suggest that

919
00:42:17,990 --> 00:42:29,400
the chemical structure of
benzine was a ring structure.

920
00:42:29,400 --> 00:42:37,650
So Kekule suggested
a carbon ring.

921
00:42:37,650 --> 00:42:42,030
Up until this time, people
didn't have the common

922
00:42:42,030 --> 00:42:45,800
understanding that carbons could
link to themselves, let

923
00:42:45,800 --> 00:42:47,410
alone form a ring.

924
00:42:47,410 --> 00:42:51,400
And so now, if we go through
this, we will put, from each

925
00:42:51,400 --> 00:42:53,830
of these junctions there's the
carbon, so we have to have

926
00:42:53,830 --> 00:42:54,580
four struts.

927
00:42:54,580 --> 00:43:00,580
We need hydrogen, so let's put
hydrogens 1, 2, 3, 4, 5, 6, So

928
00:43:00,580 --> 00:43:03,790
there's the 6 hydrogens.

929
00:43:03,790 --> 00:43:05,880
And now, each carbon
needs 4 struts.

930
00:43:05,880 --> 00:43:09,070
So 1, 2, 3, and I'll
put a double bond.

931
00:43:09,070 --> 00:43:10,260
That will make 4.

932
00:43:10,260 --> 00:43:18,420
1, 2, 3, 4, 1, 2, 3, 4, 1, 2,
3, 4, and now this one here.

933
00:43:18,420 --> 00:43:20,720
So you have an alternating
structure of double bond,

934
00:43:20,720 --> 00:43:24,160
single bond, double bond, single
bond on the carbons.

935
00:43:24,160 --> 00:43:25,020
OK?

936
00:43:25,020 --> 00:43:30,100
So that's the way things stood
until the twentieth century,

937
00:43:30,100 --> 00:43:36,730
when on the basis of new data,
it was discovered that all

938
00:43:36,730 --> 00:43:39,110
carbon-carbon bonds--

939
00:43:39,110 --> 00:43:41,610
and I don't want to make this
a single bond, I'll just say

940
00:43:41,610 --> 00:43:48,940
all carbon-carbon bonds in
benzine, C6H6, were measured

941
00:43:48,940 --> 00:43:52,200
to be the same length.

942
00:43:52,200 --> 00:43:54,660
Well, that's a problem,
isn't it?

943
00:43:54,660 --> 00:43:57,850
That's a problem, because we
would expect that, you know,

944
00:43:57,850 --> 00:44:01,970
we know that carbon-carbon
single bond is about 1.47

945
00:44:01,970 --> 00:44:07,190
angstroms, and the carbon-carbon
double bond has

946
00:44:07,190 --> 00:44:10,220
to be shorter, because it's
double-bond, it's tighter, so

947
00:44:10,220 --> 00:44:12,070
it pulls things in.

948
00:44:12,070 --> 00:44:20,170
So that's 1.33 angstroms. And
the measurement here was found

949
00:44:20,170 --> 00:44:27,230
to be 1.39 angstroms. And 1.39
angstroms is midway between

950
00:44:27,230 --> 00:44:29,410
1.47 and 1.33.

951
00:44:29,410 --> 00:44:33,160
So people were frustrated with
this new information.

952
00:44:33,160 --> 00:44:37,820
And it was Linus Pauling who
made sense of this for us.

953
00:44:37,820 --> 00:44:43,220
Pauling, who in 1931 came
along and said,

954
00:44:43,220 --> 00:44:44,990
what we have a mix?

955
00:44:44,990 --> 00:44:47,420
What if we have a mix
of two structures?

956
00:44:47,420 --> 00:44:53,510
And he said, suppose you had
something that looked like so.

957
00:44:53,510 --> 00:44:55,530
1, 1, 1.

958
00:44:55,530 --> 00:44:59,970
So here's the set of double
bonds off of the ring.

959
00:44:59,970 --> 00:45:05,970
And what if there is a resonance
with an opposite

960
00:45:05,970 --> 00:45:09,740
hybrid, where this double bond,
instead of being here,

961
00:45:09,740 --> 00:45:10,620
goes over to here?

962
00:45:10,620 --> 00:45:12,490
So now we have this?

963
00:45:12,490 --> 00:45:15,480
And he said, if the system
resonated between the

964
00:45:15,480 --> 00:45:18,280
structure on the left and the
structure on the right, the

965
00:45:18,280 --> 00:45:24,410
time average value of the
carbon-carbon bond length

966
00:45:24,410 --> 00:45:32,470
would be around 1.39 angstroms.
So this is a

967
00:45:32,470 --> 00:45:42,410
resonant hybrid structure, to
account for the mix of single

968
00:45:42,410 --> 00:45:46,960
and double bonds, which gives
rise to the current

969
00:45:46,960 --> 00:45:49,710
representation of benzine
as simply this.

970
00:45:49,710 --> 00:45:51,610
So we're not saying this
is single or double.

971
00:45:51,610 --> 00:45:55,570
It's a resonant between
one and two.

972
00:45:55,570 --> 00:45:57,350
OK.

973
00:45:57,350 --> 00:46:00,000
The other thing is, if all of
these bonds are the same

974
00:46:00,000 --> 00:46:05,190
length, and that means that
between the 12:00 position

975
00:46:05,190 --> 00:46:10,170
here and the 2:00 position,
there is pi bonding, and then

976
00:46:10,170 --> 00:46:14,020
along this double bond, there's
pi bonding, and then

977
00:46:14,020 --> 00:46:17,760
along this double bond,
there's pi bonding.

978
00:46:17,760 --> 00:46:20,940
But if all of the bonds are the
same length, I can't say

979
00:46:20,940 --> 00:46:24,770
that the pi bonds are confined
to where the double bonds are

980
00:46:24,770 --> 00:46:29,050
indicated, because resonance
indicates that it could be

981
00:46:29,050 --> 00:46:30,500
between adjacents.

982
00:46:30,500 --> 00:46:32,190
So that means that
the electrons, in

983
00:46:32,190 --> 00:46:34,960
fact, can go all around.

984
00:46:34,960 --> 00:46:40,040
So resonance, then, means that
the pi electrons are

985
00:46:40,040 --> 00:46:41,290
delocalized.

986
00:46:49,050 --> 00:46:51,540
And now here's some
better drawings.

987
00:46:51,540 --> 00:46:52,710
It's hard to draw that.

988
00:46:52,710 --> 00:46:53,680
So here they are.

989
00:46:53,680 --> 00:46:53,940
OK.

990
00:46:53,940 --> 00:46:55,800
So this is a nicer drawing
of benzine.

991
00:46:55,800 --> 00:46:59,760
So you can see, when all of
these bonds are resonant, it

992
00:46:59,760 --> 00:47:02,240
doesn't matter whether I choose
this front one as the

993
00:47:02,240 --> 00:47:03,670
double bond, or the
one next to it.

994
00:47:03,670 --> 00:47:06,290
They're all the same length,
and so the electrons can go

995
00:47:06,290 --> 00:47:06,840
all around.

996
00:47:06,840 --> 00:47:09,920
And you can imagine, if I did
this with graphite, and I kept

997
00:47:09,920 --> 00:47:15,710
going, well, if the electron can
go here, then it means it

998
00:47:15,710 --> 00:47:17,640
can go here, which means it can
go here, which means it

999
00:47:17,640 --> 00:47:18,340
can go everywhere.

1000
00:47:18,340 --> 00:47:21,490
Which is why graphite is an
electronic conductor, because

1001
00:47:21,490 --> 00:47:24,180
of delocalized pi bonds.

1002
00:47:24,180 --> 00:47:24,760
OK.

1003
00:47:24,760 --> 00:47:26,300
This is 1-3-butadiene.

1004
00:47:26,300 --> 00:47:28,510
Double bond, single
bond, double bond.

1005
00:47:28,510 --> 00:47:31,710
Again, all the same length, and
you can hybridize, and--

1006
00:47:31,710 --> 00:47:32,740
This is how you start making

1007
00:47:32,740 --> 00:47:34,890
electronically conducted polymers.

1008
00:47:34,890 --> 00:47:36,630
You just go double bond,
single bond.

1009
00:47:36,630 --> 00:47:37,860
Double bond, single bond.

1010
00:47:37,860 --> 00:47:40,410
Smear.

1011
00:47:40,410 --> 00:47:41,480
That's it.

1012
00:47:41,480 --> 00:47:41,840
OK.

1013
00:47:41,840 --> 00:47:43,920
Let's jump over that.

1014
00:47:43,920 --> 00:47:48,770
Let's talk about Kekule So he
studied architecture, switched

1015
00:47:48,770 --> 00:47:49,470
to chemistry.

1016
00:47:49,470 --> 00:47:51,990
And then he got a job in London,
and he used to fall

1017
00:47:51,990 --> 00:47:54,022
asleep on the bus to
his apartment.

1018
00:47:54,022 --> 00:47:55,820
And one day he was sleeping
on the bus.

1019
00:47:55,820 --> 00:47:59,350
He woke up, and he'd been
dreaming about carbon forming

1020
00:47:59,350 --> 00:48:01,860
chains in 1855.

1021
00:48:01,860 --> 00:48:04,090
And he proposed carbon chains.

1022
00:48:04,090 --> 00:48:06,770
And then he got a job as a
professor in Belgium, at the

1023
00:48:06,770 --> 00:48:08,510
University of Ghent.

1024
00:48:08,510 --> 00:48:10,890
And one night he fell asleep
at the fireplace, and he

1025
00:48:10,890 --> 00:48:14,500
dreamt of a benzine molecule
as a snake biting its tail

1026
00:48:14,500 --> 00:48:16,900
while spinning.

1027
00:48:16,900 --> 00:48:20,230
And that's where he got the
idea of the ring molecule.

1028
00:48:20,230 --> 00:48:23,710
All he knew was that this thing
had a formula, C6H6.

1029
00:48:23,710 --> 00:48:25,510
And for this, he's dubbed
the founder

1030
00:48:25,510 --> 00:48:26,800
of structural chemistry.

1031
00:48:26,800 --> 00:48:29,240
So what's this formula
for success?

1032
00:48:29,240 --> 00:48:31,780
Well, he moved into chemistry
from another field.

1033
00:48:31,780 --> 00:48:33,880
But to dream, you've got
to get some sleep.

1034
00:48:33,880 --> 00:48:37,250
And I'm probably talking to one
of the most sleep-deprived

1035
00:48:37,250 --> 00:48:39,940
populations on this campus.

1036
00:48:39,940 --> 00:48:42,150
So I urge you to get some sleep,
and then maybe you'll

1037
00:48:42,150 --> 00:48:43,460
be able to dream.

1038
00:48:43,460 --> 00:48:44,310
Hey, don't make noise.

1039
00:48:44,310 --> 00:48:45,510
We've got two minutes left.

1040
00:48:45,510 --> 00:48:48,510
nobody's going anywhere.

1041
00:48:48,510 --> 00:48:49,350
All right.

1042
00:48:49,350 --> 00:48:54,780
So the next thing is, I want
to talk a little bit about

1043
00:48:54,780 --> 00:48:58,170
octane ratings and automobiles,
and how we go

1044
00:48:58,170 --> 00:49:01,900
from straight chains to chains
of different lengths.

1045
00:49:01,900 --> 00:49:04,530
If you're looking at combustion,
the idea is, you

1046
00:49:04,530 --> 00:49:07,730
admit gasoline, which vaporizes,
and then the piston

1047
00:49:07,730 --> 00:49:10,050
comes up, and under
high compression,

1048
00:49:10,050 --> 00:49:11,670
the spark plug fires.

1049
00:49:11,670 --> 00:49:14,490
When the spark plug fires, this
causes an explosion which

1050
00:49:14,490 --> 00:49:16,790
then pushes the piston down,
and then you've got the

1051
00:49:16,790 --> 00:49:19,730
camshaft that takes the vertical
motion and converts

1052
00:49:19,730 --> 00:49:21,010
it to rotary motion.

1053
00:49:21,010 --> 00:49:22,920
Now, if you're running an
automobile after a certain

1054
00:49:22,920 --> 00:49:26,980
period of time, the combustion
chamber becomes so hot that

1055
00:49:26,980 --> 00:49:30,400
just admitting the fuel, having
it vaporized, before

1056
00:49:30,400 --> 00:49:34,400
the piston has risen fully to
get maximum compression, this

1057
00:49:34,400 --> 00:49:36,140
thing could just explode.

1058
00:49:36,140 --> 00:49:39,070
And when it explodes, it'll send
the piston down, and it's

1059
00:49:39,070 --> 00:49:40,870
out of sequence with
the other pistons.

1060
00:49:40,870 --> 00:49:42,100
And that's when you
get the knocking.

1061
00:49:42,100 --> 00:49:44,170
Sometimes you're driving
up hill, you hear this

1062
00:49:44,170 --> 00:49:45,890
[GRINDING SOUND].

1063
00:49:45,890 --> 00:49:47,420
That's the knocking going on.

1064
00:49:47,420 --> 00:49:49,540
You need to get a tune-up,
or switch to

1065
00:49:49,540 --> 00:49:51,200
higher octane gasoline.

1066
00:49:51,200 --> 00:49:52,410
So what's going on in here?

1067
00:49:52,410 --> 00:49:55,770
What you're doing, is you're
changing the chemical

1068
00:49:55,770 --> 00:49:59,980
composition, the constitutional
isomerization.

1069
00:49:59,980 --> 00:50:05,030
And you do that in the process
by which you synthesize the

1070
00:50:05,030 --> 00:50:06,540
gasoline in the first place.

1071
00:50:06,540 --> 00:50:08,800
So the figure of merit is called
octane number, which

1072
00:50:08,800 --> 00:50:11,970
was first instituted here
in the United States.

1073
00:50:11,970 --> 00:50:14,620
And they started with
2-2-4-trimethyl-pentane.

1074
00:50:14,620 --> 00:50:17,810
It's an octane, but it's
an octane that's 2-2-4.

1075
00:50:17,810 --> 00:50:18,980
Three methyl branches.

1076
00:50:18,980 --> 00:50:20,810
So that means there's
only five left.

1077
00:50:20,810 --> 00:50:23,740
So it's a pentane with three
methyl branches.

1078
00:50:23,740 --> 00:50:26,080
And that's called 100.

1079
00:50:26,080 --> 00:50:28,290
And then is 0 is heptane.

1080
00:50:28,290 --> 00:50:30,780
If you put heptane into the
combustion chamber, you'll

1081
00:50:30,780 --> 00:50:31,920
knock yourself silly.

1082
00:50:31,920 --> 00:50:33,880
And the engine will just shake
and shake and shake.

1083
00:50:33,880 --> 00:50:37,210
So gasolines have to be
somewhere on that interval.

1084
00:50:37,210 --> 00:50:40,630
So there's the-- you know,
if you tested and you had

1085
00:50:40,630 --> 00:50:43,210
something that was
trimetylpentane, 90%, versus

1086
00:50:43,210 --> 00:50:45,700
10% heptane, you'd call
it a 90% octane.

1087
00:50:45,700 --> 00:50:47,080
And you can have octane
numbers higher

1088
00:50:47,080 --> 00:50:48,530
than 100, by the way.

1089
00:50:48,530 --> 00:50:50,820
It just depends on what
the repression is.

1090
00:50:50,820 --> 00:50:54,700
And oddly enough, when you when
you increase the octane,

1091
00:50:54,700 --> 00:50:57,510
you make the fuel more
difficult to burn.

1092
00:50:57,510 --> 00:51:00,300
Because you want it to
burn only on demand.

1093
00:51:00,300 --> 00:51:03,750
Fuel that just burns whenever
it wants leads to random

1094
00:51:03,750 --> 00:51:06,440
events in the engine, and that's
not good, if you want

1095
00:51:06,440 --> 00:51:10,210
to get good thrust. So oddly
enough, high octane gasoline

1096
00:51:10,210 --> 00:51:12,910
requires more ignition
than low octane.

1097
00:51:12,910 --> 00:51:14,760
And the additives
are tetraethyl

1098
00:51:14,760 --> 00:51:16,480
lead or ethyl alcohol.

1099
00:51:16,480 --> 00:51:23,490
And from that, you know now, we
get E10, which is gasohol,

1100
00:51:23,490 --> 00:51:24,840
10% alcohol.

1101
00:51:24,840 --> 00:51:28,720
E85 is 85% ethyl alcohol.

1102
00:51:28,720 --> 00:51:31,140
And all of this you
get by synthesis.

1103
00:51:31,140 --> 00:51:33,500
You know, playing with the
catalysts, temperatures, and

1104
00:51:33,500 --> 00:51:36,360
so on, to get the right
mix to get good fuel,

1105
00:51:36,360 --> 00:51:37,380
and get good emissions.

1106
00:51:37,380 --> 00:51:39,825
And you can decide amongst
yourselves whether going to

1107
00:51:39,825 --> 00:51:43,670
E85 high levels of ethanol,
ethanol derived from corn, is

1108
00:51:43,670 --> 00:51:46,970
that smart, is that
food for fuel?

1109
00:51:46,970 --> 00:51:50,710
You know, what's the sensible
use of agriculture, algae,

1110
00:51:50,710 --> 00:51:51,960
switchgrass?

1111
00:51:51,960 --> 00:51:52,720
All of that stuff.

1112
00:51:52,720 --> 00:51:55,150
I mean, it's all loaded
into here.

1113
00:51:55,150 --> 00:51:56,660
All loaded into here.

1114
00:51:56,660 --> 00:51:58,620
So yeah.

1115
00:51:58,620 --> 00:52:00,410
With that, I think
we'll adjourn.

1116
00:52:00,410 --> 00:52:02,200
I'll see you on Wednesday.