WEBVTT

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Prof: So in 1832,
as we saw at the end last time,

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and together they worked on the
oil of bitter almonds,

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which is making its way around
-- it's benzaldehyde --

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which is making its way around
here.

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So there's the bottle that's
coming around.

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What did you notice about it?

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Where is it?

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What do you notice about it
Devin?

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Student:
>

00:38.710 --> 00:39.710
Prof: Yeah.

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Student:  About the
smell?

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Prof: What does it smell
like?

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Is it almonds?

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Turn it around,
look at the -- turn it upside

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down.

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What do you notice?

00:59.100 --> 01:02.230
Student:  There's a
little bit of solid in the

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bottom.

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Prof: Yeah,
it's half solid.

01:05.019 --> 01:07.619
Benzaldehyde is the oil
of bitter almonds;

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not the solid of bitter almonds.

01:10.230 --> 01:17.640
What does it say on the label,
written by hand?

01:17.640 --> 01:19.090
Somebody's initials, J.W.

01:19.090 --> 01:22.070
Student: J.W., 11/29/95.

01:22.069 --> 01:25.019
Prof: So it was opened
in 1995, thirteen years ago.

01:25.019 --> 01:27.049
When it was opened it was a
liquid.

01:27.049 --> 01:29.239
Now it's half solid.

01:29.239 --> 01:33.679
How do you figure that?

01:33.680 --> 01:35.580
Well something must've happened.

01:35.580 --> 01:37.950
So what did it react with,
in the bottle?

01:37.950 --> 01:41.720
Yoonjoo?

01:41.720 --> 01:42.750
Student:  Oxygen.

01:42.750 --> 01:44.070
Prof: Oxygen.

01:44.069 --> 01:45.019
Okay?

01:45.019 --> 01:48.139
So oil of bitter almonds;
they analyzed,

01:48.140 --> 01:54.980
C_7H_6O, and they found that it
reacted with oxygen to get

01:54.980 --> 01:56.180
C_7H_6O_2.

01:56.180 --> 01:57.380
Right?

01:57.379 --> 01:59.259
They also reacted it with
bromine.

01:59.260 --> 02:01.110
The halogens were common,
as we'll see,

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for reagents in those days.

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Got C_7H_5OBr.

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They reacted it with chlorine,
and also that product with

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potassium iodide,
or ammonia, or lead sulfide.

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And they got all these
compounds.

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And what did they do with them
when they got them?

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They smelled them. Right?

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What was the main thing they
did?

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Student:  Tasted it.

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Prof: No that's not the
--

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it's true that they probably
tasted,

02:26.520 --> 02:30.270
that they tasted them,
but that's not the main thing

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they did that gave them unique
information.

02:33.580 --> 02:34.560
Student:  Weight.

02:34.560 --> 02:40.840
Prof: What about the
weight?

02:40.840 --> 02:43.430
What was the main technique
that we've been talking about

02:43.434 --> 02:44.134
all the time?

02:44.129 --> 02:44.939
Dana?

02:44.940 --> 02:45.880
Student:  The analysis
of combustion.

02:45.878 --> 02:47.458
Prof: They did an
elemental analysis;

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ultimate analysis of what the
ratio of the elements.

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So that's what they had. Right?

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So big deal.

02:54.128 --> 02:55.878
What do you get from the
analysis?

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What can you infer?

02:58.819 --> 03:01.009
Here were these guys;
you could now compete with

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them, right?

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This is what they found out
during that month of

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experimentation,
and they came up with a theory

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that revolutionized organic
chemistry,

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as of that time and for the
next twenty years.

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So what did they notice?

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Claire?

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Student: They noticed
the carbon chains.

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Prof: Pardon me?

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Student: The carbon
chains.

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Prof: Well how would you
know it's a chain?

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The numbers don't tell you it's
a chain.

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What?

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Student: The presence of
the hydrocarbons.

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Prof: Well it's,
it's got hydrogen and carbon in

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it.

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That's true.

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But they also have oxygen and
nitrogen, chlorine and other

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things.

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What could you make out of this?

03:56.550 --> 03:59.050
Brian?

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Student: C_7H_5.

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Prof: Yeah.

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All of them have at least
C_7H_5.

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Some of them have more hydrogen
than that, but nothing has less

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than C_7 or less than H_5.

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Can anybody carry that any
further?

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Student: C_7H_5 is
non-reactive.

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Prof: Pardon me?

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Student: It's non -- the
C_7H_5 is the unreactive part.

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Prof: Yeah.

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What would they have called it;
the thing that you have it

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there and then it reacts and
gives this, that,

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or the other thing?

04:31.430 --> 04:33.010
What did Lavoisier call it?

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Student:  The radical.

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Prof: The base,
or the radical.

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But actually the radical is
more than C_7H_5,

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the thing that persists.

04:44.949 --> 04:46.549
What else?

04:46.550 --> 04:48.730
Prof: O.

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So C_7H_5O persists through all
these transformations.

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So it looks like that's some
sort of a core that gets

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modified.

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Okay?

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But it's there all the time.

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It's like a radical. Right?

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So it was called the benzoyl
radical.

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They thought up that name at
that time, and the idea of using

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the suffix -yl,
to denote a radical.

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So if you denote the benzoyl
radical by Bz --

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you see that you started,
the oil of bitter almonds is

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BzH,
and then the acid is BzOH,

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and the acid chloride is BzCl
and Br and I and NH_2 and two

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Bz's,
together with S, at the end.

05:40.529 --> 05:42.119
Okay?

05:42.120 --> 05:46.130
So a radical can be the base of
more than just an acid.

05:46.125 --> 05:46.715
Right?

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Lavoisier had the idea that you
react it with oxygen and you get

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an acid.

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But here you can react it with
all sorts of different things

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and get different compounds.

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But the base is still there,
the benzoyl radical.

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So this gave rise to the idea
of organic dualism.

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Remember, we had this dualism
last time.

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There were positive things and
negative things and they could

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associate and trade partners.

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But maybe the difference in
organic chemistry is that you

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have radicals,
things that are plus or minus,

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but they're more complicated
than just single atoms.

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There are combinations of
elements that function in

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organic chemistry;
and that's what makes it

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different from inorganic,
according to this theory.

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So then the idea is to find all
these organic radicals,

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that make organic chemistry
special.

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So during the 1830s these
compound radicals were

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discovered everywhere.

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For example,
in Germany, Liebig found

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acetyl.

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And Bunsen, in Heidelberg,
found cacodyl;

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which is named because it
smells so awful.

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Right?

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Or Berzelius in Sweden found
ethyl.

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Or Piria in Italy got salicyl.

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And Dumas got a whole bunch of
them, in Paris:

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methyl, cinnamyl,
cetyl, ethylene.

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All these radicals were
discovered.

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So the thought was this is the
way to organize organic

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chemistry.

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And that theory,
the dualism applied to organic

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theory, the radical theory,
survives today in our

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nomenclature.

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Right?

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So, for example,
we talk about ethyl chloride.

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That's not one word,
it's two words,

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with a space.

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Right?

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And the reason is it's
dualistic.

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It's a positive ethyl and a
minus chlorine.

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Right?

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So it's two things that have
come together.

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thought up,
comes from a Greek word,

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So it's the substance of stuff.

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Okay, so now ether was
something that had been known

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for a long time,
and it came from a Greek root

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which means to shine.

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So in the 1700s it was -- so it
had been applied to the sky.

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It was transferred from the
idea of shining,

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to the idea of the clear sky,
and from that to a colorless

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liquid.

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So when they distilled
something out of alcohol that

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had been treated with acid,
and they got this clear stuff

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that was clear as the sky,
they called it ether. Right?

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Which we call diethyl ether
nowadays.

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So that's where
"ether"

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came from.

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So hence eth-yl was the
matter that appears in ether.

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So it was like two benzoyl
radicals with sulfur.

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Right?

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You can have two ethyl radicals
with oxygen.

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Right?

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And that was then eth-yl
-- right?

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-- the material of ether.

08:50.419 --> 08:51.009
Okay?

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How about methyl?

08:52.000 --> 08:56.370
Well meth comes from the
Greek word meaning wine or

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spirit.

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Right?

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And the -yl,
that same root,

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but a different meaning this
time.

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Remember, it can mean matter --
that was the one before -- or it

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can mean wood,
and in this case it means wood.

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So what does it mean,
meth-yl,

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if the -yl means not the
substance of but means wood?

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Student: From wood.

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Prof: Pardon me?

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Student:  From wood.

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Prof: From wood.

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What from wood?

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Student:  Wine.

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Prof: The spirits,
from wood.

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So you've heard methanol called
wood alcohol -- right?

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-- because you get it from
distilling it.

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But the first word was
methylene, and ene is the

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Greek feminine patronymic;
it means "the daughter

09:40.030 --> 09:40.450
of."

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And ene,
ine, one,

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all of those are like that;
like Persephone,

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or Antigone means the "one
who goes against her

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parents,"
and so on.

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So ene was the Greek --
so what did meth-yl-ene mean?

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It meant the daughter of wood
spirits.

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So the theory was that wood
spirits, that is,

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wood alcohol,
was a combination of methylene

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plus water.

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So methylene thus,
if wood alcohol is CH_3OH,

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then methylene was
CH_2_; which then you

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add water and you get wood
alcohol.

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So that's where the name
methylene came from.

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Right?

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So then in 1840 -- that was
1835, so five years later --

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they decided that they needed
the radical CH_3.

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So they named it methyl,
from methylene.

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Right?

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And then ethylene came;
that name came in 1852,

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because it was related to
ethyl, which had already been

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named, the same way that
methylene was related to methyl.

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Okay?

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So that's where these names
came from.

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They all have their root in the
radical theory.

10:59.769 --> 11:02.589
Now, that's C_1 and C_2,
methyl and ethyl.

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How about C_3 and C_4,
do you know what they're named?

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Roots?

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How about C_3,
do you know what C _3 alcohol

11:10.985 --> 11:11.275
is?

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Students:  Propyl.

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Prof: Propyl.

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And C_4?

11:13.580 --> 11:14.520
Students:  Butyl.

11:14.519 --> 11:15.329
Prof: Butyl.

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So where do those names come
from?

11:16.820 --> 11:20.970
Okay, C_3H_7_ is
propyl, and by the same

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reasoning as before,
C_3H_6 is propylene;

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or propene, sometimes it
shortened.

11:27.559 --> 11:27.999
Okay?

11:28.000 --> 11:31.920
And butyl and butylene,
or butene.

11:31.918 --> 11:36.268
Okay, now butylene comes -- the
C_4 acid is butyric acid,

11:36.269 --> 11:40.619
which had already been named,
because it's the stuff that

11:40.619 --> 11:43.259
makes rancid butter smell bad.

11:43.259 --> 11:43.379
Okay?

11:43.379 --> 11:46.629
So people worked it up and
found butyric acid;

11:46.629 --> 11:48.889
so that's where butyl comes
from.

11:48.889 --> 11:49.829
But how about propyl?

11:49.830 --> 11:53.100
It has a very much more
interesting origin.

11:53.100 --> 11:57.930
Okay, so protos means
first, and pion means

11:57.932 --> 11:58.452
fat.

11:58.450 --> 12:02.660
So propion was the first fat.

12:02.659 --> 12:03.819
In what sense?

12:03.820 --> 12:06.880
Well these carboxylic acids
came from fats,

12:06.876 --> 12:07.456
right?

12:07.460 --> 12:09.510
And they were called fatty
acids.

12:09.509 --> 12:12.849
And they behaved like fats,
they dissolved in organic

12:12.851 --> 12:13.431
solvents.

12:13.431 --> 12:14.011
Right?

12:14.009 --> 12:17.359
But the very -- the ones with
the fewest number of carbons,

12:17.360 --> 12:20.890
with just one carbon -- that's
formic acid that you get by

12:20.889 --> 12:23.119
destructive distillation of
ants,

12:23.120 --> 12:27.400
or acetic acid,
from vinegar -- those are

12:27.397 --> 12:29.747
miscible with water.

12:29.750 --> 12:33.720
But the C_3 is the first one
that's not freely miscible with

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water;
it behaves more like a fat.

12:36.164 --> 12:36.664
Right?

12:36.658 --> 12:41.718
So the first fatty acid is
propionic acid.

12:41.720 --> 12:45.950
So propyl, propylene are the
C_3s.

12:45.950 --> 12:51.810
Okay, after that you get into
numbers, the roots for numbers.

12:58.316 --> 13:04.346
Gay-Lussac as the spokesman for
French chemistry.

13:04.350 --> 13:07.220
You see, he was born on the
14th of July,

13:07.221 --> 13:11.171
a reasonable date for somebody
to lead French chemistry,

13:11.168 --> 13:12.028
in 1800.

13:12.028 --> 13:15.838
So for eighty-four years --
well, for part of eighty-four

13:15.835 --> 13:19.025
years, he was the leader of
French chemistry.

13:19.028 --> 13:22.508
There he is with some
decoration on him.

13:22.509 --> 13:23.319
I'm not sure what it is.

13:23.320 --> 13:26.290
I'd like to find out.

13:26.288 --> 13:31.348
So he was the Post-Napoleonic
guardian of the French tradition

13:31.346 --> 13:32.586
of chemistry.

13:32.590 --> 13:38.210
The French had what most people
regard as a terrible system,

13:38.210 --> 13:43.260
which is they had chairs,
you know, for professors.

13:43.259 --> 13:45.639
But you could have more than
one chair.

13:45.639 --> 13:48.749
So a single individual could
tie up three different

13:48.753 --> 13:51.403
appointments,
and you didn't have as many

13:51.395 --> 13:54.565
people able to exercise their
ingenuity in developing

13:54.567 --> 13:55.357
chemistry.

13:55.360 --> 13:58.480
So he had the chair at the
Sorbonne;

14:02.788 --> 14:07.288
And he was a persistent
opponent of Liebig and

14:07.288 --> 14:08.488
Berzelius.

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But in 1837,
after this radical stuff got

14:11.586 --> 14:13.656
going --
and he had discovered four

14:13.658 --> 14:16.968
radicals himself,
of which he was quite pleased

14:16.971 --> 14:21.691
-- he and Liebig happened to
meet during a speaking tour in

14:21.692 --> 14:24.282
England,
and they got in conversation,

14:24.278 --> 14:26.928
and Dumas decided,
on the basis of that meeting --

14:26.933 --> 14:29.303
though not Liebig --
that they were now great

14:29.304 --> 14:31.904
friends and could collaborate
from here on in.

14:31.899 --> 14:34.959
So he wrote this long thing,
in flowery French,

14:34.964 --> 14:38.434
in 1837, "A Note on the
Present State of Organic

14:38.427 --> 14:39.757
Chemistry."

14:39.759 --> 14:43.079
So this is five years after the
Radical Theory began.

14:43.080 --> 14:46.300
He said: "Sixty years have
hardly passed since the ever

14:46.303 --> 14:48.653
memorable time when this same
assembly"

14:48.652 --> 14:52.112
--
he was speaking to the Paris

14:52.110 --> 14:54.540
Academy --
"heard the first

14:54.541 --> 14:57.741
discussions of the fertile
chemical doctrine which we owe

14:57.744 --> 14:59.464
to the genius of Lavoisier.

14:59.460 --> 15:03.710
This short span of time has
sufficed to examine fully the

15:03.706 --> 15:07.496
most delicate questions of
inorganic chemistry,

15:07.500 --> 15:11.090
and anyone can easily convince
himself that this branch of our

15:11.087 --> 15:14.437
knowledge possesses almost
everything that it can with the

15:14.440 --> 15:16.970
methods of observation
available."

15:16.970 --> 15:20.800
So check off inorganic
chemistry, we've got that now.

15:20.799 --> 15:21.499
Okay?

15:21.500 --> 15:25.950
"There barely remain a few
cracks here and there to fill

15:25.952 --> 15:26.772
in."

15:26.769 --> 15:32.129
So this is the persistent
myopia of leaders of science.

15:32.129 --> 15:35.799
As I mentioned before,
when we were speaking of

15:35.804 --> 15:39.644
Lavoisier, this certainly
persists 'til today.

15:39.639 --> 15:43.209
So Dumas goes on:
"In a word,

15:43.210 --> 15:46.070
how with the help of the laws
of inorganic chemistry can"

15:46.072 --> 15:47.002
--
incidentally,

15:46.998 --> 15:49.098
this is all one sentence,
of course.

15:49.100 --> 15:50.660
This is "in a word",
right?

15:50.658 --> 15:53.378
So he really liked speaking,
right?;

15:53.379 --> 15:55.129
flowery language.

15:55.129 --> 15:58.569
"How with the help of the
laws of inorganic chemistry can

15:58.565 --> 16:01.995
one explain and classify such
varied substances as one obtains

16:02.000 --> 16:04.900
from organic bodies,
and which nearly always are

16:04.897 --> 16:07.327
formed only of carbon,
hydrogen, and oxygen,

16:07.326 --> 16:10.166
to which elements nitrogen is
sometimes joined?"

16:10.168 --> 16:14.228
So if it's all in the analysis
of what atoms are there,

16:14.231 --> 16:17.321
how can you have so many
different things?

16:17.317 --> 16:18.067
Right?

16:18.070 --> 16:22.150
"This was the great and
beautiful question of natural

16:22.148 --> 16:24.918
philosophy,
a question well designed to

16:24.917 --> 16:27.857
excite the highest degree of
competition among

16:27.860 --> 16:29.040
chemists."

16:29.039 --> 16:33.379
Name two, right?

16:33.379 --> 16:36.069
"For once resolved the
most beautiful triumphs were

16:36.065 --> 16:37.135
promised to science.

16:37.139 --> 16:39.959
The mysteries of plants,
the mysteries of animal life

16:39.964 --> 16:41.924
would be unveiled before our
eyes;

16:41.918 --> 16:45.088
we would seize the key to all
the changes of matter,

16:45.086 --> 16:47.066
so sudden, so swift,
so singular,

16:47.072 --> 16:49.372
that occur in animals and
plants;

16:49.370 --> 16:53.540
more importantly we would find
means of duplicating them in our

16:53.544 --> 16:54.964
laboratories."

16:54.960 --> 16:58.040
(This would make a good
research proposal,

16:58.043 --> 16:58.723
right?)

16:58.720 --> 17:01.270
"Well, we are not afraid
to say it,

17:01.269 --> 17:04.559
and it is not an assertion
which we make lightly:

17:04.558 --> 17:08.258
this great and beautiful
question is today answered;

17:08.259 --> 17:11.669
it only remains to follow
through on all the consequences

17:11.672 --> 17:13.442
which the solution entails.

17:13.440 --> 17:16.930
In fact to produce with three
or four elements such varied

17:16.930 --> 17:19.440
combinations,
more varied perhaps than those

17:19.438 --> 17:21.678
which make up the whole
inorganic kingdom,

17:21.680 --> 17:25.700
nature has chosen a path as
simple as it was unexpected;

17:25.700 --> 17:29.900
for with elements she has made
compounds which behave in all

17:29.904 --> 17:33.474
their properties like elements
themselves."

17:33.470 --> 17:35.400
(That is, radicals -- right?

17:35.400 --> 17:37.430
-- that persist through these
reactions.)

17:37.430 --> 17:40.840
"And this,
we are convinced,

17:40.836 --> 17:46.156
is the entire secret of organic
chemistry."

17:46.160 --> 17:47.820
Great and beautiful questions
to answer.

17:47.818 --> 17:51.258
It only remains to follow
through the consequences;

17:51.259 --> 17:52.849
compounds which behave like
elements.

17:52.848 --> 17:56.208
"Thus organic chemistry
possesses in its own elements,

17:56.210 --> 17:59.290
which sometimes play the role
of chlorine or oxygen"

17:59.288 --> 18:01.028
--
what does he mean,

18:01.029 --> 18:04.239
play the role of chlorine and
oxygen?

18:04.240 --> 18:07.410
How come radicals sometimes
play the role of chlorine and

18:07.410 --> 18:07.920
oxygen?

18:07.920 --> 18:09.610
What would that role be?

18:09.608 --> 18:11.268
Student:
>

18:11.269 --> 18:12.199
Prof: Pardon me?

18:12.200 --> 18:13.510
Student: Oxidation.

18:13.509 --> 18:16.819
Prof: No.

18:16.818 --> 18:22.788
What roles do things play in
this theory that he's using?

18:22.789 --> 18:24.149
Lucas?

18:24.150 --> 18:24.630
Student:  Plus and minus.

18:24.630 --> 18:25.760
Prof: Plus and minus.

18:25.759 --> 18:27.589
So sometimes they're like
chlorine or oxygen.

18:27.589 --> 18:28.739
What does that mean?

18:28.740 --> 18:29.710
Students:  Negative.

18:29.710 --> 18:32.110
Prof: Sometimes they're
negative, right?

18:32.108 --> 18:33.888
"And sometimes,
on the contrary,

18:33.890 --> 18:35.720
they play the role of
metals."

18:35.720 --> 18:37.220
Sometimes they're positive.

18:37.220 --> 18:41.150
"Cyanogen, amide, benzoyl,
the radicals of ammonia,

18:41.150 --> 18:43.710
of aliphatics,
of alcohol, and analogous

18:43.711 --> 18:46.081
substances,
these are the true elements

18:46.077 --> 18:48.427
with which organic chemistry
operates.

18:48.430 --> 18:51.230
To discover these radicals,
to study them,

18:51.231 --> 18:54.581
to characterize them,
has been our daily study for

18:54.582 --> 18:55.952
ten years."

18:55.950 --> 18:56.510
(Okay?

18:56.507 --> 18:59.847
So they're plus and they're
minus.)

18:59.849 --> 19:04.189
"Sometimes, none the less,
our opinions have appeared to

19:04.188 --> 19:06.478
differ,
and then, with each of us drawn

19:06.483 --> 19:08.463
on by the heat of our battle
with nature,

19:08.460 --> 19:11.850
there arose between us
discussions whose liveliness we

19:11.845 --> 19:12.735
both regret.

19:12.740 --> 19:15.850
Actually when we were able to
discuss questions which

19:15.854 --> 19:18.554
separated us in several friendly
meetings,

19:18.548 --> 19:20.848
we soon realized that we were
in agreement on the

19:20.852 --> 19:21.862
principles….

19:21.858 --> 19:25.738
We then understood that united
we could undertake a task before

19:25.740 --> 19:29.620
which either of us in isolation
would have recoiled….

19:29.618 --> 19:32.828
We will analyze every organic
substance...

19:32.828 --> 19:36.368
to establish reliably what sort
of radical it refers

19:36.369 --> 19:37.689
to…."

19:37.690 --> 19:39.790
So that is what everybody
should do.

19:39.788 --> 19:41.988
Then you'll know all about
organic chemistry.

19:41.990 --> 19:45.430
"Each of us has,
in fact, opened his laboratory

19:45.429 --> 19:48.799
to all young men who were
motivated by true love of

19:48.799 --> 19:50.549
science;
they have seen all,

19:50.548 --> 19:51.338
understood all.

19:51.338 --> 19:54.878
We have worked under their
eyes, and have had them work

19:54.881 --> 19:57.361
under ours,
in such a way that we are

19:57.364 --> 20:00.634
surrounded by young rivals,
who are the hope of science,

20:00.634 --> 20:03.754
and whose work will be added to
ours and mingle with ours,

20:03.750 --> 20:07.750
for it will have been conceived
in the same spirit and carried

20:07.748 --> 20:09.648
out by the same method."

20:09.650 --> 20:10.240
Right?

20:10.240 --> 20:14.420
So if everybody does what we
say they should do,

20:14.424 --> 20:15.944
then we got it.

20:15.940 --> 20:17.060
Okay?

20:17.058 --> 20:20.768
"This is not an effort
conceived for personal gain or

20:20.765 --> 20:23.425
in the interest of narrow
vanity."

20:23.430 --> 20:25.570
Far be it from us.

20:25.568 --> 20:28.068
"No, and in a
collaboration which is perhaps

20:28.073 --> 20:30.163
unheard of in the history of
science,

20:30.160 --> 20:33.480
this is an undertaking in which
we hope to interest every

20:33.484 --> 20:35.034
chemist in Europe."

20:35.029 --> 20:37.139
So everyone should work on this.

20:37.140 --> 20:40.340
So we'll go to the funding
agencies and tell them this is

20:40.336 --> 20:42.846
the only kind of research you
should fund;

20:42.848 --> 20:44.698
forget these other guys out
there.

20:44.700 --> 20:47.980
This is true love of
science, right?

20:47.980 --> 20:50.970
And conceived in the same
spirit and carried out by the

20:50.969 --> 20:51.799
same methods.

20:51.798 --> 20:56.038
So this is megalomania,
and doesn't show much

20:56.039 --> 20:57.389
imagination.

20:57.390 --> 21:01.380
Now, but there was a problem
with dualism.

21:01.380 --> 21:03.530
So, for example,
suppose you have benzoyl

21:03.526 --> 21:06.486
chloride,
which remember was by reacting

21:06.489 --> 21:10.199
benzaldehyde or benzoyl hydride
with chlorine,

21:10.200 --> 21:14.480
and you get benzoyl chloride
and HCl as the other product.

21:14.480 --> 21:17.990
Now HCl is quite clear,
it's H+ and Cl-.

21:17.990 --> 21:19.950
What's benzoyl chloride?

21:19.950 --> 21:23.230
It's obviously benzoyl+ and Cl-.

21:23.230 --> 21:27.490
And what problem does that
create?

21:27.490 --> 21:29.200
What, Russell?

21:29.200 --> 21:30.800
Student: The benzoyl is
minus before,

21:30.799 --> 21:31.959
but hydrogen --
Prof: Ah ha.

21:31.960 --> 21:35.140
But how do you get benzoyl
hydride, plus,

21:35.144 --> 21:35.544
plus?

21:35.542 --> 21:36.262
Right?

21:36.259 --> 21:37.649
So there's something weird
going on.

21:37.650 --> 21:40.000
So this is a problem.

21:40.000 --> 21:44.300
In the 1840s and 1850s,
the French discovered a

21:44.297 --> 21:46.867
competing theory --
or invented,

21:46.872 --> 21:49.782
I should say -- a competing
theory called the substitution

21:49.779 --> 21:51.579
theory,
or the type theory,

21:51.577 --> 21:55.317
or the unitary theory,
as opposed to the dualistic

21:55.315 --> 21:57.805
theory,
the plus, minus idea.

21:57.808 --> 22:00.868
So these began to compete with
one another.

22:00.868 --> 22:05.288
And it started at a ball in the
Tuileries Palace in 1830.

22:05.288 --> 22:09.408
This picture is from 40 years
later, or 37 years later.

22:09.410 --> 22:12.230
But what happened is they got
the ball started,

22:12.230 --> 22:14.060
all the people came dressed up
fancy,

22:14.058 --> 22:17.598
and they began to cough and
choke because the room was

22:17.598 --> 22:19.668
filled with some noxious gas.

22:19.670 --> 22:22.800
And when they discovered it
came from the candles,

22:22.801 --> 22:25.041
they asked Dumas to look into
it.

22:25.038 --> 22:29.418
And he identified the culprit
as HCl, because it turned out

22:29.417 --> 22:32.057
that the candles were very
white.

22:32.058 --> 22:35.768
The wax had been bleached with
chlorine, and when they were

22:35.770 --> 22:37.500
burned HCl was given off.

22:37.500 --> 22:43.110
So the question is,
what is it that holds chlorine?

22:43.108 --> 22:46.088
How did this fat,
in the candles,

22:46.094 --> 22:48.524
fix chlorine gas?

22:48.519 --> 22:50.559
Well you're in a position to
understand that now.

22:50.559 --> 22:54.709
We can think about mechanisms;
in fact, two ways that the

22:54.708 --> 22:57.818
hydrocarbon could fix chlorine.

22:57.818 --> 23:01.598
Now, suppose we try -- there's
chlorine that is being used to

23:01.602 --> 23:02.802
bleach the stuff.

23:02.798 --> 23:05.608
Let's try for a HUMO/LUMO
approach.

23:05.609 --> 23:07.479
What makes chlorine reactive?

23:07.480 --> 23:11.040


23:11.039 --> 23:12.479
High HOMO or low LUMO?

23:12.480 --> 23:15.340
What's unusual about chlorine?

23:15.339 --> 23:19.909
Student:  Low LUMO.

23:19.910 --> 23:20.880
Prof: Pardon me?

23:20.880 --> 23:21.390
Student:  Low LUMO.

23:21.390 --> 23:23.950
Prof: Why do you say so
Claire?

23:23.950 --> 23:26.530
What is the low LUMO?

23:26.528 --> 23:28.728
Student:  It's the Cl-Cl
bond.

23:28.730 --> 23:31.140
Prof: Right,
the σ* of Cl-Cl,

23:31.138 --> 23:34.048
which is low because chlorine
has a high nuclear charge.

23:34.048 --> 23:38.598
Okay, now we need a HOMO to
react with it.

23:38.598 --> 23:41.968
Now, one of the more
interesting hydrocarbons,

23:41.971 --> 23:45.041
in this regard,
is one that had been known

23:45.042 --> 23:49.092
already, for fourty years,
to react with chlorine.

23:49.088 --> 23:52.538
And it was because of that
reaction it was called the

23:52.540 --> 23:56.130
"olefiant gas",
and was by this time known to

23:56.125 --> 23:56.785
be C_2H_4.

23:56.788 --> 23:57.518
Right?

23:57.519 --> 23:59.759
So we would write it with a
double bond.

23:59.759 --> 24:01.919
"Olefiant",
because ole,

24:01.917 --> 24:03.697
oil, and fiant,
to make;

24:03.700 --> 24:05.630
so it's the stuff that makes
oil.

24:05.634 --> 24:06.124
Right?

24:06.118 --> 24:08.728
And we'll see the reaction that
makes oil here,

24:08.726 --> 24:10.366
its reaction with chlorine.

24:10.368 --> 24:16.348
So what makes the olefiant gas
reactive?

24:16.349 --> 24:17.129
Kevin?

24:17.130 --> 24:19.150
Student:  Poor overlap.

24:19.150 --> 24:21.580
Prof: Right,
so poor overlap makes a high

24:21.577 --> 24:21.937
HOMO.

24:21.940 --> 24:23.820
And remember the name of it?

24:23.819 --> 24:25.919
Student:  π.

24:25.920 --> 24:26.420
Prof: π.

24:26.420 --> 24:29.290
So the π electrons
because of poor overlap are a

24:29.294 --> 24:29.904
high HOMO.

24:29.900 --> 24:32.790
So we can use those electrons
to mix with the low LUMO;

24:32.788 --> 24:36.748
and again, one of these
make-and-break situations.

24:36.750 --> 24:40.400
And chloride leaves and you get
this thing, which has a positive

24:40.397 --> 24:40.917
charge.

24:40.920 --> 24:43.640
Now that thing itself is
reactive.

24:43.640 --> 24:48.360
What do you make -- where is a
low LUMO in this one?

24:48.359 --> 24:49.669
Pardon me?

24:49.670 --> 24:50.930
Student:  On the
positive charge.

24:50.930 --> 24:52.010
Prof: Speak up please.

24:52.009 --> 24:53.209
Student:  On the
positive charge.

24:53.210 --> 24:54.550
Prof: Where the positive
charge is.

24:54.548 --> 24:57.448
There's a vacant orbital on
carbon, an atomic orbital of

24:57.446 --> 24:58.866
carbon that's not shared.

24:58.869 --> 25:00.229
So there's a low LUMO.

25:00.230 --> 25:01.210
Where's a high HOMO?

25:01.210 --> 25:02.980
Have you got that too Virginia?

25:02.980 --> 25:05.790
Student:  On Cl.

25:05.788 --> 25:08.698
Prof: Chlorine has
unshared pairs,

25:08.698 --> 25:09.278
right.

25:09.279 --> 25:10.289
Bingo!

25:10.288 --> 25:12.908
So, in fact,
both those things happen at

25:12.909 --> 25:13.379
once.

25:13.380 --> 25:15.630
It's not that one happens and
then the other.

25:15.630 --> 25:17.080
Both those things happen at
once.

25:17.078 --> 25:19.978
And you can see it by looking
at molecular orbitals.

25:19.980 --> 25:24.180
So there's the HOMO of the
ethylene or olefiant gas,

25:24.183 --> 25:26.743
and the σ* LUMO.

25:26.740 --> 25:27.820
So those things mix.

25:27.818 --> 25:31.258
The blue orbitals overlap and
mix, shift electrons toward the

25:31.260 --> 25:33.640
other one;
the chloride breaks away.

25:33.640 --> 25:38.370
But at the same time the HOMO
of the chlorine mixes with the

25:38.374 --> 25:40.224
LUMO of the ethylene.

25:40.220 --> 25:43.750
So you're making two bonds at
once, two pairs of electrons.

25:43.750 --> 25:47.460
So you make that three-membered
ring, with two new bonds,

25:47.457 --> 25:50.367
and the chloride,
as we said, breaks away.

25:50.368 --> 25:55.968
Okay, so we've got that
substance now.

25:55.970 --> 25:58.580
And now it itself is reactive.

25:58.578 --> 26:01.768
Can you see what would be
reactive about that cation

26:01.770 --> 26:02.710
intermediate?

26:02.710 --> 26:06.130
What are you probably looking
for, a LUMO or a HOMO?

26:06.130 --> 26:06.710
Student:  A LUMO.

26:06.710 --> 26:07.540
Prof: A LUMO.

26:07.538 --> 26:11.418
Angela, do you have an idea of
what could be a LUMO here?

26:11.420 --> 26:13.610
Student:  The chlorine
has a positive charge.

26:13.608 --> 26:15.818
Prof: It's true that the
chlorine has a positive charge.

26:15.818 --> 26:20.448
Does it have a vacant orbital,
an unoccupied molecular

26:20.454 --> 26:21.334
orbital?

26:21.329 --> 26:21.879
Student:  No it doesn't.

26:21.880 --> 26:23.930
Prof: No,
it turns out it's got two

26:23.930 --> 26:24.780
unshared pairs.

26:24.778 --> 26:27.978
So it doesn't have any -- it's
not like the carbon plus was.

26:27.980 --> 26:30.740
But the plus will make orbitals
low in energy.

26:30.740 --> 26:32.620
So what's a vacant orbital of
this thing?

26:32.618 --> 26:33.968
All it's got is σ
bonds.

26:33.970 --> 26:38.970


26:38.970 --> 26:42.040
But what makes -- suppose all
you have in your molecule is

26:42.042 --> 26:44.412
σ bonds,
but you want to have an

26:44.414 --> 26:46.304
unusually low energy vacant
orbital.

26:46.301 --> 26:46.951
Right?

26:46.950 --> 26:48.300
The plus charge will help.

26:48.299 --> 26:50.799
But what orbital will you have?

26:50.798 --> 26:51.618
Student:
σ*.

26:51.619 --> 26:52.289
Prof: σ*.

26:52.289 --> 26:53.339
Now you got two choices.

26:53.338 --> 26:56.308
You got carbon-carbon or
carbon-chlorine.

26:56.308 --> 26:58.738
Which one's more likely to be
low energy?

26:58.740 --> 26:59.860
Student:
Carbon-chlorine.

26:59.859 --> 27:00.839
Prof: Why?

27:00.838 --> 27:02.928
Student:  Because the
chlorine --

27:02.930 --> 27:04.710
Prof: Say it --
Student:  Chlorine has a

27:04.710 --> 27:05.690
high effective nuclear charge.

27:05.690 --> 27:07.360
Prof: Right,
chlorine has a high nuclear

27:07.362 --> 27:07.692
charge.

27:07.690 --> 27:09.530
So a σ*
carbon-chlorine,

27:09.526 --> 27:11.766
would it be big on carbon or
big on chlorine,

27:11.770 --> 27:12.180
Sam?

27:12.180 --> 27:13.550
Student:  Big on carbon.

27:13.548 --> 27:16.038
Prof: Big on carbon,
because the bonding orbital was

27:16.037 --> 27:16.717
big on chlorine.

27:16.722 --> 27:17.112
Right?

27:17.108 --> 27:18.868
This is the kind of stuff we're
talking about.

27:18.869 --> 27:20.339
So σ*.

27:20.339 --> 27:22.149
And there it is.

27:22.150 --> 27:25.120
Okay, there's a localized
σ*.

27:25.119 --> 27:29.319
Big on carbon, the black one;
small on chlorine;

27:29.319 --> 27:30.689
and antibonding between them.

27:30.690 --> 27:32.690
Now what are you going to --
there's the low LUMO.

27:32.690 --> 27:36.870
What do you have for a high
HOMO, to react with it?

27:36.868 --> 27:44.558
You have to think back to
what's been happening.

27:44.559 --> 27:45.359
Sherwin?

27:45.358 --> 27:46.368
Student:  The chlorine
one.

27:46.368 --> 27:48.808
Prof: The chloride that
you had at the beginning,

27:48.810 --> 27:50.320
that you lost in the first
step.

27:50.319 --> 27:52.109
Okay, so we bring it over here.

27:52.109 --> 27:53.349
So it'll have good overlap.

27:53.349 --> 27:56.189
It comes up, makes a new bond;
that make and break.

27:56.190 --> 27:57.020
And you get that.

27:57.019 --> 28:01.859
And that was the reaction in
1795 that resulted in ethylene

28:01.858 --> 28:04.528
being called the olefiant gas.

28:04.528 --> 28:07.418
Because this is the oil that
was made, by reacting it with

28:07.421 --> 28:07.981
chlorine.

28:07.980 --> 28:10.860
So that was already a very old
reaction at this time;

28:10.858 --> 28:13.388
the "oil of Dutch
chemists",

28:13.387 --> 28:17.417
because it was four Dutch
chemists who reported that oil.

28:17.420 --> 28:21.370
Okay, so there's one way that
you can fix chlorine,

28:21.365 --> 28:24.595
make it part of a hydrocarbon
molecule.

28:24.599 --> 28:26.249
It's addition to an alkene.

28:26.250 --> 28:28.900
So if the hydrocarbons are
unsaturated, if they have some

28:28.902 --> 28:30.612
double-bonds,
then they'll react with

28:30.606 --> 28:32.166
chlorine to fix the chlorine.

28:32.170 --> 28:33.870
So that's one possibility.

28:33.868 --> 28:35.858
But how about if you don't have
a double bond?

28:35.859 --> 28:37.379
How about if you have methane?

28:37.380 --> 28:46.400
What's the problem now,
in doing an analogous reaction?

28:46.400 --> 28:47.030
Sherwin?

28:47.029 --> 28:48.359
Student:  You don't have
the π in there.

28:48.359 --> 28:49.039
Prof: Pardon me?

28:49.038 --> 28:49.948
Student:  We don't have
the π in there.

28:49.950 --> 28:50.810
Prof: You don't have a
π.

28:50.809 --> 28:53.759
You don't have a low LUMO.

28:53.759 --> 28:55.729
So you can't do a HOMO/LUMO
reaction.

28:55.730 --> 28:56.170
Right?

28:56.170 --> 28:58.960
These are our model,
saturated alkanes,

28:58.961 --> 29:02.191
like methane,
our model of things that aren't

29:02.193 --> 29:04.843
unusually high or unusually low.

29:04.838 --> 29:07.178
So you have to have another
trick.

29:07.180 --> 29:11.520
And here's the trick;
that the chlorine-chlorine bond

29:11.517 --> 29:12.117
is weak.

29:12.118 --> 29:15.008
It's only 58 kilocalories per
mole.

29:15.009 --> 29:19.139
And one of the reasons for that
is that the chlorine has so many

29:19.144 --> 29:20.264
unshared pairs.

29:20.259 --> 29:22.969
So you mix -- if you were
trying to form a π

29:22.971 --> 29:25.481
orbital in chlorine,
you have two electrons in the

29:25.479 --> 29:27.819
p orbital here,
two electrons in the p

29:27.819 --> 29:28.419
orbital here.

29:28.420 --> 29:29.250
They overlap.

29:29.250 --> 29:34.730
Is that going to be bonding,
if you mix these two orbitals?

29:34.730 --> 29:35.640
You'll obviously mix them.

29:35.640 --> 29:38.810
When you mix two orbitals you
get a lower one and a higher

29:38.806 --> 29:39.136
one.

29:39.140 --> 29:41.850
Will it be bonding?

29:41.848 --> 29:46.118
This one will be bonding but
this one is anti-bonding.

29:46.119 --> 29:48.149
Everybody with me on this?

29:48.150 --> 29:50.200
Now, so Kate,
what would you say?

29:50.200 --> 29:54.950
Is it going to be net favorable
or unfavorable?

29:54.950 --> 29:59.440
Two electrons went down in
energy, two electrons went up in

29:59.442 --> 30:00.142
energy.

30:00.140 --> 30:02.600
But the ones that went up,
went up a little more than the

30:02.602 --> 30:03.352
down went down.

30:03.349 --> 30:04.739
So that's unfavorable.

30:04.740 --> 30:09.540
So having so many unshared
pairs weakens the single bond.

30:09.539 --> 30:11.719
So chlorine has a weak bond.

30:11.720 --> 30:15.490
Now still it's worth 58
kilocalories per mole,

30:15.487 --> 30:17.577
which is plenty strong.

30:17.579 --> 30:19.689
It doesn't just break.

30:19.690 --> 30:21.980
You got to do something to help
it to break.

30:21.980 --> 30:25.670
And what you can do is -- I've
made it in this weird color,

30:25.666 --> 30:27.126
which is hard to see.

30:27.130 --> 30:29.910
Why?

30:29.910 --> 30:32.030
Anybody know?

30:32.028 --> 30:32.978
Student:  The color of
chlorine.

30:32.980 --> 30:33.610
Prof: Pardon me?

30:33.608 --> 30:34.508
Student:  It's the color
of chlorine.

30:34.509 --> 30:36.529
Prof: That's the color
of chlorine.

30:36.529 --> 30:38.869
It absorbs visible light.

30:38.868 --> 30:42.948
Now how does it take on energy,
when it absorbs visible light?

30:42.950 --> 30:45.090
Where does the energy go,
in the molecule?

30:45.089 --> 30:47.419
Does anybody know?

30:47.420 --> 30:48.430
Dana?

30:48.430 --> 30:48.970
Student: Electrons are
promoted.

30:48.970 --> 30:49.630
Prof: Can't hear very
well.

30:49.630 --> 30:51.060
Student:  Electrons get
promoted to higher --

30:51.058 --> 30:54.598
Prof: Electrons go from
orbitals to higher orbitals.

30:54.598 --> 30:56.988
So you can put -- and the next
higher orbital is

30:56.992 --> 30:57.912
σ*.

30:57.910 --> 31:00.900
And what happens if you take an
electron and put it in

31:00.903 --> 31:01.923
σ*?

31:01.920 --> 31:06.120


31:06.119 --> 31:09.639
It breaks the bond. Right?

31:09.640 --> 31:12.260
That's what happened up at the
top, when the chlorine broke,

31:12.263 --> 31:12.623
right?

31:12.618 --> 31:15.848
You put electrons into
σ*.

31:15.848 --> 31:18.598
So you can do it with light,
as well as with some HOMO

31:18.596 --> 31:19.216
attacking.

31:19.220 --> 31:24.240
Okay, so we have -- in fact,
I said LUMO when I was talking

31:24.238 --> 31:27.438
about ethylene;
I meant HOMO up above,

31:27.442 --> 31:30.672
I think, some three or four
minutes ago.

31:30.670 --> 31:32.360
Okay, so the bond breaks.

31:32.359 --> 31:35.109
But it doesn't break into ions.

31:35.108 --> 31:39.538
It breaks one electron going
each way, because that's easier.

31:39.539 --> 31:40.079
Okay?

31:40.078 --> 31:45.178
And notice that we draw curved
arrows for that too,

31:45.180 --> 31:48.330
but you draw arrows with a
single barb rather than a double

31:48.326 --> 31:50.226
barb,
when it's just one electron

31:50.233 --> 31:53.403
rather than a pair of electrons
that's executing the motion

31:53.403 --> 31:54.663
we're talking about.

31:54.660 --> 31:57.580
Okay, so now we have two
chlorine atoms.

31:57.578 --> 32:01.268
And now we can do the trick
with the chlorine atom,

32:01.273 --> 32:05.193
because we have this SOMO,
and it can mix with the C-H

32:05.190 --> 32:09.170
bond to make a new bond;
that is, one electron in the

32:09.173 --> 32:11.093
C-H bond now goes each way.

32:11.088 --> 32:14.118
One goes to complete the pair,
to make HCl,

32:14.115 --> 32:16.635
and the other one is left on
carbon.

32:16.638 --> 32:17.358
Right?

32:17.358 --> 32:19.878
So it's very much like the
reaction above,

32:19.884 --> 32:23.644
but it's single electrons that
are doing the moving instead of

32:23.640 --> 32:24.810
electron pairs.

32:24.808 --> 32:28.768
And the nice thing about this
is you still have a radical.

32:28.769 --> 32:29.819
It must be so.

32:29.818 --> 32:33.158
If you start with something
with an odd number of electrons,

32:33.160 --> 32:35.250
and react it with something
with an even number of

32:35.246 --> 32:36.646
electrons,
you must be left,

32:36.652 --> 32:38.812
at the end, with an odd number
of electrons.

32:38.807 --> 32:39.257
Right?

32:39.259 --> 32:43.049
So CH_3 is such a radical,
and it can react with

32:43.054 --> 32:47.494
something, to break another
bond, and it reacts with the

32:47.493 --> 32:49.273
weakest bond,
chlorine.

32:49.270 --> 32:50.240
Right?

32:50.240 --> 32:54.610
So now you have methyl chloride
-- you've incorporated chlorine

32:54.613 --> 32:58.143
into the alkane -- and you have
a chlorine atom.

32:58.140 --> 33:01.800
Why is it neat,
that you have a chlorine atom?

33:01.799 --> 33:04.269
What's great about that?

33:04.269 --> 33:04.939
Student:
>

33:04.940 --> 33:06.440
Prof: Dana,
what did you say?

33:06.440 --> 33:07.220
Student:  That was what
you started with.

33:07.220 --> 33:09.390
Prof: That's what you
needed at the beginning.

33:09.390 --> 33:11.740
That's why you used light,
in order to get that.

33:11.740 --> 33:14.200
But you don't need any more
light now.

33:14.198 --> 33:14.728
Right?

33:14.730 --> 33:16.720
That can go back and start over
again.

33:16.720 --> 33:18.210
So it's a "chain"
reaction.

33:18.210 --> 33:22.330
It's called a free-radical
chain reaction.

33:22.328 --> 33:25.778
And so you can get lots of
products from just one initial

33:25.779 --> 33:28.799
photon of light,
that started this chain along.

33:28.798 --> 33:30.888
So these are two completely
different ways.

33:30.890 --> 33:33.050
The first, the top is an
"addition"

33:33.053 --> 33:35.783
of chlorine to an alkene,
and the bottom is called

33:35.778 --> 33:37.798
free-radical
"substitution"

33:37.799 --> 33:40.599
of chlorine for hydrogen,
and involves SOMOs,

33:40.596 --> 33:42.376
rather than HOMOs and LUMOs.

33:42.380 --> 33:43.280
Chris?

33:43.279 --> 33:47.079
Student:  If you have a
second chlorine radical from the

33:47.077 --> 33:49.317
first breaking…
Prof: Yeah.

33:49.318 --> 33:52.858
Student:  …why
does it break a second chlorine

33:52.858 --> 33:55.438
molecule, rather than using the
other --

33:55.440 --> 33:58.790
Prof: Because they have
to find one another.

33:58.792 --> 33:59.332
Right?

33:59.328 --> 34:02.598
They've gone off -- it'll take
forever before they by chance

34:02.602 --> 34:04.602
encounter one another in
solution.

34:04.598 --> 34:06.528
They'll react with many
molecules.

34:06.528 --> 34:09.548
If you try to generate too many
chlorine radicals,

34:09.550 --> 34:12.740
so the concentration gets high,
then their concentration will

34:12.735 --> 34:14.575
drop again,
or not get so high,

34:14.577 --> 34:17.057
because they find one another
and combine.

34:17.059 --> 34:21.139
But as long as they're rare,
they can survive.

34:21.139 --> 34:25.549
You know what the license plate
of New Hampshire says on it?

34:25.550 --> 34:30.040
"Live free or die."

34:30.039 --> 34:32.779
Okay?

34:32.780 --> 34:36.320
I use that joke later on.

34:36.320 --> 34:39.760
Okay, 1830s to 1850s,
we have this substitution or

34:39.762 --> 34:41.522
type or unitary theory.

34:41.518 --> 34:44.258
It doesn't involve the
plus/minus stuff.

34:44.260 --> 34:45.040
Max?

34:45.039 --> 34:46.429
Student:  Is that kind
of like how CFCs work?

34:46.429 --> 34:47.569
Prof: Is it kind of like
what?

34:47.570 --> 34:49.450
Student:  How CFCs
destroy the ozone.

34:49.449 --> 34:50.579
Prof: I couldn't hear
clearly.

34:50.579 --> 34:52.749
Student:  Is that how
CFCs break down the ozone?

34:52.750 --> 34:54.670
Prof: Yeah,
they involve -- that's a

34:54.668 --> 34:56.998
free-radical chain reaction,
the ozone reduction.

34:57.000 --> 34:57.670
Yeah.

34:57.670 --> 35:00.610
We'll talk about that a little
bit later, I hope.

35:00.610 --> 35:05.060
Okay, so there's more trouble
for radicals,

35:05.056 --> 35:07.276
from Dumas in 1839.

35:07.280 --> 35:10.920
And that is that they had this
-- remember, acetyl radical had

35:10.918 --> 35:12.588
been discovered by Liebig.

35:12.590 --> 35:17.230
So there was this great element
that would survive from reaction

35:17.228 --> 35:18.258
to reaction.

35:18.260 --> 35:20.890
But here was a reaction with
chlorine,

35:20.889 --> 35:23.719
of this kind that Dumas had
been studying,

35:23.719 --> 35:26.959
where you start with acetic
acid, acetyl OH,

35:26.960 --> 35:31.180
react it with chlorine,
and you get a chloroacetyl.

35:31.179 --> 35:33.769
So the element has been changed.

35:33.769 --> 35:35.059
It's been transmuted.

35:35.059 --> 35:38.149
It doesn't go unchanged from
reaction to reaction.

35:38.146 --> 35:38.646
Right?

35:38.650 --> 35:40.460
And, in fact,
it goes even further.

35:40.460 --> 35:44.470
It can react again to give
dichloroacetyl or

35:44.469 --> 35:46.149
trichloroacetyl.

35:46.150 --> 35:49.390
All the hydrogens can be
substituted, as we now know by

35:49.393 --> 35:51.863
the kind of mechanism,
the SOMO mechanism,

35:51.858 --> 35:56.058
we just studied;
free-radical chlorination,

35:56.061 --> 35:57.911
chain reaction.

35:57.909 --> 36:02.419
So hydrogen can be substituted
by an equivalent amount of

36:02.422 --> 36:04.682
halogen, or oxygen,
right?

36:04.679 --> 36:08.959
But all these things you get,
when you change a radical into

36:08.956 --> 36:11.636
something else,
when you transmute it,

36:11.639 --> 36:13.669
have similar properties.

36:13.670 --> 36:17.200
All of these acids -- acetic
acid, chloroacetic,

36:17.195 --> 36:19.515
dichloroacetic,
trichloroacetic,

36:19.518 --> 36:22.798
are all acids;
they all taste sharp and so on.

36:22.795 --> 36:23.225
Right?

36:23.230 --> 36:24.800
So they're similar.

36:24.800 --> 36:28.470
So they don't change the type.

36:28.469 --> 36:31.089
That's where this idea of Type
theory came on.

36:31.090 --> 36:33.940
You get the same type of
molecule, even after you have a

36:33.942 --> 36:34.722
substitution.

36:34.719 --> 36:39.399
So by 1853, four types were
recognized as prevalent.

36:39.400 --> 36:42.210
One was water,
another was hydrogen,

36:42.206 --> 36:46.776
another was hydrochloric acid,
and another was ammonia.

36:46.780 --> 36:48.510
So, for example,
you could have these

36:48.505 --> 36:50.845
structures;
and this drawing with a curly

36:50.853 --> 36:54.183
bracket like this was the
notation used by the people who

36:54.179 --> 36:55.309
did Type theory.

36:55.309 --> 36:58.059
So you have water,
hydrochloric acid,

36:58.061 --> 36:59.821
hydrogen and ammonia.

36:59.820 --> 37:02.080
And you could exchange,
make exchanges,

37:02.076 --> 37:03.086
for the hydrogen.

37:03.085 --> 37:03.615
Right?

37:03.619 --> 37:04.549
Substitution.

37:04.550 --> 37:08.800
So, for example with ammonia,
you can substitute ethyl for

37:08.802 --> 37:12.682
hydrogen and you could get
ethylamine, diethylmanine,

37:12.682 --> 37:14.252
or triethylamine.

37:14.250 --> 37:16.010
But these were all basic.

37:16.010 --> 37:20.180
Why would we say they're basic,
in the sense of acid base?

37:20.179 --> 37:22.959
Why do we say they're basic?

37:22.960 --> 37:24.820
They react with acids, why?

37:24.820 --> 37:25.810
Sherwin?

37:25.809 --> 37:27.009
Student:  The unshared
pair.

37:27.010 --> 37:28.570
Prof: Yeah,
they all have the unshared pair

37:28.568 --> 37:29.458
on nitrogen, we would say.

37:29.460 --> 37:33.230
But they said they're just the
same Type of molecule.

37:33.230 --> 37:34.040
Okay?

37:34.039 --> 37:37.589
Or you could have ethyl
alcohol, which is of the water

37:37.590 --> 37:38.060
type.

37:38.059 --> 37:43.439
Or the potassium salt thereof,
which they would say is the

37:43.440 --> 37:46.650
potassium-ethyl analog of water.

37:46.650 --> 37:49.880
Or of the HCl,
you could have ethyl iodide,

37:49.880 --> 37:53.960
where you exchanged hydrogen
with ethyl, and exchanged

37:53.956 --> 37:55.876
chloride with iodine.

37:55.880 --> 37:59.380
Okay, but in fact these two
things could react with one

37:59.380 --> 38:02.990
another to give this ether;
which is another thing that's

38:02.987 --> 38:05.487
still like water,
clear liquid and so on.

38:05.489 --> 38:06.109
Okay?

38:06.110 --> 38:07.630
Fairly unreactive.

38:07.630 --> 38:13.740
So this particular reaction was
named for the work,

38:13.739 --> 38:18.139
in 1850, of Williamson in
England.

38:18.139 --> 38:20.829
So it's called the Williamson
Ether Synthesis.

38:20.829 --> 38:24.659
And we'll talk about that again
later.

38:24.659 --> 38:26.159
But it's quite an old reaction.

38:26.159 --> 38:30.099
So how about the theory of
these types?

38:30.099 --> 38:32.799
So notice it's unitary,
not dualistic.

38:32.800 --> 38:35.720
They're just things that are
holistic, right?

38:35.719 --> 38:37.349
Not plus/minus.

38:37.349 --> 38:40.779
Dumas said that molecules are
like planetary systems,

38:40.780 --> 38:44.660
like the sun and its planets,
"held together by a force

38:44.659 --> 38:48.279
resembling gravitation,
but acting in accord with much

38:48.280 --> 38:50.130
more complicated laws."

38:50.130 --> 38:54.140
He didn't think it was gravity,
but it was some force holds

38:54.141 --> 38:56.011
this assemblage together.

38:56.010 --> 38:59.310
And Williamson,
Alexander William Williamson,

38:59.306 --> 39:03.576
who we just mentioned making
ether, said this is something

39:03.579 --> 39:04.179
new.

39:04.179 --> 39:08.339
And notice it's because it's a
very young guy that has a new

39:08.335 --> 39:11.505
idea, not like these
imagination-starved older

39:11.505 --> 39:12.275
people.

39:12.280 --> 39:15.670
At this time Dumas was
40-years-old.

39:15.670 --> 39:19.010
He's 4/7ths as old as I am,
right?

39:19.010 --> 39:22.580
So he was really getting over
the hill.

39:22.579 --> 39:25.529
"A formula"
-- the young guy says --

39:25.532 --> 39:29.282
"may be used as an actual
image of what we rationally

39:29.275 --> 39:33.275
suppose to be the arrangement of
constituent atoms."

39:33.280 --> 39:35.220
This is entirely new.

39:35.219 --> 39:38.309
Formulas, at least since
Dalton, were only what the

39:38.311 --> 39:40.971
elements were and what ratios
they're in;

39:40.969 --> 39:43.629
not how they're arranged. Right?

39:43.630 --> 39:48.240
But he said,
"We can think that they're

39:48.239 --> 39:51.619
like an orrery,
which is an image of what we

39:51.615 --> 39:54.815
conclude to be the arrangement
of our planetary system."

39:54.820 --> 39:57.060
Do you know what an orrery is?

39:57.059 --> 39:59.399
It's a thing like this,
you know, where you have a

39:59.400 --> 40:02.270
mechanical model of the solar
system and you turn a crank and

40:02.268 --> 40:05.558
the moon goes around the earth,
the earth goes around the sun,

40:05.561 --> 40:08.131
and a bunch of moons go around
Saturn and so on.

40:08.130 --> 40:09.880
Have you seen these devices?

40:09.880 --> 40:10.970
Okay, that was very popular.

40:10.969 --> 40:16.159
There was a show of Joseph
Wright of Derby here at Yale

40:16.163 --> 40:17.513
last summer.

40:17.510 --> 40:20.010
So butyl bromide,
you remember,

40:20.010 --> 40:23.510
is a residue of radical
dualism, right?;

40:23.510 --> 40:25.750
plus-butyl, minus-bromide.

40:25.750 --> 40:27.910
But there's another name for
butyl bromide.

40:27.909 --> 40:31.339
Do you know what it is?

40:31.340 --> 40:33.340
You know the other name for
butyl bromide?

40:33.340 --> 40:36.340
We haven't talked about
systematic nomenclature yet,

40:36.344 --> 40:37.764
so you probably don't.

40:37.760 --> 40:40.470
But it's also called
bromobutane.

40:40.469 --> 40:44.179
But bromobutane is not two
words, it's one word.

40:44.177 --> 40:44.807
Right?

40:44.809 --> 40:47.859
And that's a relic of the
unitary theory,

40:47.858 --> 40:51.748
the substitution theory,
that it's butane in which a

40:51.746 --> 40:54.946
hydrogen has been replaced by
bromine.

40:54.949 --> 40:59.709
Okay, so Berzelius,
in 1838 when these things came

40:59.706 --> 41:01.886
along,
said: "By reacting

41:01.887 --> 41:05.017
chlorine with ordinary ether
produced a very interesting

41:05.016 --> 41:08.096
compound which he reckoned,
according to the theory of

41:08.097 --> 41:10.917
substitutions,
to be an ether in which 4 atoms

41:10.916 --> 41:13.896
of chlorine replaced 4 atoms of
hydrogen."

41:13.896 --> 41:14.476
Right?

41:14.480 --> 41:18.070
So Dumas says that in these
types you can replace hydrogen

41:18.068 --> 41:18.948
by chlorine.

41:18.949 --> 41:20.679
What would Berzelius think
about that?

41:20.679 --> 41:25.189
What kind of theory is he
advocating?

41:25.190 --> 41:29.890
Remember, we talked last time
about Berzelius.

41:29.889 --> 41:32.799
He was the originator of
dualism, plus/minus.

41:32.800 --> 41:38.750
What would he think of
replacing hydrogen by chlorine?

41:38.750 --> 41:39.830
Lucas?

41:39.829 --> 41:41.879
Student:  It's
impossible.

41:41.880 --> 41:42.690
If chlorine is minus,
hydrogen is plus.

41:42.690 --> 41:43.740
Prof: Right.

41:43.737 --> 41:46.607
So here's what he said:
"An element as eminently

41:46.606 --> 41:49.636
electronegative as chlorine
would never be able to enter

41:49.639 --> 41:51.239
into an organic radical.

41:51.239 --> 41:55.269
This idea is contrary to the
first principles of

41:55.273 --> 41:56.823
chemistry."

41:56.820 --> 41:57.450
Okay?

41:57.449 --> 42:00.659
And in that same paper,
in 1838, he talked about

42:00.659 --> 42:04.959
tartrate losing an atom of water
-- but you mean it's a molecule

42:06.260 --> 42:07.770
But the interesting thing about
that,

42:07.768 --> 42:11.868
it's not transformation,
but that this is the first time

42:11.867 --> 42:16.517
the letter R was used,
to talk about a generic radical;

42:16.518 --> 42:18.298
"R"
stands for radical.

42:18.295 --> 42:18.735
Right?

42:18.739 --> 42:19.879
So we still use that.

42:19.880 --> 42:24.660
So, so much of what we do
nowadays derives from this

42:24.664 --> 42:25.514
period.

42:25.510 --> 42:27.160
Okay?

42:27.159 --> 42:31.319
So the principal journal at
that time,

42:31.320 --> 42:34.050
in chemistry,
was the Annalen der Chemie

42:34.045 --> 42:36.795
und Pharmacie,
which was originally the

42:36.804 --> 42:41.394
Annalen der Pharmacie;
but Chemie was added.

42:41.389 --> 42:43.609
And you see who put it out.

42:43.610 --> 42:47.080
It says: "With the
collaboration of Dumas in Paris

42:47.077 --> 42:48.937
and Graham in London."

42:48.940 --> 42:51.780
And Graham is one of the guys
out in front of the building

42:51.780 --> 42:52.130
here.

42:55.030 --> 42:58.180
but actually it was Liebig,
he was the one.

42:58.179 --> 43:02.519
And later the journal came to
be called Liebig's

43:02.518 --> 43:03.558
Annalen.

43:03.559 --> 43:04.339
Right?

43:04.340 --> 43:07.430
So he was the one in charge,
but he'd added these other

43:07.429 --> 43:09.259
people, just sort of for show.

43:09.260 --> 43:12.900
Okay, so in 1840,
there were a series of papers

43:12.900 --> 43:13.850
published.

43:13.849 --> 43:16.689
The first of them was by his
so-called collaborator,

43:16.693 --> 43:19.653
Dumas, On the Law of
Substitution and the Theory of

43:19.648 --> 43:20.428
Types.

43:20.429 --> 43:22.379
This was a 40-page paper.

43:22.380 --> 43:25.090
And it begins with this
question, number one there:

43:25.088 --> 43:28.338
"Can one substitute the
elements that play their role in

43:28.340 --> 43:32.080
any simple or compound substance
equivalent for equivalent?"

43:32.079 --> 43:35.389
So can you make a new atom take
the role of an old atom?

43:35.389 --> 43:39.769
And you won't be surprised that
in 40 pages he concludes the

43:39.771 --> 43:40.961
answer is yes.

43:40.960 --> 43:44.320
But immediately following this
is a note from the editor,

43:44.315 --> 43:48.025
which says "Remarks on
the Previous Paper."

43:48.030 --> 43:49.210
And it's by J.L.

43:49.210 --> 43:51.070
at the bottom, Justus Liebig.

43:51.070 --> 43:53.700
And he says,
begins: "I am a far cry

43:53.697 --> 43:57.567
from sharing the ideas that
Monsieur Dumas has linked to the

43:57.572 --> 44:00.992
so-called laws of the
substitution theory."

44:00.989 --> 44:04.109
And then there's another paper,
by another Frenchman,

44:04.114 --> 44:07.244
Pelouze, on "The
Substitution Law of Monsieur

44:07.237 --> 44:08.437
Dumas."

44:08.440 --> 44:11.290
And after that lengthy paper,
there's a letter,

44:11.289 --> 44:14.609
"On the Law of
Substitution and the Theory of

44:14.614 --> 44:17.434
Types,"
with a footnote that says it

44:17.425 --> 44:19.595
was a letter to Justus Liebig.

44:19.599 --> 44:21.689
And you notice it's dated Paris.

44:21.690 --> 44:24.670
And it's the only paper that's
in French, in his particular

44:24.668 --> 44:25.078
issue.

44:25.079 --> 44:28.459
And there's another page.

44:28.460 --> 44:31.680
It's got some curious formulas
in them that have a lot of

44:31.677 --> 44:32.307
chlorine.

44:32.309 --> 44:35.459
We'll come back to that in just
a second.

44:35.460 --> 44:40.150
And it's by a chemist that no
one had heard of before called

44:40.150 --> 44:43.650
S.C.H. Windler -- this letter
to Liebig.

44:43.650 --> 44:46.280
And then the next paper is also
"On the Reaction of

44:46.277 --> 44:48.767
Chlorine with the Chlorides of
Ethanol and Methanol,

44:48.768 --> 44:51.328
and Several Points of the Ether
Theory,"

44:51.329 --> 44:55.199
by Regnault,
who was a French chemist.

44:55.199 --> 44:58.069
Now this is that letter,
translated.

44:58.070 --> 45:00.960
"Paris,
1 March, 1840.

45:00.958 --> 45:02.178
Monsieur!

45:02.179 --> 45:05.449
I am eager to communicate to
you one of the most striking

45:05.447 --> 45:07.137
facts of organic chemistry.

45:07.139 --> 45:10.319
I have confirmed the
substitution theory in an

45:10.320 --> 45:14.280
extremely remarkable and
completely unexpected manner.

45:14.280 --> 45:18.620
Only now can one appreciate the
great value of this theory and

45:18.615 --> 45:22.165
foresee the immense discoveries
that it promises to

45:22.170 --> 45:23.380
reveal."

45:23.380 --> 45:26.830
So it starts -- it's got a
complicated description of all

45:26.827 --> 45:28.947
the --
light that was used sometimes

45:28.945 --> 45:31.915
and the various distillations
and crystallizations,

45:31.920 --> 45:36.310
and the crystals are described.

45:36.309 --> 45:38.059
But he started with manganese
acetate,

45:38.059 --> 45:42.029
which had this formula with the
acetyl radical in it,

45:42.030 --> 45:45.530
and was able to chlorinate --
to substitute the hydrogens with

45:45.529 --> 45:46.159
chlorine.

45:46.159 --> 45:50.639
So there's already a validation
of the substitution theory.

45:50.639 --> 45:51.829
But it went further.

45:51.829 --> 45:57.009
A subsequent reaction exchanged
the O in manganese oxide with

45:57.014 --> 46:02.284
chlorine, and a further reaction
replaced the manganese itself

46:02.284 --> 46:03.844
with chlorine.

46:07.407 --> 46:09.717
chlorine and the oxygen with
chlorine,

46:09.719 --> 46:12.929
but still it preserved its
type.

46:12.931 --> 46:13.761
Right?

46:13.760 --> 46:15.460
So it was the same kind of
substance still,

46:15.460 --> 46:17.040
even though it was entirely
chlorine.

46:17.039 --> 46:19.179
"For all I know,
in the decolorizing"

46:19.177 --> 46:21.407
(that is bleaching)
"action of chlorine,

46:21.409 --> 46:24.119
hydrogen is replaced by
chlorine, and the cloth,

46:24.119 --> 46:26.199
which is now being bleached in
England,

46:26.199 --> 46:29.859
preserves its type according to
the substitution laws.

46:29.860 --> 46:32.590
I believe, however,
that atom-for-atom substitution

46:32.588 --> 46:34.988
of carbon by chlorine is my own
discovery.

46:34.989 --> 46:37.779
I hope you will take note of
this in your journal and be

46:37.777 --> 46:40.107
assured of my sincerest regards,
etc.

46:40.110 --> 46:41.710
S.C.H.***Windler."

46:41.710 --> 46:44.550
And there's a footnote,
which says: "I have

46:44.547 --> 46:48.107
learned that there is already in
the London shops a cloth of

46:48.110 --> 46:51.130
chlorine thread,
which is very much sought after

46:51.126 --> 46:53.656
and preferred above all others
for night caps,

46:53.661 --> 46:55.411
underwear, etc."

46:55.409 --> 46:59.109
Now this is,
you'll not be surprised a pun,

46:59.108 --> 47:04.038
because the name is pronounced
schvindler or swindler.

47:04.039 --> 47:08.409
So where do you think this came
from?

47:08.409 --> 47:13.509
Liebig didn't have enough sense
of humor to do such a thing.

47:13.510 --> 47:15.010
Who was the joker?

47:19.646 --> 47:22.676
and Berzelius thought it was so
fun that he forwarded it to

47:22.675 --> 47:23.245
Liebig.

47:25.585 --> 47:26.955
Liebig published it.

47:26.960 --> 47:27.580
Right?

47:27.579 --> 47:28.159
>

47:28.159 --> 47:30.499
Which didn't make Dumas any
happier.

47:30.503 --> 47:31.043
Right?

47:31.039 --> 47:35.059
So this was a -- Liebig at
least thought it was funny,

47:35.061 --> 47:35.821
I guess.

47:35.820 --> 47:40.570
Okay, so in 1849 Kolbe prepared
the free methyl radical,

47:40.572 --> 47:44.722
the actual element,
which had never been prepared

47:44.719 --> 47:46.189
before, CH_3.

47:46.190 --> 47:48.570
He did it by electrolysis.

47:48.570 --> 47:53.470
So when you electrolyze acetic
acid it turns out you can get

47:53.467 --> 47:57.947
hydrogen, hydrogen gas,
and CO_2, and what analyzed for

47:57.951 --> 47:58.371
CH_3.

47:58.365 --> 47:59.275
Right?

47:59.280 --> 48:02.050
So he had prepared the actual
radical.

48:02.050 --> 48:06.080
Now, of course,
it was discovered ten years

48:06.079 --> 48:09.629
later that he hadn't prepared
CH_3.

48:09.630 --> 48:13.820
It had that analysis,
but actually it was C_2H_6;

48:13.820 --> 48:16.410
it was the dimer of CH_3.

48:16.409 --> 48:18.779
Okay, but at the time it was
thought to be justification of

48:18.780 --> 48:19.640
the radical theory.

48:19.639 --> 48:23.489
So these two theories were
competing with one another.

48:23.489 --> 48:26.899
And ironically,
both the theories were

48:26.898 --> 48:31.868
supported by reactions that
actually did involve

48:31.871 --> 48:33.071
radicals.

48:33.070 --> 48:35.570
So the oxygenation of
benzaldehyde,

48:35.570 --> 48:38.590
the first reaction that
generated benzoyl,

48:38.585 --> 48:40.935
did in fact involve benzoyl.

48:40.940 --> 48:45.280
It was a SOMO reaction in which
a hydrogen atom was abstracted.

48:45.280 --> 48:47.980
And the chlorination,
as we've already seen,

48:47.976 --> 48:51.546
of a hydrocarbon like methane,
involves pulling a hydrogen

48:51.554 --> 48:52.374
atom off.

48:52.369 --> 48:55.889
And that electrolysis did
indeed generate the methyl

48:55.894 --> 48:59.904
radicals, but they were so
reactive, they found one another

48:59.904 --> 49:01.844
and dimerized to C_2H_6.

49:01.840 --> 49:05.540
So it's just sort of curious
that all these reactions did

49:05.541 --> 49:09.381
indeed involve free radicals,
but no one was truly aware of

49:09.376 --> 49:09.836
it.

49:09.840 --> 49:13.840
So next time we'll see what
resolved all this.

49:13.840 --> 49:19.000