0:00:00.540,0:00:03.700
Let's talk about the acid-base[br]definitions for Bronsted-Lowry

0:00:03.700,0:00:04.850
and, also, Lewis.

0:00:04.850,0:00:06.560
And we'll start[br]with Bronsted-Lowry.

0:00:06.560,0:00:09.720
So, a Bronsted-Lowry[br]Acid is a proton donor,

0:00:09.720,0:00:13.850
and a Bronsted-Lowry Base[br]is a proton acceptor.

0:00:13.850,0:00:16.860
So let's, really[br]quickly, review what

0:00:16.860,0:00:18.690
this definition means by proton.

0:00:18.690,0:00:21.140
So if I look at this[br]diagram, right here,

0:00:21.140,0:00:24.400
I'm going to draw the hydrogen[br]atom, or the most common

0:00:24.400,0:00:25.330
isotope.

0:00:25.330,0:00:29.950
So hydrogen has one proton in[br]the nucleus and one electron,

0:00:29.950,0:00:31.240
somewhere around our nucleus.

0:00:31.240,0:00:32.992
So a negative charge, like that.

0:00:32.992,0:00:34.575
And so, we would say[br]this is hydrogen.

0:00:34.575,0:00:35.075
All right?

0:00:35.075,0:00:38.330
And then we put, it's one[br]valence electron, right there,

0:00:38.330,0:00:42.410
to represent the hydrogen atom,[br]or the most common isotope.

0:00:42.410,0:00:45.920
If we were to, somehow,[br]take away this electron,

0:00:45.920,0:00:48.699
we would only be left[br]with the proton here.

0:00:48.699,0:00:50.740
We'd only be left with[br]the proton in the nucleus.

0:00:50.740,0:00:53.250
And so, when we're[br]talking about a proton,

0:00:53.250,0:00:55.490
we're talking about the[br]nucleus of a hydrogen

0:00:55.490,0:00:58.160
atom, which is equal to H plus.

0:00:58.160,0:01:01.570
So, no longer are we[br]talking about the electron.

0:01:01.570,0:01:04.810
So let's see how this applies[br]to an acid-base reaction.

0:01:04.810,0:01:08.220
And so we start over[br]here with water.

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And then we have HCl[br]over here on the right.

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Now, in this bond, between the[br]H the Cl, one of those electrons

0:01:15.817,0:01:18.400
came from the hydrogen and one[br]of them came from the chlorine.

0:01:18.400,0:01:20.520
So let me just go ahead[br]and draw those in.

0:01:20.520,0:01:23.350
So the one from the hydrogen,[br]I'm going to put in blue here.

0:01:23.350,0:01:27.790
And that's this electron from[br]hydrogen, right here in blue.

0:01:27.790,0:01:30.670
And then for chlorine, I'm going[br]to make that electron green.

0:01:30.670,0:01:32.890
So right in here, like that.

0:01:32.890,0:01:34.900
And so for this[br]acid-base reaction,

0:01:34.900,0:01:37.120
a lone pair of[br]electrons in the oxygen

0:01:37.120,0:01:39.700
is going to take this proton.

0:01:39.700,0:01:41.510
So just the nucleus[br]of the hydrogen

0:01:41.510,0:01:44.180
atom leaving the[br]electron in blue behind.

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And that electron[br]in blue stays behind

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and ends up on the chlorine.

0:01:48.560,0:01:51.200
So let's go ahead and draw[br]what we would form from that.

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We would have oxygen here.

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The oxygen had two[br]bonds to hydrogen.

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And the oxygen just picked[br]up another bond to hydrogen.

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And so, let me go ahead[br]and mark those electrons.

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So these electrons[br]in here, in magenta,

0:02:06.270,0:02:08.699
formed a new bond[br]with that proton.

0:02:08.699,0:02:10.750
So that's this bond right here.

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And then we had some[br]electrons on oxygen.

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Let me go ahead and[br]make those in red.

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So these electrons in red on[br]the oxygen didn't do anything.

0:02:19.332,0:02:20.290
So they're still there.

0:02:20.290,0:02:21.370
So they're right here.

0:02:21.370,0:02:22.870
And that's going[br]to give that oxygen

0:02:22.870,0:02:24.840
a plus one, a formal charge.

0:02:24.840,0:02:28.970
And so this is the[br]hydronium ion, H3O plus.

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Our other product,[br]we would also make--

0:02:31.670,0:02:33.600
we would have our[br]chlorine, which

0:02:33.600,0:02:37.240
had three lone pairs of[br]electrons around it already.

0:02:37.240,0:02:39.380
And then it picked up[br]both of those electrons.

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Let me go ahead and mark them.

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The one in green that[br]it had originally

0:02:42.540,0:02:44.020
brought to the dot structure.

0:02:44.020,0:02:46.980
And also, the one[br]in blue, the one

0:02:46.980,0:02:48.710
it took from hydrogen like that.

0:02:48.710,0:02:51.110
So chlorine now has[br]a negative charge.

0:02:51.110,0:02:52.780
So it's really the[br]chloride anion.

0:02:52.780,0:02:55.900
So this would be Cl[br]minus, like that.

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So let's identify our[br]Bronsted-Lowry Acid

0:02:58.630,0:03:01.110
and our Bronsted-Lowry[br]Base for this reaction.

0:03:01.110,0:03:04.700
So let's go back over here[br]and see what happened.

0:03:04.700,0:03:09.700
So the H20, the water,[br]acted as a proton acceptor.

0:03:09.700,0:03:11.910
It accepted a proton from HCl.

0:03:11.910,0:03:15.790
So water would be our[br]Bronsted-Lowry Base.

0:03:15.790,0:03:18.440
And HCl donated a[br]proton to water.

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So HCl would therefore be[br]our Bronsted-Lowry Acid.

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So let's go ahead and identify[br]conjugate acid-base pairs here.

0:03:27.380,0:03:30.470
So if HCl is our[br]Bronsted-Lowry Acid,

0:03:30.470,0:03:33.530
I could think about its[br]conjugate base over here

0:03:33.530,0:03:35.180
would be the chloride anions.

0:03:35.180,0:03:39.240
So this would be the[br]conjugate base over here.

0:03:41.780,0:03:45.190
So H2O was our[br]Bronsted-Lowry Base,

0:03:45.190,0:03:47.700
and then over here, we can[br]find its conjugate acid, that's

0:03:47.700,0:03:48.910
H3O plus.

0:03:48.910,0:03:53.382
So this would be the[br]conjugate acid, over here.

0:03:53.382,0:03:55.590
So when you're looking for[br]conjugate acid-base pairs,

0:03:55.590,0:03:57.940
you're looking for[br]one proton difference.

0:03:57.940,0:04:01.940
So H2O and H3O plus are a[br]conjugate acid-base pair.

0:04:01.940,0:04:06.060
And HCl and Cl minus are a[br]conjugate acid-base pair.

0:04:06.060,0:04:08.690
And if we look at what we[br]have in the right here,

0:04:08.690,0:04:12.812
we are now saying H3O plus is[br]an acid, and Cl minus is a base.

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And so, one thing[br]you'd think about

0:04:14.270,0:04:16.920
is H3O plus donating[br]a proton to Cl minus.

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And so, we'll draw a little,[br]tiny arrow going back

0:04:19.430,0:04:20.339
to the left.

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Because the equilibrium for this[br]reaction lies far to the right.

0:04:23.980,0:04:26.640
So we're going to get a lot more[br]of your products on the right

0:04:26.640,0:04:27.139
here.

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But just thinking about[br]these definitions,

0:04:28.890,0:04:30.900
right, H3O plus would[br]be donating a proton,

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and Cl minus would be[br]accepting a proton.

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The chloride anion would[br]be accepting a proton.

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But again, we know[br]HCl is a strong acid,

0:04:37.440,0:04:40.800
so we know the equilibrium[br]lies far to the right.

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So that's the idea[br]about Bronsted-Lowry.

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Let's look at[br]another definition,

0:04:45.080,0:04:48.140
which is actually a[br]little bit more broad.

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So this is a Lewis[br]Acid and Lewis Base.

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So a Lewis Acid is an[br]electron pair acceptor.

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And so, an easy way to remember[br]this is, acid acceptor.

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And a Lewis Base is an[br]electron pair donor.

0:05:03.600,0:05:05.850
And so, one way to remember[br]that this Lewis Base is

0:05:05.850,0:05:09.060
an electron pair donor is[br]to, if you think about this b

0:05:09.060,0:05:10.420
being lowercase.

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And then just flipping it[br]around, you would get a d here.

0:05:14.580,0:05:16.070
So you get d.

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So a base is a donor.

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So let's look at[br]this reaction here.

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And we have this cyclic[br]ether, over here on the left.

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And then we have borine[br]over here on the right.

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Now, notice there's no octet of[br]electrons around boron, right?

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Boron is only surrounded[br]by six electrons here.

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And that makes it very reactive.

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Boron is SP2[br]hybridized, which means

0:05:37.700,0:05:39.455
it has an empty p orbital.

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And so, let me go ahead and[br]represent the empty p orbital

0:05:41.830,0:05:42.370
like this.

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It's able to accept[br]a pair of electrons.

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And the ether over here is going[br]to donate a pair of electrons.

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And so, let's go ahead[br]and show what happens.

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The oxygen here is going to[br]donate a pair of electrons

0:05:55.810,0:05:57.740
into the empty orbital.

0:05:57.740,0:05:59.470
And there's going[br]to be a bond that

0:05:59.470,0:06:02.410
forms between the[br]oxygen and the boron.

0:06:02.410,0:06:07.440
So the ether over here is[br]donating a pair of electrons.

0:06:07.440,0:06:09.830
So that must be our Lewis Base.

0:06:09.830,0:06:12.610
And borine, over here, is[br]accepting a pair of electrons.

0:06:12.610,0:06:14.292
So that's our Lewis Acid.

0:06:14.292,0:06:15.750
Let's go ahead and[br]draw the product

0:06:15.750,0:06:18.720
for our Lewis acid-base[br]reaction here.

0:06:18.720,0:06:23.876
So we have our oxygen is[br]now bonded to the boron.

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The boron is still bonded[br]to three hydrogens,

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so we draw those[br]in there like that.

0:06:28.940,0:06:32.060
And let's follow[br]some of our electrons

0:06:32.060,0:06:34.420
here before we finish[br]drawing everything in.

0:06:34.420,0:06:38.170
So these electrons in[br]magenta formed this bond

0:06:38.170,0:06:40.260
between the oxygen[br]and the boron.

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And then we also had some[br]other electrons on that oxygen.

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Let me identify those.

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So these electrons right here[br]in red are still on that oxygen.

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So they are right[br]here on that oxygen.

0:06:51.440,0:06:54.800
That oxygen therefore, has[br]a plus one, a formal charge.

0:06:54.800,0:06:57.280
So plus one formal[br]charge on oxygen.

0:06:57.280,0:07:01.750
And boron gets a negative one[br]formal charge now like that.

0:07:01.750,0:07:06.210
And so, that's one Lewis[br]acid-base reaction here.

0:07:06.210,0:07:08.050
Now the Lewis[br]acid-base definition

0:07:08.050,0:07:11.160
is, once again, more[br]inclusive than Bronsted-Lowry.

0:07:11.160,0:07:14.080
If we actually go up here[br]to the previous reaction,

0:07:14.080,0:07:18.040
we can actually classify[br]these using the definition

0:07:18.040,0:07:20.110
for Lewis Acid and Lewis Base.

0:07:20.110,0:07:23.920
So let's look again at[br]what's happening here.

0:07:23.920,0:07:28.560
So water is donating[br]a pair of electrons.

0:07:28.560,0:07:31.310
Well, according to Lewis[br]Base, electron pair donor.

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So we could say that water, we[br]could say this is a Lewis Base.

0:07:35.970,0:07:39.610
And HCl is accepting[br]a pair of electrons.

0:07:39.610,0:07:41.690
So electron pair[br]acceptor is Lewis Acid.

0:07:41.690,0:07:43.480
So we could call[br]this a Lewis Acid.

0:07:43.480,0:07:47.250
So notice, it doesn't matter[br]what definition you use.

0:07:47.250,0:07:49.700
If you use Bronsted-Lowry,[br]this is your acid.

0:07:49.700,0:07:51.380
If you use Lewis,[br]this is your acid.

0:07:51.380,0:07:54.802
Or if you use,[br]over here for base,

0:07:54.802,0:07:56.760
this is your base,[br]according to Bronsted-Lowry.

0:07:56.760,0:07:59.420
This is also a base[br]according to Lewis.

0:07:59.420,0:08:02.870
And Lewis Acid and Base also[br]have particular importance

0:08:02.870,0:08:07.660
in organic chemistry because[br]you can talk about the term

0:08:07.660,0:08:12.200
Lewis Acid as being[br]synonymous with electrophiles.

0:08:12.200,0:08:15.580
So you could say this[br]is an electrophile.

0:08:15.580,0:08:19.180
And then, you could say a Lewis[br]Base is an electron pair donor.

0:08:19.180,0:08:21.120
That's a nucleophile.

0:08:21.120,0:08:23.340
And nucleophile,[br]electrophile are

0:08:23.340,0:08:26.630
extremely important[br]concepts to understand

0:08:26.630,0:08:29.595
when you're talking[br]about organic chemistry.