Lecture 003

Instructor: Jean-Claude Bradley, Drexel University
View Lecture


1
Chem. 241 - Lectures 3
1 DISCLAIMER: This text is being provided in a
rough-draft fashion. Communication Access
2 Realtime Translation (CART) is provided in order
to facilitate communication accessibility and may
3 not be a totally verbatim record of the
proceedings.

8 LECTURE 3
9 Okay. So what we're going to do
10 now is look at especially covalent bonds and
11 how we can figure out how atoms are
12 connected together to form more complicated
13 molecules. So we're going to learn how to
14 draw Lewis structures. You probably already
15 know how to do this, but I'll show you a way
16 of doing it so that you can find the
17 solution to the Lewis structure very quickly
18 for more complicated cases.
19 Okay. So I'm going to show you
20 that method and that method is on the first
21 blog. Right here, Lewis dot approach to
22 molecular structure. So we're going to
23 apply this today and you should be able to
24 do any Lewis structure after that.
25 So I'm going to start with the
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11
Chem. 241 - Lectures 2 and
1 same example, hydrogen, since we already
2 know the answer. We're talking about Lewis
3 structures. So if we follow this little
4 algorithm that I gave you, it has six steps.
5 The first step is to compound the total
6 number of electrons available, and that's
7 where you pull out that valence periodic
8 table, all right?
9 So carbon is four, nitrogen is
10 five, oxygen is six, fluorine is seven, neon
11 is eight, and hydrogen is one. Okay? So
12 that tells us how many electrons we have
13 available. We have 1 plus 1. So I'm only
14 talking about valence electrons.
15 Now the next step is to figure out
16 this number 2: Find out how many electrons
17 are needed. When I refer to "needed," I'm
18 talking about the octet rule. And the octet
19 rule states that you want eight electrons
20 for each carbon, nitrogen, oxygen, and
21 fluorine and related elements. So sulfur,
22 phosphorous, iodine, all those little other
23 elements that we drew in that little
24 periodic table, the same thing. They all
25 need eight electrons because of the octet
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12
Chem. 241 - Lectures 2 and
1 rule. Hydrogen only needs two.
2 So what we're going to try to do
3 is figure out how we can have a molecule so
4 that every atom satisfies the octet rule.
5 Okay?
6 So we need -- well, I have two
7 hydrogens, and each hydrogen needs two
8 electrons. So that's 2 plus 2 is 4. Okay?
9 So that's the octet rule part.
10 So the next step is, we figure out
11 how many electrons are shared. And then we
12 divide by 2 to get the number of bonds in
13 the molecule. So this should make some
14 sense.
15 I have two electrons available;
16 however, I need four. So I'm going to have
17 to share a certain number of electrons. How
18 many? Exactly 4 minus 2. I need to share 2
19 electrons. By definition, a bond, a single
20 bond, is two electrons.
21 So I divide 2 by 2, and I come up
22 with 1, okay? So for this example, it
23 actually takes a lot more time than the way
24 we did it, you know, earlier, where we just
25 drew the electrons.
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13
Chem. 241 - Lectures 2 and
1 You see, when you do molecules
2 that are far more complicated than knowing
3 the number of bonds in the molecules, it is
4 critical to being able to solve the problem
5 quickly. So I'm going to be doing examples
6 that are increasingly more complex until we
7 cover examples that you should be able to do
8 anything.
9 So knowing that we have one bond,
10 the next instead of is you write out the
11 atoms. In this case, we have two. There's
12 only one way to link two atoms together with
13 a single bond, and that's like that.
14 Sometimes we will have a choice
15 and we will talk about how we decide how to
16 put the bonds. When you only have two
17 atoms, you don't have a choice and you have
18 to put it like that.
19 So it looks like we're done, but
20 there's actually a couple more things to
21 worry about in order to make sure that we
22 have a correct answer.
23 The next thing we're going to do
24 is number 4 here. After placing the bonds,
25 complete the octets. What I'm doing here
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14
Chem. 241 - Lectures 2 and
1 is, I'm looking at each atom and counting
2 how many electrons are around it. If I look
3 at the left hydrogen, I count all of the
4 electrons until the bond. So I have two
5 electrons that are surrounding that hydrogen
6 for the octet rule. Well, hydrogen needs
7 two electrons so, I don't have to add any
8 electrons if I had some things that were
9 missing. We're going to do that in the next
10 example that we do.
11 So, you know, by symmetry, the
12 other hydrogen also has two electrons. So
13 we have satisfied the octet rule.
14 The last thing you have to worry
15 about is counting electrons around the atoms
16 and placing the charges. So when I'm
17 counting for charges, I only count one
18 electron per bond because charges have
19 nothing to do with the octet rule; charges
20 have to do with on average how many
21 electrons are around each hydrogen.
22 So if I count one electron per
23 bond, I have one electron on each hydrogen
24 for charges. Hydrogen normally has one
25 electron; so, therefore, it is not charged.
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15
Chem. 241 - Lectures 2 and
1 So it is really important to do
2 that last step because if you get everything
3 else right but you don't get the charge
4 right, you will have a wrong answer, and
5 it's going to lead you to wrong solutions
6 for some of the problems we're going to do.
7 So when we come up with a charge,
8 you will see how that works. But in this
9 one, it doesn't have a charge so we're
10 pretty much done.
11 If you had an issue with the with
12 the charges, you can always recheck your
13 molecules to make sure that the octet rule
14 is satisfied everything. So that number 6
15 is just check up on it.
16 So any questions on that? We're
17 going to do a bunch of example so is if it's
18 not all clear now, it will be all clear.
19 Okay. Next example is fluorine,
20 F2. So we're going to have available, need,
21 share, and then bonds. Always the same
22 thing.
23 Okay. So how many do I have
24 available in this molecule? Each fluorine
25 is what? Seven. So how do I know that?
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16
Chem. 241 - Lectures 2 and
1 This is where you go back to the valence
2 periodic table. You look up fluorine --
3 seven, and that's it.
4 So we have seven, but we have two
5 fluorines. So that's 7 plus 7=14. How many
6 do we need? 16. How do I know that?
7 Again, I look here, and it tells me that for
8 each carbon -- nitrogen, oxygen, fluorine --
9 I need eight. So 8 plus 8 is 16.
10 I'm going to share 16 minus 14=2
11 electrons. And divide that by 2 and find
12 out that I have one bond.
13 So I have two atoms. I have to
14 connect them together and make a molecule,
15 so I have to at least put the bond between
16 the two atoms, right?
17 So now if we stop here, this is
18 incorrect, because a Lewis structure a
19 complete Lewis structure, satisfies the
20 octet rule, and all the valence electrons
21 are shown and all the charges are shown, so
22 we're not done here.
23 We're going to look at the next
24 step. So after placing the bond which we
25 just finished, we complete the octets.
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17
Chem. 241 - Lectures 2 and
1 So the fluorine has, for octets,
2 two electrons around it, so it's actually
3 missing six to be able to come up to eight.
4 So I'm going to add six electrons around the
5 fluorine, but I'm going to do it in pairs.
6 So two on the top, two on the left, two on
7 the bottom. Okay? So I'm completing the
8 octet rule at this point. And by symmetry,
9 the fluorine on the right, I have to add six
10 electrons.
11 Okay. So the next step is, we are
12 going to count and place the charges. So
13 we're going to count the electrons per
14 charges. So when I count the charges, I
15 only count one electron per bond, but I
16 count all the other electrons.
17 So one for the bonds, two, three
18 four, five, six, seven. So for charges, I
19 have seven electrons around the fluorine.
20 Fluorine normally has seven electrons;
21 therefore, it's not charged. So I don't
22 have to put a plus or a minus anywhere
23 Okay? So it's not very
24 complicated, but it's one step above
25 hydrogen. There's something new in that
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18
Chem. 241 - Lectures 2 and
1 example.
2 Oxygen is the next one, O2. So
3 available, need, share, number of bonds to
4 be filled out.
5 So oxygen is in the column of six
6 valence electrons. So that's 6 plus 6=12.
7 How many do we need? So we have, you know,
8 any atom that's listed here, oxygen is
9 listed. It needs eight. So that would be
10 8+8=16.
11 Share is 16. So we're going to be
12 sharing 16-12=34. 4 divided by 2=2.
13 Okay? So it's useful to know that
14 there are exactly two bonds in oxygen. So
15 let's see how we are going to put them.
16 Well, if you only have two atoms,
17 it's not really very difficult. There's
18 only one place to put them, and that's
19 between the two atoms. So the first bond
20 links the two atoms together. But I have to
21 put two bonds total, so the only place I can
22 put it is here.
23 Okay. So now I'm going to go a
24 little bit more quickly with each example,
25 okay?
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19
Chem. 241 - Lectures 2 and
1 For each oxygen, now we're going
2 to complete the octets. How many electrons
3 do I have to put on? Four. I have four
4 electrons per octet already there. I only
5 need four more.
6 So, again, putting them as pairs,
7 I put the four electrons like that. And by
8 symmetry, I will do the same thing with the
9 oxygen on the right. Okay, now we have the
10 eight electrons per octet, so it's
11 satisfied.
12 Next thing we're going to count
13 the charges. One two tree four, five six.
14 Again, it's only one electron per bond, so I
15 have six valence electrons -- I have six
16 electrons per charge. Oxygen normally has
17 six electrons, so it's uncharged.
18 So, once again, with the simple
19 examples, you know they're not going to be
20 charged. Now it's complete. That's the
21 full Lewis structure.
22 Okay. Let's do nitrogen next.
23 N2. Available, need, share, and number of
24 bonds.
25 Okay. So going back to the table,
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20
Chem. 241 - Lectures 2 and
1 nitrogen is in the column with five valence
2 electrons. So I have five plus five
3 available. Okay? Available valence
4 electrons. Nitrogen is one of the atoms
5 that requires eight to satisfy the octet.
6 So 8+8=16. I have to share 16-10, which is
7 6, which tells me that I have 6 divided by
8 2=3 bonds. So once again, it's useful to
9 know that going in.
10 I only have two atoms. So there's
11 only one place I can put those three
12 bonds -- between the two nitrogens.
13 Now I'm going to satisfy the octet
14 rule. I have six electrons on each nitrogen
15 for the octet rule, so I'm only missing two.
16 Put them in a pair like that. Opposite for
17 the triple bond. By symmetry, the nitrogen
18 on the right would have two electrons.
19 Counting for charges each one of
20 the bonds contributes one electron so
21 there's one, two, three. And then we count
22 all the electrons. Four, five. So we have
23 five electrons. Nitrogen normally has five
24 electrons. So, again, uncharged.
25 Okay. Let's start to put more
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21
Chem. 241 - Lectures 2 and
1 atoms and see how this works out. So if I
2 try methane, CH 4, the same thing -- we are
3 going to look at available, how many we
4 need, how many we share, and then the number
5 of bonds.
6 So the carbon is four. And each
7 hydrogen is one. So to make it very
8 explicit here, 4+4x1, that totals up to 8.
9 So how many we need is going to be
10 8 for the carbon, and this is where people
11 often make a mistake. Hydrogen is 2, it
12 requires 2. So I have 4 of them, and that's
13 4x2=8+8, total of 16
14 So I'm going to have to share
15 16-8, or 8 electrons. Number of bonds is 8
16 divided by 2=4. Again, not a bit surprised
17 for this molecule because I'm starting
18 something simple, so we can build up to it.
19 We have carbon. I have 4 bonds
20 and I have 4 atoms to connect it to so
21 there's only one way to do that. Hydrogen
22 can't have more than one bond, so the only
23 thing I can do is put the four bonds around
24 the carbon. So how many electrons does
25 carbon need to complete the octet in this
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22
Chem. 241 - Lectures 2 and
1 case?
2 It's already full. It already has
3 eight electrons. So there's nothing to add.
4 For charges, I have one, two,
5 three, four. Carbon normally has four, so
6 it's uncharged so we're done here.
7 Carbon dioxide, CO2. Available,
8 need, share, and number of bonds.
9 So carbon is going to need four.
10 And each oxygen is 6. So 6x2=12+4=16. So
11 we're going to need the carbon. And the
12 oxygens each require 8. 8x3=24. So we have
13 to share 24-16, so we have to share 8
14 electrons. That tells us we have 8 divided
15 by 2, and that's 4 bonds. So we have four
16 bonds and we have three atoms.
17 So now we have more than one way
18 of solving this issue, right? We can join,
19 you know, the three atoms in a triangle. We
20 can do all kinds of things like this. So
21 this is where you have to use heuristics to
22 tell you what is likely to be the most
23 stable form of this.
24 Generally, when you have one atom
25 followed by, you know, a whole bunch of
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23
Chem. 241 - Lectures 2 and
1 another one of oxygen, you're going to put
2 that single atom in the middle and surround
3 it. So if I follow that, it's going to work
4 95 percent of the time.
5 We will see maybe a couple of
6 exceptions to that, but that's pretty good
7 heuristics to follow. So following that, I
8 would put the carbon and then I would put
9 the oxygens on either side.
10 Okay? So what's the minimum I
11 need to hold the structure together? One
12 bond on the left, one bond on the right.
13 But I have to do something with all the four
14 bonds that I know are in that molecule.
15 So, you know, again, here I could,
16 you know, draw a bond between the two
17 oxygens and maybe make a triangular
18 structure, but as we will find out a little
19 bit later, three-membered rings are unstable
20 usually. So that's not going to be your
21 first choice.
22 So if I can't make a triangle out
23 of it, the only thing I can do is to put
24 double bonds. So I'm going to add C double
25 bond 0 on the left, C double bond 0 on the
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24
Chem. 241 - Lectures 2 and
1 right.
2 Okay? So now I'm going to
3 complete the octets. So I add four
4 electrons on the oxygens, and the carbon
5 already is satisfying the octet rule.
6 Looking at charges -- one, two, three, four,
7 five, six electrons around the oxygen.
8 Oxygen normally has six, so that's
9 uncharged. Carbon -- two, three four,
10 carbon, it only has four, so it's also
11 uncharged. So that's complete, the CO2
12 Okay? So let's look at BF3, boron
13 trichloride. Available, need, share, number
14 of bonds. So available, let's go back to
15 the table here. Boron has three valence
16 electrons. And the chlorine has seven.
17 That's 24, right?
18 How many do we need? How many
19 does fluorine need to complete the octet?
20 Eight. How many does boron need to complete
21 the octet? Boron is not listed in the list
22 of atoms to complete the octet rule, so
23 that's one thing you have to watch out for.
24 Boron will not satisfy the octet
25 rule, so you simply cannot use this
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25
Chem. 241 - Lectures 2 and
1 procedure. You're going to end up with a
2 molecule. If it doesn't satisfy the octet
3 rule, that doesn't mean you can't form a
4 molecule. It just means that it will not
5 satisfy the octet rule, so you don't do
6 this.
7 I'm not going to give you problems
8 that are terribly complicated with boron, so
9 you can pretty much figure out what has to
10 happen. The boron has three valence
11 electrons and it's bonding with three atoms.
12 So there's really not much else for it to do
13 except take each one of those valence
14 electrons and use it to form a covalent bond
15 with each fluorine like this.
16 So notice that in the structure,
17 which, if I wanted to show the bonds, this
18 would still not be complete because I have
19 not shown the long pairs on the fluorines.
20 So you'll notice with this
21 example, the borine follows the octet rule,
22 but the boron only has six electrons, and
23 that's just the way it is, okay? So if it's
24 a boron, it just doesn't satisfy.
25 Let's look at ammonia, NE3. So
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26
Chem. 241 - Lectures 2 and
1 nitrogen is five. NE hydrogen is 1. So we
2 have 8 electrons available. We need 8 for
3 the nitrogen and 2 for each hydrogen.
4 3x2=6+8=14. We have to share 14-8, which is
5 6. So we have 6 divided by 2, so it's 3
6 bonds.
7 So each hydrogen cannot have more
8 than one bond to it, so the only way I can
9 hook this together with the nitrogen in the
10 middle is to use up my 3 bonds. And now if
11 I go to the next step, I have to complete
12 the octets. Each hydrogen is satisfied.
13 The nitrogen only has six
14 electrons. It's missing two, which I will
15 put. And for charges, one, two, three,
16 four, five. Nitrogen normally has five
17 electrons, so uncharged.
18 Okay. Let's look at carbon
19 monoxide, CO. Available, need, share, and
20 number of bonds. Available, we have four
21 from the carbon and 6 from the oxygen, and
22 that gives me 10 total. We need 8. Plus 8,
23 that's 16. So we have to share 16-10, which
24 is 6. That means we have 6 divided by 2, so
25 3 bonds.
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27
Chem. 241 - Lectures 2 and
1 As we start to get into more
2 complicated examples, it becomes more and
3 more useful to know how many bonds we have.
4 There's only two atoms. I have to
5 put the three bonds between the carbon and
6 the oxygen like that. So the next step is
7 to complete the octets. The carbon has 6
8 electrons around it already. It's only
9 missing two 2. Same thing for the oxygen.
10 Now, if we look at charges, for
11 the carbon, one, two, three from each bonds,
12 four, five. But carbon normally has four
13 electrons, so it has an extra electron.
14 Electrons are negativity charged; therefore,
15 I have a formal charge on the carbon of
16 minus 1. So I don't have to write 1. If I
17 just put a minus, it implies I have one.
18 The oxygen -- I have one, two,
19 three, four, five electrons. Oxygen
20 normally has six. It's missing an electron.
21 So if I'm missing a negative charge, I go to
22 positive. So it has a plus 1 charge. I
23 just put a plus on it.
24 Now, after you're finished placing
25 charges, the total charge in the molecule,
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28
Chem. 241 - Lectures 2 and
1 you draw has to be the same as the one in
2 the problem. So my total charge in CO is
3 zero. I have minus 1 and plus 1, so that
4 cancels out. That has to happen. So if it
5 doesn't happen, you made a mistake
6 somewhere, okay?
7 Okay. Now let's get some other
8 kinds of examples. SO, one of the oxides of
9 sulfur. Available, need, share, and bonds.
10 So sulfur is 6. Oxygen is also 6.
11 That's 12 electrons. We need 8+8=16. We
12 have to share 16-12 which is 4. That means
13 we have 4 divided by 2, or 2 bonds. So I
14 only have two atoms. That makes it pretty
15 straightforward. I have to put the two
16 bonds between the sulfur and the oxygen.
17 Completing the octets. Sulfur is missing 4.
18 Oxygen is missing 4. And if we count the
19 charges, we will find six electrons on the
20 sulfur. Okay?
21 * * *
22
23
24
25
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Lecture 002

Instructor: Jean-Claude Bradley, Drexel University
View Lecture


1
Chem. 241 - Lecture 2
1 DISCLAIMER: This text is being provided in a
rough-draft fashion. Communication Access
2 Realtime Translation (CART) is provided in order
to facilitate communication accessibility and may
3 not be a totally verbatim record of the
proceedings.
4
* * *
5
6 Lecture 2
7 Okay. So we're going to start with
8 electronic configuration, so this will be a bit of
9 a review for you, but you have to have this
10 material fresh in your mind to actually see how we
11 will implement it. If you remember all this, just
12 bear with it a little bit.
13 You're going to be applying two rules
14 that you should be familiar with the -- the Pauli
15 solution principle -- and, by the way, the
16 software I'm using to write it on, I'll make that
17 available to you as a PDF, so you don't have to
18 worry about copying everything down because it
19 will be available in an easily printable format.
20 So the Pauli solution principle has to
21 do with the fact that only two electrons can
22 occupy one orbital.
23 And the other rule we're going to need
24 to be able to use to deal with electronic
25 configuration of the first ten elements is the
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2
Chem. 241 - Lectures 2 and
1 Hunds rule, where electrons like to be unpaired if
2 possible.
3 Okay. How many of you remember these
4 two rules? Okay, good. So we're going to apply
5 these. And we're basically going to, like I said,
6 fill up the first ten elements. So we're going
7 from hydrogen to neon. And these little lines
8 that I'm drawing are the orbitals, and those will
9 be the orbitals where we have to apply the Pauli
10 solution principle and the Hunds rule.
11 So as we go from the top to the bottom,
12 we're adding one electron per each element. So
13 hydrogen has one electron. And let me use a
14 different color here. We can show that electron
15 with a half arrow either pointing up or pointing
16 down. The direction of the arrow has to do with
17 the skin of the electron, which we don't have to
18 get into; it's just that you need to know that
19 this can either be up or it can be done.
20 So when we move the helium, we have two
21 electrons. Apply the two rules, put the helium.
22 So following the two rules, we put the first
23 electron there and the second electron. It
24 doesn't have another orbital of the same energy,
25 so the other electron can't remain unpaired so
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3
Chem. 241 - Lectures 2 and
1 we're going to be forced to pair it. And the way
2 we demonstrate that is by drawing a down arrow
3 next to the up arrow. So now we have two
4 electrons in the orbital, and it's filled up so we
5 can't put any more in there.
6 What is the name of this first orbital?
7 1S. So obviously, I'm going to have to draw more
8 lines here. I'm going to draw all the lines for
9 all the elements, and I'm leaving them blank until
10 I fill them up.
11 So continuing on with helium, it has
12 three electrons total. So the first one goes in
13 the first orbital. And the second one goes in the
14 same orbital, different direction. And then the
15 third one we put in the next orbital. So the
16 first orbital is 1 and the second orbital is 2S.
17 So now we continue with beryllium.
18 It has four electrons. Now I just filled up
19 the 2S orbital, so when I go to boron, that
20 has five electrons and I now have to use
21 these other three orbitals that are of the
22 same energy, and those would be the 2P
23 orbitals.
24 So I have 2PX, 2PY, and 2PZ. And
25 there's no particular reason for that order;
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4
Chem. 241 - Lectures 2 and
1 it's just distinguished between them.
2 They're absolutely the same energy. So that
3 like electron, then I have to put it in the
4 2PX orbital like that
5 Okay? So now we have one more
6 electron -- one, two, three, four, five --
7 and now we have three orbitals that are the
8 same energy. So the electrons will be
9 unpaired if possible according to the Hunds
10 rule, so we will put them as unpaired. So
11 I'm going to have one in 2PX and one in 2PY,
12 for example.
13 With nitrogen, I have one, two,
14 three, four, five, six, seven. And, again,
15 I'm putting another unpaired electron
16 because it's the same energy. All the 2P
17 orbitals are the same energy.
18 Oxygen -- one, two, three, four,
19 five, six, seven. And now the eighth one,
20 now I'm forced to pair it because I've run
21 out of orbitals of the same energy that are
22 vacant. So I'll put in the 2PX, for
23 example.
24 With fluorine, we fill this up
25 where I'm going to have to pair the electron
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5
Chem. 241 - Lectures 2 and
1 and the 2PY orbitals.
2 And, finally, neon has all of the
3 two P orbitals completely filled up with
4 paired electrons, okay?
5 So this is something I'm taking a
6 bit of time to go through because we will
7 need this when we look at molecular orbitals
8 that is based on this theory. So for now,
9 this should be a refresher.
10 The other reason I go through this
11 is because I want to point out a concept
12 which is valence electrons. When we look at
13 making molecules from collections of atoms,
14 those atoms are connected together with
15 bonds. And it turns out that not all of the
16 electrons in the atoms participate in that
17 bond formation; only the valence bonds
18 participate. So I'm going to put a square
19 around the valence electrons.
20 So, for example, for hydrogen and
21 helium, well, those are all the valence
22 electrons; that's all it has. But when I go
23 from lithium to neon, the 1S orbital is not
24 a part of the valence electrons.
25 So I'm going to put a square
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6
Chem. 241 - Lectures 2 and
1 around just the two orbitals, the 2S and 2P
2 orbitals.
3 So those are called valence
4 electrons. And so if I ask, you know, how
5 many electrons does carbon have? what I'm
6 really interested in is the four electrons
7 that are in the valence.
8 So generally when we talk about
9 how many electrons each atom has, we're
10 referring to valence electrons as we count
11 them
12 Any questions on this?
13 (No questions.)
14 Okay, so the next thing I wanted
15 to with these valence electrons is rewrite a
16 little useful periodic table for you with
17 the valence. The periodic table. So these
18 are the elements that we're going to be most
19 concerned with in this class: Hydrogen,
20 boron, carbon, nitrogen, oxygen, fluorine
21 phosphorous, sulfur, chlorine, bromine, and
22 iodine. We can put even lithium and sodium
23 on the left.
24 The reason this is a valence
25 periodic table is that we're going to divide
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7
Chem. 241 - Lectures 2 and
1 this up into columns and only worry about
2 the number of valence electrons. So
3 hydrogen has one valence electron; boron has
4 three; carbon, four; nitrogen and
5 phosphorous have five; oxygen and sulfur
6 have six. And the halogens -- fluorine
7 chlorine bromine and iodine have -- have
8 seven.
9 Okay? So those elements are going
10 to behave in pretty similar ways. For the
11 two elements have the same number of valence
12 electrons, there will be differences in how
13 they react, but there will be a lot of
14 similarities as well as to how they format
15 bonds with other atoms.
16 So this is something that, you
17 know, you should keep handy when you're
18 doing problems because you're going to need
19 to use it constantly.
20 Okay. So keeping this in mind,
21 let's now talk about actually making
22 molecules from atoms. Well, let's consider
23 the simplest thing we can consider, which is
24 which is two hydrogen atoms coming together
25 to make hydrogen gas, H2.
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8
Chem. 241 - Lectures 2 and
1 So hydrogen has one electron, and
2 I'm getting the Lewis structures here, so
3 this should look pretty familiar. I put
4 hydrogen and then I put a dot, or sometimes
5 we use an X. But the point is, you show
6 that there's only one electron.
7 If I want to show two hydrogen
8 atoms coming together, I can show one
9 electron and the other hydrogen. And then
10 when they come together, I can draw the two
11 electrons on top of each other between the
12 two hydrogens.
13 And what I've done here is, I've
14 created a bond, but there are two kinds of
15 bonds that we're interested in. This is a
16 covalent bond because the two atoms are
17 sharing the electrons. Neither hydrogen has
18 those electrons entirely to itself; it has
19 to share both of them, so that's why it's
20 called a covalent bond.
21 So another way that we can draw
22 the covalent bond is to draw a line. So
23 that's how you join two hydrogens, with a
24 line. Every line you see corresponds two to
25 two electrons. So we will be doing that
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9
Chem. 241 - Lectures 2 and
1 most of the time because it's more
2 convenient than drawing a whole bunch of
3 dots. So we need to draw dots when we don't
4 have bonds; but otherwise, we can just draw
5 a line like this.
6 Let's consider another case
7 lithium fluoride. Lithium has one valence
8 electron. Fluorine has seven valence
9 electrons. But in this case, instead of
10 sharing the electrons, the lithium actually
11 completely gives up its electron, and the
12 fluorine completely takes it, so that's
13 different.
14 If the lithium gives up its
15 valence electron, it now has lost a negative
16 charge, and so it's going to be plus,
17 specifically plus 1. And the fluorine now
18 has eight electrons around it. Fluorine
19 normally has seven electrons, but it has an
20 extra one and so it has an extra negative
21 charge. That's how we know that it's
22 negative.
23 Okay. And you notice that I'm
24 drawing the electrons in certain places and
25 I'm putting them in pairs. We're going to
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10
Chem. 241 - Lectures 2 and
1 actually find out why I'm doing that, you
2 know, in the next class. But for now, just
3 note as to how the electrons go. They don't
4 go randomly around the atoms; they go in
5 pairs and they're separated by certain
6 angles.
7 * * *

Lecture 001

Instructor: Jean-Claude Bradley, Drexel University
View Lecture
1
9.26.05 Organic Chemistry 241
1 DISCLAIMER: This text is being provided in a
rough-draft fashion. Communication Access
2 Realtime Translation (CART) is provided in order
to facilitate communication accessibility and may
3 not be a totally verbatim record of the
proceedings.
4 * * *
5 INSTRUCTOR: Okay. So this is Organic
6 Chem 241.
7 Quiet, please. Thank you.
8 So for this class you received some of
9 my emails -- I'm going over where the information
10 is. Some of you have responded -- oops.
11 Okay, so you've received my emails about
12 where the class lectures are, things about
13 podcasting. For this class today, I will actually
14 go through pretty much everything that is
15 available to you and show you how to get to it,
16 answer questions, and then you should be clearer
17 at the end of this.
18 The first thing you is, you'll notice
19 that I sent you to a wiki, Chem 241, and one
20 student actually asked me why I don't do that on
21 Web CT. Well, this is an open course, meaning
22 that it has to be available to students from
23 around the world. So by putting the information
24 in the wiki logs, it gets indexed by Google, and
25 people can find the information a lot better. If
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2
9.26.05 Organic Chemistry 241
1 it's inside Web CT, basically when the class is
2 over, nobody gets the benefit. That's why this
3 information is in an open format.
4 The other reason that I bringing you
5 back to the wiki is that it's really -- think of
6 it like a table of contents. If you don't know
7 where something is, come here and take a look at
8 one the eight possible headings. If you ever get
9 confused, look back over here.
10 So the first thing that I want to point
11 out here is what you have to do in this class to
12 get points. A lot of the stuff that I will give
13 you is voluntary. You don't have to do the
14 quizzes, you don't have to play the games or do
15 any of it, as long as you score well on the the
16 two tests -- the exam and the final.
17 But the reality is that if you don't do
18 the quizzes, if you don't play the games, or you
19 don't do what you have to do, you're unlikely to
20 do well in the class. Make sure you understand
21 the distinction as to what you have to do and you
22 don't.
23 Now, basically, there's a one percent
24 extra-credit assignment, which I will get into
25 later when I go into the syllabus. That's the
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3
9.26.05 Organic Chemistry 241
1 only other place where you can earn extra points,
2 that 1 percent.
3 Aside from that, I don't take attendance
4 so there's nothing like that. You could take the
5 entire course on line fully. The lectures are
6 already recorded and you can actually listen to
7 the entire course right now.
8 Let me just take this one step at a
9 time. We will start at the syllabus. This is
10 pretty classic here. You have the courses and
11 objectives. So this course is the Introduction to
12 Organic Chemistry. We will look at molecules,
13 predicting their properties -- just basic stuff
14 like melting points, boiling points. We will look
15 at some reaction mechanisms. In the later -- in
16 the second half, we will look at SM1 and SM2
17 reactions. So pretty much the most important
18 reactions. We'll be looking at 242 and 243 later
19 on, which will be more complex stuff.
20 The textbook -- and, by the way, please
21 interrupt me with any questions. That's why I'm
22 going through this, so that you can bring up
23 issues.
24 The textbook is -- you can use a number
25 of them. I recommend that you use the Wade
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4
9.26.05 Organic Chemistry 241
1 edition five. But if you use edition four or six,
2 that's absolutely fine. It's just that the
3 problem numbers will change slightly. I think I
4 gave you the problems for editions four and five.
5 If you have six, we will see what the slight
6 differences are. Otherwise, that's fine
7 How many of you actually got the
8 book?
9 Anybody using another organic
10 text?
11 So you should do -- you know, the
12 beginning of organic chemistry is pretty
13 much the same everywhere. So if you have
14 another organic textbook and you're not sure
15 of it, just ask me, but the primary
16 information that you need to be able do the
17 problems and understand my class are from
18 the lectures and the problems that I solve.
19 So that has be your primary source.
20 You can just think of the book as
21 basically just additional reading material
22 to go a little further than what we do in
23 class. But, clearly the lectures will be
24 the primary source.
25 So the grading is pretty
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5
9.26.05 Organic Chemistry 241
1 straightforward. We will have two
2 one-and-a-half-hour exams, so 100 points
3 each. We a final of 200. Giving you total
4 of 400. That will be -- you know, the
5 percentage there is going to determine your
6 grade down here. Over 90 is A, over 80 is a
7 B, over 65 will give you a C.
8 Now, there might be a slight curve
9 to this but it will always be in your favor
10 if there is one.
11 There's an FAQ to this class. And
12 I will take a good chunk to go through the
13 whole FAQ because most of the pain in this
14 class is caused by not reading that
15 document. You have to know where to go to
16 take the tests, when you take the tests,
17 things like that. So if you're not clear
18 about that, that could be really upsetting
19 when you actually run into a problem. So we
20 will take the time to go through that.
21 The makeup test policy. I give an
22 automatic makeup for every test, but it has
23 more questions in it, all right? And I will
24 take the better of the two scores.
25 The idea behind that is that you
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6
9.26.05 Organic Chemistry 241
1 take the first test, and I expect you to
2 study for it properly to be able to do well.
3 You should be aiming to do well on the first
4 test.
5 But if, for whatever reason,
6 things don't go well on the first test, you
7 have an option to prove that you know the
8 material immediately following that with a
9 test makeup. And we will use the time in
10 class to basically go over reviews as to why
11 you didn't understand a certain concept.
12 But there's a penalty for that in
13 that you will have a lot more questions in
14 the same amount of time. So I think that
15 overall is fair for everybody.
16 Now, lecture archives are divided
17 into different sections. The theory part is
18 actually in the class blog, which we will
19 look at shortly. But the problems, the
20 problem solutions are all in Web CT. The
21 only reason for that is that there's a
22 copyright issue. I can't show the solutions
23 to the problems because Prentice Hall isn't
24 happy about me doing that, so I have to hide
25 it and put it in Web CT. But otherwise,
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7
9.26.05 Organic Chemistry 241
1 everything else is on the blog
2 Okay. Grading policy we went
3 through.
4 The extra credit. If you're
5 interested in doing that, we will talk more,
6 come and see me. To give you an idea about
7 of what this is about, up to 1 percent of
8 the grade -- so it's not a huge percent, but
9 there was like six students last term who
10 would have gone from B to A or from C to B
11 if they had just done the one percent extra
12 credit.
13 You know, it's not so much that
14 everybody in the class will do it, but it
15 should be an incentive if you're interested
16 in doing the project.
17 But the primary reason for doing
18 the extra credit is really for your own
19 benefit so that you can integrate the
20 material better.
21 And the way that it works is that
22 you go out and find a reference in a
23 peer-reviewed journal that has something to
24 do with a reaction that we do in class. We
25 will look at stuff that has to do with free
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8
9.26.05 Organic Chemistry 241
1 radicals. A good example of that is the
2 ozone layer and how it gets destroyed.
3 It doesn't have to be long; it
4 could be just a couple of sentences, but I
5 want to see a picture of the reaction you're
6 doing and a link to the original article,
7 and that's it. If you do that, then you get
8 full points usually.
9 Now, the earlier that you put it
10 up, the more time that I have to give you
11 some feedback on it. So there are two dates
12 here that are important -- November 4th and
13 November 25th. On November 4th at midnight,
14 I will go in and grade all the assignments
15 that have been put in.
16 And there will be no extensions
17 for any reason on these two dates. So if
18 you're interested in doing this, I suggest
19 that you do it as quickly as possible so you
20 have plenty of time to work out any issues.
21 If you post something and there are things
22 that are wrong in there, I can give you
23 feedback, or students in the class can give
24 you feedback so that you have time to
25 correct it before the final grade. So
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9
9.26.05 Organic Chemistry 241
1 there's two of those for the full 1 percent.
2 You have the benefit of accessing
3 previous examples of this. If you go back
4 to the Chem 242 class where they did this
5 assignment, what you will see are basically
6 examples like this.
7 You can go through -- there's
8 about 40 of these in that particular blog.
9 And you can read my comments to see if
10 that's a good way to do it or not a good
11 way. So here, if you look at the comments.
12 And this is one that's full mark.
13 Some are not going to be full marks and I
14 will explain why.
15 So if you have time, you can go
16 through that and take a look at, you know,
17 what is a good reaction to select and what
18 isn 't.
19 So there's all kinds of things
20 here. I think some of the more interesting
21 things, for example, were the Breathalyzer
22 tests the students did, the actual chemistry
23 behind it. There's a lot of very
24 interesting things that you're able to find
25 out and link to.
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10
9.26.05 Organic Chemistry 241
1 I think that's pretty much all I
2 want to say about this.
3 The only other issue about the
4 extra credit is that we will be using games
5 in this class. For example, we're using an
6 unreal tournament. So If you wish to create
7 an unreal tournament map of chemistry, that
8 can also be your 1 percent. Again, come
9 talk to me about it once you find out more
10 about how this works.
11 The material covered, at the
12 bottom of the syllabus, we have different
13 sections of what we will be doing. We will
14 start off with going back to introductory
15 chemistry, looking at electronic
16 configuration, and we will pretty quickly
17 reach doing Lewis structures, all right?
18 Now, there's a way that I teach
19 you how to do Lewis Structures. You can do
20 pretty much any structure very quickly. I
21 spend a lot of time on that. If you listen
22 to lectures, you will see how it works. If
23 you haven't, definitely get into there and
24 start to listen to the lectures and do the
25 problems for Chapter 1.
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11
9.26.05 Organic Chemistry 241
1 Chapter 2 is just an extension of
2 molecular orbitals, so we have hybrid
3 orbitals. And that's just basically how to
4 determine the geometry of the molecules once
5 you have the Lewis structure.
6 Now moving on to hydrocarbons,
7 which is the simplest form of
8 (indiscernible), and that's carbon and
9 hydrogen.
10 And then we will look at our first
11 reaction, which is the halogenation of
12 alkenes, so the reaction of bromine with
13 ethane. We will go into detail and find out
14 exactly how that happens step by step. And
15 then we have Test 1.
16 So, you know, you can listen to
17 the lecture at your own pace, but just make
18 sure that you are completely way ahead of
19 time for the Test 1.
20 Now, the Web CT -- I don't know if
21 you know there's a migration where we're
22 going to the Vista edition of Web CT. So
23 right now, everybody is getting transferred
24 over. I think this class is still not quite
25 done. As you will see when we go back to
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12
9.26.05 Organic Chemistry 241
1 the wiki, you can actually already do all
2 the quizzes and do everything you have to in
3 the prior version of Web CT if you log in as
4 guest. This week sometime, you will be able
5 to log in as yourself
6 That pretty much covers the
7 syllabus.
8 Any questions?
9 Okay, the FAQ. So the FAQ is
10 actually a blog, and it should become
11 apparent to you why I chose to make it as a
12 blog. I have one common FAQ for all
13 classes, so Chemistry 241, 242, 243, we all
14 share this common blog.
15 The other advantage is that if
16 there's a new question that I pose, if you
17 subscribe to this blog correctly, you will
18 see a new entry in it. It's basically
19 another way to keep updated about the class.
20 And I do expect you to subscribe to this
21 because I will be following most of the
22 posts.
23 So the way blogs work is they're
24 in reverse chronological order. So FAQ 21
25 is the most recent FAQ. If you want to read
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13
9.26.05 Organic Chemistry 241
1 a blog in chronological order, you just
2 scroll down to the bottom. So here's FAQ 1.
3 How does podcasting work in this
4 class? How many of you have heard of
5 podcasting? How many of you already
6 subscribed to podcasts?
7 Well, I think if you learn
8 anything from this class, you will learn to
9 use podcasting, which is very useful in all
10 kinds of different areas. There are a lot
11 of lectures now being put on podcast and on
12 iTunes, and they're free and available to
13 you, okay? So this is a resource that you
14 should at least be aware of.
15 Podcasting means you subscribe to
16 a feed and you get audio files automatically
17 copyed over onto your computer or your iPod
18 if you have one. You don't need an iPod.
19 In fact, I listen to stuff on my laptop, but
20 you can synchronize with it and listen to
21 lecture that is way.
22 The problem with the iPod is that
23 there's no video information, so I provided
24 the PDF's as well. When you go into iTunes,
25 you see a lecture an MP3 and PDF for each
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14
9.26.05 Organic Chemistry 241
1 lecture.
2 How do you do this? Well, I give
3 you information here on iTunes. I've
4 created tutorials that are 30 to 60 seconds
5 long. You click on that. We have gone back
6 to another section of the wiki.
7 This is how you subscribe to
8 iTunes. There's a screen cast. Let's take
9 a look at that. You can come back here
10 anytime and replay this. So this goes
11 through iTunes. After you download it, you
12 basically go to the music store, pick
13 podcasts, pick higher education, and then
14 you can sort however you like this.
15 The name of this class is CHEM241,
16 organic chemistry. Click on subscribe and
17 basically click on the little triangle to
18 get alll the backup results. They will just
19 be automaticically there in iTunes for you.
20 Okay, so that's one way of actually
21 accessing the class material.
22 You can also use other pod
23 catchers like iPoders is another one, but I
24 think iTunes is pretty good for the things
25 we try to do in class.
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15
9.26.05 Organic Chemistry 241
1 So we have other tutorials here.
2 If you want to use iPoder, there's a screen
3 cast. If you want to subscribe to the class
4 blog, we'll take a look at that.
5 Notice at the top of all my blogs
6 is a little button for subscribing -- click
7 through that, subscribe to it. What will
8 happen is that on the left-hand side of blog
9 lines, whenever there's a new posting of any
10 kind, whether the FAQ or the 241 class, it
11 will appear in bold on the left. So that's
12 something that you definitely need to do as
13 soon as possible.
14 How many of you have actually
15 subscribed through blog lines for this
16 class? Not too many. Again, that's
17 something I can help you with. If it's
18 still confusing after you look at the stream
19 casts, you know, the next time we meet we
20 can look at that.
21 Any other questions on podcasting?
22 Let's look at the next question.
23 When are the tests and the exams? When you
24 are able to log into Web CT -- again, that
25 should be sometime by the end of the week.
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16
9.26.05 Organic Chemistry 241
1 When you go to the quiz and test section,
2 you will see dates associated with each
3 quiz. The quizzes don't end, so they have
4 no end date, but the tests have a start date
5 and end date.
6 Typically, the first test is
7 around the end of Week 4, start of Week 5,
8 so you want to plan to have all of that
9 material covered that I've talked about up
10 to the first reaction done well before the
11 end of the fourth week.
12 Now, you will take these tests at
13 Korman. There are certain rooms. That's
14 actually the next question here, where they
15 are. You basically lock into one of these
16 Korman rooms, sit down, log onto Web CT, and
17 take the test.
18 So we use video surveillance to
19 make sure that it's you actually taking the
20 test, but it gives you the flexibility of
21 walking in pretty much anytime within a
22 four-day period. So you can take the test
23 at your own convenience.
24 Now, that means that you also have
25 to know when Korman is actually open. So
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17
9.26.05 Organic Chemistry 241
1 make sure that you look at the hours. I
2 gave you a link to know when they have
3 scheduled downtime or scheduled classes.
4 The last day is what I call a
5 "no-excuse day." Make sure you understand
6 that. If you wait until the very last day
7 to take the test, I will not accept any
8 excuse for you to get an extension. So plan
9 to do the test anytime before the last day.
10 The reason for that is at the end
11 of the last day, I open up the tests so that
12 you can see which questions you got right or
13 wrong, okay? And I'm not going to delay
14 that because somebody chose to take it on
15 the last day and had a problem. That's
16 really important.
17 What happens if you miss
18 something -- if you plan to do it on the
19 last day and missed it, too bad, take the
20 makeup. That's another reason for you to
21 take a makeup.
22 So we just went over this, which
23 Korman rooms.
24 Now, what material is covered. I
25 showed you in the syllabus. At the bottom
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18
9.26.05 Organic Chemistry 241
1 of the syllabus, there were items of what we
2 were going to cover, some of the reactions.
3 That's basically a checklist of how I make
4 up the tests. So you want to use that to
5 make sure you've actually covered everything
6 we're doing in class. And that's -- I try
7 to tell you as specifically as possible what
8 I cover.
9 Are the tests open book? Well,
10 they are. You can bring anything you want
11 into the test room, but don't mistake that
12 to think that you can do last-minute
13 studying in the test room, because there's
14 not enough time.
15 Organic chemistry, at least the
16 way I teach it and test it, is very much
17 like math. You can all the examples in the
18 world in front of you, but if you don't
19 understand addition -- you know, I will give
20 you an example of adding two numbers you've
21 never seen before.
22 So you can have all the examples
23 in front of you, but If you don't understand
24 addition, you can't do the question.
25 So organic is the same way. I
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19
9.26.05 Organic Chemistry 241
1 give you examples of reactions, make sure
2 you know how it works, and then ask you a
3 question about a reaction that you haven't
4 seen before.
5 That's why it's not a problem for
6 organic tests to be open-book. It might
7 lower your anxiety a little bit if you think
8 you might forget a few things.
9 Question 6, we already talked
10 about this. When is the grading going to be
11 released. Well, actually immediately after
12 you take your test, you will know what you
13 did, but you won't know which questions you
14 got wrong.
15 So at the end of the testing
16 period, after the last day, I'll let you
17 know which questions you got right or wrong
18 but I won't tell you what the correct answer
19 is.
20 So you still have to work to
21 figure out what it is that you didn't
22 understand about each question
23 So is Web CT available at all
24 times? Well, it should be. But it's not.
25 Sometimes there are problems. Most of the
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20
9.26.05 Organic Chemistry 241
1 problems are fixed within like ten or
2 fifteen minutes. Occasionally, there might
3 be longer problems. This is another reason
4 why you don't want to wait until the last
5 day, in case there is a problem. But Web CT
6 also schedules downtimes. So if you were
7 going to practice your quizzes over the
8 weekend, it's important that you do it on
9 that particular day. You might want to
10 check what the scheduled downtimes are.
11 How do you resolve technical
12 problems? Well, it depends on where you
13 are. If you are on campus, probably if you
14 just walk over to Korman and ask the
15 consultants, they are well trained to help
16 you with any technical issue you come
17 across.
18 If you're at home, here's the
19 phone number. Of course, if your Internet
20 goes down, you won't be able to get the
21 phone number.
22 Also you can do it on line. If
23 you click on that link, it will take you to
24 the support. They're usually really
25 responsive. Depends on where you are.
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21
9.26.05 Organic Chemistry 241
1 Honestly, I've never had a situation where
2 we had a technical problem that we couldn't
3 resolve quickly. As long as you give
4 yourself enough time to do everything,
5 you'll be okay.
6 I haven't tested this out yet. I
7 think we should be okay.
8 What does it mean that a classroom
9 is reserved? What you will see in the blog
10 sometimes is that I will say, you know, the
11 Korman 111 is reserved from noon to 3 on
12 this particular Saturday. What that means
13 is that there should be no other students in
14 there. I sometimes do that if I can. But
15 it ensures you that you will have a quiet
16 time where you can actually take the exam.
17 You don't have to take it during
18 the reserve time. Some people are not
19 disturbed by other students in there doing
20 other things. If you are, you might want to
21 schedule it at a reserved time. It will be
22 in the blog, that information.
23 Why don't you get the correct
24 answer after the tests are graded? Well,
25 basically, it's your responsibility to
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22
9.26.05 Organic Chemistry 241
1 integrate the material I'm going over. It's
2 my job to help you understand it, but it's
3 your job to tell me how you tried to solve
4 the problem so I can help you.
5 If I simply tell you what the
6 answer is, you will do exactly the same on
7 the makeup as you did on the first test.
8 That's really the kind of
9 interaction I want to have with you most of
10 the time. It's you coming to me. You know,
11 if you're not getting to the correct answer,
12 show me the steps you're taking, then I can
13 show you exactly which step where you're
14 taking the wrong turn.
15 So that's why I don't give you the
16 answers. That would be too easy.
17 So why are there more questions on
18 the makeup with the same amount of time?
19 Again, you're supposed to be considering the
20 first test as being the one where you do
21 best at. So, you know, you're going to be
22 penalized if you don't get the material
23 right away.
24 But you can still completely make
25 yourself up. There are extra questions, but
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23
9.26.05 Organic Chemistry 241
1 honestly, I don't think I've ever had a
2 situation where the student couldn't
3 complete it. It's just a little bit more
4 intense, but it's definitely doable. It's
5 not an unrealistic number of questions.
6 Question 12. Why do I get e-mail
7 notices iabout my exam room and time that
8 conflict with the times in Web CT? Because
9 you won't be taking the exam in a normal
10 classroom but in one of the Korman rooms in
11 exactly the same way as you take the tests.
12 These are all automatic. If you get an
13 alert from SAS, just ignore it
14 STUDENT: (inaudible).
15 INSTRUCTOR: Which exam?
16 STUDENT: A common exam that supposed to
17 be at 8 o'clock in the morning, aren't you
18 supposed to tell us? (Inaudible.)
19 INSTRUCTOR: That's news to me. I
20 haven't heard of that before.
21 STUDENT: It's on the schedule here
22 (inaudible).
23 INSTRUCTOR: Well, it's the first time
24 I've heard about it so I will try to find out more
25 about it.
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24
9.26.05 Organic Chemistry 241
1 So the exam period will start on the --
2 it's usually on the Friday right after the last
3 time that we get together. And you have maybe, I
4 think, until Wednesday or Thursday. So you have a
5 big chunk of time to actually schedule your exam.
6 Is there a curve? If there is one, it
7 will be in your favor.
8 Now, can you take this course if it
9 conflicts with another course? Yes, you can,
10 because the way the course is structured, I expect
11 that you should be able to do very well if you
12 take this class completely on line.
13 The last time -- all the classes I run
14 this way, we end up with an attendance rate of 10
15 to 20 percent. So as we move through the term,
16 the vast majority of you find it doesn't do any
17 good to come here to listen to me talk if you have
18 a screen cast available, which is just as good or
19 better, because you can pause it and go back and
20 forth.
21 Basically, you definitely can take this
22 class fully on line, and that has not been a
23 problem at all. We will get together, of course,
24 for workshops to go over material with, but I
25 won't be covering any material in the workshops
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25
9.26.05 Organic Chemistry 241
1 that is not explicitily covered in all the
2 lectures. So you won't be be missing anything key
3 if you don't come to class.
4 Question 15. How do I find test
5 averages? They will be posted on the blog like
6 any other announcements.
7 What's the best way to study organic
8 chemistry? First of all, keep up with the
9 lectures. As soon as you can, try the quizzes.
10 They're designed in exactly the same format as the
11 test and exam questions are.
12 Part of what you do with the quizzes is
13 going over the material. But the other thing you
14 do is look at the format of the questions, making
15 sure you don't have a misunderstanding about the
16 format.
17 So it's important for you to do the
18 quizzes even though they don't count.
19 STUDENT: (Inaudible.)
20 INSTRUCTOR: Yeah, the quizzes don't
21 count. In fact, I did make them count one term
22 and there weren't any more students taking them.
23 So basically, it's unwise not to do them, but you
24 don't have to do them.
25 A question in the back?
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9.26.05 Organic Chemistry 241
1 STUDENT: (Inaudible.)
2 INSTRUCTOR: Yeah, you have an infinite
3 number of tries with the quizzes, and that's just
4 the Web CT. You don't have to wait for it to be
5 activated; you can go directly into the existing
6 version of it and log in as a guest and take it.
7 If there are quizzes that you don't
8 understand, find the part that covers the topic
9 and listen again. As you're more familiar with
10 the way the lectures are archived, there's an MP3
11 audio, a PDF, and screen cast.
12 If you're looking for any material in
13 class, the quickest way to find material is to
14 look at the PDF, see roughly where it is, so like
15 if it's Page 3 out of 9, you know it's a third of
16 the way through. That's the quickest way by far
17 to find information. You don't have to listen to
18 the whole screen cast if there's only one part
19 you're interested in. You should be able to fine
20 any information you want immediately.
21 If you do that and still don't
22 understand, make a list of those concepts, and
23 when we have workshops, 1we can work on that.
24 One.drexel.edu is slow sometimes, but
25 what can you do? Two ways of accessing Web CT,
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27
9.26.05 Organic Chemistry 241
1 and one is through 1.webct.edu, which makes you
2 log in a couple times. If there's a problem with
3 1.drexel and you don't have access to Web CT, you
4 can directly access Web CT.
5 The link I'm giving you here is
6 webct.drexel.edu, and this address is valid for
7 the previous version of Web CT. The new version
8 of Web CT, as soon as I know the link, I'll put it
9 up. If you click on this link, you can actually
10 log in as a guest.
11 What do you do if your computer crashes
12 during the test? As long as you keep clicking
13 save, nothing will happen. You could even go to
14 another computer, restart it, and it will
15 remember. Obviously, click "save" every time you
16 make a selection.
17 How do you save the flash file? I've
18 only had one student ask this. If you're
19 interested in doing that, you can go through this.
20 If you're not, that's okay, it's not important.
21 As long as you have a connection, through the
22 Internet you will have all the screen casts.
23 Do you have to use Cite U Like? Maybe
24 you can think about if you would like to do it or
25 not and how you would like to structure it. I can
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9.26.05 Organic Chemistry 241
1 answer these questions if more detail. The Cite U
2 Like is a website that forces you to have the
3 proper reference when you're citing peer-review
4 journals look at the example in chemical 242. We
5 don't have to go into the details about that
6 today.
7 How do you subscribe to an RSS feed?
8 RSS stands for "really simple syndication," and
9 it's basically a way for people to automatically
10 get updates from various RSS feeds. Some are like
11 news; a lot of people get news like that.
12 Everyone who actually maintains a blog has an RSS
13 feed you can subscribe to.
14 There are two different kinds of feeds
15 relevant here. The one RSS is the one you text
16 for the class; that's where you use blog lines.
17 The other RSS subscription that's important is for
18 the pod cast.
19 I use the same blog. Not everybody
20 does, but I do it for simplicity. That's why you
21 need a pod catcher to get the files, and you need
22 a normal aggregater to get the text.
23 Again, if this isn't making any sense to
24 you at all, bring your laptop and we can set you
25 up. That's basically the idea.
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9.26.05 Organic Chemistry 241
1 I've linked here all the things we need
2 to subscribe to and have shown you the tutorials.
3 STUDENT: (inaudible).
4 INSTRUCTOR: When you subscribe to.
5 STUDENT: Blog.
6 INSTRUCTOR: To the class blog?
7 STUDENT: Yeah.
8 INSTRUCTOR: No, it's completely
9 anonymous. So anyone can subscribe. There's no
10 password.
11 All right. So there's a lot of
12 questions. You can come back to this if you're
13 unclear on any of this.
14 I have a little bit of time left here.
15 The third entry here is the actually class blog.
16 There are two things you will find here. Mainly
17 the arrest curve lectures and the class
18 assignments that you do. If you do one of the
19 class assignments you will be putting it in the
20 blog so you have to get me to add you as a number
21 if you do the assignment.
22 Right now, all there is really is just
23 the lectures. So again, it's reverse
24 chronological order. If you want to go to the
25 first lecture, you scroll down. What you see in
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9.26.05 Organic Chemistry 241
1 the first entry is the Lewis approach to molecular
2 structure this is what I go through in the first
3 lectures.
4 And the classes are numbered so it's
5 from 1 to 39. The only one not in there right now
6 is class one because that's this class I'm doing
7 now. It's being recorded now and archived. But
8 all the other lectures in lecture format are
9 actually already there.
10 So you can look at the PDF. Again, the
11 streaming screen casts that's in the same flash
12 format.
13 Scroll down. See this little cursor
14 here? you can move it anywhere inside of the
15 class. Okay?
16 There's also the PDF. This is going to
17 crash my computer. Acrobat is a little finicky
18 sometimes. So the PDF is basically all of the
19 screens that are in the screen cast that are just
20 available as separate static products.
21 So if you were looking for particular
22 material, I suggest you start with the PDF. And
23 let's say you were interested in this valence
24 periodic table. So you notice this is Page 3 of
25 4. So roughly, I would go, you know, somewhere
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9.26.05 Organic Chemistry 241
1 about three quarters through the screen cast to
2 try to find where I talk about that. That's the
3 easiest way to find something.
4 And the other one is the MP3. When
5 you're accessing the blog in this way, this is not
6 a pod cast; this is just a website you can go
7 through. And technically you wouldn't have to
8 subscribe to the podcasts or the blog, but if you
9 don't, you won't know when anything has been
10 changed.
11 So the reason you want to use the RSS
12 subscription is to know that something has changed
13 so that you don't have to keep checking the whole
14 website, okay? But you can certainly just go to
15 this blog and download, you know, the file
16 individually.
17 Now, if you use iTunes to do that, this
18 is what it will look like. So in iTunes, you see
19 here the Lecture 38, Lecture 38 PDF. So the audio
20 and the file will actually be here. That's how it
21 shows up on here.
22 Let me just give you a taste of what the
23 quizzes look like in Web CT. Any one of you can
24 do this now. You're not dependent on
25 (indiscernible). Let me see if...
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9.26.05 Organic Chemistry 241
1 This is the course menu, and one of them
2 will be quizzes and tests. It will show up "begin
3 quiz," and then you can just take it.
4 So here I'm testing you on the Lewis
5 structures, testing you on the charges on the
6 individual atoms, which, as soon as you listen to
7 the first lecture, will make more sense.
8 This is where you can come to test
9 your knowledge. And, again, the tests will
10 be very similar to this.
11 Okay. So really the only thing
12 that's in Web CT is the quizzes and the list
13 of the problems from the book.
14 Okay. Let's try to wrap this up
15 here. You see here, there's a button for
16 workshops. Give me a couple minutes,
17 please. Quiet.
18 So the workshops are preplanned up
19 to a certain point. I want to be able to
20 spend time with you that's most productive,
21 so that means I want to work with the things
22 you're having the most trouble with.
23 I'm out of town next week so the
24 next class when we meet together is going to
25 be October 5th, on Wednesday. And I have
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33
9.26.05 Organic Chemistry 241
1 your schedule, so subscribing to the class
2 RSS feeds, FAQ podcasts, how to update the
3 wiki, the electronic configuration in the
4 Lewis structures.
5 So I will give you additional
6 problems to work on. You can work either by
7 yourself or with a team. So when you come
8 in, sit next to people you want to work
9 with. And as you go through the problems, I
10 will circulate and help you try to find out
11 where you are having difficulty with each
12 problem.
13 But anything is fair game here
14 STUDENT: You don't have a time for
15 these workshops, do you?
16 INSTRUCTOR: It's the class time. Yeah,
17 this will be the last formal lecture that we have.
18 STUDENT: Wednesday and Friday won't be
19 formal classes?
20 INSTRUCTOR: All the formal classes are
21 already recorded, so those are now assignments for
22 you. You are expected to watch the archived
23 lectures. So then when you come to the workshops,
24 I expect that you've looked at the lectures, tried
25 to do the problems, and now we will try to figure
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34
9.26.05 Organic Chemistry 241
1 out what you have a problem with.
2 You don't have to come to every
3 workshop. If what we're going to be talking about
4 isn't relevant to the problems you're having, you
5 don't even need to come to the workshops.
6 You can e-mail me a request with a
7 topic, and I will add it as we have time.
8 Answer your question?
9 STUDENT: (Inaudible.)
10 INSTRUCTOR: This week? No, I'm out of
11 town this week.
12 STUDENT: These dates are the only time
13 there will be a workshop.
14 INSTRUCTOR: In the coming future.
15 STUDENT: You can refer to this page for
16 any date of the workshops?
17 INSTRUCTOR: Exactly.
18 * * *
19
20
21
22
23
24
25
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