 We are going to continue talking about ways to draw organic molecules We're going to talk about how to draw resin structure resin structures Lewis structures today And then at the end of class we're going to do an active learning activity I have to get a certain amount done in three lectures for the filming and after we're done with that Then we're good to go to do whatever we want. Okay. All right, so we talked last time about drawing 3d structures and So 3d structures not worrying too much about these until we get to chapter 5 And then when we get to chapter 5 we'll be drawing these all the time, but when you draw a 3d structure Correct bond angles are included or I should say correct bond angles are required Okay, so we're trying to convey how something is looks in three-dimensional space We said with a Lewis structure you don't have to show correct bond angles But with a 3d structure will sometimes see it drawn 3d dash wedge is is one way to do it So for example, this bond angle should look to be about 120 How do we know that bond angle is 120 degrees well, we're going to talk about that coming up. Okay, if you don't remember that from jikim And then we have this here That should look to be a little smaller than 120 a 109.5 Well, how do we know that's 109.5 again? We're going to talk about that coming up All right, so that's what we have when we have a 3d structure and then Another way to draw structures that I'm sure that you haven't seen a skeletal or bond line structures This is going to save us a lot of time When we're drawing and if you look at the structures that we have on the very first page of the notes There's a lot of skeletal structures in those and if you had to draw them with every single ad and it would take you a long time to do that Okay, so that's the whole idea. So it's a simplified way of drawing Especially drawings that contain rings. It's very very helpful when it's above a structure that contains rings So the guidelines assuming assume that there is a carbon at the junction of any two lines are at the end of any line So for example if I have this that means that at this juncture right here Right there. That means there's a carbon at the juncture of any line is a carbon Assume there are enough hydrogens around each carbon to make it tetravalent. So Carbon would that means carbon would have four bonds. So the the three hydrogens. These are three hydrogens here Okay, so this is a carbon. This is a carbon with three hydrogens This is a carbon with three hydrogens the carbon in the center needs two more hydrogens to be to have four bonds Tetravalent another way of saying it has four bonds. So that's what that would be So this structure here is equivalent to that it saved us a lot of time in drawing. Okay, so we do use skeletal structures There are some students who just don't ever feel comfortable with skeletal structures And if they see a skeletal structure on a test, they write it out with all of the atoms there and there's nothing wrong with that That's perfectly fine. Okay So you have to so carbons are understood hetero atoms hetero atoms are things other than carbon like The most famous ones for us are oxygen nitrogen and the halogens. You do have to draw those Carbon atoms in a straight chain are drawn as a zigzag Lone pairs are often left out and are understood. Okay may not be understood by everybody, but they are understood You always have to include formal charges Okay, you have to include formal charges because if one of these two carbons on the end here had a formal charge I wouldn't it wouldn't be having that many hydrogens So we it needs to be clear to anybody in the whole world what you're trying to convey And so we always need formal charges in all of the different ways that we have to draw structures Okay, again, lone pairs don't have to have so the skeletal structure of the sample compound that we've already talked about Would we look like this? Okay, so let's label what that means Okay, so this one right here. That's a that's a CH3. That's an end of a line Therefore, it's a CH3 There is a hydrogen bonded to this carbon. We want to make that carbon tetravalent. It's not charged So it needs to be tetravalent. Okay, so the hydrogen bonded to this carbon is Not required you can draw it if you want so we can we can actually use a combination of condensed and Skeletal You can draw it if you want And I think that looks a little weird without that hydrogen drawn in so I don't think I ever draw it that way I think that that hydrogen I draw it in okay This oxygen right here has a positive charge. This is required Okay, and this hydrogen right here is also required It's required It's only not required when you have it bonded to a carbon but if you have a hydrogen bonded to a heteroatom you have to draw the hydrogen in this hydrogen is required because It is bonded to something other than carbon Questions so far on skeletal structures anybody All right, so let's redraw the following compensating all atoms lone pairs and formal charges Okay, so I'm looking at this carbon right here that carbon right here is bonded to three things It's at the juncture of two lines That means that there's a hydrogen there. So let's draw all of the atoms in Loan pairs are not required. You can draw them in though. I'm going to draw them in just for the heck of it Okay, so it's going to look like that. That's what that means and Rings especially we're going to draw this. So this is a this is a six-membered ring with carbons all in the ring Let's draw that It just takes a lot longer to draw. I'm so glad we have the shorthand way of doing it Okay, so this carbon has two hydrogens to make it tetravalent This carbon has two hydrogens to make it tetravalent This carbon has two hydrogens this carbon has two hydrogen That carbon's got a negative charge. So what do we put on that carbon? How many hydrogens? One hydrogen and a lone pair Now the lone pair is not required. I Like to put it there myself. I usually do put that there. Okay, so I'm going to go like this Yeah, but the back. Oh, yeah Go ahead This one here. Yeah, I heard yeah, you I usually know when I made a mistake because I'll hear a little And I should just ask you I gotta learn to just ask you Yeah, I'm missing a carbon. See I would have missed that one on the test Okay Yeah Everything else good everything else looks good to me So you see you have to know carbon with a negative charge has three bonds and a lone pair So it may be worth your while to like just memorize those those those common charges that we're going to see over and over again Okay, so let's see Keeping yeah Yeah, generally not drawn that way but right now you haven't heard that rule so it's okay go at it, you know Sapling will not let you do that. So it's probably a good idea not to sapling will mark it wrong Okay, there's also something else about sapling sapling will sometimes I think I've taken them all out Sapson sapling will sometimes draw them like this Turn that on That's not legal That's not legal Okay, you can't draw it that way You know like I could put a CH3 here, but these carbons here are not okay. You don't want to draw it that way That's not really skeletal if you're putting a carbon at the end of every line Okay, so I believe I've taken them all out if if I did leave one in where they draw it that way please let me know so I can remove it from the Worksheet, okay It is common to use more than one type of structure So again, if you turn to that very first page of the notes they use a combination of skeletal condensed You know it's We're not super strict about this So for example All right, so I didn't want to draw out that oxygen carbon bond And I didn't want to draw the three bonds to hydrogen for that. That's okay This is condensed and and CH3's are those are called methyl groups We're going to talk about that nomenclature coming up later in the quarter But it's super common just to write them a CH3 without drawing them all completely out And and maybe you don't like the way this looks with this sometimes I feel that way I don't like the way this looks with this bond here. And so I will sometimes write a CH3, okay So like that I will say that you want to I Will say one thing here if you draw see CH3 you can draw like this and then sometimes and then you can also draw it like this or you can draw it like this It's perfectly fine to draw it like that if you go into chem draw and you and you try to label a bond And you write CH3 it will flip it around so it's this way, okay? So it will flip it around automatically That's legal though. And so is that legal to write it like that But it is not legal to do that with say an OH so OH here This should be OH not not OH Okay, so carbon gets things that oxygens and nitrogens don't you don't want to draw it that way, okay? So this is a problem So you may just want to flip these things around anyway Okay, so we have some flexibility here how you want to draw things and again if you want to draw every single bond There is absolutely nothing wrong with that Questions on skeletal structures Let's talk about how to draw Lewis structures It's a mixed bag in here. Some of you are really good at Lewis structures Some of you are not and some of it depends on your Preparation for this class so for example if you had AP chemistry in high school and you skipped over chem 1a That's where we learned to draw Lewis structures. So you've looked you've missed out on that information on that And so and also it might have been a couple years since you've had AP chemistry So we start from ground zero here and and talk about how to do this Couple things are different than in some ways. It's easier than G cams G cam you have the whole periodic table here We just have a really small amount of the periodic table and so But one thing that's really different is in G cam you always had a central atom when you were drawing Lewis structures We don't necessarily have a central atom So for example, where's the central atom here? There is no central atom. Okay, so that's something that's completely different All right, let's talk about the traditional method and then we're gonna have shortcuts that we can do and as you go along You'll be adopting more of the shortcuts Arrange atoms in the proper orientation. We have condensed structures. So that's easier for you to do than maybe in G cam Some of the valence electrons for all atoms Sometimes we don't even have to do that But if you have a charged molecule, I highly recommend that you add up the electrons. Okay, so you make sure you're drawing it correctly Distribute electrons by placing bonds between atoms one bond is to electrons use remaining electrons to satisfy the duet rule You're gonna distribute the extra electrons. We'll look at some examples. That's the best way to see how to do this If all of the valence electrons are used and an atom doesn't have an octet then then You're gonna form multiple bonds where possible. Okay, so that's what we're gonna be looking at here The other way to do this is to use the honk one two three four rule for neutral compounds Again, if you don't if you have something that's not a neutral compound. It's charged I will I really highly recommend you take the extra step to count electrons So here we go here. Let's start the loose structure for CH3 cl. Okay, I'm going to add up electrons first Carbon has four electrons Hydrogens has there's how many hydrogens we have three hydrogens so three times one electron so that's three electrons and Chlorine has seven if we add that all up we get 14 electrons total So by the way that number when you add up all the electrons should be even If it's not even that means that you have an unpaired electron. That is called a radical I will not be giving you anything that has a radical So if that number is not even you've made a mistake go back and see where you made the mistake, okay? Now Honk one two three four rule carbon needs four bonds, so let's draw carbon with four bonds Hydrogen has one bond so we can put a hydrogen and it doesn't matter where on this for you put the hydrogen You can go here. You can go here and then we have a chlorine left over and Now let's add up the electrons. We have two for each bond to four six eight ten twelve fourteen Okay, that works out really well That was just using the honk rule But also the condensed structure does tell us that we have a ch3 and then that's bonded to a cl So I mean we really didn't need you know, we could use any of those That's an easy one to draw. Okay, and then we just give Clark chlorine its lone pairs and because it's neutral we We know we're not going to have any Formal charges on any atoms, okay? So hopefully they'll all be that easy on the test, huh? That is multiple ways to do it All right. Oh, I do want to you. I know you've already turned the page. Sorry about that. I do want to say a couple things here Don't forget to bra draw long non-bonding electrons or lone pairs Also known as lone pairs if it's a Lewis structure. I want to see all of them and Don't use lines for lone pairs in Okam I know you like that little shortcut, but we don't use it in Okam so what I mean is and Let's change the color here. So it shows up a little better We don't want to do this Okay, and so the reason why we're I'm just showing you a bunch of shortcuts So we don't take away your lines because we we want to make you take longer to draw We take away the lines because they can be very confusing Okay, like so for example like if you have a carbon with the line Is that a carbon or is it a chlorine and Since we have formal charges if you have a line there What if that's what if you have a negatively charged chlorine? Is it is it is the line for the lone pair or as did you leave off the negative charge? And the other thing is we use curvy arrows when we're drawing when we're reacting Molecules with each other and if you use a curvy arrow, you know, you haven't if let's say you had an arrow coming in somewhere here, okay now That seems super clear there, but you haven't graded 400 exams to see that it could be very confusing and unclear So no lines for lone pairs here. Okay, so we just take a little extra time to draw the long Okay, I already did the shortcut follow the honk one two three four rule Okay, but let's just do it here anyway carbon four bonds hydrogen and chlorine One bond each and so carbon has four bonds, so it's got to have four bonds here Four bonds three of them to our hydrogen one of them to chlorine. All right, let's do the structure for ethylene So when we get into 51b, you'll be able to draw ethylene just by being given the name right now You're not going to be able to do that So let's go ahead and add up electrons for ethylene. We have two carbons so two times four Equals eight electrons We have four hydrogens four times one equals four electrons We have 12 all together and So it says there's a CH2 followed by CH2. So let's draw the CH2 CH2 again, these bond angles don't make any difference here. It's a Lewis structure now let's Distribute electrons. We've already distributed some of them. We have two for every bond two four six eight ten One more pair of electrons. Okay, let's put that here. We can put that on either carbon Okay, so we see that this one does not have an octet If we have a lone pair next door and we have don't have an octet that means we can draw a bond there So we can just take these electrons and move them. I'm going to move them So they're between the two carbons, so I'm going to turn that lone pair into a covalent bond and Then I'm going to draw it like this And again these hydrogens that are on the top if you do them going down doesn't matter. Okay, it's the same compound questions on that one anybody Okay, CH3 CHOH plus Okay, let's do that we have two carbons that's two times four electrons I'm going to go across this way have a little bit more room that way. We have five hydrogens That would be five times one We have one oxygen That's six electrons We have a positive charge Okay, so technically this this should be drawn like this with that positive charge outside the bracket because that positive charge is not Going to be on hydrogen, so that should be drawn outside the brackets Okay, plus a Charge if it's a positive charge we remove an electron if it's a negative charge we add an electron It's an easy thing to forget I'm going to remove an electron because it's a positive charge minus one electron and then that it ends up to 18 electrons Easy to forget to do that if I forgot to do that Then I would have 19 electrons and I would say to myself wait This is supposed to be even if it's not even I've made a mistake and then you look and it's 18 electrons Okay, so let's distribute the 18 electrons here But first of all, let's take that condensed structure and convert it into to show how that the bonding is or it has in this molecule So we have CH3 We have carbon bonded hydrogen And then we have an oxygen bonded to hydrogen So it looks like that should look like that. All right, we have 18 electrons to distribute Let's distribute those 18 electrons We've got how many so far two four six eight ten twelve fourteen I'm going to distribute the electrons to the more electronegative atom first Okay, so since I don't really have a central atom here. I'm going to give them to oxygen here Two four six eight ten twelve fourteen sixteen eighteen. Okay, so if I draw it like that then Looks like oxygen is not charged carbon is not charged, but this is charged. What's the charge on that? Positive charge so you can see that by looking at it you could use the formula you could memorize it or The way I do it is I what I say is okay This carbon here owns one electron from each of these bonds for the purposes of formal charge only One electron from each bond so carbon owns one two three. It should be four So it's down one electron Okay now you can draw it that way or You know you see something without an octet. So what did we do over here? We should put a positive charge here What did we hit when we have a lone pair right next to a positive charge? That means that we can move those electrons here and we can make up a bond there Okay, so we actually have two different ways to draw this structure. So if you drew either of these They would both be correct. There are two resonance structures When we have multiple ways that we can draw something those are resonance structures So now the oxygen had blue two lone pairs one of those lone pairs We moved over and notice I put the arrow the curvy arrow to move those two electrons halfway in between the carbon and the oxygen We've taken that lone pair and we've turned it into a covalent bond now this carbon is no longer charged But this oxygen is charged So let's let's do it that way. So oxygen owns All the lone pairs and one electron from each bond one two three four five Five electrons. It should be six right Oxygen group six should be six. So that means that we have a positive charge there Okay, again feel free to use the formula, but don't I will see exams where Students use the formula for every single atom including the hydrogens including things that have a zero Formal charge and those are students that don't finish the exam And so I want you to make sure that you are only calculating that for things that need it So don't forget formal charges and also make a little check for yourself each structure should have the same net charge All right, so a structure number one We know the overall structure has to have a positive charge Structure number one has a positive charge structure number two has a positive charge Okay, so I in order to go from structure one to structure two. I used a curvy arrow Curvy arrows show movement of a pair of electrons the and it's really important. You have the board have the right direction Okay, so the tail shows where the electrons are coming from let's draw it this way Begins at the current position of the electrons The curvy arrows and the head shows the new position of the electrons. So this arrow came from this lone pair here It's gonna the arrows are gonna come from either a lone pair or a bond This comes here from this lone pair. That's where they are currently located This shows where we're moving them between those two that carbon and that oxygen Right questions Any questions Important points about this example Yeah It does matter in this case we're moving two electrons So we have a full head on the arrow if we're moving a single electron. We use a half ahead on the arrow. Okay, so fish hook All right more questions All right, so we can represent this above molecule by more than one Lewis structure So if I gave you this molecule and asked you to draw the Lewis structure on the test You would get credit for either one of those structures. It would both be correct Resident structures differ only in the arrangement of electrons not in connectivity So when we draw resident structures, we don't want to be moving around atoms atoms stay exactly where they are We only move electrons Okay, and we use a resonance arrow. This is a resonance arrow Generally speaking when we have a series of resonance structures, we use a resonance arrow and we use brackets We also use brackets to indicate resonance structures The actual structure of the molecule is a resonance hybrid of these two structures. They are not in equilibrium So I'm going to write that in red. They are not in equilibrium All caps for that Because there's a tendency even when you know this and you learn this to still think of them going back and forth They are not in equilibrium. So let's review our arrows. We have a resonance arrow here Equilibrium arrow we have an arrow going one direction. We have an arrow going the other or we have it like this You'll see both of those. Those are equilibrium arrows not to be confused with a resonance arrow We have a reaction arrow, you know a plus b goes to C. That's straight And then we have curvy arrows So this answers your question over here That's a curvy arrow showing the movement of a pair of electrons and then we have a fish hook arrow Showing the movement of a single electron. So those are all the arrows. So that's not an equilibrium arrow We're going to need an analogy for this because it's hard not to think of those things Going back and forth So this is a plum. This is an apricot This is a pluot Okay, so you cross a plum and an apricot you get a pluot. So the pluot is the analogy for the hybrid When you have a pluot sitting in your hand It is not changing back and forth from a plum to an apricot to a plum to an apricot from a plum to an apricot It's a pluot. Okay, so that's the true structure So our hybrid is the pluot. That's the true structure of the molecule And I can say that a bunch of times, but you're always going to think of that thing going back and forth But yeah, they're not they're not going back and forth So what we're going to do is we're going to draw a hybrid structure Now again weird steps happens when you go from a Mac to a PC. So number four should be correct on your page So I want you to be able to draw hybrid structures. And I think That seems to be the hardest thing in this chapter for students to draw the hybrid so What you're going to do is you're going to draw everything that's not changing all of the single bonds you're going to draw You're going to draw dotted lines for pi bonds that are changing location are not showing in every resident structure You're going to do that when I draw hybrids. I leave off lone pairs and completely ignore them It's too confusing. So forget about the lone pairs Draw the bonds any bonds that are changing are dotted Partial charges for charges that are changing locations. So in that last structure, we had a positive charge on carbon in one of the structures We had a negative charge We had a zero neutral charge on carbon and then in the other structure We had a positive charge on oxygen in the other structure. We had a zero formal charge. So that means those would be partial charges and To make this easier. I don't know how it did that with to make this easier But let's draw them. Let's draw a hybrid structure for that compound. We just drew I'm drawing in the lines that are not changing single bonds between each of the atoms And I'm going to scroll back up to see which one I drew first You don't have to turn the page it's all the way up here All right, so when there's so notice in the first structure here I have a single bond between the carbon and the oxygen here. I have a double bond So that's the the pi bond is going to be dotted I'm leaving off the lone pairs because it gets too confusing in this structure right here a positive charge on carbon in this Structure, it's zero. So it'll be a partial positive in this structure I have a zero charge on oxygen in this structure. I have a positive charge so that will be a positive Okay, so let's go back and do that All right, so dotted line here positive partial positive here because We're changing charge on that atom Oxygen here also has a partial positive charge And so what we see is that the positive charge is shared between two atoms. It's not just on one of them It's shared Okay, so the positive charge is shared between The carbon and the oxygen So we have delocalized electrons. That's going to be a big deal here in this class delocalized electrons Okay, and the reason these are positive is that we have For this carbon right here. It has a positive charge in the first structure and zero charge in the second and The same thing goes for the Same thing goes for the other. Okay, so that's how that's what I would want if I have you draw a hybrid Questions on drawing hybrids anybody If you wanted to In one resident structure the oxygen has two lone pairs in the other resident structure It only has one. So I would just draw one lone pair here But again, I really think it's easier if you don't do that. Okay More questions on hybrids More important important points about resident structures resident structures are not real Okay Any individual resident structure does not accurately represent the structure of the molecule only the hybrid does so the hybrids real The resident structures are not real that being said we're going to be drawing resident structures all year long So they're real enough for that we need to draw them They're not in equilibrium. We already said that they're not isomers Two isomers different the arrangement of both atoms and electrons Whereas resident structures differ only in the arrangement of electrons. Okay, so for example if we go from here to here if we take the Electrons in one of those pi bonds and we move it on to oxygen we get this structure So the electron pair Moves to a different location. I have not moved any atoms. I'm just moving electrons That means that to a different location. That means they are resident structures Over here, you can see that. Okay. We're moving electrons and we're moving an atom So this hydrogen here is bonded to oxygen and now it's bonded to here So so the atom is moving to a different location It's a hydrogen moves to a new location. So we say The term we'd use for that is they have different connectivity the atoms are connected differently So these are actually constitutional isomers. So so I rarely use the word just isomers Okay, they're because we want to be more specific. These would be constitutional isomers so so same Molecular formula different connectivity Okay, so more things I want to say about these resident structures They're not equivalent in energy So when we draw a hybrid we kind of draw it as if that hybrid we've already drawn It's kind of like you have 50% of this one and 50% of that one. It's not really true in reality So one of the things we want to be able to do is rank resident structures So we can see which one's more important which one's less important. Okay so What makes a good resident structure? Well the best resident structures are the most stable So let's look at what we're going to be looking for Rule number one. These are by the way. These are in order of importance In order of importance. I wrote that in the different colors. So that would stand out The most important thing is rule number one resident structures with more bonds and fewer charges are more stable Resident structures in which every atom has an octet are more stable Resident structures that place a negative charge on more like your negative atom are more stable Okay, so rule number one and rule number two go together and they are the most important So for example coming straight out of G chem if I asked you which one of these resident structures was most important 99% of you would say That one's more important because oxygen's more electronegative Then carbon and so it's much less happy with a positive charge. It's what most of you would say However This carbon does not have an octet. This carbon also has this also has one less covalent bond here Okay, there's one less covalent bond here. So it's not it's not the best one Okay, so we would call this one minor We would call this one major So the charge is the last thing you look at the first thing you look at is have we maximize the number of covalent bonds? Do all atoms have an octet? So this is a minor. We call this a minor resonance Contributor and this is a major resonance contributor Okay, so if we count all the covalent bonds we have fewer we have Fewer covalent bonds by one We only have seven over here. We have eight more covalent bonds. That's better more important Here we have eight Carbon has no octet Over here all atoms have an octet and this this first resonance the second resonance structure does have in all honesty It's got one knock against it. So here positive charge On more electronegative atom So that's bad, but it's not bad enough to make this one It's not bad enough to make this one the worst resonance structure One with a carbocation is the worst resonance structure Alright, so we want to look for the these following features in order of importance. There's a couple additional points. I want to make It is okay to have carbon with less than an octet in a resonance structure Carbon gets a free ride here Carbon can have would be without an octet in a resonance structure We even have a name for it carbocation, but it is never but never draw oxygen nitrogens or the halogens without an octet Now there are a couple of questions in Smith where they do just that not okay I don't you will never you will never draw it in any of my exams for the whole year Okay Don't draw resonance structures with the two plus or a two minus charge. Oh There's a couple of times when they do them Are you see things like ozone? We have three oxygens in a row. I Will never have you draw two plus or two minus charge on anything ever Okay, extremely miners should never be included never ever exceed an octet for second row elements No Texas carbon no pentavalent carbon. Okay So they have four bonds Okay, there is an additional Under the practice link we have lots of extra things we throw in there And there's a little handout about drawing resonance structures I think it would be worth your while to take a look at that This is one of the most important things we learn that we will need a good grounding in all year I do want to come back. We're not going to be able to finish it, but I do want to come back and We have an in-class activity I didn't get enough done so we can't probably won't finish it We will finish it at the beginning of class the last time next time Okay, so what do I want here? Tell me what you want to do. I want to open up this Come on or maybe we won't Word is not responding Okay, hang on. We're going to get started here We've got a minute and a half We're going to take advantage of that minute and a half All right So when you can work on this at home, and we're going to come back and talk about it on Friday So when when we did this we said if you have oh, sorry So here's what we're looking at Condensed structure CH3 CO2H. We said it looks like this not this not this And so what we're going to do and we will work in groups when we come back It's too late to do it right now, but we'll work we were we will work in groups And I want you to draw a Lou structure for this for this and for this and so in other words add up all the electrons Distribute them do exactly what we did in class today And what you're going to find out is there's a problem with this one and a problem with this one We'll talk more about that on Friday