okay here we are on make this part three of chapter three and in part to the when we last talked this is the last slide we got to and this question is asking us to rank these four compounds in terms of increasing boiling point okay then it's a classic kind of question you might see in an exam and let me change this to laser pointer so that doesn't quit so a quiz going away I want to point out that if if you use these less than signs what this is saying and in sample answer a this is saying that a boiling point is less than B's which is less than C's which is less than DS so we're going increasing boiling point from a low boiling point to a high boiling point so as we look at these I think the first thing that should jump out at you is we have two alcohols and those guys are going to be our winners they are going to have the highest boiling point and so N equals C or D as the lowest boiling can be eliminated right out of the chute so we can eliminate C right out of the chute okay so C and D are going to boil highest and so we look at our options here we've got C and D as the highest and these first two and the this option D and then what about this one e they are equal to each other I was look at those two molecules and let's determine how they differ okay so we have a ch2oh and a ch3 we have a CH ch2oh and a ch3 it turns out that these are actually the same molecule they're just slightly different depictions and so I actually access this I didn't write this particular question but so the the designer of this question in this case showed the three-dimensional structure of the ch2 there they just use a a condensed structural drawing and and then Nick they use three-dimensional structure of the ch3 here we're here to issues of structural drawing so those two are exactly actually the same alcohol okay and they are ethanol ch3 ch2 O H that's ethanol ch3 ch2 O H that's ethanol so those two are the same alcohol so they're gonna have the same boiling point so right there it tells us that E is correct well let's think about this clearly they're alcohols are gonna have higher boiling points they do have a slightly lower molecular weight than either of these two I haven't actually calculated the molecular weight but if you have one two three carbons and an oxygen that's going to be two carbons and oxygen hands down in terms of molecular weight so this is a little bit higher in molecular weight but it does not have an alcohol all it has is a carbonyl and yes the carbonyl would have a polar bond here there'd be a slight partial negative charge on the O a slight partial plus charge on the carbon so you'd get dipole-dipole interactions but remember dipole-dipole interactions are much weaker intermolecular forces than our hydrogen bonds that you would see in alcohols okay so this guy is actually going to boil it a little bit lower temperature than these two and maybe quite a bit the molecular weight helps this have a little bit higher boiling point than if this had the same molecular weight as these two it would it would make a difference in you know how closely or how much more so this had the same molecular weight ooh it would boil quite a bit lower than it does with having a higher molecular weight but the bottom line is that hydrogen bond II and the alcohol Trump's the dipole-dipole interactions that you get from a carbonyl okay this compound it turns out has no hetero atoms in it and organic chemists use the word hetero to describe anything other than carbon and hydrogen okay and so this is a hydrocarbon has no oxygens has no nitrogen's has no Sulphurs etc therefore it is not very polar and in fact will get to this point here in a few minutes but it turns out that carbon and hydrogen have about the same electronegativity and I can never remember these numbers and you know it's one of them is 2.4 meters 2.2 that's electronegativity value and that's just not a big enough difference for all intents and purposes carbon hydrogen have the same electronegativity okay so there are no polar bonds in this molecule therefore this is very nonpolar and the only interactions it's going to have that will influence its boiling point our van der Waals attractions van der Waals attractions are the weakest attractions then come dipole-dipole interactions then hydrogen bonding or interactions are way stronger than any either dipole-dipole interactions or van der waals okay so because this only has van der waals it will have the lowest boiling point and so that's why it comes first so it boils lower than a a has dipole-dipole interactions when these carbonyls line up there was a slide in earlier you can go back and look at that earlier slide show and and you know if I haven't mentioned it these slides are available on Learning Suite and you can download them and look at them you know as still slides and think about them but anyway this is the right answer B boils lower temperature than a and which foil is lower than the C which is equal to D is actually are the same compound and that's so E is a correct answer in there okay all righty let's talk about polar bonds vulnera at it okay so this scheme here kind of show us how HCl is formed when hydrogen hydrogen atom with one electron reacts with a chlorine atom with an unfilled valence shell so this only has seven electrons and it wants to have eight remember that all first and second row atoms want to have an octet as as do third row atoms let me get down into the fourth row yeah transition metals and me have the D orbitals that can be filled as well and so there's a whole new rule called 18 electron rule but right now we're just going to confine ourselves to the first second and third rows and they like to have eight electrons in their valence shell and that's why that was that's what drives the bonding between the hydrogen atom and that chlorine now we have eight electrons around chlorine and two around hydrogen and that satisfies the noble gas configuration for hydrogen when it has two electrons it has a config electron configuration of helium that makes this guy happy with 80 electrons here that gives chlorine the know the electron configuration neon and that's the driving force for the octet rule okay all right but what I want to point out is that chlorine is much more electronegative than hydrogen and I don't have a periodic table on these slides but let's imagine the periodic table looks kind of like this you got hydrogen over here dips down you come over here and sure here's helium and then the rest of the tables like this right say this kind of like almost like u-shaped I'm trying to like trace out what the periodic table would look like okay if we had it to look at and so hydrogen is over here on the left-hand side of the periodic table which means it is not very electronegative and it would vastly prefer to have a plus charge on it and so it's not very electron withdrawing and chlorines over here on the right-hand side say third row element right underneath fluorine and so it's pegged up here in right-hand side of the periodic table which means it's quite electronegative okay and I don't you know you could memorize the numbers but the electronegativity numbers are hard to remember so generally speaking what you should remember whenever you see a periodic table put your cursor or think in your mind down here in the left hand side corner of the periodic table these are your most electropositive Adams's or less they are at least electronegative and as you move this way across the periodic table kitty-corner across the periodic table you get more and more electronegative okay bottom line is a chlorine is more electronegative than hydrogen and so the two electrons in this bond which it represented here the red one and the blue one are in that bond those two electrons are actually pulled a little bit closer okay they actually are not right in the middle of this bond they are actually sucked more towards the chlorine and that gives the chlorine a partial negative charge and the hydrogen and partial plus charge okay that is typically depicted by this kind of a kind of symbolism when we draw an arrow like this and this vertical line means that at this end there is a partial plus charge on in this case we're looking at HCl but anytime you see something drawn like this what this means is that the head of the arrow is pointing to an area of electron richness okay and the tail and the arrow with the with the vertical lines written across root indicates that there's a as a plus charge at this end and a negative charge at that one but their partial charges so this right here is telling you basically this okay that there is a partial negative charge on chlorine and a partial plus charge on hydrogen and we see this all the time that shows you what's called the dipole moment of the molecule and molecules that are polar are said to have dipole moments and they measure those in units of Dubai's and I honestly don't know exactly how they calculate a dubai but it has an actual value and polar molecules have dipole moments and you can represent the dipole moment with this arrow with the vertical line indicating that there's a partial plus charge on that in a partial negative on them okay so let's take a look and let me change back to the arrow and hopefully this will if I move this it won't go apparently if you stop moving it for whatever reason it goes to sleep and it takes well to get it back that's kind of annoying it's also a little easier to point what I want to point out is that all of these molecules are polar okay because they have polar bonds in them and I'd like you to get into habitat anytime you see what's called a hetero atom okay these are non hydrogen or carbon things okay oxygen or nitrogen or sulfur the common hetero atoms or halogens look at the carbon to which is attached and think about the the fact that that bond is going to be polar okay the carbon will be less electronegative than any of the hetero atoms okay so you'll have a partial negative charge on the nitrogen and a partial plus charge on that carbon that's because that nitrogen is more electronegative more electron electron withdrawing and those two electrons are in that bond that nitrogen will pull those electrons closer to it do a better job kind of hoarding for lack of a better term the electrons pulling towards the nitrogen that puts the partial plus charge on the carbon and the partial negative charge on the end okay similar similarly I have a partial negative charge on the OH partial plus charge on the carbon partial negative charge on the Oh pressure plus charge on the carbon so there's a polar bond there a polar bond there a polar bond there okay we can go through all of these and let's do this one we have a partial negative charge on the nitrogen okay so those electrons in that bond actually pulled closer to the nitrogen and the that partial plus charge is actually quite large because the O is also pulling electrons towards it so you know if we were to compare the partial charge on this carbon right here versus the partial charge on that carbon the one down here would have a greater partial plus charge because you have the O and the n both pulling electrons away from the carbon okay so it's kind of similar to dil here you have two O's okay pulling electrons away from that carbon so that carbonyl has a substantial partial plus charge on it actually a larger partial plus charge doesn't say that one that carbon only has 100 attached to it this one has two okay so it's kind of it kind of is a little bit additive and we won't go into how additive you know if it's exactly you know proportional in terms of additivity but bottom line is that that carbon is much more electron deficient has a large L partial plus charge on it because there's two O's attached to that carbon and say this one which only has 108 a CH to it same thing here this carbonyl has 100 that carbon only has 100 that Cornell has a 100 so each of these carbons is has does have a partial plus charge on it but it is not as large a partial plus charge as that one okay and we can do this whole same kind of analysis all the way through look at this carbon this bond right here the carbon here has a partial plus charge on it that has a partial negative okay now it turns out that the electrons are our bonds aren't really pipes but I like to use the analogy let's just pretend that the bond here is like a pipe okay and the electrons are like ping-pong balls inside of the pipe and the atoms are like vacuum chambers they're connected yeah so we've got two vacuum chambers connected to each other yeah a pipe and we've got two ping-pong balls in the in the pipe and let's say at time 0 we turn on both of these vacuum chambers at exactly the same time and this guy is the stronger vacuum because it has its more electronegative these ping-pong balls will be sucked more closer to that vacuum than they will to that one because this is a weaker vacuum I'm using the analogy it's not a perfect analogy but the analogy is if if electronegativity were like vacuum okay which is not really but this is a good analogy the stronger vacuum would be the more electronegative atom and it would pull the electrons towards that this guy would have an electron deficiency because the ping-pong balls are pulled closer to that stronger vacuum okay and that's true for any carbon to hetero atom bond that one's polar that one's polar that one's polar that one's polar blah blah blah hopefully you get it and it's somewhat additive such that this carbon has two O's attached to the same carbon okay so that's going to be more electron deficient and say this one which only has one o attached to the carbon okay alright we'll come back to that in a minute here's a structure of fentanyl it is responsible for causing or 50% of the opioid opioid related deaths in 2016 and I'll bet ya I don't haven't looked to see up to update this but I'm going to guess it costs at least that many deaths in 2019 there's been an opioid pandemic for lack of a better term where Americans have been turning towards you know heroin I think that's the main one heroin laced with fentanyl and it's got some fairly polar bonds in it let's take a look at it and you think about it go ahead and pause this if you want and ask yourself what are the polar bonds in fentanyl okay and then we'll go on okay here's a polar bond there is a polar bond there is a polar bond okay the polarity is such that the N has a partial negative charge on it okay that has a partial plus charge that has a partial plus charge that has a partial plus charge okay if we were to compare the partial plus charge on that carbon versus that one versus that one which would you guess has the largest partial plus charge on it between this one this one and that one think about it this carbon here has an electronegative oxygen an electronegative end okay both oxygen in or up here on the right hand side of the periodic table and you know if we're looking at the second row we go boron carbon nitrogen oxygen fluorine okay so carbon is actually to the left-hand side of nitrogen and oxygen as you go towards the right on the periodic table you get more and more electronegative so these two guys nitrogen and oxygen are more electron withdrawing than a carbon and so that carbons have in his electrons pulled big time that way and that way so this has the largest partial plus charge on it compared to that carbon or that carbon we also have three other polar bonds here's one there's one and there's one okay again we have a partial negative charge on the nitrogen partial plus charge their partial plus charge their partial plus charge there okay so as we move forward we'll begin to see that being able to recognize a polar bond is really huge in organic chemistry and we'll show you why here in just a minute okay and we'll get there alright so here's an exercise for you go ahead and pause this and pull out a sheet of scratch paper and draw the partial charges on the following bonds you'll need to get out a periodic table okay and I don't have one in these slides but you need to get one out and use that because what you're going to do is you're going to put the partial negative charge on the more electronegative atom and the partial plus charge on the less electronegative atom again remembering as we go from the bottom left-hand corner of the periodic table move towards upper right-hand corner we get more and more electronegative so if you're in the same row as you go to the right on the same row the periodic table the atoms get more and more electronegative okay so let's do that we'll go ahead and pause and then we'll see the answer chlorine is more to the right than silicon so the partial negative of their partial plus charge their nitrogen is to the right of carbon on the periodic table say Rose a personal negative their partial plus charge their chlorine actually is below fluorine okay so as you go down a down a column okay you go from more electronegative to less electronegative again it's kind of kiddy Korner yeah so fluorine is above chlorine so we're going to put a partial negative on fluorine partial plus on chlorine nitrogen is to the left of oxygen so in a row yeah the as you go to the right you get more electronegative so oxygen is to the right of nitrogen in the periodic table so partial negative of their partial plus charge there and there are your answers and the partial is indicated with that Delta that's what the Delta means that that's not a full-blown plus charge you know and how big it is is it 0.5 of a charge of 0.6 0.3 doesn't matter we're and that's one of the things I love about O chem is it is okay is actually very qualitative and that's honestly I'm a qualitative kind of guy and actually would rather do artsy kind of stuff than calculations that's just the way I'm wired and so anyway we're not really gonna worry about the absolute magnitude okay we're just gonna talk about this qualitatively okay let's introduce some new terms okay um adam said our electron rich okay are called nucleophiles and that word if you break it down to its component pieces nucleo and file file means lover okay and so things are electron rich are lovers of nuclei okay they would like to share their electrons with nuclei that are electron-deficient elect electrophiles are lovers of electrons and they are usually electron deficient okay so that little exercise we did back here plays into this to where if you look at a polar bond you can identify what we call the nucleophilic end and the electrophilic end okay this end and the partial negative charge anything this has a partial negative charge on it is nucleophilic okay it has an electron richness and that one's not so those two with a partial negative they have electron richness and so they would like to react with something that's electron deficient okay these guys are electron deficient so they would like to pick up electrons so these are what we would call the electoral these two are electrophilic there is a electrophilic there's electrophilic the electrophilic atom in those of those bonds okay alright so that's taken right out of your textbook and she just kind of highlights the electrophilic atom in a bond to a hetero atom such as carbon to nitrogen carbon to oxygen or carbon to a halide okay so where that's the partial negative charge on it there's a partial plus that carbon with the partial plus plus that is the electrophilic carbon okay it loves the electric electrons it wants to pick up electrons electrophiles our electron deficient okay that carbon is electrophilic it's electron deficient the telltale sign or what kind of a dead giveaway on most nucleophiles is that they have at least one lone pair okay so all oxygens are nucleophilic all nitrogen's are nucleophilic there's a personal negative charge on that Oh partial plus charge their partial plus charge there personally I get a charge on the n partial plus on the carbon partial Plus on the carbon blah blah blah so anytime you see a lone pair those guys are good nucleophiles also multiple bonds are nucleophilic okay so the PI bond in a carbon-carbon double bond or in carbon-carbon triple bonds there's two pi bonds and they're easily broken okay we'll get back to that as we move along okay so there they are nucleophilic okay so I'm here we have what would have been an iclicker but we're not doing that long distance but we're asked here to classify each of the atoms indicated by the arrow as to whether or not they are nucleophilic or electrophilic again nucleophiles are electron rich and electrophiles are electron poor okay all right so go ahead and pause this and assigned four atoms one two three and then forum oh why don't I have five and six and seven but oh well okay all right is that atom electrophilic or nucleophilic what kind of partial charge does I have on it is it more or less electron electronegative than a bromine bromine is pegged under and call and group seven carbons Group four so seven is to the right of 4 yes bro means down a little bit but it's pegged to the right of 4 subbro means actually more electronegative so bottom line is you see any halogen it's going to be more electronegative than carbon so you have a partial negative charge on the bromine partial plus charge on the carbon atom 1 that carbon is an electrophile the BR is a nucleophile okay I promise this is so important I know it may be a little bit like oh man what do we have to know this for you will see as we move forward that this is fundamental okay to just about every reaction you see in O chem and we're going to see by Tommy gets Route 352 we will have seen hundreds and hundreds of reactions that are really best understood being able to look at a polar bond and say hey you know what that bonds polar those electrons are not shared equally by the carbon and the bromine and in fact bromine in this case wins out and and and pulls the electrons closer to it which gives bromine a partial negative charge in the carbon a partial plus charge okay again the electrophile has a partial plus charge on the nucleophile has a partial negative ok PI bonds are inherently nucleophilic so I encourage you know that again this has a greater electronegativity so the partial negative charge on it has a partial plus charge so that will be our electrophile and that will be our nucleophile same thing here that's nucleophilic because that partial negative charge and that is electrophilic because it has a partial plus charge and we can do look at these bonds individually as well and do a similar kind of analysis okay here's kind of a fun example turns out that this principle plays a huge role in all of organic reactions and we have quite a few organic reactions in biological systems and so what is talking about is how s adenosylmethionine is made and this is the body's source of a ch3 group which is called a methyl group and this thing is abbreviated si M and if you I'm sure in biochemistry you'll see it sa M that's the structure of si M and it actually delivers a methyl to a nitrogen and that's what that's abbreviate here that's the ch3 ch3 on adrenaline okay that ch3 comes from SI m okay and anyway so how do we how do we make s adenosylmethionine our bodies take methionine which is a commonly occurring naturally occurring alpha amino acid and ATP which I'm sure you've all heard of before has this phosphate group this bond is very polar between the carbon and the O so we have a partial plus charge on carbon partial negative on the oh and that partial plus charge attracts the partial negative charge on the sulfur so this sulfur has you know is more electronegative than the two carbons so you have a partial negative charge on the sulfur two lone pairs he's a good nucleophile he's electron rich he sees the partial plus charge on that carbon which is electron deficient he's a good elect electrophile right here so these electrons come in and we form a bond as this sulfur attacks that carbon those electrons actually come here and attack that carbon we form a new carbon two sulfur bond this group leaves okay this bond breaks and this takes off this is an example what we call it a sn2 substitution reaction which we will see in I think is chapter 7 where a nucleophile comes and attacks an electrophile kicks off a leaving group okay this will leave to make triphosphate and we have now formed that bond it made a bond between sulfur and this carbon is carbon and I'm highlighting right here okay was that one so this s comes in attacks that carbon kicks that out and we make that bond okay and now as you might guess we have a partial we have a full plus charge on s that gives makes s even more electronegative and pulls the electrons towards it and that bond big-time to where we have a very substantial partial plus charge on that carbon and along comes a precursor to adrenaline which does not have that methyl group on it just has an NH 2 NH 2 is the electron rich and it will come along and form a bond will attack that carbon and break that bond and that process of the NH 2 attacking carbon attaches a ch3 to the NH two kind of cool ok so by light and that's how you make adrenaline and the adrenaline release of adrenaline is responsible for what they call the flight or fright response to where an animal or human being if you're scared you know hard starts to beat like crazy that's because Adrenaline's been released now remember which gland releases it but when your heart starts to pound because you're scared or if it you know if you were you know if there's an earthquake or something you want to run your adrenaline boo kicks off and off you go okay and so without any s am okay this is this an essence on the finding you wouldn't be making adrenaline and without adrenaline you couldn't have that flight or fright response so kind of scary that was a joke okay alright let's talk about the polarity of molecules in general the polarity of a molecule is the sum of all the bond polarities in the molecule so far we've been talking about bond polarities okay and here's an example this is methanol the most simple aldehyde of all it has a partial negative charge on the Oh pressure plus charge on the carbon and we depict that by showing that arrow okay so the entire polarity of this molecule is basically due to the Pilates at bond but there are other molecules that have other polar bonds and bottom line is you take and you sum up these dipoles okay to arrive at what's called the dipole moment for the entire molecule okay and that dipole moment is given represented by the symbol mu okay its measured in two-bys and it's a vector sum okay or it is a vector with with a quantity misspelled quantity there okay with both magnitude and direction the molecular dipole moment is the vectors vector sum of the individual dipole moments I I would stop and digest this internalize this okay so the the dipole moment of the entire molecule is a vector sum of the individual dipole moments of the bonds okay so methane now the whole molecule is polar because we have one bond as polar and the dipole moment is basically expressed by by that that's something that is that symbol but in co2 we have two polar bonds each of the bonds is Buller okay the polarity of the bond is represented by this symbol the partial plus charge on the carbon partial negative on the O but we also have another co bond with a partial plus charge on the carbon and a person that your charge on the oh okay well because the the dipole moment of the molecule the whole molecule is the vector sum of the dipole moments of the individual bonds okay these two guys cancel each other out we did a vector sum we just take the tail of this one and add it to the head of that one and they basically cancel out such as the overall polarity of co2 is zero okay the dipole moment is zero co2 is not polar okay even though it does have polar bonds okay the owner all molecule is nonpolar so beware of that in a in an exam setting question might be you know which of these compound over all you know which of the molecules is polar you know these two we could add those two pitted against each other which of the two is polar the answer would be that this one is but if the question said which of them have polar bonds okay both of them have polar bonds okay but the polarity of this bond cancels out the polarity of that bond to make the overall polarity of the entire molecule zero okay so this guy the molecule is not polar even though it has polar bonds so me where that kind of subtle difference all right let's talk about vector Suns our textbook doesn't go into it at this level or in this way I think is very useful to go back and remember that vectors can be added very simply so let's say we have vector a and vector B okay and we want to add them together how do we do it we take B and we put its tail on the head of a just drag this over put it on there now that we've done right there okay so a plus B gives you this okay and then you draw in a new vector here's the vector son okay the blue is the vector son and so if you add a and B together that is your vector sum okay does that make sense okay all righty so let's take a look at dichloromethane okay a very simple organic molecule and let's see if it's polar okay we have parcel negative charge on the chlorine Martian plus charge on the carbon partial negative on chlorine partial plus plus on the carbon very much like co2 as drawn here you would expect the dipole moment of the entire molecule here to be zero because you have a bond dipole moment going this direction okay and when going that direction and they are of equal magnitude exactly how many what the dip eyes they are you know we're not going to get into that but hopefully should say that that's CCL and SEC al all right those bonds are identical so just like co2 the dipole moment of that should be zero right as drawn okay but this comes back to what I said in an earlier slide raised talked about function is determined by form or form determines function so the actual structure of this molecule has a huge impact on is polarity and actually as drawn this this structure has drawn does not represent the true three-dimensional shape of dichloromethane and here is the true three-dimensional shape okay because that carbon is tetrahedral these two chlorines occupy these positions and those two hydrogen's occupy those and here's an important if we were in class I'd hold up a model and show you but if I put my two hands on those chlorines what I want want you to know is that these guys are parallel to me and these guys are are perpendicular and so maybe the hand thing didn't help you but let's think of the chlorine and that carbon neck those guys are in the plane of the page and can you see how that kind of looks like a V it looks like a V right an inverted V alright there's an important point to lock into early on and that is that a tetrahedral carbon is essentially just a carbon with two perpendicular V's okay attached to that carbon so here's one V H carbon H that's a V that is perpendicular at 90 degrees to this V okay this V is inverted okay CLC Cl there it's in the plane of the page and it's an inverted V this is a regular kind of V with the bottom of the V down but we have an H carbon H you got two V's perpendicular at 90 degree angles okay that is the true structure of dichloromethane that does that is not the three-dimensional structure back through methane this is three dimensionally what's going on now well I saw the fact that carbon is tetrahedral and we know the bond angle for tetrahedral carbon is 109.5 that puts both these chlorines in the back carbon in the same plane as a V and these guys in a perpendicular V okay all right here's our two bond dipoles okay partial flusters their partial negative their partial plus charge their partial negative their to add them we're just going to drag this one over and put the tail on the head of this one that's what I've done right here and then complete this kind of triangle and there is our vector sum okay so the overall dipole moment of the molecule is represented by the red arrow it's a vector sum of the bond dipoles these are the bond dipoles in black they're the bond dipole moments the dipole moment for the whole molecule is the vector sum and it definitely is going one direction it's not canceled out like in co2 so dichloromethane actually is a polar molecule okay exactly how fuller we're not going to get into but it's definitely polar okay how about this one carbon tetrachloride okay if you take and you draw carbon with four chlorines out like a like a cross yeah that's going to give you the wrong answer well actually in this case does work but there is the three-dimensional structure of carbon tetrachloride we've got your two V's okay these are in the plane of the page that's perpendicular here are our dipole our bond dipoles okay one two three four but take this one over we're going to drag it to the tail and the head will be here we'll connect the tail to the head there is the vector sum these two bond dipoles and here's the vector sum of the top two and I didn't draw this exactly to scale but the bottom line is this would be the the same magnitude as that one and so they cancel each other out just like in co2 such the carbon tetrachloride the overall molecule is nonpolar that guy's not polar even though it does have polar bonds it has four polar bonds but their vector sums of of each two vectors cancel out these vector sums cancel each other out and make the whole molecule not polar okay how about bf3 what is the structure bf3 going to look like based on the Vesper theory an atom with three ligands on it is going to be what it's going to be linear tetrahedral or trigonal planar it's going to be trigonal planar right so let's draw it out as bf3 it is flat that means the boron and all three fluorines are in the same plane and each of the BF bonds are polar or fluorine is much more electronegative than boron for each of these bonds so each bond has a dipole moment and now to determine the polarity over a molecule we're going to go ahead and add this vector to that one just drag this one up with the tail there the head will be there and then we complete the addition by drawing and that this is the vector sum product of those two vectors these two right here were this one with that one added to it okay we made we drag this one up with the tail right here the head will be going there that's right here and then we complete that by drawing in that's the vector sum the vector sum actually cancels out that bond dipole and so the net polarity of the molecule is zero bf3 is not polar okay the molecule self does not have a dipole moment but it does have polar bonds it has three polar bonds but they you know they cancel each other out this vector sum is equal and opposite magnitude from that one okay how about that molecule is that one polar go ahead and pause this and flush you scratch paper and think about them we're going to a partial negative charge here partial plus there so we'll have the the bond dipole will look like this with the head of the arrow there okay the bond I pull this and we'll have the head of the arrow going that way and so we take in drag this bond dipole over here put the tail over there and then complete the sum okay that's right there so there's nothing canceling anything out and so yes this molecule is polar okay so good this one is that one polar and it turns out that may be quite easy to guess by now that that one is not polar I said you add the two vectors this one's going out way that one's going that way you put them you know tail to head when you have the two vectors like the don't form the triangle you the vector sum on this guy is zero just like it is in dichloro excuse me in co2 and carbon tetrachloride so this molecule is not polar even though is close cousin the one with the two chlorines let's see where is it one of the two chlorines on the same side of the double bond that guy is polar when are on opposite sides the double bond that is not or okay how about this molecule is that polar versus let's stop and talk about what it is and that will maybe even tip the hand so you you know need have to think about in terms of vector sums but turns out this is Teflon and Teflon is a polymer and has multiple CF two repeating units over and over and over again okay and so what we're gonna do to determine the overall polarity the molecules we're gonna draw bond dipoles so here's one there there's one there we're gonna take this one and we're going to drag it over and add it onto that one and we're going to do the sum and the sum will be right there okay do that same analysis down here the sum will be here sum will be there some will be there blah blah blah long story short the vector sums actually are pointing in this opposite direction with equal magnitude these cancel each other out and that makes it so that Teflon is not polar okay that's why when you pour water into your Teflon pan your water beads up right because it water is polar and that's species or substances of the same polarities tend to attract to one another and so since Teflon is not polar it's not attracted to water so the water tries to get away from it that's why it beads up right it's trying to get away from the nonpolar Teflon okay that's kind of cool all right don't worry too much about this it's just I just found this on the Internet and you know just had a free copyright thing so I could show it but this just gives the actual dipole moment for chloromethane so methane with one chlorine for dichloromethane this is showing the vector sum here there's a diaper bond dipole of chloromethane this is dye chloromethane has a vector sum going that way trichloromethane has a vector sum in a polar molecular dipole and here's carbon tetrachloride with four chlorines on it and these are measured dipole moments and so chloromethane is quite polar more polar than dichloromethane which is more polar than trichloromethane and tetrachloromethane is not polar at all don't memorize these numbers but I think the trend is useful to be aware of okay this just is thrown in to highlight that in boron trifluoride with boron attached to three fluorines okay there are polar bonds each of the three bonds is polar but the net dipole of the moment of the molecule is zero so boron trifluoride is not polar don't miss that one that's a classic kind of bread-and-butter o chem topic you see on MCATs and dads all the time okay this one is just thrown in it used to be that our author in an earlier edition made the point that methane with different halogens on it has different boiling points and so as we go from this one to this one to this one we get greater Van der Waals interactions and she claimed that because this one is bigger kind of more rod-like and you get greater potential for greater Van der Waals interactions that this one would have a higher boiling point than this one would have a higher boiling point than that one would have a much higher boiling point than that one so that makes sense this is kind of more you know it's not more rod-like but it is you know there's potential for greater Van der Waals interactions and that that is reasonable and very theoretically that makes sense but it turns out that the actual data don't fully support them so yes this guy does have the highest boiling point it is higher than so it's 43 centigrade versus 3.5 for the methyl bromide which is that guy but for whatever reason with a chlorine there it's actually almost as high as an ID so this one's an outlier and but otherwise the trend works okay that this one has the lowest boiling point and this one's this one's higher and that's the highest of all but this one's an outlier so don't worry about that she pulled this in subsequent editions of the textbook because it didn't quite fit the theory and so that kind of gives you so I don't worry about this just just just kind of points out the reality of life okay that some things don't fit in nice little boxes so don't worry about it alrighty what we got going on here okay what I'd like you to know I'd like you to be able to recognize polar bonds be able to predict which bonds would be more polar based on electronegativity and rank compounds according to predicted polarity and be aware that exceptions exist and remember that the more polar molecule is the higher boiling point will be and the higher its melting point will be all other things being equal okay in a hydrogen bonding Trump's dipole-dipole interactions and dipole-dipole interactions trump van der Waals okay here's another couple of important slides and not sure how long we've been going I don't want this to be too long so maybe we'll go ahead and close this out just for the fun of it and let's do that so we have a little bit shorter video to look at and we can break into two pieces so let me go ahead and stop recording