let us now learn how to list all the possible intermolecular forces that a molecule could have and it's basically kind of a systematic way for us to be able to determine what is the strongest one that is we need to be able to list all of them and then determine which of the strongest well the strongest one of course is going to be iron interaction and the weak is going to be at the end dispersion forces so um the thing to remember about these intermolecular forces that we have is that they are not mutually exclusive a molecule could have a hydrogen bond and dipole-dipole interaction and dispersion force all at the same time or can even have ionic components at the same time remember organic molecules have various kinds of functional groups between one to the next so in fact you can have a molecule that are you know positively charged exactly ionic on one charge and then have a dipole interaction and also have a dispersions and so on and so forth so organic molecules are large so we need to be able to list all of them um to be able to distinguish and then predict their typical property so again they're not mutually exclusive a molecule could have all of these at the same time especially when you're talking about organic molecule so the first things first is that before we begin i want to mention that all molecules have this have this force remember the dispersion force is simply that you have electrons and the electrons kind of move around inside the molecule and on occasion it is slightly imbalanced it's a little bit more positive on one side to the other all molecules have electrons and fluctuation and therefore all molecule would have a different dispersion force so regardless what it is you can have table salt you can have ammonia you can have water all molecules have dispersion then the other thing that i want to mention is that hydrogen bond is a subset of a dipole-dipole interaction so whenever you have a molecule with a hydrogen bond you would always always have a dipole-dipole interaction but it is not always the case the other way around you can have a molecule with dipole-dipole interaction but cannot do hydrogen bond all right so those are kind of the cases that i want to mention before we begin so let's do some example let's do our favorite molecule water so what are the interaction possible between one water molecule with another water molecule let's me let me draw it this way right well if you have one water molecule interacting with other ones then the intermolecular forces is going to be between oxygen and hydrogen right so that's kind of the interaction that we have and and whatever else so as always we always have dispersion so i'm just going to list dispersion immediately and what else well we can have interaction between this oxygen hydrogen oxygen right so remember hydrogen bond is fun so this particular interaction here is going to be a hydrogen bond because the hydrogen is clamped between fluorine oxygen or nitrogen or any combination of the three so it's a hydrogen bond and because hydrogen bond is a special kind of dipole-dipole interaction it also have a dipole-dipole interaction what else does this particular molecule have ionic interaction hopefully you can see that water is not an ionic molecule it's not an ion it's not it doesn't have metal and non-metal components it's it's completely non-metal so it's going to have no ion ion interaction now out of these three intermolecular forces which one is going to be the strongest or it's going to be hydrogen bond so that's an example what else well let's look at another molecule let's look at a molecule of like that let's look at an alkene um let's look at the molecule from the bottom i always have dispersion what else well i mentioned before that alkene are considered entirely non-polar right so this particular molecule is not going to have any dipole-dipole or hydrogen bond because it's completely nonpolar and therefore there's no dipole-dipole attraction there's more hydrogen bond and there's no ionic interaction so the only forces that an alkene would have would be just a dispersion force so that means if i were to predict what is the physical property of the circular molecule i would probably predict that it's probably either gaseous or liquid or even if it's a liquid it's going to have a fairly low boiling point so so that's kind of an example of its application i don't i don't have a table and data in front of me but i can predict based on listing the intermolecular forces that this is probably either a gas or a liquid or if it's a liquid it's going to boil fairly easily let's do another one so that was just a molecule with just a dispersion force let's do a molecule that have right so let's do a molecule that looks like this what would be the intermolecular forces that um two chloro butyl two chlorobutane could have um well in this case um it always have dispersion and is this molecule have a dipole-dipole interaction or a hydrogen bonding well let's see well this chlorine here is uh if you look at the lewis diagram would have a bunch of electron density because there's a bunch of lone pair so it is it it's not balanced compared to the alkane so in fact it will have a dipole dipole interaction because this side here would be a little bit more negative and then the rest of the side here is going to be a little bit more positive right so what happens that we're going to have if we have another molecule it's going to have kind of the same structure as well that is you have chlorine that is slightly negative and then you have the alkane chains that is slightly positive just because it has less electron density so in fact we do have an imbalance in the electron density it's not completely symmetrical if you want to think it that way so in this case this is also have a dipole dipole interaction now do we have a hydrogen bond in this case well let's look at it in a lewis diagram it might be a little bit easier to see that way so we have carbon carbon carbon carbon oh my my lines keeps disappearing on me as i add them they keep disappearing ah this is gonna um it's it's a it's a part of the program it just thinks that if it's a line you're trying to scratch it off um as you can see that drawing chlorobutane takes a long time because and that's really why we no longer uses a lewis diagram to describe organic molecules because it is it will take a while for us to draw it but any case i'm going to be lazy and just kind of do it this way right so let's look at this interaction between hydrogen and chlorine from one molecule with another molecule with the hydrogen and chlorine in them do we consider this a hydrogen bond this interaction here well this is going to be partially positive this is partially negative right is this a hydrogen bond and hopefully you can see that this hydrogen is clamped between chlorine and carbon so it's not fo n so it does not have hydrogen bond this is this is a dipole dipole interaction this that's a dipole dipole interaction but it's not hydrogen bond because it's not f o n so that's an example of a molecule with dispersion and dipole-dipole let's do one last one um let's do ammonia ammonia have a molecular formula of nh3 so you have a lone pair nitrogen and then three hydrogen or amin if you like if you kind of want to think of it as one of your organic molecules well what happens if you have two ammonia together what kind of intermolecular forces can we have between one ammonia to the next well it always have dispersion next do we have dipole-dipole interaction or hydrogen bond well remember dipole-dipole simply imbalance in electron density so you can see that there's a lone pair here and then there's no lone pair on the bottom here so it's not symmetrical so therefore there is a dipole dipole and do we have a hydrogen bond in this case and hopefully you can see that yes we do have a hydrogen bond between one to the next and the hydrogen bond is basically this interaction between this hydrogen with this nitrogen and you can see that the the hydrogen is clamped between f o n or chem or combinations of the above so this molecule would also have a hydrogen bond and it's not an ionic molecule so it doesn't have ion ion interaction all right so those are some examples of identifying all the list of intermolecular forces that a molecule could have