Video instructions and help with filling out and completing Will Form 8815 Representation

Instructions and Help about Will Form 8815 Representation

Hydrogen bonding can be so confusing so I want to talk about some of the common mistakes people make so you won't ever make them okay so hydrogen bonds are a type of inter molecular book in intermolecular bonds form between molecules that's why we call them intermolecular now this between part is super important between two different molecules I'm underlining it twice in red okay let's look at hydrogen bonds in some ethanol molecules so ethanol is an alcohol and if we could take a drop of ethanol and zoom in zillions and zillions of times in it this is what we'd see we'd see a bunch of different molecules all twisting around in two different orientations and here they are so where are the hydrogen bonds in these molecules well as I said earlier intermolecular bonds hydrogen bonds form between molecules okay so this can't be a hydrogen bond because it's not between molecules okay the CH that can't be a hydrogen bond either because it's in the same molecule it's not between molecules and the CC it can't be a hydrogen bond either because it's in the same molecule not between different molecules okay so that's the first important thing to keep in mind if a bond is in just one molecule it's not an intermolecular bond and it's certainly not a hydrogen bond okay so that means that the hydrogen bond has to be between different molecules here's how it works in hydrogen bonding an H in this case an H connected to know is bonded to an O on another molecule okay so this H is attached to an O and so it will form a hydrogen bond with this L over here I'll indicate this hydrogen bond we couple red dots okay so there's a hydrogen bond here this H connected to the O here can form a hydrogen bond with this o over here on this other molecule so again a hydrogen bond I'll indicate with a couple of these red dots so there's a hydrogen bond here okay now a common mistake that some people make is they think anytime there is an H it can form a hydrogen bond between molecules okay so they say oh there's an H here connected to the C there's an H here connected to the C so this can form a hydrogen bond right no it can't it has to be an H that's connected to an O bonding with another oh in this case so it can't be this H with a C and this agency that's not either bond another mistake is taking an H it's connected with a C and connecting it with an O okay that's kind of half right because in this case O's are forming hydrogen bonds but if the H is connected with a see of it cannot form a hydrogen bond either it's got to be an H connected with an O making a bond with an O on another molecule this is wrong this is wrong this these two hydrogen bonds between the molecules this is a way to go okay so now that you know how to find and draw hydrogen bonds let's talk about how hydrogen bonds form in the first place okay here I have two ethyl molecules they're going to form a hydrogen bond between okay in this case it's all about the Oh mah okay so the only H in this molecule are connected to each other with this line which indicates that it's a covalent bond that's holding them together they're sharing electrons to form this covalent bond so they're stuck together because they're sharing electrons here's the thing though with sharing they are not sharing those electrons equally okay the oxygen has what we call a higher electronegativity all that means is that when it shares with hydrogen it hogs the electrons okay so it's maybe supposed to be sharing equally but instead it's hogging the electric because it has these extra electrons that it's hogging it has a little bit of a minus charge okay because of those electrons that are spending more time with it so we can write this minus sign here in this squiggle it's actually a lowercase Greek Delta letter D up it is a lowercase Greek letter Delta okay that's what I meant to say okay so anyway we have this lowercase Greek Delta with a negative sign meaning that o is a little bit negative because it's hogging those electrons on the other hand hydrogen here is getting the electrons hogged away from so it's missing those electrons so it has a lower case Delta plus it's a little bit positive okay now the same thing is happening over on this molecule the oxygen is hogging electrons so it has a Delta minus sign because it has a little bit of a negative charge those extra electrons it's hogging away and the H which is getting thieved away from here it has a little bit of a positive charge so now you can see what's going on in here is that the negative I mean the positive hydrogen here is going to be attracted to the negative oxygen so this attraction it's sort of like magnets you know how magnets attract together it's like this attractive force between the positive hydrogen and the negative oxygen so we can say that the hydrogen bonds are formed because o is hogging electrons from H it's making oh a little bit negative makes H a little bit positive so this positive image is going to be attracted to a negative O on another molecule now here's the thing earlier I said that if an H is bonded to a C it will not form a hydrogen bond here's why it's because C and H share their electrons evenly in this bond because they're sharing them evenly it's not possible for the C to become