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Current time:0:00Total duration:12:04

Polymerization of alkenes with acid

Video transcript

let's say we have some chloro ethene here and you wouldn't have to call this one chloro f1e because if you just go to the pleura theme there's only one way to draw this and the common name for klorel chloro ethene is vinyl chloride so let's say we have a bunch of chloro F Dean molecules in along with or mixed with some hydrogen chloride and I've drawn all the valence electrons for the chlorine atom and I've drawn a little magenta electron the one that the hydrogen atom brought to the table so we've seen something like this before what is likely to happen well maybe one of these carbons is willing to give up an electron that electron goes to the hydrogen because this electrons already being hogged by the chlorine so this hydrogen has a partially positive has a partially positive charge chlorine has a partially negative charge so that electron would be attracted to the hydrogen then this electron can be completely hogged by the chlorine and if we had to decide which which of these carbons is more likely to give up the electron you just have to say which one is bonded to things that it can share electrons a little bit with this carbon is only bonded to hydrogen's so it is already hogging their one electron each and there are no more electrons to share with it this guy's bonded to a chlorine so the chlorine has a bunch of valence electrons it might be able to share it a little bit with this carbon if this guy became a carbo-cation so this guy will lose an electron this carbon will form the bond with that hydrogen so let's draw it out let's draw it out so let's say this carbons electron is that blue thing right there it will will we could draw it like this it goes to the hydrogen and then the hydrogen's magenta electron glow goes to the chlorine this is just a plausible mechanism now once that happens what will our setup look like what will it look like it will look will have this carbon over here bonded to two hydrogen's it has its one single bond to that other carbon that just lost its electron which is bonded to a hydrogen and a chlorine and now this carbon on the left it is now bonded to the hydrogen that electron went to the hydrogen and it formed a bond with it so then it forms a bond so that little blue electron is at this end of the I want to make it blue the little blue electron is at this end of the bond and it is now the hydrogen's electron and that magenta electron went to the chlorine so now it is a negative ion it is a chloride ion so we have chloride ion it has its standard seven valence electrons that it started off with but now it took that magenta electron from the hydrogen and so now it has eight valence electrons it gained an electron it now has a negative charge this guy over here lost an electron he now has a positive charge now the four next thing that you might expect to happen if we just followed the pattern of the last several videos is you would say hey this guy will now take an electron from the chlorine which is pot Lord the chloride anion I should say which is completely plausible but there's also a bunch of the chloromethane this isn't the only molecule of chloro at Dien that's just a chlorine not chloro ethane chloro ethene sitting around so let's let us throw another one of those in there so we have more molecules of this so he could take an electron from this from the chloride ion or or he could take an electron from this guy over here remember remember this guy this guy just like this guy who was this guy this guy is okay it doesn't require a super amount of energy to make this guy lose his electron he's bonded to other things that are willing to share with him a little bit maybe he's willing to lose his electron as opposed to the chloride ma the chloride ion so this guy has let me draw it in so this end of this bond is green and then this goes and bonds with this carbon so this will be a long bond right here so this goes and bonds with that carbon she giving that electron to that carbon and then what will our setup look like so after that happens will look like this I probably should have copied and pasted this from the get-go actually let me do that before I let me copy and paste this so now let me just draw it copy and paste this whole thing nope that's not what I wanted to do let me select it again all right copy and then paste there you go so then we have that thing and let me redraw what I had erased so that I could copy and paste and then we have this guy went over to this carbo-cation so he's no longer a carbo-cation so let me let me erase this because now he's gained an electron he gained that green electron right there he gained that green electron I'll just draw it right there and now he's formed a bond with this carbon and I'll know make it blues just so we know which carbon were talking about he's formed a bond this bond now moved over to that carbon because it went the electron went with it so now that bond is to this carbon right here that carbon right over there which is bonded to two hydrogen's two hydrogen's and now has a single bond to the electron that gave up the carbon has a single bond to that character right over here who is bonded to a hydrogen and a chlorine a hydrogen and a chlorine and since he now lost an electron he now has a positive charge so if you look at this setup right here it looks very similar to this set up although we've added one more vinyl chloride to the mix and the one that we added lost its electron or this carbon lost its electron and now it's a carbo cation so what could happen next well we have more of this vinyl chloride sitting around we have more of this vinyl chloride sitting around let me draw another vinyl chloride so I have a carbon the hydrogen a hydrogen and then it is double bonded to a carbon a hydrogen and a chlorine and let me copy and paste this I think you see where this might be going how this could keep on going and going and going so copy and then let me well I just copy that for now so what's going to happen now we have other this guy could go and give an electron to this guy and form a bond or we could have the same process happen over and over and over again so this let me get my pen tool going so this electron could be given to this carbo cation right there so this electron can be given to that carbo cation right there and then what happens well if that happens then we're going to get I'll move to the left now we have our original molecule I'm going to run out of space soon we have this original molecule and now this guy is bonded to that so this this carbon let me make this carbon right here is going to be this carbon and now it is bonded to this guy it is - this guy that orange electron is now given to this guy who was positive so that he now has let me make it a little bit neater I could do a better job than that so the carbons here the bond goes to this guy he now has the orange electron he is no longer he no longer has a positive charge he no longer has a positive charge he's got all of his valence electrons now and now this guy is bonded to two hydrogen's two hydrogen's that guy's bonded to two hydrogen's and he has a single bond this single bond right here to the carbon that just lost his electron who's bonded to a hydrogen and a chlorine and because he lost his electron he now is the carbo cation he is now a carbo cation so I think you see where we're going we can just keep adding and adding and adding to this chain of vinyl chloride so this process just went on and on and on we could make it like this we could look something like this let me see how well I can draw it so it would look like this so this is a ch3 so I'll just draw it as a CH three see and then this is bonded to this is bonded to a carbon that is bonded to a well maybe I'll call it a CH which is bonded to a chlorine so we're that were that far in the molecule and then we have let's see the part that repeats this part this part right here is going to keep repeating that part right there is going to keep repeating so that part right there and I'm going to do it like this so I'm just going to draw one of them so you have a ch2 that's that right there and then connect it to a CH which is that right there which is connected to a chlorine and so that part right there will keep repeating and then maybe the very last one so you have this guy right here that may be the very last one that joins on I mean this can happen millions of times I just made it happen two or three times it could happen millions of times and form a super long chain or a polymer and where this is the what we are describing this video is actually a polymer that you have probably dealt with at some point in your life in front in fact I guarantee there's some of it in your house right now so then we'd have that part right there and we could just make that as ch2 CH CL CL and now the way we've drawn a net is a carbo-cation but maybe we've run out of all of the all of the vinyl chloride molecules or we could also call them chloro ethene molecules and now finally now finally when everything said and done this last guy since he's run out of vinyl chloride molecules to take their electrons from he now finally takes it from the chlorine so you can imagine after this happens many many times so this repeats many times after this repeats many times then finally finally one of these electrons from the chlorine one of these electrons from the chlorine go to that final carbo cation because they've run out of other of other vinyl chlorides and then he attaches right over here to the chlorine now this is called so when we say that this might happen this repeats many times you might write an N here to show that it repeats many many times if you know how many times it means if you know that there were I don't know if you know that there were a thousand molecules here you would write a thousand repetitions but this is called a polymer polymer and the name for this molecule right here is we each of these units is vinyl chloride right vinyl vinyl chloride vinyl chloride the I guess the the official name is chloro ethene but the typical name the one people like to use is vinyl chloride that's for each of these units it's a polymer we have many of them so we'll put a poly in front of it we put a poly in front of it so this molecule right here is polyvinyl chloride or and now I think it'll ring a bell or PVC for short and you've probably heard of PVC piping it's what most people have for their plumbing it's those plastic pipes and that's what it is it's polyvinyl chloride