[Music] foreign lessons this is a B Tech applied science unit 5 chemistry and we're looking at naming alkanes using the ru pack rules so where does this fit within the specification and so this is a learning game A2 and if you haven't seen the previous video on the introduction to alkanes and alkenes I suggest you you start there first because that's going to cover these first two points and this is one of three videos where we're going to look at naming so this video is going to look at the naming of alkanes and then there's going to be another couple of videos that are going to look at the naming of alkenes and then we'll look at the naming of Halo alkit but first of all if you don't subscribe please do your support is very much appreciated please use a like and the comment features and let me know what you think so by the end of this video then you're going to be able to name these four molecules here I'm going to use these as an example and there's also going to be a task for you to have a go at the end and I'll put the answers on some basic rules to start with then whenever we draw organic molecules carbons always going to have four bonds whether that's four single bonds or a double bond and two single bonds either way it will always have a total sum of four bonds and hydrogen will always have a single Bond hadron only ever has one Bond here now when we name organic molecules there's three sections to the name to make this simple I've put them in three different colors so we have something at the beginning that we call a prefix which is usually to name any side chains or the position of any side chains and also if there's any other functional groups if we have two functional groups you may have a prefix of one of the functional groups and also some functional groups actually come as a prefix and we'll see that when we look at haloalkanes so that's the prefix the bit at the beginning the middle bit is known as the stem and that's the longest part of the chain so in this example that pent that's telling me that there's five carbons long and then at the end we have the suffix which is usually identifies the functional group in this case in so because this video is only going to look at naming alkanes we only have one suffix to worry about in this video in the next video we'll introduce more so the suffix here is just in and that's telling us that the functional group is an alkane and in terms of stem we don't need to go past 10 and those are the different names for the different number of carbons in the chain so for example pent we've just seen is five if it was eight we'd have OCT it'd be Octane and the prefix I'm going to limit this to methyl ethyl and profile in this video but there are numerous different prefixes we can have but we'll be fine in this video and with btec applied unit 5 to just stick with these three for now I will introduce more in future videos so methyl if a side chains of ch3 we have a methyl prefix and there's some examples and again towards the end of this video we're going to look at drawing those two molecules there using the naming rules so we're going to apply three rules when we name molecules the first rule is to identify the functional group now we will be limited to functional groups in this unit and in particular this video we're only looking at one functional group which is alkanes So currently we only have one suffix which is in again I will introduce further suffixes in future videos the second rule then is to identify the longest carbon chain now don't make the mistake and assume that the carbon chain is the one that runs straight through the middle because some of the side chains might actually be longer or might increase the length of the chain and we'll see some examples of that today third and finally then once you've identified that longest chain we need to Circle any side chains from that chain and once we identify those side chains we need to name them and identify the position the best thing to do then is to look at an example so the first thing we must do is identify the functional group now we've already said here that the functional group is an alkene because there's this only thing here is carbons and hydrogens it's a hydrocarbon with only single bonds so I've got to identify the longest chain don't just assume that the longest chain runs straight through the middle of the pitch because it doesn't have to so I'll show you what I mean so that could be a chair that's a chain of four but there's nothing stopping with the sin that's also a chain of four now this here would just be a chain of three so we've got three options here we've got the red which would be four we've got the gold which would also before and we've got that purple will be three so I either go with the red or the gold because they're both full now it doesn't actually matter which one I go with and to prove it I will go with both of them so I'll start with the red okay now if I start with the red I either have to number them one two three and four but you can also number them backwards you don't have to go left to right so I could go one two three four so that's a four carbon chain and it's an alkane so we're going to start with the stem Butte and I'm going to use the suffix n because it's an alkane so I've now identified this part of my molecule does it have a side chain yes it does the side chain is here what is the side chain the side chain is a ch3 group which is a methyl so it's going to be methyl Beauty in terms of the position I've got two possibilities here I've got two options it's either two or three it depends on which we have numbered the chain and the rule is you have to go with the lowest number so this would be called two methyl butane and that's if I go with the red chain what will happen if I go with the gold chain which was this one well it's still beaut so it's still butane this time though I've taken a account of this part of the molecule so it does have a side chain still has a side chain which is this chain here and it's still a methyl so it's still methyl butane let's check the numbers one two three four or one two three four now I have to go over the lowest number so it's two two methyl butane which is the exact same name as I got for the red shape so just prove that it doesn't matter which direction or which chain we pick as long as it's the longest chain next example then so number one identify the functional group well again it's just a hardware carbon with only single bonds so it's an alkane so we already know that the suffix is going to be in now I need to identify the longest carbon chain one two three four we could go one two three four or we could go one two three four five now I don't think I can get a longer chain than five on this molecule so I'm going to go with five being my longest chain and that was this way here again I can go one two three four five or I could have gone one two three four five it is important that we're aware that we can number them either direction so that's five so that's penting so for the pentane I've taken account of these part of the molecules here there is a side chain lock up the top here there's a side chain of a ch3 that's a methyl so this is methyl pentane what's the position of the methyl it's either three or three so it doesn't actually matter it's three methyl pentane next up then identifying the longest chain one two three four five one two three four five six can I beat six I don't think I can so my longest chain is six that was this way so I've got to number them one two three four five six and I can numb them reverse as well one two three four five six so that's going to account four that part of the molecule so that's six so that's going to be hex in so the stem is hex and the suffix is n does it have a side chain yes it does this is a methyl side chain and it appears on either the three or the four I've got to go with the lowest number so three methyl hexane finally final example then right now this is definitely a strange one which is why I've put this in and it might actually be beyond your unit 5 specification but I think we're best off being over prepared and underprepared so this is a carbon chain of four but it's a cyclic for okay so it's four which is Butte and it's an alkane which is in what we call this cyclobutane it's a cyclic four carbon alkane cyclobutane what I'm going to suggest you do for this page is I'm going to suggest you pause the video and you try and name these three yourself and when you're ready to hear the answer unpause the video okay let's start with this war up on the top left I've identified the longest chain as four so that's butane it has two side chains and they're both methyl so I'm calling this die missile butane what's the position well let me number them one two three four or one two three four so it's dimethyl two three dimethyl or two three dimethyl so it's actually the same nip so it's two three dimethyl butane okay let's have a look at this one here so one two three four so that's viewed in this time there's a methyl side chain so it's me Style Beauty watch the position of our methyl group one two three four or one two three four so it's either two or three methyl I have to go with the lowest number so it's two methyl butane final example then or last question down the bottom here one two three four five and be careful this one at the top is also part of the chain it's tempting here to stop at five but actually the chain continues up on the top so this is hexane and there's a methyl group on the hexane so it's methyl hexane where is it on the Chain we've got one two three four five and six or one two three four five and six so it's either three or four we call the Lost number three methyl hexane last task then is we're going to do it in reverse now so we've been given the names and these were the names of molecules we saw in the earlier part of the video I want to suggest you pause the video you try and draw these two from the names and when you're ready to see the answers unpause the video okay so the first one then I'm going to draw my stem so pent in I'm going to draw five carbons in a row of one two three four five and then there's a methyl group on the number two so I'm going to draw ch3 on that number two there and then I'm going to complete the molecule by drawing all of the hydrogens in and it's a good check at the end to make sure that you've only got one Bond on every hydrogen and that every carbon has four bonds it's quite easy to miss a bond off somewhere so double check by counting your bonds next one two two die methyl three ethyl pentane that's a bit of a mouthful right so pent in one two three four five two two dimethyl that means there's two missiles on the number two ch3 groups and there's a three ethyl now when ethyl we haven't seen yet although we did see it in the naming of the prefixes here an ethyl is a ch2 ch3 so it's a ch2 and the ch3 so this is quite a complex one to draw now I need to finish the molecule off by making sure all my carbons have got four bonds I need some more space down the bottom there we go so that's the ch3 there just making sure I'm drawing all the bonds on that's a ch3 there so that looks quite impressive that's a 2-2 dimethyl three ethyl pentane but I'm just applying those rules and that's the end of this video then please make sure you check out that next one on naming alkenes where we introduce another functional group