[Music] foreign welcome to my channel on chemistry lessons this is a b-tech applied science unit 5 chemistry and we're going to be looking at the stability of cardboard cations so where does this fit then well it's down the bottom here but it ties in as well it goes It goes perfectly with the electrophilic addition which you'll find in other videos and I'll put links in the description as well and it also relates to this symmetric and asymmetric alkene so again I'll put a link in the description for that so by the end of this video then we're going to be able to identify cardboard cations as primary secondary or tertiary we'll also look at what the cardboard cation is and then I'm going to be able to explain the stability of them and the relative stability of primary secondary and tertiary first up though if you don't subscribe please do your support it's very much appreciated please use the likes and comment features and let me know what we think so a couple of key terms then to start us off what is a cardboard cation well a cardboard cation it's a carbon that has three bonds and a positive charge so it's an intermediate these things are not stable okay so carbon will have four bonds in all stable substances this carbocation is an intermediate during a chemical reaction and R Group so an R Group is a chain of carbon atoms the most simplest group would be a methyl group or an ethyl group but they can be very long or very short but it's a carbon chain primary secondary or tertiary carbocation then well a primary carbocation is where one of those three groups is an R Group so for example we could have two hydrogens and a methyl on our cardboard cation that will be classed as a primary carbocation Ary carbocations where two of those three groups are in fact R groups so we could have two methyls we could have a an ethyl and a methyl but there's two R groups on this cardboard cation I'm going to put an ethyl under methyl and the other one is a hydrogen that'll be a secondary carbocation you might have guessed it but a tertiary Cardwell cuttings when all three groups are in fact R groups again they could all be the same they could be different I'm going to put three methyl groups and this would be a tertiary carb or cation intermediate couple of key facts then and our group is actually known as an electron pushing groups so our groups are electron pushing this means that the tertiary cardboard cations are the most stable because think about it if you've got three electron pushing R groups what that's doing is it's actually stabilizing this positive charge because this carbocation is as I've said unstable so if you've got three R groups that makes it more stable so the tertiary is more stable than a secondary and using the exact same logic then a secondary is more stable than a primary because it has two electron pushing groups instead of just one it's the relative stability of these cardboard cations that can give rise to a mixture of products a major and a minor product so in electrophilic addition reactions of alkenes there's always going to be two possible carbocations we will look at some specific electrophilic addition reactions in the next few videos but what I'm saying here is that an alkene is a carbon-carbon double bond and during that chemical reaction you get the possibility of two different carbocations so during the reaction the carbocation could be on the left or the carbocation could form on the carbon on the right so we've got two possible cardboard cations now if the alkene is symmetrical then those two carbocations are identical and you only get one product however if the alkene is asymmetrical then those two carbocations will be different and that leads to two possible products one of them being the majority or the major product and the other one would be the minor product now if you're not happy with these terms symmetrical and asymmetrical there is a video that I've done on symmetrical and asymmetrical alkenes and I will put a link in the description so just to show you what I mean here is let me come up with a symmetrical alkene so that's a symmetrical alkene there that's Bute two in now I'll use an example here of HCL so when hit CL I won't do the full mechanism I'll leave that for the next video but there's two possible products here we could have the CL here and the H would be on this one on the left hand side or the other product could possibly be the other way around where we have the CL here and the hitch on this carbon now they're actually both the same thing if you were to name those two molecules they have the exact same name two chloral butane so a symmetrical alkene will always give rise to one product there's no such thing as a major an amount of product here the very different story however with an asymmetrical alkene so I'm going to draw an asymmetrical alkene in this case I've drawn Butte one in and this time if I react it with HCL I'm going to get two possible products I'm either going to get two chloral butane or I'm going to get one chlorobutane now one of these will be known as a major product and one will be known as the minor product the easiest way or the best way for me to show this would be to actually do the mechanism now the mechanism is going to be explained in more detail in the next video but I'm going to go through it quickly here so the first step the pi Bond attacks the electrophile that's my first step and this way we've got two possible structures here is the hydrogen could either be bonded to this carbon or this carbon now if the hydrogen bonds to the carbon on the left then the carbon on the right is going to end up as the carboxation so this would be a carbocation if the hydrogen bonds to the carbon on the right the carbocation is going to be on the first carbon so I've got two possible carbor cation intermediates I'll explain this mechanism in more detail in the next video but I've got two possible cardboard cutouts here the one on the right if I look at this one first this carbocation has two R groups so this is a secondary carbocation the one on the right hand side the car will cut iron only has one R Group so this is a primary carbocation now a secondary cardboard cation is more stable because it's got two electron pushing R groups that means that the major product is going to be the one formed from the secondary carbocation and the minor product would be formed from the primary carbocation just to finish off the mechanism for you that's the final step there and on the left hand side this time that long pair of electrons goes to that one so you can see the one chlorobutane and the two chlorobutane we've got a major product and a minor product and we identify using the carb or cation intermediates the focus of this video then was just to highlight the idea of carb or cations and their stability and how that links to the major amount of product the next few videos in the playlist you're going to see the specific reactions and I'll specifically talk about major and minor products there too thanks for watching