let's talk about the differences between addition elimination and substitution reactions these are all three very broad types or categories of organic reactions so on the screen that you can see I have put one of each of the three broad categories or types of reactions an elimination an addition and a substitution I haven't told you which is which I want you if you know nothing about this just to take a look at it quickly and see which one you think represents addition which one represents elimination and substitution based on the words so addition what that means to add substitution what that means an elimination to remove when given a specific organic reaction so for example reaction One you need to be able to look at the reaction and identify what is happening in the reaction what type of reaction it is if it's addition substitution elimination and the more specific name of the reaction and the reaction conditions required for the reaction to take place so what needs to be put in place in order for the reaction to proceed for example do I need heat do I need a acid Catalyst those are all reaction conditions and now what I like about the three broad ways in which we can categorize these sorts of reactions is because the name tells us way more than we need to know about the reaction so addition reactions that involves adding as the name suggests substitution reactions involve swapping I want you to think of if you watch a sports game and they say that they are going to put the substitute on the field they are swapping a player on the field with another player they're replacing one with the other so that is substitution and then elimination which means to remove to eliminate or to remove so if we take a look at these examples over here in this reaction I have a double bond a compound with a double bond I've got an alen so something with double bonds and I am adding HH now I hope that it's clear that because there's a double bond over here if I reacted with hydrogen H2 there's essentially a space over here for this hydrogen to take and there's a space over here for this hydrogen to take assuming of course that we end up breaking that double bond and then placing or adding the hydrogens in those open spaces so my resultant product would be three carbons like that all surrounded by hydrogen remember the original compound looked like this we broke the double bond forming a single Bond and that leaves space where the hydrogen can be added over here and the hydrogen can be added over here as you can see we are going from something with double bonds to something with single bonds so as soon as you see a reaction where I go from double bonds to single bonds you know you are dealing with an addition reaction if you take a look at the substitution reaction over here over here I have an alcohol it's got a o group group I am adding it to HCL hydrogen chloride now what makes this different to the addition reaction even though I just said we are adding hydrogen chloride this is not an addition reaction because can you see that this has single bonds over here there's no open space if I can say it that way for another hydrogen to slot in anywhere all the spaces here are full every carbon has four bonds however what I can do is I can swap the o with the c so everything else stay is the same you can see all the original hydrogens but instead of the O I'm now going to put the CL in its place and then think about it this o joins up with this H the O has now been removed it joins up with this H to form H2O and this is called a substitution reaction can you see that I start with something that has single bonds and I end with something that are single bonds so single to single substitution single to single substitution and then we have elimination or removing so as you can see I have a single bond compound over here in fact it is an alcohol and what I can do is I can remove the O and an adjacent hydrogen so adjacent means on the carbon next to and an adjacent hydrogen and what we will then be left with so these are going to be removed eliminated we take them away so we're going to have the three carbons these hydrogen remain I have not removed them they're staying all of these are staying but I've removed the one that was here and the hydrogen that was here and now in order to make every carbon happy they all need to have four bonds so this carbon over here this first carbon only has three one 2 3 in order to make it have four bonds I need to put in a double bond the second carbon now also has four bonds 1 2 3 4 and the third carbon has four bonds and this is an elimination reaction Okay so we've gone from something with single bonds only to something with double bonds and that's why I like summarizing the differences between addition substitution and elimination reactions in this way based on what they looked like so if they had single bonds before and what they look like after so if they have double bonds before and based on that change we can identify if it's an addition substitution or an elimination now each of these three broad categories of reactions have reactions under them different types of reactions that you need to know so these are the addition reactions that you need to know I will go over addition in its own separate video here are the substitution reactions that you need to know and these are the elimination reactions that you need to know I cover all three of these major types of reactions in their own videos but if I had to give you something like this and based on what we spoke about just in this lesson if I had to ask you what type of reaction so what's the broad category that is represented by a what would you tell me so a is going from compound p which is clearly an alcohol so it has single bonds to an alken we don't know what alken is yet but we know that an alen has double bonds so remember we spoke about it if we go from single bonds to double bonds this will be an elimination reaction elimination we're removing something it has single bonds we would have to remove something to make it have double bonds and therefore going the other way around going from something with double bonds to single bonds so reaction B that would be addition I hope that that makes sense what about C so going from compound P this way we are adding hbr but there is no space to add so it's not addition so I know we're adding we're reacting it with hbr but what is going to happen is the O will end up swapping with the BR so it'll be single bonds to single bonds it'll end up being substitution and what would then happen is if we go backwards so C to P so going from X to p going along reaction C that would also be substitution so knowing how to identify if it's addition elimination or substitution is a very very important First Step then obviously you need to understand the specific reactions that fall under the broad categories and then the reaction conditions and you'll be able to complete past paper questions like this with me in no time and if we had to take a look at this one what type of reaction is reaction to an example of so we need to think this is an alcohol it has single B bonds and alkenes have double bonds so going from single bonds to double bonds so if you can't see it just draw it out quickly so we would have an alcohol something like that with the single bonds like that and I'll get into how I know that it looks actually exactly like this in a second so this is what the alcohol will look like it's got single bonds and we end up with an alken which we know has double bonds so in order to make it have double bonds I need to take the O away okay and then an adjacent hydrogen you can't take off another hydrogen from the same carbon because then the carbons are not going to have enough bonds I'll do this in a later video so 1 2 3 4 1 2 3 4 this looks a bit funny you might be used to more seeing it like this it doesn't really matter how you draw it this carbon has two hydrogens and this carbon has two hydrogens what I'm trying to show you is we went from something with a single Bond only to an alen which has double bonds but how did we get there we had to remove we removed the O and we removed an adjacent hydrogen because we removed Reaction 2 has to be elimination and just quickly for your information how did I know that the alcohol would look the way that I drew it when I drew the alcohol I drew it like this how did I know that it was going to have exactly two carbons how would I know that well I know it working backwards in this diagram it says here I add the alcohol to P unknown reactant and reaction One happens and I end up with Ethyl propanoate what is ethyl propanoate it's an Esther and we know that Esters are made up of alcohols and carboxilic acids I hope you know that so P would be a carboxilic acid and we can actually take it one step further we can speak about exactly which alcohol and exactly Which carboxilic acid because we know the name so remember in Esther the first part of the name comes from the alcohol so Ethel tells that it comes from the alcohol ethanol that's where this came from that's how I know to draw with two carbons so the alcohol was ethanol and the carboxilic acid was propanoic acid just as a side note and that would make reaction One be an esterfication reaction okay making an Esther esterfication but that's another video I hope that this makes sense please you need to know how to identify if a reaction is addition substitution and elimination then I'll see you in the next video where we look at addition reactions more closely and the different types of addition reactions bye everyone