 So, let's begin this video by looking at these organic reactions. Now you must be wondering what are these big molecules doing in a p-block element video, right? Well for starters let me tell you that as we learn more about any particular subject all of these distinctions like organic, inorganic, physical all of these start blurring out you know. They don't really make much sense after a certain point it's all just science. With less we will still figure out what these reactions or big molecules as we say are doing in this video. For now what I want you to do is pay attention to the reagents you know the catalyst that is used in these reactions. See what is happening with them. Don't worry about these big molecules you know or how this reaction is occurring. Ignore all of that and simply pay attention to what a group 13 elements are doing here. Okay. Watch the video and see if you can figure it out yourselves. So well here we are and what do we see? Well one of the first things that you will notice is that all of a group 13 elements have acquired a negative charge. For instance look at the first reaction the lone pair of electrons on nitrogen have gone to boron and nitrogen acquires a positive charge and boron gets a negative charge. In the second reaction something happens to this particular alkyl chloride such that we get a carbocation but look what's happening to our aluminum chloride. AlCl3 becomes AlCl4 and aluminum gets a negative charge and what about the third reaction? Yes it looks complicated but all we need to do is simply look at what's happening to gallium correct. Gallium again ends up getting a negative charge even though it is GCl3. So what's happening here is the triple bond or the pi electrons here have shifted to gallium and here carbon gets a positive charge and gallium gets a negative charge. So in general you can see that all of these elements are accepting a pair of electrons and what else is common between all of them? Well you can see that they are all in their trivalence state as well. So what is trivalence state? That is they are in their plus 3 oxidation state. Okay. So what exactly is going on here? Well one of the characteristic features of group 13 elements is that all of these elements form electron deficient compounds in their trivalence state and it's not just halides of group 13, hydrides like BH3, ALH3 all of these compounds are also electron deficient in nature. In other words they all act as lowest acids and that's what we will see in this video. We will see why they act as lowest acids and where can we use this particular behavior. Now as we know group 13 elements have 3 electrons in their valence shell, 2 electrons in SR battle and 1 electron in PR battle right? So that means to attain a stable electronic configuration it needs to lose 3 electrons or gain 5 electrons and what do you think it would prefer? Losing 3 electrons or gaining 5 electrons? Of course this is right. Why would any atom want to gain 5 electrons and become so unstable? That means in their group oxidation state which is plus 3 the central atom will end up having only 6 electrons around it. For instance let's assume that E is one of a group 13 elements and whether these elements lose electrons or share electrons with another atom we can see that at the end of the day the central atom has only 6 electrons around it. That means it has an incomplete octet and this inherent electron deficient nature comes in pretty handy for us and we can use these compounds as lowest acids. Now what does a typical lowest acid do? They simply accept a pair of electrons from an electron drift species or a lowest base to form a complex or an adduct right? For instance let's take BCL3 as a lowest acid and when it reacts with an electron to species or a lowest base like ammonia we know that the lone pair of electrons on the nitrogen atom goes to boron correct? So finally we end up getting BCL3 minus and NH3 plus. So this is how a typical lowest acid base reaction looks like. So let's now see how this behavior or the ability of group 13 elements to act as a lowest acid helps us in organic reactions. Ok so let's look at our first reaction here. Here we can see that BF3 is reacting with a carbonyl compound that is a compound which has C double bond O group. Now here BF3 not only acts as a lowest acid but also as an activating agent for this particular reaction. See we will not go into the details of the mechanism here but what we mean by activating is that we need more positive charge on the carbon atom here. Now that can happen if this electron density on the pi electrons get shifted upwards and that's exactly what happens as you can see here. Now the question is how does our lowest acid or BF3 help in activating this particular reaction? Well you see the lone pair of electrons on the oxygen atom acts as a lowest base and BF3 here is obviously a lowest acid right? And what happens in a typical lowest acid base reaction? Well the lone pairs go into the electron deficient boron atom but where in the boron atom does it go? We know that the electronic configuration of boron is 1 is 2, 2 is 2, 2p is 1 that is there is only one electron in the P orbital. That means we still have MTP orbitals available right? And that's exactly where the lone pair of electrons go. So as you can see here not only is our MTP orbital getting filled but boron finally gets a complete octet. So this is how BF3 or a lowest acid helps in activating this reaction. The carbon ends up getting a more positive charge and boron has a complete octet. Now something quite similar happens in this particular reaction as well but instead of oxygen it is a lone pair of electrons on the chlorine that goes into the MTP orbitals of aluminium and when that happens you get the intermediate which is CS3CO plus and aluminium becomes negatively charged that is ALCl4 minus or in other words you have your aluminium with completely satisfied octet. Now benzene reacts with this particular intermediate and gives you the final product here. So we won't get into the details of the reaction here again but what you need to know is that the driving force for this reaction is a need for aluminium to get a complete octet. Now there is another interesting thing about this reaction. You see when we carry out this reaction laboratory we make sure that there is absolutely no trace of water. Now why is that? Because if you have water you know the lone pair of electrons on the oxygen atom can go into the aluminium right? I mean as far as a group 13 element is concerned all it needs is a complete octet. It can be from the lone pair of electrons of oxygen of water or from this particular compound. So in order for water to not interfere in this reaction and generate this intermediate we have to make sure that the reaction is carried out in an anhydrous environment. Now let me ask you something. Do you think that this electron deficient nature of all of these group 13 elements is the same? Well turns out that this trend actually decreases down the group. That means BCL3 is a better Lewis acid than ALCl3 which is a better Lewis acid than GACL3 and so on. Now why do you think this happens so? Well one of the reasons is that the stability of the plus 3 oxidation state decreases down the group but more importantly electronegativity also decreases down the group. Now as we know electronegativity is a tendency of an atom to attract an electron pair. So if that goes down it means that the Lewis acid nature also decreases right? That means the compounds no longer become interested in taking up electrons or act as a good Lewis acid and that's exactly what happens here. So folks that's pretty much it about the electron deficient nature of group 13 elements. So I hope you now have a fair understanding of why group 13 elements are electron deficient and where we can use their Lewis acid nature.