 see here, we have 6 pi electron and hence it is aromatic. We have 2 plus 2, 4 pi electron and it is anti aromatic. This has sp3 sp3, so it is non aromatic. This carbon atom is sp3 non aromatic. It has 2 pi electron for n equals to 0 is true, so it is aromatic. It has 4 pi electron anti aromatic. It has 6 pi electron again aromatic. It has 2 pi electron. This carbon atom is sp3 hybridized non aromatic. This has pi with pi electron or electron, so it is anti aromatic. So it is 2 plus 2, 4 pi electron means what? It is anti aromatic. So this is 5 pi electron or electron if you have then non aromatic, not anti aromatic. Now you see here, oxygen has 2 lone pair. Out of this, one lone pair is involved in resonance and other lone pairs perpendicular to the plane of this ring. So we will count only one lone pair for the to decide the aromaticity of this compound. So we have 2, 2, 4, 2, 4, 6, 8. We have 8 pi electrons and hence it is anti aromatic. Remember one thing always if an atom contains 2 lone pairs then to decide aromaticity will count only one lone pair. Always remember one thing this is very important. Count only one lone pair. So here the oxygen contains 2 lone pair will count only one, so 1, 2, 3, 4, 4 into 8 pi electron anti aromatic. You see this is one electron which is present perpendicular to this plane because the 1 pi electron is available here in lateral overlapping. This lone pair is not involved in resonance. You must remember this pyridine the name of the compound is this lone pair is not involved in resonance. We will calculate 6 pi electron and hence it is aromatic. You see when I save number of pi electrons we always count the pi electrons or lone pair which are involved in resonance. That is the thing. So here you see this lone pair is involved in resonance. So we have 6 pi electrons aromatic. Out of 2 only 1 is involved 2 plus 2 4 pi electron and hence it is anti. You see these examples we have 2 or 2 1 is available in the resonance 2, 4, 6, 6 pi electrons aromatic. It is a conjugated system, we get 4 pi electron anti aromatic, 2, 4, 6 pi electron aromatic, 2, 4, 6 pi electron aromatic, 2, 4, 6, 8 pi electron. So like this we have discussed many examples. There are few more examples left. So we will see those examples in the next session and then there is one more case. How do we decide aromaticity in multiple cyclic molecule in which we have more than one cycle present. And there are few cases also in this double bond is present outside the ring. How do we assign that like in this case like the ring is conjugated and we have double bond outside the ring also. So those kind of examples some miscellaneous examples we will see in the next session and we will also see one case where we have multiple cycle compound and how do we assign aromaticity, non-aromaticity and anti-aromaticity in those molecules. So we will see in the next session. Thank you. So what is aromaticity? Aromaticity is what it is the property of cyclic planner conjugated system. Cyclic planner conjugated system. It provides extra stability to the molecule. It provides extra stability to the molecule. Stability because of aromaticity dominates on all other factors. If the molecule is aromatic then its stability will be maximum. That is what you have to keep in mind. And the next thing is how do we understand that the molecule is aromatic. So for that what we have like I have written over here it must be a cyclic system, cyclic system, it must be planner conjugated system, cyclic planner conjugated system and it must have 4n plus 2 pi electrons. 4n plus 2 pi electrons where n is the natural number can be anywhere 0, 1, 2 and so on. This rule is given by Huckers, one scientist the name is Huckers and we call it as Huckers rule. 4n plus 2 pi electron Huckers rule. So for example you see the very common example of aromatic compounds if you take it is benzene ring. So in benzene ring you see all the p orbitals are parallel and in this also the molecular orbital forms the molecular orbital forms. So this 6 pi electron 2 plus 2 plus 2, 6 pi electron are present in pairing in molecular orbital. Present in pairing in molecular orbital. And because of this only since there is no unpaired electron it is highly stable that is why we say aromatic compounds are highly stable. Now there is one more type of term we have here that is anti-aromatic. First we will discuss all this term and then we will see examples on this. Anti-aromatic is what in short we will write aromatic compound as A. Anti-aromatic will represent by A dot A right. In this all conditions are same like the system must be cyclic planar conjugated number of pi electrons should be 4n pi electron. This is the only difference here. Cyclic planar conjugated is same as aromatic compounds but the number of pi electron is different which is 4n pi electron when n is in natural number it can have 0, 1, 2, 3 and so on. So if you calculate here I forgot to tell you one thing if you calculate the number of pi electrons here we can say we have 6 pi electrons in the benzene ring and if you cross check with Huckel's rule we know when n is equals to 1 it gives 6 pi electron. So this number of electron satisfies Huckel's rule for n is equals to 1. It is cyclic planar follows Huckel's rule and hence this compound is aromatic. So here also the same thing we have but the only thing it has 4n pi electron present. For example you see if I take this one cyclic butadiene you see it is planar all carbon atom is sp2 hybridized cyclic also conjugated system also there pi sigma pi and number of pi electrons if you see here it is 4 which follows this rule 4n pi electron okay so 4n is equals to 1 it follows 4n pi electron 4n is equals to 1. So this 4 pi electron is in this also hybrid orbital forms sorry molecular orbital forms in this one and in the molecular orbital we have two unpaired electrons one is paired and the other two is unpaired in the molecular orbital okay so in this molecular orbital because of this two unpaired electron this molecule is highly unstable because of two unpaired electrons okay. Now the third type of compound we have here is non-aromatic and non-aromatic in short we write na okay these compounds are not cyclic right if cyclic then not conjugated if cyclic then not conjugated okay these non-aromatic compounds are actually normal compounds at room temperature. For example you see right these examples are non-aromatic compounds first of all this is not cyclic not cyclic so non-aromatic this one is cyclic but it is not a conjugated system conjugated system when I say it means it should it is completely conjugated right like you see here this carbon atom is sp3 hybridized okay and the delocalization of electron from here to here only this part is not involving resonance so this is not a complete conjugated system okay because this carbon atom is sp3 hybridized any cyclic molecule if the sp3 hybridized carbon atom is present it is non-aromatic always okay so the point is what this is the normal compounds at room temperature this is highly unstable compound and this is highly stable so because of aromaticity it provides high stability to the compound okay and then we have non-aromatic compounds normally at room temperature and then anti-aromatic compounds so stability order if I write down here this order they have asked many times in the exam stability order we have aromatic first then non-aromatic and then anti-aromatic the order of stability is this okay this you must remember it is very important okay so this is the few examples we have discussed few like the theory we have discussed for aromaticity anti-aromaticity and non-aromatic compounds okay now in this session the examples are very important okay so we will see the examples next few examples I will write down and then we will discuss we will start from the very basic one the engine ring okay guys welcome back to the Centrum Academy again last class friends we have discussed about aromaticity okay and we have also seen few examples of aromaticity what is aromatic compounds okay how it provides the you know extra stability to the molecule okay we have also discussed non-aromaticity and anti- aromatic compounds okay what are the condition for aromaticity and anti- aromatic compounds and non-aromatic compounds are there that we have already discussed and we have also seen few examples based on it okay and like I said in the last session that in the next session we will also see some miscellaneous examples of aromaticity and then we will also discuss how do we decide aromaticity in multi-cyclic compounds okay so now in this session we are going to discuss the some miscellaneous examples of aromaticity and let us start with this session like with this examples of aromaticity okay so first of all I will just write down here aromaticity okay like I said that for aromatic compound it must be cyclic planar conjugated system which has 4n plus 2 pi electron okay so we will see few examples here okay so now we are going to solve these questions so you see this compound we call it as furan okay and like I discussed in the last session that whenever an atoms in the ring contains two lone pair so only one lone pair is if it is possible then involving resonance okay so out of this two lone pair one lone pair is involving resonance this molecule has 6 pi electron and it is aromatic okay 2 4 6 pi electron aromatic similarly thiopene also has 6 pi electron and aromatic okay now you see this molecule has this electron is involved in resonance okay this one is not involved in resonance this lone pair okay 2 4 6 this molecule also has 6 pi electron and it is also aromatic compounds similarly it has 1 2 3 pi bond 6 pi electrons compound is aromatic okay in this one you see resonance is possible because of vacant p orbital 2 plus 2 4 pi electron and this is anti aromatic okay here you see this molecule we call it as inorganic benzene inorganic benzene or we also write it as borazole inorganic benzene or borazole you must have seen in the book that they have drawn a coordinate bond here like this like this and like this coordinate bond why because all this boron atom you see they have vacant p orbital okay this can accept this lone pair of electron from this nitrogen atom okay so we have we have a coordinate bond from this to this this to this and then this to this inorganic benzene okay so we have 3 pi bonds here you see 1 2 3 3 pair of lone pair we have here it has 6 pi electron and hence this is also an aromatic compound okay this one you see 2 4 6 pi electron it is aromatic okay this molecule has 8 pi electron and according to that it should be anti aromatic okay it should be anti aromatic but it is not anti aromatic but it is non aromatic in nature non aromatic in nature why what happens here see if the cyclic compounds contains 7 or more atom okay then the molecule changes its plane okay so this becomes non-planar then so that is the point we will write down here note down this point the number of atoms present in the ring is more than or equal to 7 then then the molecule changes its plane its plane and loses conjugation loses conjugation okay and when conjugation is not there it cannot be aromatic or anti aromatic okay hence in all these cases whenever the carbon whenever the ring contains more than or equal to 7 atoms it must be non aromatic okay so this compound is non aromatic similarly you see here we have 1 2 3 4 8 pi electron but the compound is non aromatic okay 7 atoms are there here what happens 1 2 3 6 pi electrons molecule is aromatic okay remember this boron has vacant p orbital okay so resonance possible here okay similarly here you see this carbon atom has positive charge 2 4 6 6 pi electron and this is also aromatic in nature conjugation is also there but here you see this carbon atom is sp3 right so the molecule is what non okay the molecule is non aromatic there are few examples important examples of aromaticity we have discussed okay there are also few questions in which the double bond is present outside the ring okay so in that case what we should do that we are going to discuss now I will write down the few questions and then we will discuss now we will discuss this you see here we have double bond oh here in this case whenever we have double bond present outside the ring then we will try to draw the resonating structure of this like the first example I am taking this one here you see the molecule is this double bond oh and here we have lone pair if you draw the resonating structure of this one okay so what happens this lone pair comes over here and this pi electron goes here right and we always draw this resonating structure with this double bond double bond which is outside the ring so the resonating structure here it is you see n double bond this will be as it is and here we have o negative h n for nitrogen we have positive okay now you see this molecule this molecule has 6 pi electron and hence it is aromatic so we will first draw the resonating structure and then we will get the idea whether it is aromatic or anti aromatic you see here this molecule has 6 pi electron and hence it is aromatic in nature okay in this also what we will do this lone pair comes over here and this pi electron goes here right again in this ring you see it is 6 pi electron this is also aromatic okay in this what happens this pi bond will shift here will get a positive charge here right 2 pi electron it is it has 2 pi electron which is also aromatic in nature okay again in the ring we have 6 pi electron aromatic in nature okay ring you see this it is 6 pi electron and hence this also aromatic okay this has more than 7 atoms present so this is non aromatic in nature however we can see there is a conjugation a number of pi electron if you count 1 2 3 4 5 6 so it has 12 pi electron right non aromatic in nature right according to the rule if you see it should be anti aromatic 12 pi electron but since the number of carbon atom is more than 7 hence it is anti sorry non aromatic okay similarly you see this molecule has 6 pi electron aromatic in nature again here if you draw the resonating structure this will be the resonating structure so it also has 6 pi electron in the ring which is aromatic right these are the few examples we have discussed where we have only one cyclic cyclic compounds are there it means only one cycle we have here so what happens if you have multi cycle compounds means more than one cycle is present in a compound then how do we assign aromaticity and non aromaticity or anti aromaticity okay so next we are going to discuss those examples in which we have multi cyclic compounds okay