 We are going to discuss the basic strength. Like few things I have written over here since I have already discussed this in the previous classes. So, basic strength is what? We define basis strength by two types, intensity to donate lone pair or which can increases concentration of OH minus ion in its aqua solution. This definition generally we use in nitrogen containing compound, right? So, basis I have classified into two categories, general base and nitrogen containing compound. General base we have already discussed. So, I am not going to discuss this again here, right? Nitrogen containing compound like ammonia and its derivative we will discuss here, right? Now, see I have taken these two bases here and I have written the reaction with H 2 O, right? Since these are bases, so I have taken your K b 1 and K b 2 because the reaction is reversible in nature. So, I have written a reversible or equilibrium constant, ok? So, N is 3 plus H 2 O the product will be this, CS 3 CO minus H 2 O the product will be this, ok? Now, we know exactly we have already done chemical equilibrium and there we have already discussed that when equilibrium constant increases, the reaction has more tendency to go into forward direction, ok? Now suppose if this K b value increases, right? Any one of this K b value increases, then the reaction has more tendency to go into forward direction and the reaction goes into forward direction, the concentration of OH minus ion increases in the solution and when concentration of OH minus ion increases, the basicity increases, right? And that is what I have written here. K b increases forward reaction, concentration of OH minus ion increases, base strength increases. Base strength if you want to define, it is the amount of OH minus ion produces in aqueous solution, when one molar substance we have taken, right? With one molar of substance, what is the amount of OH minus ion produces in the solution is the basic strength or base strength of that particular compound, right? So, P K b we already know it is minus log of K b, right? So, what we can say, basicity is directly proportional to K b and inversely proportional to P K b, ok? So, like acidity we have already done, acidity directly proportional to K a, inversely proportional to P K a. Similarly, we can do this. So, when you know the K b value, you can have the idea, you may have the idea of basicity and P K b, right? K b will have exactly the same order of basicity and reverse order of P K b, right? So, they may also ask you order of P K b, P K b anything. So, if you know this relation, you can do this. Now, the point is how do we define basicity, right? So, for that I have taken this example here you see, right? So, all this example you see, this compound is non aromatic, aromatic and anti aromatic. So, when it is aromatic, this lone pair is delocalized. It is not available here on nitrogen, ok? So, when it is not available, it is delocalized in the ring. So, if it is not available, we cannot donate this lone pair and that is what the basicity nature, ok? So, since it is delocalized, so it will not be able to donate this lone pair, so its basicity will be minimum, right? Non aromatic and anti aromatic, non aromatic is more stable, right? So, this will have the order N A then and then anti aromatic, ok? So, this is the basicity order we have. So, the compound which is anti aromatic in nature is most basic, right? Anti aromatic in nature is most basic, nitrogen containing compound, ok? Aromatic is highly stable because of delocalization of lone pair, that is why it is least basic, then non aromatic and then anti aromatic, ok? Similarly, one more example if I write down. So, here in this case the order will be this is 3, this is 1 and this is 2. Another example you see, in this 2, this is aromatic compound and this lone pair is localized. It is not delocalized, it is not involved in resonance, right? So, order of basicity will be, one more thing we will discuss here, if the lone pair is involved in conjugation, right? When lone pair is involved in conjugation, the basicity decreases, ok? So, what we can write conjugated lone pair, lone pair is less basic than non conjugated lone pair, ok? For example you see, this lone pair is in conjugation with this and hence this is less basic. Another example I can write, the order of basicity will be this. Next example you see, order of basicity will be this. So, like you see conjugated whenever lone pair is involved in conjugation, right? Then the basicity decreases because the lone pair is not exactly available on to the nitrogen atom. This type of question you may also keep in mind, lone pair, right? Now if you have to compare the basicity, we will check the hybridization here. It is sp hybridized, it is sp2 and this is st3, ok? So, sp hybridized is most electronegative and hence the tendency to donate lone pair of electron will be less. So, order of basicity will be c maximum then b and then a, ok? So, what we can say, basicity in this kind of question, we can generate this as basicity is inversely proportional to the percentage as corrected, right? More percentage as corrected, more will be the electronegativity and hence less will be the basicity. One very important comparison we have here, this is alpha and this is beta, which one has more basicity, ok? So, this lone pair you see, it is delocalized, delocalized, but this one is localized. It is not in conjugation, right? So, basicity of beta is more than, ok? So, like this you can easily compare the basicity order of various nitrogen containing compounds. Two, three different examples we have discussed, aromaticity, non-aromaticity, anti-aromaticity. Then we discuss the conjugation part, we discussed hybridization also and this is also a part of conjugation, ok? Like this also they can ask the question, ok? So, whenever here they ask you the protonation type, like the protonation takes place at first carbon or second carbon, the nitrogen, first nitrogen or second nitrogen, the nitrogen which is more basic protonates first, right? So, that will be at beta position, right? It is derivative, basicity of any lane and its derivative, ok? So, you see the first example we are going to discuss here, aniline is nothing but phenyl amine, this molecule, right? Phenyl amine. Few examples we will discuss here, this is aniline and basicity of aniline we will discuss here, the tendency to donate to donate electron, ok? That is what we have to discuss. For example, you see here these two examples, ok? Now, this CS3 at para position it shows plus H effect, right? CS3 at meta position shows plus I effect, ok? So, what happens with this plus H and plus I effect? Both are electron releasing group, right? Both are electron releasing group, right? So, because of electron releasing tendency finally, the electron density on this nitrogen atom increases and hence, basicity increases, right? So, all those electron releasing group increases basicity and electron withdrawing group decreases basicity. So, in these two examples if you consider, since plus H effect dominates over plus I, so the basicity of this group is more, right? Now, to you know to sum up this discussion, ok? You see all these examples I have written over here, even I have already solved it, ok? You can easily see CL, CCL3 and CCL3 here, minus H and minus I, because of minus H the basicity will decrease more, right? Hence the order will be this, ok? Now, minus M and minus I here, because of minus M the basicity will decrease maximum. So, minus I will be more basic, plus H plus H, because of plus H basicity increases, right? So, plus H of CS3 is more the hyper conjugating conjugative tendency of CS3 is more than to that of CD3. So, basicity order will be this, plus M minus I, obviously plus M shows higher basicity order will be this, minus I and here we have little bit of minus I tendency, because this carbon is sp2, this carbon is sp hybridized. If you compare these two, this more group has more tendency to withdraw electron, right? Hence the effect here will be less, here will be more of this one, basicity of this compound will be less, order will be this. Now, friends that important thing here that we are going to discuss is ortho substituted naline, right? In case of ortho substituted naline, how do we assign basicity order, ok? So, first of all we are going to take this example and we will discuss what happens in ortho substituted naline. For example, you see this is ortho substituted naline, when you put this into water H2O, it forms. So, here you see it forms NH3 plus in this. So, what happens here? Plus we also get here OH minus, right? And this will have some equilibrium constant that is KB, ok? Basicity of naline is defined by the amount of OH minus ion we are getting here, ok? Now, you see because of this steric repulsion, this reaction has very less tendency to go into forward direction, right? So, what we can write? Because of steric repulsion, this reaction has very less tendency to go in forward direction. So, what happens? Hence the concentration of OH minus ion will not produce that much, ok? Or this reaction, what we can write? The concentration of OH minus ion decreases and the reaction has more tendency to come into backward direction, right? To minimize the repulsion, right? And that is why the basicity of orthoaniline, of orthoaniline is lesser than meta or paraaniline. This is what we have here, right? So, in case of ortho substituted aniline, the basicity will be minimum, right? If we are comparing this with what? Meta and para substituted, ok? Now, you see the example I have taken here, right? So, for this one, you see here we have what this effect, one term I have to write down here. This effect since this is the protonation of aniline, right? This reaction is nothing but the protonation of aniline, ok? Now, because of this steric hindrance, the protonation is hindered, right? So, this effect we call it as SIP, SIP, steric inhibition of protonation, right? And because of SIP, steric inhibition of protonation, basicity, basicity decreases, right? Remember in case of ortho substituted benzoic acid, there we have SIR, steric inhibition of resonance, ok? Here we have steric inhibition of protonation, ok? So, because of SIP, basicity decreases. Now, here in the first case ortho substituted, we have SIP, here we have plus H and here we have plus I, plus H and plus I. So, the first one you see, because of SIP, the basicity will be least, right? So, here the basicity order A will have minimum, because of SIP, because of plus H, basicity increases, right? Then we have B and C will have maximum basicity, ok? This is what we do in case of ortho substituted aline, SIP will takes in place. Now, few more examples if you discuss here, compare the basicity of these molecules, these three molecules you see. Here we have SIP, here we have minus I and here we have minus H, right? So, because of SIP, the basicity will be least, this is the third one, right? Because of minus H, the basicity will decrease more. So, this is first and this is second, right? SIP minus I and minus H minus M, right? So, maximum we have in case of minus I, because minus M will decrease even more, right? Then we have 2, this is because of SIP 3, basicity decreases, right? Here also you see the larger group at ortho, similar order we have here, SIP, right? Here we have plus I, right? And here also we have plus I, because hyper conjugation is not possible, there is no alpha hydrogen here, right? Plus I, so this is obviously the least one, ortho substituted, plus I effect is more over here. So, this is first and this is second, okay? So, this is how we can compare the basicity of aniline, okay? One more example we will discuss here. Always take care, here we do not have alpha hydrogen, no alpha hydrogen. Here also the same question we have, I am taking this separately, no alpha hydrogen. So, we have plus I effect possible here, not plus H. Here also we do not have alpha hydrogen, anyway it is at meta position, so it is plus I also. Now, since this molecule is closer to this here, hence the basicity will be more in case of plus I here, right? Because both shows plus I nature, okay? So, this like this you know we can compare the basicity of aniline. One or two more question we will discuss the last two questions in this example, okay? So, now what happens? Here we have steric repulsion, steric hindrance and to minimize this N O 2 change a display and hence in this case minus M here is not possible. Here minus M is possible, right? Here what we have? We have little bit of minus I, if any effect we consider, we have minus I. Minus M will decrease more, basicity here it will be maximum. These three molecules you see, we have to compare the basicity order, okay? Now you see in this case, this lone pair and lone pair can show basicity, but when we compare with this, here what happens? The H plus here or any proton, H plus here will forms a chelating compound here, right? A cyclic kind of compound we get, right? So, which we call it as chelation and because of this chelation the basicity of this kind of compound will be more. This kind of cyclic ring would not possible here in this case because nitrogen is here and here. Here in this case chelation is possible hence the basicity is more. This is some like it is few miscellaneous examples we have, you must keep in mind, okay? Now here you see if this lone pair involve in resonance and you draw the resonating structure here, you will get something like this. Here we have the positive sign on nitrogen, hydrogen is there, okay? Now you see this point here, it is the bridge head position, bridge head, okay? And we know at bridge head position, sp2 hybridization is not stable, okay? Hence the tendency for this lone pair to involve in resonance with this oxygen will be very least in comparison to this one, right? Hence the basicity is more for this compound, right? This structure is not possible. This one is possible. That is why the basicity of second one is more, okay? Now you see what happens here the repulsion is more, steric repulsion is more. Hence what happens? An H3 hole twice changes its plane and H3 hole twice changes its plane and the lone pair on nitrogen, lone pair is localized, right? But since the repulsion is less here, right? Here the lone pair is delocalized with the benzene ring, right? So when the lone pair is delocalized, so electron density will be less over here, right? Tendency to donate electron is more for this molecule, okay? And that is the basicity order, okay? So these are the few, you know, miscellaneous examples I have done, okay? You must keep these three examples in mind so that whenever you get similar kind of questions, you can do that, okay? So there are few things, basicity we have done actually. There are few