 Hello friends, good morning again, and welcome back to Centrum Academy. Last class, friends, we have discussed about the acidic nature of phenol, and we have also seen few problems into that. Now, to write down the order of acidity of various derivative of phenols, various phenol molecules. One more very important order we have, which is the boiling point order of nitrophenol. So, we will see the boiling point order of nitrophenol. Nitrophenol will have ortho-parallel metanitrophenol. For example, you see this is OH and OH and NO2 at ortho position, it is ortho-nitrophenol. This one, metanitrophenol, OH and NO2, this is para-nitrophenol, okay? So, the boiling point order of ortho-para and metanitrophenol we have here. You see what happens in case of ortho-nitrophenol, which is nothing but if I write down the molecule, just do the one small change here. I'll write down in this way, O minus double bond O and positive charge of nitrogen. Similarly, we have O minus double bond O and positive charge of nitrogen. Then we have O minus double bond O and positive charge of nitrogen. This is ortho-nitro, ortho-parametanitrophenol. So, in case of ortho-nitrophenol, what happens will have intramolecular hydrogen bonding, okay? OH and this O minus, this is we have intramolecular hydrogen bonding possible. In ortho-nitrophenol, we have intramolecular hydrogen bonding and here we have intramolecular hydrogen bonding possible. How it is there that you see, if I draw the another molecule of phenol like this, suppose we have the another molecule like this we are drawing and O2 here and OH here, right? Or in para-nitrophenol, we have intramolecular hydrogen bonding, this you see. This is what intramolecular hydrogen bonding possible. Intramolecular hydrogen bonding because this NO2 and OH group present in the molecule is not close enough and hence the intramolecular hydrogen bonding is not possible. Now because of intramolecular hydrogen bonding, boiling point decreases and intramolecular hydrogen bonding, boiling point increases, okay? Boiling point decreases and boiling point increases and hence the order of boiling point of nitrophenol is maximum for para-nitrophenol, maximum for para and then we have metanitrophenol, metanitrophenol and in the last we have ortho-nitro phenol, right? So order is this, PMO you have to memorize for this one. This is the order we have of boiling point that is PMO, para-nitro, metanitro ortho-nitrophenol, okay? So what happens? Due to presence of very stable resonating structure in para-nitrophenol, it gains significant dipolar character and develops a very strong intermolecular hydrogen bonding that is the intermolecular force of attraction. That's why it has maximum boiling point. This intermolecular hydrogen bonding is strong in comparison to intermolecular hydrogen bonding that's why the order is this, okay? The similar reason we have for the order of solubility. Solubility order is also same which is nothing but this. Para is maximum, then meta and then nitro, right? Then ortho, right? The reason is also same. So this is an important comparison we have boiling point order of nitrophenol. They ask this question many times in various competitive exams. The acidity we have discussed, boiling point we have discussed. Now the next thing we have to understand here is the method of preparation of phenol, okay? The next thing is method of preparation, okay? The first method we have from aryl sulfonic acid, from aryl sulfonic acid. What happens with aryl sulfonic acid you see? Aryl sulfonic acid is nothing but this molecule. Benzene ring and SO3H present on the ring. When this is heated with NaOHH2, NaOHH2, then it forms the sodium salt of this acid which is SO3NA, which is again fused with NaOHH2 molecules of NaOH we are taking, fusion takes place and it converts into Na2CO3 and ONA here, Na2SO3 and ONA here, plus Na2SO3. This is when heated with HCl acid forms NaCl and we get phenol as one of the product OH plus NaCl. This is the preparation of phenol from aryl sulfonic acid. Aryl sulfonic acid is nothing but this molecule, aryl sulfonic acid, okay? Now the next method of preparation, next method of preparation we have from disonium salt, from disonium salt. Disonium salt we can take benzene disonium chloride or benzene disonium bisulphate. Disonium salt we can take here, either we can take benzene disonium chloride or we can also take bisulphate, bisulphate. You see this reaction, benzene disonium bisulphate is nothing but this molecule, N2 plus HSO4 minus. When it is heated with water, N2 molecules goes out, we get OH plus N2 plus H2SO. This H plus strong water takes this HSO4 minus forms H2SO4 and N2 molecules goes out and then OH minus attached on the ring, okay? This process is known as steam distillation. This method is a steam distillation. These are the direct reactions we have. You need to know what product we get under this reaction, okay? Generally the reaction which involves disonium salt, N2 gas always evolve into that, always comes out, correct? So this is the reaction we have. If you take N2 by benzene disonium chloride that is N2 plus Cl minus, then we'll get HCl here and instead of H2SO4, we'll get HCl, okay? The next method of preparation we have is third one, reaction of phenolic ester, reaction of phenolic acid with soda line, phenolic acid with soda line. The process is known as distillation. This process is distillation process. Phenolic acid is this OH COOH, this is phenolic acid. When it is heated with soda lime, soda lime is a mixture of NaOH with CaO. When you heat this with this mixture, first it forms sodium phenoxide with ONA plus N2CO3 goes out and when it is hydrolyzed, acetic hydrolysis, it converts into phenol and NaOH, okay? This is the reaction we have. Na2CO3 forms here, one of the product of this is Na2CO3 and here we have NaOH, excess of NaOH we are taking here, right? We can also prepare phenol by catalytic oxidation, like from toluene. We can also prepare phenol from toluene and it's again a direct reaction and in this the toluene is heated with oxygen molecule in presence of the catalyst, okay? In presence of a catalyst, okay? So you see the reaction, the toluene is this molecule, benzene with CH3 on the top and when it is heated with oxygen molecule in presence of a catalyst like magnesium or copper sulfate, MNSO4 or CUSO4, this converts into OH. This is catalytic oxidation, okay? So these are the reactions we have through which we can prepare phenol. One more very important reaction we have that is cumene phenol process, okay? The production of phenol from cumene, okay? I'll write down this in the next page and the last method of preparation we have here is cumene phenol process, okay? That is the fifth one, cumene phenol process. This reaction is a bit important among the all that we did so far, okay? Now in this process what happens? In this process I'll write down first the theory we have here. In this process, cumene is oxidized in O2, in O2, in alkaline medium, in alkaline medium and forms, and forms cumene hydroperoxide, hydroperoxide, peroxide forms in this step. Cumene hydroperoxide which is then decomposed, which is then decomposed by S2SO4, acidic medium, S2SO4 into phenol. This is the whole process we have, okay? First, oxidation in O2, in alkaline medium forms hydroperoxide and then decomposition with acid, that is S2SO4. You see the reaction here is what? Cumene is nothing but we have a benzene ring and on this benzene ring isopropyl group is attached. CH, CH3 and CH3, this is cumene, okay? When the reaction takes place with O2 in the first step we have in alkaline medium, OH- and in the second step we have acid, S2SO4. So the product we get here, first of all I'll write down the product. The product is phenol, pH, OH and will get acetone in this, phenol and acetone we get, CS3O, CS3. How the reaction proceeds, you see? First of all, when this cumene, when the cumene is heated with oxygen in alkaline medium, it forms cumene hydroperoxide which is nothing but pH, CCH3, CH3OOH, this is cumene hydroperoxide, cumene hydroperoxide. Now in acidic medium what happens? H plus we have the oxygen here, protonates in acidic medium. This oxygen which has lone pair on it, this protonates in acidic medium and it forms this one, which is pHC, CH3, CH3, oxygen, oxygen, H, H, positive charge on it, okay? Finally in the next step, the phenyl ion, this takes this bond pair of electron and it rearrange itself onto this oxygen and this H2O goes out, okay? So the product here we get is pHO, CCH3, CS3, positive charge on this carbon plus H2O, okay? And when you have H plus H2O here, sorry, H2O, this H2O behaves as a nucleophile attacks onto this, attacks onto this positive charge carbon atom and it forms pHO, CCH3, CH3, H2O. OH2, positive charge on it. Now from this, H plus comes out, one of this H plus comes out, deprotonation, minus of H plus, this H plus comes out and it forms pHO, COH, CH3 and CH3. Now this lone pair of oxygen again protonates in the next step and it forms pHOH, positive charge on it. COH, CH3 and CH3, right? Now to stabilize this positive charge on oxygen, positive charge on oxygen, this pHOH, positive charge CCH3, OH, CH3, this bond breaks and will get phenol. This takes this bond pair of electron, comes out as pHOH plus the molecule left here is CH3, CCH3, OH and positive charge on this carbon. Because this bond pair is taken up by oxygen. Finally, H plus comes out into this deprotonation takes place and it forms CH3, C double bond O, CH3 and H plus goes out. So this is the mechanism of this reaction. So overall we'll get phenol and acetone in this reaction. So cumene under oxidation, right? And then acetic hydrolysis, H2SO4 we use for that purpose, H2SO4 and H2O, it forms phenol and acetone. This is again the preparation method of phenol from cumene. This reaction is important among all the reaction that we did so far for the preparation of phenol, okay?