 Hello. Good afternoon. Yeah, it will be saved. Yeah, it will be saved. You can watch it whenever you want Whenever you have time you can watch it later or also It will be saved in this channel Okay, good afternoon everyone. Please type in your name In the comment box, please fast Hello, apple. How was your exam? How was your exam Lalitha shares? How was it? Hello, Lakshya Ishika. Hi Okay, chemistry was the best. Okay, can we start now guys last class we have discussed optical isomerism and we have seen few examples also That uh, how do we uh, see the optical activity of a compound? How do we analyze the optical activity of a compound? Correct and uh, this is essential condition for a compound to show optical activity is the karelity, right the karel Lady has nothing to do with karel centered. Okay, you must keep this in mind Right, so there are actually few uh terms that we use in optical isomerism. Okay Few terms we use in optical isomerism Uh, that we are going to uh study today and the first term we have here that is Enantiomerism write down Enantiomerism this term will use in Uh hydrocarbon also that's why we are uh discussing these things Okay, write down compounds which are not the definition of enantiomerism The compounds which are not Which are not superimposable mirror image Mirror image of each other the compounds which are not superimposable And mirror image of each other called called enantiomers and this phenomenon This phenomenon Enantiomerism This is the definition of enantiomerism. We have okay now the term that we have used here is superimposable Okay, superimposable. We haven't discussed yet So what is superimposability? Or what is the superimposable? How do we understand that the two compounds are superimposable to each other, right? Those compounds when you put one over the other Right, they does not look like the different compounds. They look like the same compound Those compounds are said to be superimposable to each other like hands, right the left and right hand Left and right hand are superimposable or not. Can you tell me? Superimposability if I talk about our left and right hand, is it superimposable? Hands are not superimposable Okay, what about others? No, see superimposability. I'll discuss now See first of all hands are not superimposable to each other. Okay. For example, suppose if I take this example That is The molecule we have is this We have C double bond C Hydrogen, chlorine Hydrogen and chlorine, right? So this is cis or trans Correct. This is trans Now the two example I have taken Both are trans actually and one is the mirror image of other one. This is supposed the mirror we have So when you take the mirror image of this compound, you will get this Okay When I ask you whether these two compounds are superimposable or not the answer is What would be the answer for this one? These are superimposable Yes or no Superimposability means what you'll take this molecule Correct Just you hold this molecule and try to fit under this molecule If over this hydrogen atom if you have hydrogen only Over the chlorine atom if you have chlorine only over this carbon. We have carbon only then only it is superimposable Correct. So what happens? We'll hold these two carbon atom and we'll try to put this carbon over here and this carbon over here So what happens you see here? Like you have to imagine this okay So when you substitute this carbon over here on this carbon atom and this carbon over here on this carbon atom So this carbon right hand side. We have hydrogen. So this carbon is here. So right hand side We have hydrogen. So here we have hydrogen and chlorine here We have chlorine and hydrogen similarly this side. We have chlorine hydrogen chlorine hydrogen So hence these two compounds are non superimposable non superimposable Right So when it is non superimposable and mirror image of each other then this pair of compounds We call it as these are enantiomers of each other Okay enantiomer we always define for a pair of compounds enantiomer of each other Correct means superimposability means what it is the ability of a compound to overlap the overlap its own mirror image Right or overlap onto the other compounds if that is exactly if all the atoms overlap with the identical atoms then only it is superimposable No, that's what I'm coming to that point ishika I'm coming to that point ishika Now you may have this doubt first of all we'll pick this carbon and we'll Put these two carbon atom over here and then we'll check right now the question is what Whether we can flip this one of this molecule or not because one doubt you may have that we can flip this molecule The whole molecule we can flip like this Okay Like this we can flip 180 degree and then we can put this molecule over here then it will be superimposable Right. Yes mega right when you flip this compound and then put it over here then the compounds become superimposable Correct, but this kind of flipping means out of the plane this when you flip this molecule like this try to analyze this structure Okay, when you flip this molecule, right? So when you flip this molecule this kind of flipping we call it as uh This flipping is the flipping is out of the plane actually or we call it as the rotation is out of the plane So out of the plane Rotation is there So in this kind of molecule on in this thing out of the plane rotation is not allowed We cannot rotate the molecule out of the plane in the molecule you can rotate. What is the meaning? You see in the plane you can rotate the meaning is what see this carbon You cannot flip like this like this you cannot flip Okay, because then this flip will be out of the plane this flip is out of the plane like I'll write down here Try to understand this very carefully. Okay. This flip is out of the plane rotation But within the plane you can rotate the molecule means what you can rotate the molecule like this Like this you can rotate so in the plane rotation is allowed Right, but out of the plane you cannot flip the molecule like this And then you can try to superimpose if you rotate this molecule also like this Correct Then again the relative position of the atom will be same the molecule remains the same And again, it will not be superimposable Is it clear superimposability? Let me know So you must remember one thing any molecule if you have to identify pair of molecule They are you know In ensures or not then what we'll see we'll see the mirror image of that molecule If that particular molecule is superimposable to its mirror image Then it is they are not in ensures because the condition is what? Not superimposable and mirror image of each other So in other way what we can write also in ensures are In ensures are a pair of compounds pair of compounds which are non superimposable non superimposable mirror image of each other Correct in ensures are non superimposable mirror image of each other. Okay. That is what you have to keep in mind So whatever the molecule you have we'll try to get the mirror structure Sorry mirror image of that and we'll try to see whether it is superimposable or not and in this Course we will not molecule will not rotate the molecule out of the plane Right this kind of flipping is not allowed, but we can rotate the molecule within the