So, today we are discussing the rules for resonating structures. The primary rule which will come up again and again is that all resonating structures and canonicals should have A valid Lewis dot structure. Now what we are implying by the term valid Lewis dot structure?
When we are stating that there should be a valid Lewis dot structure, what we are actually implying is that all the atoms, we are writing a valid Lewis dot structure. For proper Lewis structure, when we are stating proper Lewis structure, we are trying to imply all atoms, all atoms, all atoms must have, must have complete octet. To serve as valid individual structures, the atoms in question must have complete octane. Now, look at this structure.
These are very important and interesting examples. Similar questions are given in the chemical bonding study material. Look at this case.
Here hydrogen has two electrons in its valence shell. Carbon has formed four bonds. Forget the negative charge. This negative charge is a formal charge.
Forget the negative charge. Forget the negative charge. But since you have a negative charge on this carbon, the carbon atom is able to complete its update.
Now there are four bonds. Four bonds means how many pairs of electrons? Four pairs of electrons. So 80 electrons in total. These carbon tells...
eight electrons this hydrogen has two electrons this hydrogen has two electrons this oxygen again this oxygen again has a positive charge now we know that oxygen being an electronegative atom we know that oxygen being an electronegative atom is not very comfortable in the positive terms right but note This oxygen has a single bond with hydrogen. What is hydrogen? If you denote the bottom node, it will just drop out. Here, there is a single bond with hydrogen.
Two bonds on this side with the carbon. So, there are three bonds in total. So, three pairs of electrons. How many electron pairs?
Three. There is a node pair. Please note, there is a node pair.
So, how many? Three pairs of... Bonded electrons is 6 plus 2A.
So even this oxygen has a complete optin. Has a complete optin. But the hydrogen has two electrons.
So it has a complete duplet. So this will be a valid Lewis dot diagram. What is a valid Lewis dot diagram? A valid Lievenstraut diagram is one in which all the atoms have either concrete octet or concrete duplicate. Draw this one.
Draw this one along with the explanations that I have just now given. Okay. The performance you want...
I forgot to tell you that I have been sleeping at night. Now, you can watch my vlog and understand. I really forgot. Ok, with this, I can do a bit more of the resonating structure. Here, I am using a carbon.
Carbon is a negative charge miscellaneous. I will do it. I will touch this.
Can you see? I am touching it. I am trying to do a bit more. The second language that we have...
Yes, tell me. Sir, the last time you said that the class that you took, that class has been uploaded on your website? Uploading on the website is a problem. Practically speaking, my space is over.
My driver's space is almost over. So, what I am doing is recording on two devices. You can see one live recording here.
Second, I am recording in a better quality on my phone. I have recorded for 22 minutes. It is a 4.54 GB file. How are you?
So today I am doing a demo, see how much is it? So this is on YouTube channel Bring it Sir, minimum class notes The file is very difficult What is the name of the hamster? Sir, minimum class notes are given If you upload the video in Bajar Mati If you upload the video in Bajar Mati, you can give the last note The last note? Yes I see this is a little bit technical The method is not perfect yet. I am learning it from the beginning.
Once again coming back. In 2002, my computer was running at a high speed. I have used touch.
Tell me. I understood that the program is part 1. We are doing part 1 of organic care. We are doing part 1 of organic care.
We are doing part 1 of organic care. We are doing resilience. This part is overlapping for two chapters. It's overlapping between chemical potting and GOC.
GOC and chemical potting is the common part, resonance. So we are dealing with resonance now. And at this point, I have seen that they have made two canons. Yes, they have put a rod on it.
If they have shifted the electron cloud to the opposite direction, what will happen? Aman? Yes, I have a message for you. I have sent it to the North India Company.
Yes. Look what I have here. I have shipped the Pilectron clamp to Monopsy. This is our organic chemistry. Usually, we have a lot of carbon-meta-acid transfer.
After that, we have created this structure. If we study this structure, we can understand that this carbon has six electrons in its valence shield. I have given you an arrow drop. I have given you a double headed arrow.
Where is this? Here. Here?
Here. Carbon toxin. Carbon toxin, yes. This arrow has a proper arrowhead.
A concrete arrowhead. So it indicates transfer of two electrons. Two electron transfer.
It is written. This carbon has three bond pairs. So total six electrons.
Here are two electrons. Here are two. Here are two.
Total six electrons. Total six electrons means that this compound, in this compound, carbon is electron deficient. Carbon is two electron deficient.
From? From the office Sir, I can't see the board Which place? Sir, I can't see the board I was standing there No, no, sir, I can't see it No, the screen is not working No, no, no, no, you look at me, look at Krishna, she is the God Not chemistry, chemistry, fight, not fight The people in chemistry, chemistry, fight, they are not there Look at Krishna, she is the God Which is called DT Can you see the screen?
Yes We are using two devices In this case, the carbon is 2 electrons short of octet So what we have to do is All the resonating structures must have proper Levy structure So this is not a proper Levy structure This is not a proper Levy structure We will try to avoid canonicals in which The Lewis structure is missing. Earth, Earth, all the atoms do not have only octets. But the problem is that, the structure that we see, we draw. We draw in many places.
We give space in some places. When we give space and when we give space, that is a part of the experience. You see. I will give you a small example.
Last class we were talking about benzene. I told you that benzene has two similar looking canonicals. These are canonicals of benzene which are formed when the electron pairs, the pi electron pairs, Shift position, where they will again move. See, I have shared the meme type, I have taken a stick and cut it. Not a serum, but when they will shift position, again it will come back to this one.
So resonance structures or canonicals, if they are identical, like identical twins, they will give some additional stability to the compounding question. If resonance structure is similar looking, How can they increase or decrease the stability of canonicals? What is it?
Here, look at this. Apart from these two, we have to find another canonical structure. One of them is positive, the other one is negative. So, here is plus and here is minus.
So, what did we do? I am telling you why this was here. Why this was here? What I did? I gave one bond to this static.
I moved this bond to the pair. Think about it. When I shifted the electron pair.
See what I did to it. This is not given by the head of this carbon. But both electrons shift onto this carbon. Both electrons shift onto this carbon.
The one at the bottom. Please try to understand and remember this one. Please try to understand and remember this one. In this bond, there are two electrons.
One belongs to this carbon only. This electron was in this carbon only. The other electron was in this carbon only.
So when two are at... When two electrons shift this carbon, one of them was already below that. So, it became an extra, hence the negative charge.
Negative charge means that two electrons, one below and one beside, are connected. I have taken this to the bottom. So, for benzene, we can draw two canonicals which will be identical.
which will be identical but with different positions for their double dots but for the third one or even we can draw similar fourth one as well. What is there? Now, my negative and positive chart.
Now, what is happening is, I will clarify these things again and again. These four structures are the most mistaken of these two. These two atoms, the lower carbon and the upper carbon, are not octeted.
The plus charge means that the electrons are hot. That means it is not a valid Lewis dot structure. Pikachu!
These two are not valid Lewis dot structures. Okay, now, this is the first mistake. I said that in many cases, we may not be valid Lewis dot structures, but we will give representation to them.
When will we give? What was the starting molecule here? Neutral.
Starting molecule was already neutral. From that we are creating four species. So starting with If the molecule is neutral, if I separate the four molecules, it will add a destabilizing factor. Again, starting molecule is neutral, I separated the four molecules. We all know very well that if we separate neutral from negative positive charge If we separate a negative and a positive from neutral What will it do?
It will destabilize the molecule. Why will it destabilize? What will the negative and positive do? It will try to go away. Natural tendency What I am doing against that is that I am separating them.
What am I doing? I am giving the system energy The system is giving energy, what is happening for that? The system is getting the destabilization in the system.
I gave the energy, where did the energy go? The energy of the system is being added to the potential energy. The energy of the system is going out. So, the system is getting destabilized. Understood?
So, that is the first problem. What is the second problem? The structure I drew is not a Lewis dot structure. We generally avoid drawing these two dots.
There is one dot, it will work. Two dots will work. Rishi clear. Ishan, Rishi.
okay Yes, yes, yes Whenever whenever there is there is some kind of charge separation in a molecule to generate that charge separation Molecule has to have energy supplied from somewhere It may not be a human source or a some... You will not physically go and separate the churches, so it has to acquire the energy from somewhere. Whatever be the source, it will lead to certain amount of destabilization. So between these two, between the four canonicals that I have known, these two will be the more stable ones. It's a very common question in J.E.M.N. that out of the following which one is most stable or which one is the least stable canonical mark both table so here these will be the most stable canonicals now these canonicals you will find that often people avoid but in most books it's not mentioned anywhere as to why we tend to avoid