 Ok. Organic chemistry. So, what are we going to study in organic chemistry? We will study about hydrocarbons, right? What are hydrocarbons? Hydrocarbons and its derivative. This is what we are going to study in organic chemistry about hydrocarbons and its derivative, right? What are hydrocarbons? Hydrocarbons are the compounds of carbon and hydrogen, right? Hydro is for hydrogen, carbon is carbon, right? So, in organic chemistry we are going to discuss about hydrocarbons and its derivative, right? For example, you see alkene. Alkene is an example of hydrocarbon, yes? What is the general formula of alkene? Cn, H2n plus 2, right? One example we can take which is ethane, Cs3, Cs3. This is one hydrocarbon because the organic compound contains only carbon and hydrogen into this, right? If one of the hydrogen here is replaced by any other group or atoms, suppose Cs3, Cs2 and one hydrogen is also replaced by O H or if you write Cs3, Cs2, Cn, any other compounds also we can write, ok? These two compounds are what? These two are the derivative of this hydrocarbon, right? Derivative of this hydrocarbon. This is known as hydroxy derivative of ethane. This is chloro derivative of ethane. The general name is halo derivative of ethane, right? This compound is alkyl halide. The general name is alkyl halide, ok? Alkyl halide and this one is alkohalide. The general name is alkohalide. Similarly, we can have aldehyde present over here. We can have ketone also, right? We can have estates possible. All those compounds we are going to study in organic chemistry, right? We are going to discuss about alkenes, physical properties of alkenes, alkenes, preparation in properties, alkynes, preparation in properties, alkohal preparation in properties. So, basically all compounds that we see in organic chemistry, the entire syllabus is about what? Preparation in properties, ok? Now, when preparation in properties are concerned, so there are only reactions, ok? We have chemical reactions and chemical reactions will have its own, you know, mechanism. Mechanism means what? How the reaction is proceeding? Step by step description of any reaction, ok? What are the intermediates involved? How the intermediates are getting stable in the reaction? What are the various factors we have which stabilizes intermediate, right? So, stable intermediate gives you major product, ok? Unstable intermediate gives you minor product, ok? So, stability of intermediate, how to decide that we have already discussed in GOC? What are the various intermediates we have? We have carbocation, carbonyl and free radical, right? Benzyne nitrenes also we have. Nitrenes and carbons we will discuss in specific chapters, ok? In what all reactions are involved, these kind of free radicals, correct? So, this is the thing we are going to discuss in organic chemistry. So, first of all, the naming of organic compound we will see and this comes under nomenclature, ok? Naming of organic compound, organic compound. So, before going into the IUPAC nomenclature of organic compounds, there are two-three things we have to understand first, ok? This is the nomenclature chapter. Yes, nomenclature, ok? Nomenclature and isomerism we will discuss now, ok? There are, no, two-three things we have to understand. First of all, the first thing is the representation of molecules, the representation of molecules. There are three different way through which the molecules can be represented. The first one we write down, the first one is dash formula, dash formula, condensed formula and bond line structure, ok? The first one is dash formula, dash formula, ok? So, the first, suppose the examples we are taking is C H 3 or C 2 H 6, C 2 H 6 is the thing, right? This molecule we can represent as carbon-carbon single bond and each carbon atom we have three hydrogen. We know carbon is what? Carbon is tetravalent, right? So, each carbon atom must have four bonds, right? So, one carbon atom contains three hydrogen and both carbon atoms are attached to each other by a single bond, right? So, this one is dash formula. Dash formula of propane is what? All these are hydrogen, this is the dash formula of propane, correct? Next, we write down the second one, condensed formula, condensed formula. Condensed formula of ethane, if I write down this one, in this we do not represent carbon-hydrogen bond. Carbon-hydrogen bond we do not represent, ok? So, we will write this part as C H 3, carbon-carbon bond we will have here against C H 3, this is condensed formula of ethane, ok? Similarly, the condensed formula of propane is what? C H 3, C H 2, C H 3. So, we do not represent carbon-hydrogen bond in this formula, ok? The third and the last representation we have, that is bond line structure also. So, under condensed formula do we have to write H 3 C for the first thing or can we write C H 3? We can write, see actually carbon attached with carbon, right? So, it is better to write H 3 C, if you write C H 3 also it is not wrong. Here you see, this means what? This hydrogen carbon is not attached, carbon and carbon bond is there, that is why we write H 3 C, but if you write this one also it is fine. So, can I say C H 2, C H 3 whole twice? Yes, you can say that, you can write on this one. C H 2, C H 3 whole like this, but this is not condensed formula, ok? In condensed formula carbon-carbon bond we show, carbon-hydrogen bond we do not represent, but this is also same thing. It means this C H 2 has two methyl group attached, ok? Bond line structure, bond line structure of suppose I am taking butane, butane has four carbon, right? Bond line structure of butane is this, this is bond line structure of butane, ok? It is exact because each carbon atom is S 3 3 hybridized, so you cannot write no, it is not a straight chain, carbon-carbon bond always is exact bond we have, right? All these corners, this point, this point and these points, these points are carbon, right? So, in this representation we do not show carbon and hydrogen bond, ok? It is understood that one carbon can have maximum four bonds, so this carbon attached with this carbon with one single bond, it means we have three hydrogen present here, right? How many hydrogen here? Two, how many hydrogen here? Two and here we have three. So, in this structure we do not show carbon-hydrogen bond, ok? It is just a line with bond. For, you know, this is also if you write down two methyl propane, this is also a condensed formula. The name of this compound is two methyl. You have done this chapter in the school? Yes, we started in school. We will see how to write down these names, if you will see one by one, but this is again, this corner is one carbon, this corner is one carbon, this is one carbon and this is another carbon, right? Two methyl propane, ok? Classification of compounds, organic compounds, open chain or cyclic compounds, ok? Open chain compounds we also call it as acyclic, ok? Open chain we also call it as acyclic, acyclic in open chain or same thing. Open chain then we have two types, saturated and saturated and unsaturated. Any example of saturated compounds? The general thing is alkene. Alkene is a saturated compound, ok? Unsaturated are all those compounds which contains multiple bonds, right? That is alkene and alkene. What is the general formula of alkene? CnH2n plus 2 for alkene and for alkyne and for alkyne, this is the classification. Cyclic compounds we have two types, one is homocyclic and other one is heterocyclic. Homocyclic compounds are those compounds in which we have only one type of atom present in the ring. All atoms are same, so homocyclic, ok? We will see some examples into this, ok? Homocyclic compounds then we have two types, we will see for example of this. What is the example of homocyclic? Benzene. Benzene. Heterocyclic any example? Aniline. Aniline, no, aniline we cannot say. Pyridine you can say, furan you can say, ok? So write down the example of heterocyclic compound, pyridine, right? Pyridine the example is what? The structure is this, this nitrogen present and it is called pyridine double bond. This is pyridine. That is pyridine. It has it outside the ring. It is outside the ring, come on. Homocyclic and heterocyclic, these are again two types. It can be aromatic or tally cyclic, right? Aromatic we have two types that is benzenoid and non-benzenoid. Benzenoid and non-benzenoid. All these are not that important. The only thing is aromatic compounds are those compounds which has cyclic structure and 14 plus 2 pi electron conjugated system, ok? So it can be benzenoid, benzene means which has the structure of benzene, right? We have discussed anthracene, right? Anthracene has one benzene structure, right? So those are benzenoid compounds and non-benzenoid also. We have for example, tropillium cation is a non-benzenoid compound, right? Aromatic but non-benzenoid. There is no benzene structure in it, ok? So these are the classification of organic compounds we have. Understood? So what is the example for non-benzenoid? Non-benzenoid is this. There is no benzene structure, this non-benzene, right? Elycyclic compounds are those compounds in which we have cyclic structure. Suppose we have this structure and some chain also we have, some chain also present in this, apart from means Elycyclic plus cyclic, both structures, ok? That is Elycyclic compound, ok? We have a side chain plus ring structure. That is Elycyclic compound, ok? Can a heterocyclic thing be benzenoid? Yes, possible. Kiran is a benzynoid, what do you say? Heterocyclic benzenoid. No, aromatic can be benzenoid. Heterocyclic is also benzenoid possible. Benzene, this is tropillium cation, tropillium, LIEU, tropillium cation. Benzene is also benzenoid structure, no? It is also benzene structure only means there are 6 atoms in the double bonds. It does not have to be carbon, all of them. Yes. So, if you replace this nitrogen atom by carbon, it is a benzene structure. It is similar to benzene structure, that is benzene. So, if there are 2 atoms in the non-carbon, it is still the benzene structure. Yes. So, it is just the hexagonal non-carbon. Yes. Means, anthracene structure is what, you see this? So, even if you are not getting benzene, it will be a benzenoid. You can see. Benzenoid structure. This is also anthracene, benzenoid structure, you see. This is also similar to benzene. Ok. So, we will see the nomenclature one by one. The first one, we will see the nomenclature. See, one thing you see, why alkenes are said to be saturated compounds? There is no addition reaction possible. Because saturation means what? Carbon has already 4 bonds present here. Right. So, further addition on this carbon is not possible. Carbon will not show penta valency. Ok. But if you have an alkene, suppose C double bond C and it has 2 double bonds, then an electrophile attack on to this carbon, then this carbon shift on to this carbon atom, this pair of electrons. Right. So, this side of addition reaction is possible in unsaturated compounds, right, alkene or alkyne. That is why these compounds are unsaturated addition reaction possible in this. Understood. Right. That is why alkene are said to be saturated, but alkenes and alkynes are unsaturated compounds.