IUPAC NOMENCLATURE OF ORGANIC COMPOUNDS - LEC-1

Added: 2026-05-12

[00:00:00]Hello everyone and welcome to the first lecture of IUPC nomenclature of organic compounds. Under this topic we are going to learn how to name a particular organic or the carbon containing compound.

[00:00:16]Now this how to name a particular compound is given by UPSC. So, UPSC standardizes how we can name a particular given compound. Very much like our names. Okay, it has the first name, the middle name and the last name.

[00:00:35]Likewise, IO UPSC says that for a given organic compound, it also must have three parts. The middle or the most important part as per IUPAC format.

[00:00:53]The most important part is the middle part or the root.

[00:01:01]Whatever comes before root is called prefix.

[00:01:08]And the part of the name that follows the root is called suffix.

[00:01:17]Further the prefix and the suffix are divided into two two parts. Prefix is further divided into a secondary two degree means secondary prefix and a primary or onederee prefix.

[00:01:37]Then comes root or root word followed by the suffix.

[00:01:42]Again suffix is divided into two parts.

[00:01:45]The primary suffix and the secondary suffix.

[00:01:56]Now we will see one by one what each of these part means. Let us start with the most important part that is root word.

[00:02:08]This root word, this root word [clears throat] tells us about the number of carbons.

[00:02:16]Number of carbons present in parent carbon chain.

[00:02:30]for short parent carbon chain we will call P CC C. Sir, what is parent carbon chain? Let us learn this. Okay. The simplest carbon compound which is known to us is methane. All right. So we have methane. The simplest carbon compound.

[00:02:49]We know that carbon has four electrons in its outermost shell and it will form single bond with each hydrogen using one of these electrons each of these electrons. All right.

[00:03:04]For short we will write this as C H4.

[00:03:09]So here we are given a carbon compound having only one carbon.

[00:03:14]When only one carbon is present in our carbon chain or the parent carbon chain, the root word, this root word is going to be called as meth or myth.

[00:03:28]M E T H meth.

[00:03:31]Now instead of bonding with hydrogen, this carbon could have bonded with one more carbon.

[00:03:41]All I did is I removed one hydrogen and replaced it with carbon. Now the carbon has four valency. You see this one valance is satisfied. Three valencies will remain total four valances. Let us keep hydrogen at each place. So now we have sir CH3 bonded to CH3.

[00:04:05]CH3 bonded to CH3. Now we will say that our parent carbon chain or the carbon chain has two carbons root word will become eth or it.

[00:04:22]Likewise as the number of carbon goes on increasing. So when the number of carbons when the number of carbons when the number of carbons is one then the root word becomes myth.

[00:04:40]When the number of carbons are two then it becomes it. If it is three then it becomes prop. Likewise four then but five then pent.

[00:05:00]Likewise if the number of carbons are six the root word would become hex.

[00:05:06]Seven then it would become hept. 8 then it would become octed. Nine then it would become non.

[00:05:18]Further if it is 10 then we would we would call it deck 11 then undeck 12 then do deck and so on. All right. So let us come back to our format. So format is divided into three parts.

[00:05:39]Prefix root suffix. Prefix further divided into secondary prefix primary prefix. Likewise, suffix divided into two parts, primary and secondary. We are right now focusing on the root part.

[00:05:53]Root part tells us how many carbons are present in a parent carbon chain. For example, if the number of carbons is equal to one, the root would become myth. If it is two, it would become it.

[00:06:10]If it is three, it would become prop and so on.

[00:06:17]The secondary suffix, the next part I'm going to pick up is the secondary prefix. The secondary prefix tells us about the substituents.

[00:06:32]Substituents, there might be more than one substituent. So in case we have more than one substituents then substituents are written in alphabetical order along with locans.

[00:06:57]All right sir what are substituents? Let us try to understand what are the substituents. Okay.

[00:07:05][clears throat] As I told you, we will have a parent carbon chain like this and it may have any number of carbons.

[00:07:29]So this we shall say is our parent carbon chain. Now whatever is left outside of parent carbon chain, let us say there is a one carbon here. Let us say there is one carbon here. It is not possible to include them in our parent carbon chain. So these guys they become our substitutes.

[00:07:56]How to name these substitutes? So it's quite simple. For example, I told you sir, CH4 is methane.

[00:08:06]CH4 is methane.

[00:08:10]CH3 CH3 is called ethane.

[00:08:17]Likewise, propane, butane and so on.

[00:08:21]From methane, if I remove one hydrogen, see methane was looking somewhat like this.

[00:08:30]If I remove this hydrogen from here, then I will be left with CH3 and one free valency.

[00:08:40]This part CH3 with one valency. See CH4 is methane. CH3 with one valency is called myth.

[00:08:52]Again, myth is the root word.

[00:08:55]What is that in? What? Okay. over here.

[00:08:57]We will discuss that. Likewise, in case two, I'll simply free one valency over here. I had C H3 CH3 like this.

[00:09:11]If I free one valency over here, what I'm left with is CH3 CH2 with a free valency.

[00:09:20]Very much like methane became methile, ethane would become ethile.

[00:09:30]Likewise, propane from propane. If you remove one hydrogen, if you free one valency, it would become propile from butane.

[00:09:44]If I remove one hydrogen, it would become butile, pentile, hexile and so on.

[00:09:53]In general, I can say that in general we can say that from alkan if I remove one hydrogen methane gives methile, propane gives propile, alkan gives alky.

[00:10:13]For example, let us say that I have two substituents methile and ethile. Then how would they be named or how would they be written in secondary prefix?

[00:10:24]First ethile would be named then methile. Why? Alphabetical order.

[00:10:29]Alphabetical order means if you look up for these two words in dictionary then ethile word would occur before methile.

[00:10:37]Okay. Ethile would occur before methile.

[00:10:41]Why sir? In ABC D E comes before M.

[00:10:43]That's called alphabetical order. Okay.

[00:10:46]Any word that would occur first in a dictionary is given preference. It is written first.

[00:10:53]Likewise, butile and propile. Of course, B comes before P. So, butile would be written first in the secondary prefix, then propile. Sir, how about butile and ethile? What if we were given butile and ethile? A, B, C, D, E. So, B comes first, E comes later. Butile would be named first. Ethile would be named later. So this is how we go about with substituents.

[00:11:19]There are few more substituents.

[00:11:23]The most commonly known substituent is from alkan. We remove one hydrogen we get alky. By the way this substituents which have one valency free. So with that valency what it is going to do is that substituent is going to going to hold the parent carbon chain.

[00:11:44]Again methane we removed hydrogen. So it has one free valency like this one free hand. So with that one free hand it is going to hold to PCC parent carbon chain.

[00:11:57]Such substituents which have one hand or one valency free are called monovalent radicals. What are they called?

[00:12:08]Monovalent radicals or monovalent substituents.

[00:12:17]We could also have balent substituents or balent radicals. If we had to not remove one but remove two hydrogens's then instead of monoalent I would get balent radical. Likewise if I had to remove three hydrogen I would get trivalent substituent. For example, for example, for example, let us say [clears throat] that from methane if I remove one hydrogen I get methile. But if I remove two hydrogens's then I get all right two valance is free sir. Two valence is free. So this is not called methile. It has to have some other name. This is called methilelyine.

[00:13:08]methilely bean and this is going to be our bialent radical or balent substituent.

[00:13:21]Let us see some more. Let us see some more.

[00:13:26]We'll have CH3 CH3. So from CH3 CH3 I removed two valances.

[00:13:34]So I had three hydrogens's I removed two. So I'm left with one very much like methane becomes methileine.

[00:13:43]Ethile would become ethileine.

[00:13:51]Please pay attention that [clears throat] in case of sorry in case of methane I removed these two hydrogen's that is I removed hydrogen's from the same carbon.

[00:14:05]Likewise in case two, in case of ethane, I removed two hydrogens from the same carbon. The substituent came to be known as ethiledine or ethylidine.

[00:14:17]However, if I had to remove one hydrogen from here and one hydrogen from the next carbon, this positioning is called vinal. These carbons are vinyl means neighbors. Whereas okay, I'll come to come to that. So when the hydrogen is removed from two adjacent carbons, it doesn't become ethileene.

[00:14:39]It becomes in this case ethylene or ethylene.

[00:14:45]These are called bivalent radicals. Some other substituents which we must remember is florine.

[00:14:56]The name of this guy would become fluo.

[00:15:01]Likewise chloro. Likewise bromo iodo and so on.

[00:15:17]All right.

[00:15:19]So that was our secondary prefix.

[00:15:24]Root word indicates how many carbons are there in PCC.

[00:15:28]Secondary prefix tells us about gives us information about substituents.

[00:15:34]The primary prefix. The primary prefix.

[00:15:38]The primary prefix tells us whether the parent carbon chain is cyclic or non-cyclic.

[00:15:48]Okay. Cyclic would be like this. 1 2 3 4. And the fourth carbon is connected with the first one. So it forms a cycle that's called cyclic. Whereas if they were not connected however if they were not connected then it would look 1 2 3 4. This is non-cyclic.

[00:16:10]If a given PCC or the given compound doesn't contain cycle then primary prefix is not important.

[00:16:18]Primary prefix is not a essential part of nomenclature. Primary prefix may be there. In some cases, it may not be there. All right.

[00:16:29]So, primary prefix tells us whether given compound is cyclic or not. If it is cyclic then prefix will come as cycl like this.

[00:16:47]How many carbons are there? Check. 1 2 3 4 5 6. So the root would become hex and the primary prefix would become cylo. So it will become cylo hex.

[00:17:10]However, if it is not cyclic then it is not mandatory for us to write. There are some hydrocarbons which have some weird structure. So something like this.

[00:17:28]So now it doesn't have a one cycle rather it has two cycles one on the right side one on the right left side.

[00:17:35]In those cases I will not write primary prefix as cylo but I would write it as bicycllo.

[00:17:47]or like this there is one carbon outside like this it's like a bridge we have a normal hexagon cycllohexane and then there is a bridge like this over there all right so they are called bicycllo there are one more type of cyclic compounds they are like like this where two rings are fused using only one carbon. So one carbon is common. They are called spyro.

[00:18:28]Spyro. So the primary prefix could be only one of these three. It could be cylo, it could be bicycllo or spyro.

[00:18:37]Otherwise there will be no primary prefix. Fourth option is no primary prefix. It's not a compulsory part of IOPS in every compound will not have primary prefix. Every compound may not have secondary prefix root. That's why I said is the most important part in our J syllabus. Cylo is the most important.

[00:18:59]Bicycllo spyro may be asked but not very important as in rarely asked. All right, let us move [clears throat] to the primary suffix.

[00:19:12]The primary suffix tells us whether our PCC or our hydrocarbon is saturated or unsaturated.

[00:19:22]Saturated or unsaturated like this. Sir, what do you mean by saturated and unsaturated?

[00:19:33]When in a given hydrocarbon you see all single bonds like this 1 2 3 4. So when all the carbons are held by a single bond then we say that such a hydrocarbon is saturated.

[00:19:52]Saturated saturated means it already has maximum number of hydrogens that it can hold.

[00:19:59]Whereas if I have one double bond say then we say that such a such a hydrocarbon is unsaturated.

[00:20:11]Presence of even one double bond will make it unsaturated. And same thing is true about a triple bond as well.

[00:20:21]If all carbons If all carbons are linked together by a single bond saturated if there is at least one double or a triple bond then unsaturated.

[00:20:37]In case in case our PCC is saturated then the primary suffix would become in like it in this guy is it. So e it is root word and the primary suffix since they are linked together by single bond would become ein. The name of CH3 CH3 compound in that case would become it in mit in.

[00:21:10]Likewise 1 2 3 4 but all are single bonds. Therefore, the name of this particular compound would become but in but tells us that this particular compound has four carbons.

[00:21:29]In tells us that all carbons are bonded together by a single bond sir. How about the prefix part? There is no prefix.

[00:21:44]There is no prefix. Why? because it is not cyclic. So cylo is not required.

[00:21:51]The primary prefix is not required.

[00:21:53]Secondary prefix is substituent. Do you see any uh branch coming out from here?

[00:22:00]Do do you see any substituent uh connected with this PCC? No. So my point is that prefix is completely optional.

[00:22:08]Optional as in not optional for us. But for a given hydrocarbon prefix may be there, may not be there. But root 100% will be there. This [clears throat] 1 2 3 4 5 and the fifth and the first one is connected.

[00:22:29]In this case you see sir there are five carbons. If there are five carbons in that case the root would become pent.

[00:22:39]The root word would become pent. All are single bonded. So it would become the primary suffix would become a. Now think about primary prefix.

[00:22:53]Is it cyclic? Yes. So the name would become cyclopentane.

[00:23:00]Likewise the name of this guy would become cyclop hexane.

[00:23:15]>> [clears throat] >> So if there all are single bonded then in if there is at least one double bond then in if there is at least one triple bond then if there is double bond also and there is triple bond also then what then it would be in.

[00:23:39]Okay. In both will be there. If there are two double bonds, if there are two carbonarbon double bonds, then we will call it a diin.

[00:23:53]A di means two. In means sir double bond. E means a double bond. In means a single bond. In means a triple bond. A diin means there are two double bonds.

[00:24:09]If there are two triple bonds then the primary suffix would become a diion.

[00:24:18]A diion that a is important.

[00:24:22]All right.

[00:24:24]And then the most important part after root word of course would be the secondary suffix which tells us about something called as functional group which tells us about something called as functional group. Sir what is functional group? Let us check.

[00:24:57]The secondary suffix let us say that I was having methane. So I had four hydrogens's and the fourth hydrogen. Okay, the hydrogen which was present over here, I replaced it with something other than hydrogen or carbon.

[00:25:17]Like for example, I replaced it with oxygen and hydrogen.

[00:25:25]This particular O this particular group of atoms or a single atom in some cases will make drastic changes in the behavior of this particular compound. So CH4 belong to a different category and CH3 along with O now belongs to a different category. So what is that category that itself is called functional group because it will change the very characteristic the very behavior of that particular compound. So O is called alcohol.

[00:26:04]alcohol.

[00:26:06]Likewise, I may have CH3 CH3.

[00:26:15]But now this hydrogen I replaced with O. Which functional group is this? This is a alcohol functional group.

[00:26:29]There are various functional groups. All right? So I'll give you the list of these functional groups along with their priorities. Sir why priority? We'll discuss it.

[00:26:44]One functional group looks like this CO.

[00:26:50]It is called caroxyic acid.

[00:26:56]This gets the highest priority. So priority means what? I'll explain you.

[00:27:04]S O3 H S 3 O's and H this is called sulfonic acids that is second in priority.

[00:27:17]Then comes a category called as esters. So I'm simply replacing hydrogen with R. So what is R? some carbon chain one carbon 2 carbon 3 carbon it could be any carbon chain they are called esters esters then we have okay in this case I will replace O with Clen X is what X is a H hallogen it could be chlorine bromine iodine like that they are called acid helides acid helides This next case I will replace this O with NH2 they would be called amides. Now from amides if I try to remove water see water is what? H2 and O. If I remove this water H2 and O then what will I be left with? H2 o. What would I be left with sir? You would be left with carbon and nitrogen. You would be left with carbon and nitrogen. H2 and O1. These are called cyanides.

[00:28:30]But cyanide is called common name. We don't generally use it in UPSC standards. We rather call them nitrides.

[00:28:42]Next [clears throat] in priority are alihides then ketones.

[00:28:52]So the difference between alihide and ketone is that alihide has a hydrogen on one side and a carbon chain on other side. Say the C double bondo with carbon on one side, hydrogen on the other side.

[00:29:05]Whereas ketone has carbons on both side.

[00:29:07]This oxide also carbon this side also carbon. carbon yabic carbon but alihides are not like that only on one side they will have carbon other side they will have hydrogen so we have alihides ketones after that we will have O means alcohol finally we will have amines there are a few more functional groups but these are the most important ones which are required for our IUPAC nomenclature. So let us quickly revise what we have done today. We learned that any carbon compound in order to name it we need to follow one format of UPSC.

[00:29:54]According to that format name should have three parts. The middle part would be called root. The part before it would be called prefix. The part after that would be called suffix. The prefix is divided into two parts. primary, secondary, root in middle and then suffix also divided into two categories or two parts primary and the secondary suffix. The root tells us how many carbons are present in parent carbon chain. The prefix secondary prefix the very first part speaks about the substituents. Sir, what are substituent?

[00:30:32]Sir, if there is this carbon chain S carbon chain s then it is not possible for me to include this carbon in the chain.

[00:30:44]Okay. So whatever is this hanging outside this guy or let us say here there is something like bromine and so on then they would be called as substituents. Secondary suffix will have substituents.

[00:30:58]Primary suffix will tell us whether the particular compound is cyclic or not cyclic. If it is not cyclic, you need not write anything in primary prefix. If it is, then we need to write cyclone.

[00:31:11]Root word tells us about the number of carbons in the parent carbon chain. For example, over here parent carbon chain has five carbons. So the root would become pent.

[00:31:24]Primary suffix then would become all our single bonds. So in prop in the last part the secondary suffix the most after root the most important part is the secondary suffix which is the functional group.

[00:31:41]Now in this case in this case the name would be pent in where is the functional group? There may not be functional group. I told for us to have functional group we need to replace one of the hydrogen with something called as hetero atom like O like SH like NH2 some something other than carbon and hydrogen or some unique group we will place. So secondary suffix likewise is not very important not very important in a sense optional it may be or it may or it may not be there. All right.

[00:32:21]So for a given hydrocarbon root will 100% be there. Primary suffix will 100% be there but all other parts may or may not be there. So today we only focused on one part of UPS in the manature and that's what that is the format of IOPS in the manature. prefix root suffix prefix divided into secondary primary then root then primary suffix secondary suffix. So that's it for today. In our next class we will learn how to what is PCC. I mean I have just explained it to you but in next class in detail we will learn what is PCC and if I'm given a particular compound how to select PCC.

[00:33:12]Thank you.