so in your previous video we have talked about the different types of carbons we have talked about the primary carbon secondary carbon tertiary carbons primary carbon definition is the carbon usually connected are connected to one carbon atoms if any carbon connected with two carbon atoms that's the secondary carbons and if any carbons is connected to three carbon atoms and we've got tertiary carbons we have solved the problem problem for these structures we counted uh how many primary carbons how many primary hydrogens how many secondary carbons how many tertiary carbons on this for this uh structure in our previous video now we're going to count how many primary carbons primary hydrogen secondary carbon secondary hydrogens and tertiary carbon tertiary hydrogens present in this structure so this is an isobi isobutane structure c4h10 so primary carbons how many primary carbons can you see here again the definition is the carbon should be connected with one carbon atom so this carbon here is connected with only one carbon atom so this is a primary this carbon right here is connected with this carbon atom so that's the primary and the top carbon here this is also connected with this metal carbon so this is also primary so we have three primary carbon and each of the carbon has three hydrogens for three times three nine so you will end up with three primary carbons nine primary hydrogens then is there any secondary carbon can you see that um see if you look at here you can see the there is no carbon connected with two carbons so this carbon connected with one carbon this carbon connected the middle carbon connector with one carbon second carbon and third carbons so it looks like this is a tertiary carbon so there's no secondary carbon there for no secondary hydrogens but tertiary carbons if you look at here so this carbon is connected with these three carbon atoms so here is the one carbon second carbon third carbon so this is there's one tertiary carbon and one hydrogen attached to the tertiary carbon so this is required tertiary hydrogens so this is how you have to actually can figure out what is the primary carbon secondary carbon tertiary carbon and what are primary hydrogen secondary hydrogen tertiary hydrogen so um the starched hydrogen in an organic compounds now the next topic we are going to focus on isomerism uh before we discuss that we first need to know the the type of alkene so straight channel can we discuss this one in saturated alkanes uh topic so stretching alkene usually an alkene that has all this carbon connected in a row so that is stretching carbons and branched chain alkane usually alkene that has a branching connections of carbons so if you look at here in the first cases this is stretching carbon so this is the structural formula of c4h10 and this is also isobutane c4h10 but this has a branching connection so this is a branched chain alkane and this is straight chain alkane and then we are going to talk about isomers isomers are usually the type of compound with same molecular formula but different structure so isomers again they have the same molecular formula but they have different structure sometimes their connectivity difference sometimes their geometrical uh position is different so those are isomers so they are not the same they are not the same um structure but they have the same molecular formula if you look at this two compound here so this is like c4h10 this is a straight chain and this is a branch chain alkane it also has the same molecular pharmacy for h10 but these two have different structure that indicates that c4h10 uh this two are isomers all right so isomers means compounds with the same molecular formula but different structure so that's the definition of isomers before we talk about a little bit more on isomers i would like to warn you here when you have a stretching like these so those are organic molecules and we see that in on in this straight chain the carbons are connected by single bonds and we all know the single bonds are usually formed when the two orbital sp3 orbital of this carbon and this carbon they do head on over 11 from that covalent bonds so heading over um because these bonds are from from here to normal lamps they can rotate so if you rotate it like here like in this direction then you can see the molecules will take this shape so if we just simply rotate around the bonds it doesn't produce a different structure it is the same structure molecules so in this case here so these ones ch3ch2ch2ch3 and this one where the last methyl group the cast groups are positioned like this way but these two are the same uh they do not have different connectivity so so they have the same connectivity therefore these two are the same molecules so rotation around the bond does not produce isomers all right so just remember that now we're going to figure it out how many isomers one can obtain from a given molecular formula if you have molecular formula which has four carbon atoms and if it is c4h10 that's the alkene formula the maximum isomer you will end up with it will be two if you have five carbons alkane c5h12 that give you maximum isomer three six carbon uh alkane uh with the molecular formula c6h14 you will end up with five isomers if you have seven carbons or c7 a16 you will end up with nine isomers eight carbons um with the molecular formula c8h18 and the fossil for isomers is 18. and so on so you can see here c9h20 can give you 35 isomers and c10h22 can give you 75 isomers so we're not going to talk about uh those 75 isomers or 35 isomers or 18 isomers we're going to talk about the carbon um from c4h10 to c6h14 we're going to figure out how many isomers can be formed from those molecular formula and how can you draw those isomers right so again the strategy is usually for small hydrocarbon molecules eight or fewer carbon atoms it is relatively easy to determine the number of structural isomers by trial and error so that means you have to try and see whether they are the difference or they are same so this is how you can end up with all those isomers so first let's solve one problem together that will probably help you to understand how to uh how to draw those how to draw the several isomers for a given molecular formula so here we have a formula c6h14 and to write the structural form to write the all the isomers so first what we are going to do we are going to start by connecting the carbons in a line so we have six carbons so we can write all six six carbons in a line and then what we're going to do then we'll determine the carbon skeleton of other isomers so we'll always first with the six carbon then we'll start with the five carbons in a in a chain in a line and then we will play with one carbon and then we'll start with the four carbon then we'll play with two carbon so that's how we will end up with the number of required isomers for c6h14 we know c6h14 will produce a maximum of five isomers from that table so so what we are going to do first we so this is one isomer six lines six carbons in a row uh so now we have five carbons in a row so we have one carbon so we can put that one carbon on carbon number two again remember here is if we put the car this carbon extra carbon on carbon number one that will be the same as this one so those two structure would be the same so you cannot put this this extra sixth carbon on carbon number one you have to start putting on carbon number two then other way you can do it you can put it on carbon number three so this is how you will have two different structure if you want to put this carbon on this carbon again that would be the same like this one right so only possibilities with five carbon and with the six carbons you will have these two possible structure then next thing what we are going to do we are going to start we are going to write four carbons in a line and then play with two carbons so we have four carbons in the line here one two three four and then we are adding two extra carbon on carbon number two again if you're adding on carbon number two then you will end up with this or even if you take those two carbons and add on carbon number two and carbon number three then you will end up with this last final isomers so now you can see c6h14 can have maximum five isomers we have one two three four five those are the carbon skeleton of all the isomers the next job we are going to do fill in the hydrogens to give each carbon four bonds so we know the terminal alkene the beginning carbons and n carbons usually get three hydrogens and middle carbons usually get two hydrogen so this is how you'll end up with this structure straight chains hexane now you have here five carbons again you can fill with the hydrogens so you can fill with the hydrogens you can fill with the hydrogens you can fill with the hydrogens so that will give you the structural formula for all five isomers of c6h14 if you're asked to write all those fives all those skeleton structure for the c6h14 so then you can convert all these the structural formula into the skeleton formula and that will look like this so this is all the skeleton formula for the five structural isomers of c6h14 all right so that take us our next lecture problem here practice draw the three structural isomers of n c5 h2 we know if you have c5 h2 that has maximum of three isomers um so again the first thing what you have to do you write first five carbons in a line so that will give you one and then you play with the four carbons and then if then you then you ride all the four carbon in your line and play with the front the fifth carbon and this is how you'll end up with uh all those isomers so c5 hdf all the carbons five carbons in your line so that's the first isomers then you have all the four carbons in the line so that will give you the second isomers and then as you see here you put this you put this carbon on the second carbon if you put it on this carbon it will be the same then another possibility is here you draw all three carbons together in a line in the play with two carbon put the those two carbon on the middle carbon so that's how you'll end up with this uh structure so these three isomers are for c5 again you can draw the two isomers of c4h10 so this should be two isomers because we have learned from the table c4h10 can give you maximum two isomers so two if you want you can pause the video you can write the two isomers of c4h10 so here is the the all the four carbons in a in a line and then you fill with the hydrogen that's the first one the second one you write all three and play with the fourth one so you can place those fourth carbon on the middle carbon that will end up with give you that will give you the second isomers for c for h10 so that pretty much concludes this video about the isomers