[Music] hello students today we discuss about confirmation and physical properties of six membered ring system okay so first we see about the planar conformation of six membering system cyclohexane so this is the planar structure of [Music] planar structure of cyclohexane [Music] then next is the chair conformation and the last one is the board conformation okay these three are the structures or conformations of six membering system cyclohexane planar structure chair conformation and boat conformation out of this three confirmation chair conformation is more stable so we write here this is more stable more stable and second board confirmation is less stable less stable conformation okay so how this chair conformation is converted into the board conformation and board conformation is changes into the chair conformation but before that we see how we convert planar conformation into the chair conformation okay so first you see here how we convert planar into the chair conformation if you have any substituent present on the six membered ring system okay so first we take a simple six membered ring system chair and what are the actual positions on that chair okay so here we take molecular formula of this cyclohexane is c 6 h12 c6 h12 okay so what are the positions of 12 hydrogens and it can be represented see here this is your chair and we already [Music] draw here red lines which shows the position of hydrogen present on that carbon atom here another six hydrogens are written by yellow choke okay so this is only for our convenience okay see here we can divided this 12 hydrogens into two sub parts [Music] red colored hydrogens these are the red color six hydrogens and these six hydrogens are beta hydrogens beta hydrogens so what is mean by beta hydrogens beta hydrogen means those hydrogens are present on above the plane above the plane so what is the meaning of beta beta means [Music] above the plane and yellow colored six hydrogens are alpha hydrogens alpha hydrogens so what does it mean by alpha alpha means below the plane [Music] below the plane so you remember this positions means what if you draw any substituent on that carbon atom on this carbon atom at that time axial position is fixed okay and equatorial p position is also fixed on this carbon atom means what actually actually you can represent equatorial position like this here on this carbon atom equal position is beta okay so these six beta hydrogens can further divided into two subclass okay out of this six we can further divided three hydrogens and here also three hydrogens okay so these three hydrogens are equatorial and these three hydrogens are axial ok so six hydrogen can be subdivided into three equatorial and three axial hydrogen so we represent that okay first you see here i can circle here by red chalk these are the axial protons this one is also axial and this one is also axial so these three red colored axial protons which are circled those are axial one then i represent another three red colored hydrogen by square okay so these three equatorial beta hydrogens are next are yellow colored hydrogens and these can also sub divided into three hydrogens equatorial and three hydrogens axial okay so this two types are there subclass we call these are the subclass of alpha hydrogen and here we can also write alpha protons by circle alpha axial this is alpha axial this one is second alpha axial and this one is the third alpha axial so these are the three alpha axial protons next sorry this is alpha excel next alpha equatorial protons which are squared first equatorial second equatorial and this is third equatorial proton okay so these three equatorial protons are placed here so we see here all these 12 protons are present on this chair and its positions are fixed its positions are fixed means what out of these 12 hydrogens it can be subclasses sub classified into the six alpha and six beta hydrogens then six beta hydrogens can further subdivided into the c three alpha three axial beta hydrogens and three equatorial beta hydrogens okay and here six hydrogens which are alpha hydrogens they are further classified into the three alpha equivalent and three alpha axial one okay so you remember these positions okay then next point is planar conformation how we can convert planar conformation into the chair conformation so you remember this position first and then you try to draw planar into the chair conformation okay so first suppose we try to write methylcyclohexane this is planar structure methyl cyclohexane so we write this bond by dotted line this is not a simple one ok so how we can convert this planar structure into the chair conformation so according to the projection formula we can say that dotted line can be represent for the alpha groups alpha groups okay so suppose this is first carbon atom and on shear conformation when we trying to convert that into chair at that time any one out of the six carbon atom you can choose as a first carbon atom okay so this is your first carbon atom and this first carbon atom is alpha this first carbon atom is ah okay so you can try to put this methyl group at the alpha position okay so here i write this is your alpha methyl alpha methyl and which is placed at the equatorial and you don't write by dotted line why because itself equatorial position can represent the side of that methyl group okay so we don't write by dotted line okay so equatorial methyl is nothing but the planar structure of this methyl cyclohexane okay then next point is how we can convert one chair into the another chair through board conformation okay so here i have one model and on the basis of that model i will try to show you what is the chair conformation okay so this is the chair conformation of six member ring system and according to that here four carbon atoms are present in one plane and another two carbon atoms are out of the plane okay so this first carbon atom is below the plane and second one is above the plane okay and this middle four carbon atoms are present in one plane okay so these are not fixed position in six member ring system why because this ring is continuously rotating this ring is continuously rotating in this fashion okay so no any carbon is above the plane and no any carbon is below the plane these are not a fixed position of that carbon so that axial and equatorial position of all hydrogens will change continuously and that's why it gives a single broad peak in nmr spectroscopy all these 12 hydrogen can give a single broad peak in nmr spectroscopy why because all these c or 12 hydrogens can behave as like a same okay then so how we can convert this one share one chair into the another chair so how we can lift this carbon atom like this and another carbon atom we can change its position at that time it will convert one chair into the another one okay so how it will convert one chair into another chair okay through both confirmation [Music] we try to draw its energy profile diagram okay suppose this is your first year and here this is your another chair okay another chair here first year first year will convert it will increase its energy and first chair will convert into the half chair [Music] half chair then that half chair convert into the twisted boot convert into the twisted boat this is first twisted boat then twisted boat is convert into the board conformation this is board conformation then board conformation further convert into another twisted board okay then this twisted board convert into the half chair and then last structure of after that half chair we get here another cheer okay so this is simple conversion of one chair into another chair through this five conversions or five confirmations so here we write this is half chair [Music] half chair which is highly energetic structure which is highly energetic conformation then this is twisted boot this is boat and this one is shear conformation so from this energy profile diagram we can conclude that more stable structure of six membering system is chair conformation either this chair or this one both are more stable structures or more stable conformations and half shear conformations are highly unstable conformation high energetic conformation so that chair or six member ring is not present in half chair conformation it is only go through that confirmation but chair is converted into the board confirmation through this half chair half chair will convert into the twisted but twisted boat is stable than that of boat confirmation twisted boat is more stable than that of boat conformation and half shear is less stable than that of chair board and twisted board conformation okay so you remember these points so we write here stability order stability order of these five structures okay first more stable stable to unstable so highly stable chair chair conformation is highly stable than that of half chair sorry twisted boat twisted boat is more stable than that of both board confirmation is more stable than that of half chair so this is simple stability order chair is more stable twisted boat is less than chair boat is less than twisted board and half shear is highly unstable highly unstable structure okay then next point is [Music] substituted cyclohexane so first point is monosubstituted cyclohexane so here we take one example this is planar structure of cyclohexene suppose we write here methyl group methyl and i write here this bond by curl curl bond so we try to convert that planar structure into the chair conformation how many chair conformations are possible from this okay see here suppose curl bond means we don't get any idea about the position of methyl group present on that carbon atom so i write here one is the axial position this is one of the possible then uh another one is equatorial methyl group this is axial and this one is equatorial okay so this axial methyl group [Music] can represent in planar structure by wedge line by wedge line here we see this equatorial methyl group in shear conformation can represent by dotted line okay so you remember these two points wedge line is used for the groups present on above the plane and dotted line we use for the groups which are present on [Music] below the plane so remember student these points first one and this one is the second point this is wedge line which land can give idea about the position of that group on the respective carbon atom suppose we write in a group by wedge line at that time you can see here i write here this methyl group by wedge line okay so position of that methyl group is axial one why because axial bond is beta or above the plane and here this dotted line i can represent by equatorial bond why because this equatorial bond are present below the plane are present below the plane so you remember this point also here mono substituted now the question arises here out of these two structures suppose this is a structure and this one is b structure out of these two structure which one is more stable these two structures are not equally stable so that one is more stable and another one is less stable so which one is more stable for that we can see here this methyl is present on axial carbon at axial position and this methyl is present at equatorial position okay so for getting some idea about the stability of the methyl group either on axial and on equatorial position you try to write the hydrogens adjacent or hydrogens present on the third carbonate with respect to methyl group these two hydrogens are there so we try to take a model here you see this is a mono substituted cyclohexane and this methyl group i fix here this is axial one and uh these two hydrogens which are present on the one three diaxial position so that you can see here or you can understood very well this is a position of methyl this is hydrogen this one is another hydrogen which are present on one three diaxial position okay so these are the one three diaxial positions okay so they will interact these two hydrogen will interact with this methyl group at that time we get here two one three diaxial interactions one there are some steric crowding because of bulkier methyl group than that of hydrogen that's why this structure having methyl group at axial position is unstable than that of methyl group present on the equatorial position okay so here i try to convert that position of methyl group right like this okay so now the methyl group is present at equatorial position and this equatorial position is out of plane so it can't interfere with any adjacent proton so that its stability is more okay so from this conclusion or from this explanation we can conclude that is compound a or isomer a is more stable more unstable than that of b so that equatorial methyl or this compound is more stable than that of a so b is more stable than that of a okay remember student then after that we can see a next point on next lecture di-substituted cyclohexane okay thank you