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Hello everyone i take the pleasure of inviting you all to this session in this session we’ll be discussing dienes diens are the organic compounds containing two carbon-carbon double bonds depending on the location of the carbon-carbon double bonds they are classified as cumulated dyeins conjugated dienes and unconjugated dienes let us see what are these different
Types of dienes in cumulated dienes there will be two carbon-carbon double bonds but these two double bonds will be shared a common carbon this type of dienes are called aliens more specifically we can call them as aliens so this is the general structure of cumulated dienes where this is one carbon-carbon double bond another carbon-carbon double bond at the
Center there is a carbon so the common carbon will be this carbon will be shared by both the double bonds next is conjugated dienes conjugated dienes are the dienes in which two double bonds are separated two double bonds are separated by a single one single bond one single bond the two double bonds the two double bonds are separated by one single bond such
Dienes are conjugated dienes there in this compounds there will be alternate double bond single bond there will be alternate double bond single bond so this is a double bond single bond double bond so double bond single bond double bond so like this there will be alternate double bond and single bond next coming to unkanjug dienes they are also called isolated
Dienes see in these dienes there is a double bond there is another double bond two double bonds are there but these double bonds are separated by two or more single bonds two or more single bonds there is a double bond and there is a double bond and this double bond two double bonds are present so it is a diene again these two double bonds are separated by many
Single bonds same thing here also this is a double bond single bond single bond single bond maybe two or more single bonds are present between two double bonds such dienes are called unconjugated dienes are isolated dienes so this is about uh definition and classification of dienes let us see the reactions of these dienes this dienes undergo reactions they are
They undergo reactions to give a cyclic compound hence these reactions are called cyclo addition reactions so cyclo addition reactions um these are the chemical reaction in which two are more unsaturated molecules combine to form a cyclic adduct in which there is a net reduction of bond multiplicity so the resulting reaction is a cyclization reaction okay
This is a cycloaddition reaction in which the two unsaturated molecule combined to give a cyclic product hence this reaction is called cyclization reaction or cycloaddition reaction let us see examples of these cycloaddition reactions this fourth addition reaction in conjugated dienes example here this is a one diene is there another um ethene is there these
Are two unsaturated reactants there are two double bonds here and these two double bonds are separated by separated by okay these two double bonds are separated here this is one double bond another double bond separated by a single one single bond hence it is a conjugated diene and this conjugated the in react with all in this reaction this ethene is called
Dienophile dienophile it has two pi electrons and it has two pi electrons and in this diene there are four pi electrons now this one each double bond accounts for two electrons there are two double bonds so four electrons four pi electrons here two pi electrons these pi electrons are shared between the six carbon atoms so therefore it is four plus two cyclo
Addition reaction four pi electron and two pi electron share electrons to form a new bond to form a new single bond and the single bond which has already forms a double bond this is a single bond here it becomes a double bond there is no bond here there is no bond here there will be a new bond formation we can see this is a new bond formation and the bond which
Is there already it forms a double bond so the two unsaturated reactant one is diene another is dienophile combined to give a cyclic compound called cyclohexene cyclohexene addition of buta one three diene this is a butane in which there are two double bonds at carbon number one and at carbon number two one three butadiene and ethene this is ethene to form
Cyclohexene this is one example of cycloaddition reaction of dienes another example let us see so this is addition of buta one three die into malic anhydride see once again here this is a diene the yin same 1 3 buta diene as we have seen in the previous example 1 3 butadiene and this is another reactant and saturated reactant is malic anhydride so this malic
Anhydride has one double bond and there are two double bonds once again four plus two five electrons addition cycloaddition reaction so this you can see the bond movement so this bond moves this side and this bond moves this side and this bond must decide to give a new compound all the bonds move simultaneously moment of electrons will be simultaneous uh this
Reaction therefore are called concerted this reactions are this this reaction is a concerted reaction since the moment of electrons takes place simultaneously at a time so this is the adduct we get addition product due to the combination of diene and dienophile the enemies one tribute a day in here and it is malik anhydride another example of um cyclo addition
Reactions so this is about dienes and different uh types of dienes and the reactions of dienes with dienophile so the classification examples and reactions of dienes okay hope it is understood thank you for watching this video
Transcribed from video
Conjugated dienes By Muneerunnisa Muneerunnisa