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Conjugated Dienes:Free Radical Addition Reaction :Vikrant Dhamak

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Hello to your student welcome to my youtube channel in this video we will see uh conjugated tines and in that we will see free radical addition reaction in the last session we have seen about electrophilic addition reaction in this session we will see free radical addition reaction and there are two kinds of an uh addition reaction that is one four and one two

Type of an additional reaction so we will see within mechanism so like the video and subscribe the channel for more updates now next point that is free radical addition reactions of conjugated tines in case of an antimarconic rule we have seen but it was only an alkene here it is conjugated lines so similar kind of an mechanism we will see in this case also

Conjugated time also undergo addition reaction by radical chain mechanism and here the addition product we get that is 1 2 and 1 4 thus the radical addition reaction of an hydrogen bromide two one three butadiene gives one bromo two butane so we will see the general reaction now see this one three butadiene uh we get one two addition product again and we get one

For addition product now which predominates again it is having some conditions and why it is now and free radical conjugation reaction because this free radical which is formed due to peroxides so it is also said to be an peroxide effect as we have seen in case of an anti marconico rule that peroxide effect it can be seen and it gives one two addition product

As well as an one for addition product products are same but which predominates so it depends on the condition and mechanism is also different now let us see the mechanism in case of an mechanism uh see this one one three butadiene as it is in one three butadiene so here it is having hbr as well as in peroxide and this peroxide as we have seen in case of an

Uh marconic of anti-marconigo proof this peroxide they will now firstly they will form radicals and this radical this reacts to radicals they will combine with it is radical ro and they will combine with hbr this hbr again that will clear and once it has been cleared once it has been cleared so now that peroxide radical plus hydrogen they will combine

And this br this bromine br radical so this br radical it will attack it will attack on the carbon number one and again that carbon number one it will clear in an homolytic manner and here we will get we will get this product after attachment of an bromine radical so this all the cleavage they are homolytic over here uh it is like an antimarconic rule that

All the cleavage they are do more lighting and once this bromine it get attached at carbon number one so it will form a free radical at carbon number two because it has been cleared homolytically so one of the electrons from this double bond it will shift towards the carbon number two and the resonating form of this that again this carbon number three and four

It will clear in a such way that it will give one of the electron towards homolytically after cleaving it it will give an electron towards carbon number uh two and three so here it will form a double bond and one of the electron it will go on carbon number four so here we can see that it is having now an free radical if we see the stability of a free radical this

Free radical it is more stable as it is secondary as we have seen in case of an anti markovnikov rule that it has a stability symbol similar like often carbocations and now this secondary radical this secondary radical it is more stable and primary radical primary radical it is less stable as a hydrogen carbonate is having only only the hydrogen attached to it

Hydrogen attached to it but here the it is in secondary so that is why it is unstable and this one is primary which is less stable now remaining part that is hbr again hbr it will be added uh hbr again it will be cleared homolytically so in this manner it will clear and once it has been cleared homolytically so the hydrogen it get attached at carbon number two

You can see in the red color that hydrogen gate attached to and carbon number two and in case of less stable radical hbr again it will clear homologically all the bond fissions they are homolytically cleared in this mechanism and hydrogen get attached to a carbon number four which is having which was having two hydrogens earlier and now we get one two addition

Product and one for addition product why one two addition because brominate has attached to a carbon number one and at carbon number two so we get this one two product and we get one for product that is bromine get attached at carbon number one and bromine get attached uh hydrogen gate attached carbon number four but the problem is that more stable radical as

In the earlier case we have seen that carbocation more stable carbocation forms and less stable alkyne the same thing happens over here that more stable radical it gives less substituted double bond which is less stable alkene which is less stable alkene so that is one two product and we get a one four product which forms uh due to a less stable radical but alkene

Whatever we get it isn’t more stable and this product it is called kinetic product as it it can be formed at lower temperatures and thermodynamic means it requires an heat energy of activation will be high so that is why we get an 1 4 product which is more stable now the thing is that which is the major product form predominantly it is either 1 2 or 1 4 in

Case of an this radical reaction to unconjugated lines stability of free radicals first thing is now stability of free radical as we have seen now earlier that stability of an carbocation now stability of infrared radicals the addition of a proton occurs as per the anti-markovnikov the stable carbon-free radical will be formed at more substituted carbon and

Carbon atom and form one two product because this as we have seen in case of an mechanism that secondary carbocations they are secondary sorry secondary free radicals they are more stable compared to in primary so we get a kinetic product that is one two product and as per the stability of free radical we should get one two product now rate of reaction the

Same is the thing again the energy of activation for the formation of an one-two product is lower and hence form faster however equilibrium is less favored for it but for one for product require a high energy of activation but equilibrium is favored because it forms a more stable alkene so when the energy of activation is high we will get uh one four kind of an

Product when energy of activation is less we will get one two kind of end product and for energy of activation we require an heat and when the reaction temperature it is again similar like if we carry out the reaction at low temperatures we will get a kinetic product and if we carry the reaction temperature at high temperatures then we will get a 1 4 product

Which is more stable alkene but less stable radical and excess of reagents when it has been utilized we will get one four kind of encoder again same is the thing that we get one for kind of an product if the reagent conditions are milder so these are the four parameters on which whether it will be 1 2 or 1 4 that will predominate thank you for watching the

Video if you are having any doubts you can comment in the comment section i will definitely answer it

Transcribed from video
Conjugated Dienes:Free Radical Addition Reaction :Vikrant Dhamak By Vikrant Dhamak