Integral Calculus> Please tell me the concept behind this qu...

Please tell me the concept behind this question of organic chemistry.A reaction in the presence of HBr

Ashutosh Pokhriyal , 5 Years ago

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3 Answers

Shah Rutvi

Last Activity: 5 Years ago

HBr in presence of peroxide is used to generate free radical. HF, HCL are not used in this process because second step involved in the reaction is endothermic.. While this is not seen in HBR. And with HI reversible reaction takes place.

Ashutosh Pokhriyal

Last Activity: 5 Years ago

I know this. It is there in theory . Please tell me its answer and mechanism involved.

I am confused about cleavage of double bond present there.

Samyak Jain

Last Activity: 5 Years ago

Addition of HBr in presence of peroxide follows free radical mechanism and

takes place according to anti-Markownikoff’s rule.

In this reaction stability of free radical decides the major product.

Initially homolytic bond cleavage of H₂O₂ takes place producing 2 OH^o radicals.

Then homolytic bond cleavage of HBr takes place, producing Br^o and H^o ;

this H^o combines with one of OH^oradicals to give H₂O.

After homolytic break of pi bond of the double bond, two carbon free radicals are formed.

Of which carbon free radical attached to phenyl is resonance stabilised and thus more stable than the carbon free radical attached to two methyl groups whose +H = 6.

Therefore, Br^o generated above forms a bond with less stable carbon radical and again H^o produced by homolytic break of HBr is linked with carbon radical having phenyl ring.

So, I think 2^nd option is correct.