In given reaction isopropyl groups are introduced at ortho position of phenol. I
ID: 699669 • Letter: I
Question
In given reaction isopropyl groups are introduced at ortho position of phenol. It is an electrophillic substitution reaction in which electrophille is alkene and OH group of phenol activates the ortho and para position of ring for electrophillic substitution.
This reaction takes place in presence of Al(OPh)3 which acts as lewis acid , a catalyst attaches to OH gp of phenol thus increases polarity of O---H bond helps in removal of H+ of OH group of phenol.
This H+ gets attached to that doubly bonded C of alkene which contain more no. Of H atoms( markovnikoff addition) resulting in positive charge on adjacent C ( stable secondary carbocation is formed). This acts as an electrophille which attacks at ortho position of phenol.
As electrophille attaches at ortho position sp2 C changes into sp3 , then elimination takes place H which is present at that C gets eliminated as H+.
This H+ attaches to O of phenol and lewis acid gets detached from it .
So in this process electrophillic substitution takes place in which addition followed by elimination takes place.
This whole process repeated again for substitution at another ortho position.
Explanation / Answer
4 AKOPh HO OH 225-230°c 200-450 psi OH OH Al(OPh)s over all yield 45-55% 225-230 200-450 psi 28-Dis opropy phenol