Organic Chemistry> Can HF , HCL and HI give markonioff' s re...

Can HF , HCL and HI give markonioff' s reaction and peroxide is organic or inorganic ?

Ashutosh , 6 Years ago

Grade 12

2 Answers

Rajat

The answer is no they can't. this is because HF HCl and HI do not undergo free radical addition to alkenes in the presence of peroxide.

the abstraction of h free radical from hydrogen Bromide is exothermic and thus feasible and reaction proceeds.

in case of HCl the H-Cl bond is stronger than HBr and does the extraction of H free radical is endothermic.

in case of HI though the extraction of H free radical is exothermic but the addition of the Ifree radical to alkene is endothermic.

Last Activity: 6 Years ago

Rajdeep

HELLO THERE!

First, you need to keep two things in your mind:

(1) The reaction that proceeds by Markovnikoff’s Rule, carbocation is formed as an intermediate.

(2) The reaction that proceeds by Anti-Markovnikoff’s Rule, free radical is formed as an intermediate.

When it comes to the Markovnikoff’s Rule:

HBr, HCl and HI -- all three halogen acids can be added to an alkene through Markovnikoff’s rule. As two degree carbocation is more stable than a one degree carbocation, if the chloride/bromide/iodide from the respective halogen acids get added to the two degree carbocation (substituted from two sides), the product will be the major product.

When it comes to the Anti-Markovnikoff Rule:

Only HBr shows Anti-Markovnikoff’s rule in presence of Peroxide. HCl and HI does not show Anti-Markovnikoff effect.

This has some reasons.

The reaction proceeds by Free radical mechanism. Bond dissociation energy, of HI, though less han HBr, when Iodine free radical is formed, it is so reactive that it forms iodine molecule (instead of attacking the alkene).

In case of HCl, it has a higher bond dissociation energy than HBr. So, the process of free radical formation is endothermic, which does not favour the reaction.

=> Generally Benzyl Peroxide, (C₆H₅COO)₂ is used for the purpose, which is of course an organic peroxide.

THANKS!

Last Activity: 6 Years ago